Competitive Programming

Methods to Solve (2000-present)

Use these filters to narrow down your next problem to solve:

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For LeetCode tasks, the DACU for the tasks seem to be in order of hundred-thousands to millions and grow quickly, thus we ignore this field.
Instead, we focus on solving the most popular study plan lists first (access to some tasks require premium subscription), e.g.,
Programming Skills (49/49; 16 premium) (MtS hints),
LeetCode 75 (75/75) (MtS hints),
Top 100 Liked (100/100) (MtS hints),
Top Interview 150 (143/150) (MtS hints),
PS: although totally not Competitive Programming related, Steven is also solving SQL (database) tasks for fun: SQL 50 (43/50) and Advanced SQL 50 (36/50) (MtS hints).

In LeetCode, Easy/Medium/Hard problems are classified as equivalent to Kattis 2.0/4.0/6.0 pointers

LeetCode Problem Title CP4+5 Hint DACU Point
lc2235 to replace with LeetCode link soon... 1.4a, One-Liner I/O just do it 0 2.0
lc2469 to replace with LeetCode link soon... 1.4a, One-Liner I/O simple C to K/F conversion 0 2.0
lc2651 to replace with LeetCode link soon... 1.4a, One-Liner I/O simple formula 0 2.0
lc2769 to replace with LeetCode link soon... 1.4a, One-Liner I/O simple formula after reading comprehension 0 2.0
lc2806 to replace with LeetCode link soon... 1.4a, One-Liner I/O rounding task; Python users have to be careful about banker's rounding 0 2.0
lc3492 to replace with LeetCode link soon... 1.4a, One-Liner I/O simple math check 0 2.0
lc0520 to replace with LeetCode link soon... 1.4d, Selection Only, 3+ Cases 4 cases 0 2.0
lc2119 to replace with LeetCode link soon... 1.4d, Selection Only, 3+ Cases True if num is 0; otherwise True only if num is not divisible by 10 0 2.0
lc1281 to replace with LeetCode link soon... 1.4e, Repetition Only break n into digits; do as asked 0 2.0
lc2154 to replace with LeetCode link soon... 1.4e, Repetition Only simple while loop 0 2.0
lc3110 to replace with LeetCode link soon... 1.4e, Repetition Only one pass; do as asked 0 2.0
lc3512 to replace with LeetCode link soon... 1.4e, Repetition Only simple sum and math check 0 2.0
lc1431 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 simple one pass check; leetcode-75 0 2.0
lc1822 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 simple one pass calculation; 3 cases; programming-skills 0 2.0
lc2529 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 just do as asked 0 2.0
lc2652 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 there are faster ways; but just do as asked 0 2.0
lc2778 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 simple control flow 0 2.0
lc2798 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 simple control flow 0 2.0
lc2894 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 one pass; positive vs negative 0 2.0
lc3028 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 just do as asked 0 2.0
lc3038 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 just do as asked 0 2.0
lc3285 to replace with LeetCode link soon... 1.4g, Control Flow, Level 1 just do as asked 0 2.0
lc1450 to replace with LeetCode link soon... 1.4h, Control Flow, Level 2 small Range-Update Point-Query task; complete search 0 2.0
lc2148 to replace with LeetCode link soon... 1.4h, Control Flow, Level 2 one pass; compare number against min and max of nums 0 2.0
lc2169 to replace with LeetCode link soon... 1.4h, Control Flow, Level 2 simulate as asked 0 2.0
lc3467 to replace with LeetCode link soon... 1.4h, Control Flow, Level 2 just count number of 0s and 1s 0 2.0
lc2455 to replace with LeetCode link soon... 1.4i, Control Flow, Level 3 even and divisible by 3 means divisible by 6 0 2.0
lc3151 to replace with LeetCode link soon... 1.4i, Control Flow, Level 3 one pass; check adjacent parity 0 2.0
lc3190 to replace with LeetCode link soon... 1.4i, Control Flow, Level 3 one pass; find non-multiple of 3 0 2.0
lc0258 to replace with LeetCode link soon... 1.4j, Function use sum-of-digits function until only one digit left 0 2.0
lc0728 to replace with LeetCode link soon... 1.4j, Function create custom function selfDividing(v) and use it 0 2.0
lc2180 to replace with LeetCode link soon... 1.4j, Function use sum-of-digits function 0 2.0
lc2239 to replace with LeetCode link soon... 1.4j, Function use abs function; simulate as asked 0 2.0
lc2535 to replace with LeetCode link soon... 1.4j, Function use sum (of list) and sum-of-digits function 0 2.0
lc3079 to replace with LeetCode link soon... 1.4j, Function make 'encrypt' function as described; apply it to all Integers; sum them 0 2.0
lc3274 to replace with LeetCode link soon... 1.4j, Function make 'parity' function; check if two coordinates have the same parity 0 2.0
lc3300 to replace with LeetCode link soon... 1.4j, Function use sum-of-digits function 0 2.0
lc3461 to replace with LeetCode link soon... 1.4j, Function create custom function process(s) and use it 0 2.0
lc0066 to replace with LeetCode link soon... 1.4k, 1D Array, Easier simulate +1 operation on an array of digits; programming-skills; top-interview-150 0 2.0
lc0153 to replace with LeetCode link soon... 1.4k, 1D Array, Easier not-intended solution: O(n) find min; top-100-liked; top-interview-150 0 4.0
lc0747 to replace with LeetCode link soon... 1.4k, 1D Array, Easier find max; one pass to compare 0 2.0
lc0896 to replace with LeetCode link soon... 1.4k, 1D Array, Easier up to two O(n) passes to check monotone property; programming-skills 0 2.0
lc0922 to replace with LeetCode link soon... 1.4k, 1D Array, Easier one pass to reorganize the integers by parity 0 2.0
lc1103 to replace with LeetCode link soon... 1.4k, 1D Array, Easier simple simulation 0 2.0
lc1470 to replace with LeetCode link soon... 1.4k, 1D Array, Easier split nums into half and reorganize 0 2.0
lc1491 to replace with LeetCode link soon... 1.4k, 1D Array, Easier (sum-max-min)/len; programming-skills 0 2.0
lc1920 to replace with LeetCode link soon... 1.4k, 1D Array, Easier just do as asked 0 2.0
lc1929 to replace with LeetCode link soon... 1.4k, 1D Array, Easier just duplicate the list 0 2.0
lc2011 to replace with LeetCode link soon... 1.4k, 1D Array, Easier just do as asked 0 2.0
lc2057 to replace with LeetCode link soon... 1.4k, 1D Array, Easier just do as asked 0 2.0
lc2951 to replace with LeetCode link soon... 1.4k, 1D Array, Easier one pass check 0 2.0
lc3206 to replace with LeetCode link soon... 1.4k, 1D Array, Easier circular array check 0 2.0
lc0832 to replace with LeetCode link soon... 1.4l, 2D Array, Easier 2D matrix processing 0 2.0
lc0867 to replace with LeetCode link soon... 1.4l, 2D Array, Easier transpose a 2D matrix 0 2.0
lc1572 to replace with LeetCode link soon... 1.4l, 2D Array, Easier sum the diagonals; do not overcount the center cell for odd n; programming-skills 0 2.0
lc1672 to replace with LeetCode link soon... 1.4l, 2D Array, Easier sum each row; keep the max row sum; programming-skills 0 2.0
lc1773 to replace with LeetCode link soon... 1.4l, 2D Array, Easier simple nx3 array processing 0 2.0
lc3386 to replace with LeetCode link soon... 1.4l, 2D Array, Easier simple nx2 matrix processing 0 2.0
lc2600 to replace with LeetCode link soon... 1.4m, Easy take 1s first; then 0s; before -1s 0 2.0
lc2739 to replace with LeetCode link soon... 1.4m, Easy simulate the process 0 2.0
lc0007 to replace with LeetCode link soon... 1.4n, Still Easy interpret x as string; reverse; convert to int again; check range 0 4.0
lc1342 to replace with LeetCode link soon... 1.4n, Still Easy logarithmic steps simulation 0 2.0
lc2899 to replace with LeetCode link soon... 1.4n, Still Easy just do as asked 0 4.0
lc3232 to replace with LeetCode link soon... 1.4n, Still Easy split the sum to 1 vs 2 digits; True if the sum is different 0 2.0
lc2139 to replace with LeetCode link soon... 1.4o, Medium backwards thinking from end state to original 0 4.0
lc2240 to replace with LeetCode link soon... 1.4o, Medium derive simple math formula; linear pass possible 0 4.0
lc2383 to replace with LeetCode link soon... 1.4o, Medium need careful observation to have O(n) solution; separate the two trainings 0 2.0
lc2605 to replace with LeetCode link soon... 1.4o, Medium a few subcases to consider: 1 digit answer or 2 digits answer 0 2.0
lc3522 to replace with LeetCode link soon... 1.4o, Medium an easier version of Kattis - basicprogramming1 0 4.0
lc0058 to replace with LeetCode link soon... 1.5a, 1D Character Array split and report as asked; programming-skills; top-interview-150 0 2.0
lc0186 to replace with LeetCode link soon... 1.5a, 1D Character Array PREMIUM - hint hidden 0 4.0
lc0344 to replace with LeetCode link soon... 1.5a, 1D Character Array in-place simple string reversal 0 2.0
lc0557 to replace with LeetCode link soon... 1.5a, 1D Character Array tokenize; reverse each token 0 2.0
lc0709 to replace with LeetCode link soon... 1.5a, 1D Character Array do as asked; programming-skills 0 2.0
lc1422 to replace with LeetCode link soon... 1.5a, 1D Character Array split string; count 0s and 1s 0 2.0
lc1446 to replace with LeetCode link soon... 1.5a, 1D Character Array one pass through array of chars 0 2.0
lc1528 to replace with LeetCode link soon... 1.5a, 1D Character Array 1D char array processing 0 2.0
lc1576 to replace with LeetCode link soon... 1.5a, 1D Character Array just do as asked 0 2.0
lc1662 to replace with LeetCode link soon... 1.5a, 1D Character Array just compare two string arrays 0 2.0
lc1704 to replace with LeetCode link soon... 1.5a, 1D Character Array do as asked 0 2.0
lc1763 to replace with LeetCode link soon... 1.5a, 1D Character Array just do as asked 0 2.0
lc1784 to replace with LeetCode link soon... 1.5a, 1D Character Array one pass check 0 2.0
lc1796 to replace with LeetCode link soon... 1.5a, 1D Character Array just do as asked 0 2.0
lc1816 to replace with LeetCode link soon... 1.5a, 1D Character Array do as asked 0 2.0
lc1876 to replace with LeetCode link soon... 1.5a, 1D Character Array brute force check 0 2.0
lc2000 to replace with LeetCode link soon... 1.5a, 1D Character Array do as asked 0 2.0
lc2027 to replace with LeetCode link soon... 1.5a, 1D Character Array one pass; process leftmost X 0 2.0
lc2138 to replace with LeetCode link soon... 1.5a, 1D Character Array split the string as asked 0 2.0
lc2609 to replace with LeetCode link soon... 1.5a, 1D Character Array we can try all possible substrings 0 2.0
lc2810 to replace with LeetCode link soon... 1.5a, 1D Character Array reverse buffer whenever 'i' is pressed 0 2.0
lc2828 to replace with LeetCode link soon... 1.5a, 1D Character Array tokenize; get first characters; compare 0 2.0
lc3216 to replace with LeetCode link soon... 1.5a, 1D Character Array try swapping swappable adjacent digits; keep the smallest 0 2.0
lc3330 to replace with LeetCode link soon... 1.5a, 1D Character Array one pass; count long press; simple math 0 2.0
lc3340 to replace with LeetCode link soon... 1.5a, 1D Character Array process the string as asked 0 2.0
lc3438 to replace with LeetCode link soon... 1.5a, 1D Character Array short string; just do as asked 0 2.0
lc3456 to replace with LeetCode link soon... 1.5a, 1D Character Array short string; just do as asked 0 2.0
lc3498 to replace with LeetCode link soon... 1.5a, 1D Character Array process the string as asked 0 2.0
lc0006 to replace with LeetCode link soon... 1.5b, Cipher, Easier index manipulation exercise; top-interview-150 0 4.0
lc0824 to replace with LeetCode link soon... 1.5b, Cipher, Easier do as asked 0 2.0
lc1309 to replace with LeetCode link soon... 1.5b, Cipher, Easier simply decryption 0 2.0
lc1313 to replace with LeetCode link soon... 1.5b, Cipher, Easier simple RLE decode 0 2.0
lc1844 to replace with LeetCode link soon... 1.5b, Cipher, Easier implement shift(c, x) function; apply it; simple decipher 0 2.0
lc3210 to replace with LeetCode link soon... 1.5b, Cipher, Easier simple rotation cipher 0 2.0
lc3270 to replace with LeetCode link soon... 1.5b, Cipher, Easier a simple cipher 0 2.0
lc0246 to replace with LeetCode link soon... 1.5c, Cipher, Medium PREMIUM - hint hidden 0 2.0
lc0443 to replace with LeetCode link soon... 1.5c, Cipher, Medium Run-Length Encoding simulation; leetcode-75 0 4.0
lc1056 to replace with LeetCode link soon... 1.5c, Cipher, Medium PREMIUM - hint hidden 0 2.0
lc2325 to replace with LeetCode link soon... 1.5c, Cipher, Medium prepare a mapper (DAT) for each character 0 2.0
lc3163 to replace with LeetCode link soon... 1.5c, Cipher, Medium Run Length Encoding variant 0 4.0
lc0008 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) tedious input parsing 0 4.0
lc0830 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) simple parsing 0 2.0
lc1078 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) simple parsing 0 2.0
lc1410 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) & is the trickiest 0 4.0
lc1678 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) simple iterative parser 0 2.0
lc2788 to replace with LeetCode link soon... 1.5d, Input Parsing (Iter) simple string split by a delimiter 0 2.0
lc0151 to replace with LeetCode link soon... 1.5e, Output Formatting, E process the string as asked; leetcode-75; top-interview-150 0 4.0
lc0482 to replace with LeetCode link soon... 1.5e, Output Formatting, E just do as asked 0 2.0
lc1108 to replace with LeetCode link soon... 1.5e, Output Formatting, E just replace '.' with '[.]' 0 2.0
lc1324 to replace with LeetCode link soon... 1.5e, Output Formatting, E use 2D grid buffer 0 4.0
lc1544 to replace with LeetCode link soon... 1.5e, Output Formatting, E just do as asked 0 2.0
lc1556 to replace with LeetCode link soon... 1.5e, Output Formatting, E add thousand separator as asked 0 2.0
lc1592 to replace with LeetCode link soon... 1.5e, Output Formatting, E just do as asked 0 2.0
lc1694 to replace with LeetCode link soon... 1.5e, Output Formatting, E just do as asked 0 2.0
lc1859 to replace with LeetCode link soon... 1.5e, Output Formatting, E shuffle the words as asked 0 2.0
lc1957 to replace with LeetCode link soon... 1.5e, Output Formatting, E reformat the input as asked 0 2.0
lc2109 to replace with LeetCode link soon... 1.5e, Output Formatting, E insert spaces as asked 0 4.0
lc2129 to replace with LeetCode link soon... 1.5e, Output Formatting, E reformat the input as asked 0 2.0
lc2710 to replace with LeetCode link soon... 1.5e, Output Formatting, E do as asked 0 2.0
lc0293 to replace with LeetCode link soon... 1.5f, Easy, Involving String PREMIUM - hint hidden 0 2.0
lc0521 to replace with LeetCode link soon... 1.5f, Easy, Involving String there are only two cases 0 2.0
lc0541 to replace with LeetCode link soon... 1.5f, Easy, Involving String process as asked 0 2.0
lc0859 to replace with LeetCode link soon... 1.5f, Easy, Involving String there are a few subcases 0 2.0
lc1455 to replace with LeetCode link soon... 1.5f, Easy, Involving String tokenize and check 0 2.0
lc1880 to replace with LeetCode link soon... 1.5f, Easy, Involving String create function toInt(s); simple comparison 0 2.0
lc1945 to replace with LeetCode link soon... 1.5f, Easy, Involving String convert string to digits; then use sum-of-digits function 0 2.0
lc2042 to replace with LeetCode link soon... 1.5f, Easy, Involving String check as asked 0 2.0
lc2114 to replace with LeetCode link soon... 1.5f, Easy, Involving String tokenize; check length; keep the max 0 2.0
lc2124 to replace with LeetCode link soon... 1.5f, Easy, Involving String check as asked 0 2.0
lc2185 to replace with LeetCode link soon... 1.5f, Easy, Involving String just do as asked 0 2.0
lc2243 to replace with LeetCode link soon... 1.5f, Easy, Involving String use sum-of-digits function; just do as asked 0 2.0
lc2255 to replace with LeetCode link soon... 1.5f, Easy, Involving String count as asked 0 2.0
lc2309 to replace with LeetCode link soon... 1.5f, Easy, Involving String just do as asked 0 2.0
lc2315 to replace with LeetCode link soon... 1.5f, Easy, Involving String count as asked 0 2.0
lc2414 to replace with LeetCode link soon... 1.5f, Easy, Involving String one pass processing 0 4.0
lc2490 to replace with LeetCode link soon... 1.5f, Easy, Involving String one pass; the array is circular 0 2.0
lc2496 to replace with LeetCode link soon... 1.5f, Easy, Involving String create custom function value(s); apply it to all strings 0 2.0
lc2544 to replace with LeetCode link soon... 1.5f, Easy, Involving String compute as asked 0 2.0
lc2586 to replace with LeetCode link soon... 1.5f, Easy, Involving String count as asked 0 2.0
lc2678 to replace with LeetCode link soon... 1.5f, Easy, Involving String count as asked 0 2.0
lc2839 to replace with LeetCode link soon... 1.5f, Easy, Involving String there are only a few cases 0 2.0
lc2942 to replace with LeetCode link soon... 1.5f, Easy, Involving String just do as asked 0 2.0
lc3019 to replace with LeetCode link soon... 1.5f, Easy, Involving String one pass check 0 2.0
lc3120 to replace with LeetCode link soon... 1.5f, Easy, Involving String count as asked 0 2.0
lc3136 to replace with LeetCode link soon... 1.5f, Easy, Involving String check as asked 0 2.0
lc2347 to replace with LeetCode link soon... 1.6a, Game (Card) apply the poker hand rules as described 0 2.0
lc0999 to replace with LeetCode link soon... 1.6b, Game (Chess) find the (r, c) of rook 'R'; simulate 4 directions of rook attacks 0 2.0
lc1222 to replace with LeetCode link soon... 1.6b, Game (Chess) check 8 directions on grid 0 4.0
lc1812 to replace with LeetCode link soon... 1.6b, Game (Chess) parity check 0 2.0
lc2660 to replace with LeetCode link soon... 1.6c, Game (Others), Easier simulate bowling scoring system 0 2.0
lc3248 to replace with LeetCode link soon... 1.6c, Game (Others), Easier simulating the movement of snake grid game 0 2.0
lc0036 to replace with LeetCode link soon... 1.6d, Game (Others), Harder 2D grid property checker in form of Sudoku puzzle; top-interview-150 0 4.0
lc0434 to replace with LeetCode link soon... 1.6d, Game (Others), Harder 1.5d 0 2.0
lc1275 to replace with LeetCode link soon... 1.6d, Game (Others), Harder simulate Tic-Tac-Toe game; programming-skills 0 2.0
lc0412 to replace with LeetCode link soon... 1.6e, Real Life, Easier classic Fizz Buzz 0 2.0
lc0657 to replace with LeetCode link soon... 1.6e, Real Life, Easier simple robot movement simulation on a virtual 2D grid; programming-skills 0 2.0
lc0806 to replace with LeetCode link soon... 1.6e, Real Life, Easier process as required 0 2.0
lc1603 to replace with LeetCode link soon... 1.6e, Real Life, Easier simple counter system 0 2.0
lc2079 to replace with LeetCode link soon... 1.6e, Real Life, Easier like in real-life 0 4.0
lc2194 to replace with LeetCode link soon... 1.6e, Real Life, Easier real-life Excel Sheet range processing 0 2.0
lc2303 to replace with LeetCode link soon... 1.6e, Real Life, Easier real-life tax calculation 0 2.0
lc2432 to replace with LeetCode link soon... 1.6e, Real Life, Easier create this log processing system 0 2.0
lc2525 to replace with LeetCode link soon... 1.6e, Real Life, Easier just categorize the boxes as asked 0 2.0
lc3168 to replace with LeetCode link soon... 1.6e, Real Life, Easier real-life waiting room simulation 0 2.0
lc0551 to replace with LeetCode link soon... 1.6f, Real Life, Medium just do as asked 0 2.0
lc0804 to replace with LeetCode link soon... 1.6f, Real Life, Medium convert string to morse; use set 0 2.0
lc0925 to replace with LeetCode link soon... 1.6f, Real Life, Medium much easier if we use Python itertools.groupby 0 2.0
lc1041 to replace with LeetCode link soon... 1.6f, Real Life, Medium virtual 2D grid traversal; simple observations; programming-skills 0 4.0
lc2299 to replace with LeetCode link soon... 1.6f, Real Life, Medium we frequently do this in real-life 0 2.0
lc1154 to replace with LeetCode link soon... 1.6h, Time, Easier use Python datetime library 0 2.0
lc1185 to replace with LeetCode link soon... 1.6h, Time, Easier classic Day of the Week task 0 2.0
lc1360 to replace with LeetCode link soon... 1.6h, Time, Easier use Python datetime library 0 2.0
lc1507 to replace with LeetCode link soon... 1.6h, Time, Easier simple date reformatting 0 2.0
lc3114 to replace with LeetCode link soon... 1.6h, Time, Easier a few case analysis; be careful 0 2.0
lc1344 to replace with LeetCode link soon... 1.6i, Time, Harder a classic clock hands angle problem; two cases 0 4.0
lc0012 to replace with LeetCode link soon... 1.6j, Roman Numerals classic Integer to Roman conversion; top-interview-150 0 4.0
lc0013 to replace with LeetCode link soon... 1.6j, Roman Numerals classic Roman to Integer conversion; programming-skills; top-interview-150 0 2.0
lc0088 to replace with LeetCode link soon... 2.2a, 1D Array, Medium do merge of Merge sort; top-interview-150 0 2.0
lc0163 to replace with LeetCode link soon... 2.2a, 1D Array, Medium PREMIUM - hint hidden 0 2.0
lc0189 to replace with LeetCode link soon... 2.2a, 1D Array, Medium simple if we can use additional O(n) space; top-100-liked; top-interview-150 0 4.0
lc0228 to replace with LeetCode link soon... 2.2a, 1D Array, Medium one pass; string formatting; top-interview-150 0 2.0
lc0605 to replace with LeetCode link soon... 2.2a, 1D Array, Medium tricky 1D array processing; leetcode-75 0 2.0
lc0941 to replace with LeetCode link soon... 2.2a, 1D Array, Medium check 1D array property 0 2.0
lc0985 to replace with LeetCode link soon... 2.2a, 1D Array, Medium sum all even integers first (sum_even); for each query, you can update sum_even in O(1) 0 4.0
lc1184 to replace with LeetCode link soon... 2.2a, 1D Array, Medium 1D circular array processing 0 2.0
lc1389 to replace with LeetCode link soon... 2.2a, 1D Array, Medium basic List ADT operations 0 2.0
lc1413 to replace with LeetCode link soon... 2.2a, 1D Array, Medium 1D array processing 0 2.0
lc1550 to replace with LeetCode link soon... 2.2a, 1D Array, Medium one pass; check three adjacent indices 0 2.0
lc1848 to replace with LeetCode link soon... 2.2a, 1D Array, Medium two passes: to the right and to the left 0 2.0
lc3069 to replace with LeetCode link soon... 2.2a, 1D Array, Medium use two arrays; do as asked 0 2.0
lc3131 to replace with LeetCode link soon... 2.2a, 1D Array, Medium find the difference of min integer in both arrays 0 2.0
lc3392 to replace with LeetCode link soon... 2.2a, 1D Array, Medium one pass through array as asked 0 2.0
lc3423 to replace with LeetCode link soon... 2.2a, 1D Array, Medium simple circular array processing 0 2.0
lc3452 to replace with LeetCode link soon... 2.2a, 1D Array, Medium just be careful with 1D array indexing 0 2.0
lc0042 to replace with LeetCode link soon... 2.2c, 1D Array, Harder find index i with max h eight; process left/right of i separately; top-100-liked; top-interview-150 0 6.0
lc0075 to replace with LeetCode link soon... 2.2c, 1D Array, Harder Dutch national flag partitioning problem; O(n) solution; top-100-liked 0 4.0
lc0238 to replace with LeetCode link soon... 2.2c, 1D Array, Harder use prefix and suffix products; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0281 to replace with LeetCode link soon... 2.2c, 1D Array, Harder PREMIUM - hint hidden 0 4.0
lc0724 to replace with LeetCode link soon... 2.2c, 1D Array, Harder similar to Kattis - pivot; leetcode-75 0 2.0
lc1732 to replace with LeetCode link soon... 2.2c, 1D Array, Harder prefix sum; keep the max; leetcode-75 0 2.0
lc1869 to replace with LeetCode link soon... 2.2c, 1D Array, Harder split s using 0 as delimiter; take token with the max length; do the same but using 1 as delimiter; compare 0 2.0
lc1991 to replace with LeetCode link soon... 2.2c, 1D Array, Harder compute prefix and suffix; similar to LC 0724 0 2.0
lc2016 to replace with LeetCode link soon... 2.2c, 1D Array, Harder compute prefix minimum for O(n) solution; O(n^2) still pass 0 2.0
lc2574 to replace with LeetCode link soon... 2.2c, 1D Array, Harder compute prefix sum and suffix sum first 0 2.0
lc2996 to replace with LeetCode link soon... 2.2c, 1D Array, Harder non-standard 1D array processing 0 2.0
lc3010 to replace with LeetCode link soon... 2.2c, 1D Array, Harder take the first index and two other indices with minimum and second minimum values 0 2.0
lc0027 to replace with LeetCode link soon... 2.2d, 2D Array, Medium use Partition algorithm (two pointers) for in-place solution; top-interview-150 0 2.0
lc0251 to replace with LeetCode link soon... 2.2d, 2D Array, Medium PREMIUM - hint hidden 0 4.0
lc0422 to replace with LeetCode link soon... 2.2d, 2D Array, Medium PREMIUM - hint hidden 0 2.0
lc0566 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D and possibly 1D matrix manipulation 0 2.0
lc0766 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D matrix diagonal checks 0 2.0
lc0883 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D matrix processing 0 2.0
lc1252 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D matrix processing 0 2.0
lc1351 to replace with LeetCode link soon... 2.2d, 2D Array, Medium go row by row; right to left, O(m+n) 0 2.0
lc2022 to replace with LeetCode link soon... 2.2d, 2D Array, Medium simple 1D to 2D matrix conversion 0 2.0
lc2103 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 3 colours; 10 rods; 2D Boolean matrix 0 2.0
lc2133 to replace with LeetCode link soon... 2.2d, 2D Array, Medium check if each row and col of a square matrix contains 1 to n 0 2.0
lc2319 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D matrix property check 0 2.0
lc2639 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D array and string length processing 0 2.0
lc3142 to replace with LeetCode link soon... 2.2d, 2D Array, Medium 2D matrix processing 0 2.0
lc0048 to replace with LeetCode link soon... 2.2e, 2D Array, Harder rotate a 2D matrix; be careful; top-100-liked; top-interview-150 0 4.0
lc0054 to replace with LeetCode link soon... 2.2e, 2D Array, Harder heavy 2D matrix indexing; use dr/dc technique; programming-skills; top-100-liked; top-interview-150 0 4.0
lc0073 to replace with LeetCode link soon... 2.2e, 2D Array, Harder three mxn passes to identify and later process those rows/cols; programming-skills; top-100-liked; top-interview-150 0 4.0
lc0240 to replace with LeetCode link soon... 2.2e, 2D Array, Harder utilize the special property; start at top-left; top-100-liked 0 4.0
lc0289 to replace with LeetCode link soon... 2.2e, 2D Array, Harder tedious 2D grid manipulation; top-interview-150 0 4.0
lc0311 to replace with LeetCode link soon... 2.2e, 2D Array, Harder PREMIUM - hint hidden 0 4.0
lc0661 to replace with LeetCode link soon... 2.2e, 2D Array, Harder 2D matrix processing; check up to 8 neighbors 0 2.0
lc0861 to replace with LeetCode link soon... 2.2e, 2D Array, Harder process row and col separately; row: prioritize values; col: prioritize on bits 0 4.0
lc1380 to replace with LeetCode link soon... 2.2e, 2D Array, Harder compute the min of each row and max of each col first; then another O(mn) pass 0 2.0
lc2373 to replace with LeetCode link soon... 2.2e, 2D Array, Harder 2D matrix processing; 4-nested loops 0 2.0
lc2946 to replace with LeetCode link soon... 2.2e, 2D Array, Harder 2D matrix processing; 3-nested loops 0 2.0
lc0004 to replace with LeetCode link soon... 2.2f, Sorting, Easier not-intended solution: sort in O(n log n) and report median; top-100-liked; top-interview-150 0 6.0
lc0217 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; check adjacent integers 0 2.0
lc0252 to replace with LeetCode link soon... 2.2f, Sorting, Easier PREMIUM - hint hidden 0 2.0
lc0268 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort nums; find first i != nums[i] 0 2.0
lc0350 to replace with LeetCode link soon... 2.2f, Sorting, Easier modification of merge of Merge sort 0 2.0
lc0414 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; remove duplicates; special cases for len 1 or 2 0 2.0
lc0905 to replace with LeetCode link soon... 2.2f, Sorting, Easier custom comparison function; prioritize evens first 0 2.0
lc0977 to replace with LeetCode link soon... 2.2f, Sorting, Easier square all integers; sort again 0 2.0
lc1030 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort by (Manhattan distance, r, c) 0 2.0
lc1051 to replace with LeetCode link soon... 2.2f, Sorting, Easier compare each element of heights with its sorted counterpart 0 2.0
lc1200 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort arr to achieve min abs diff of adjacent integers 0 2.0
lc1337 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort matrix rows by the sum of each row 0 2.0
lc1464 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; use the largest two 0 2.0
lc1657 to replace with LeetCode link soon... 2.2f, Sorting, Easier check if set of chars and its sorted frequency signatures are the same; leetcode-75 0 4.0
lc2089 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; do as asked 0 2.0
lc2164 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; custom rule 0 2.0
lc2733 to replace with LeetCode link soon... 2.2f, Sorting, Easier -1 for length 1 or 2; for length 3 or more; sort and report any index in [1..n-2] 0 2.0
lc2974 to replace with LeetCode link soon... 2.2f, Sorting, Easier sort; reverse each pair 0 2.0
lc0219 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort (keep the original indices as pair (v, i)); check successive elements; top-interview-150 0 2.0
lc1502 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort; check gap of successive elements; programming-skills 0 2.0
lc1637 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort; remove duplicate x-s; check successive elements 0 2.0
lc1984 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort; check elements that are k indices apart 0 2.0
lc2231 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort even and odd digits separately; construct the largest number 0 2.0
lc2342 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sum-of-digits function; sort by (sod(n), n); check successive elements 0 4.0
lc2395 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort the sum of all subarrays of size 2; check adjacent entries 0 2.0
lc2465 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort; two pointers: smallest and largest 0 2.0
lc2500 to replace with LeetCode link soon... 2.2g, Sorting, Simple Greedy sort each row; process per column 0 2.0
lc0001 to replace with LeetCode link soon... 2.2h, Sorting, Harder classic; O(n log n) solution: sort + two pointers; or hashing; top-100-liked; top-interview-150 0 2.0
lc0041 to replace with LeetCode link soon... 2.2h, Sorting, Harder O(n log n) solution; sort first; case analysis; top-100-liked 0 6.0
lc0280 to replace with LeetCode link soon... 2.2h, Sorting, Harder PREMIUM - hint hidden 0 4.0
lc0581 to replace with LeetCode link soon... 2.2h, Sorting, Harder there are O(n log n) easy sorting vs O(n) clever linear pass solutions 0 4.0
lc1356 to replace with LeetCode link soon... 2.2h, Sorting, Harder transform arr[i] into tuple (bitcount of arr[i], arr[i]); sort; output the second field 0 2.0
lc1451 to replace with LeetCode link soon... 2.2h, Sorting, Harder stable sort by (len(w), w) 0 4.0
lc1460 to replace with LeetCode link soon... 2.2h, Sorting, Harder check if the sorted versions of target and arr are equal 0 2.0
lc2418 to replace with LeetCode link soon... 2.2h, Sorting, Harder sorting with custom comparison function 0 2.0
lc2545 to replace with LeetCode link soon... 2.2h, Sorting, Harder sort a 2D matrix as asked 0 4.0
lc2785 to replace with LeetCode link soon... 2.2h, Sorting, Harder separate vowels and consonants; only sort the vowels 0 4.0
lc3194 to replace with LeetCode link soon... 2.2h, Sorting, Harder sort; use two pointers on extreme ends and move inside 0 2.0
lc3446 to replace with LeetCode link soon... 2.2h, Sorting, Harder just sorting; but on diagonals of 2D grid (two cases) 0 4.0
lc1122 to replace with LeetCode link soon... 2.2i, Special Sorting counting sort variant using arr2 order 0 2.0
lc2717 to replace with LeetCode link soon... 2.2i, Special Sorting two passes of bubble sort; one to the right; one to the left 0 2.0
lc0136 to replace with LeetCode link soon... 2.2j, Bit Manipulation XOR all integers; leetcode-75; top-100-liked; top-interview-150 0 2.0
lc0191 to replace with LeetCode link soon... 2.2j, Bit Manipulation bit_count; top-interview-150 0 2.0
lc0201 to replace with LeetCode link soon... 2.2j, Bit Manipulation hint: use LSOne; top-interview-150 0 4.0
lc0338 to replace with LeetCode link soon... 2.2j, Bit Manipulation bit_count; trivial; leetcode-75 0 2.0
lc0461 to replace with LeetCode link soon... 2.2j, Bit Manipulation bit_count of x^y 0 2.0
lc0476 to replace with LeetCode link soon... 2.2j, Bit Manipulation same as LC1009 0 2.0
lc0762 to replace with LeetCode link soon... 2.2j, Bit Manipulation check if bit_count in [2, 3, 5, 7, 11, 13, 17, 19] 0 2.0
lc1009 to replace with LeetCode link soon... 2.2j, Bit Manipulation XOR x with (11..1) 0 2.0
lc1318 to replace with LeetCode link soon... 2.2j, Bit Manipulation check all 31 bits; a few sub-cases per bit; leetcode-75 0 4.0
lc1486 to replace with LeetCode link soon... 2.2j, Bit Manipulation generate nums as asked, then XOR all its elements 0 2.0
lc2220 to replace with LeetCode link soon... 2.2j, Bit Manipulation xor and bit_count 0 2.0
lc2859 to replace with LeetCode link soon... 2.2j, Bit Manipulation use bit_count to identify Integers with k set bits 0 2.0
lc3226 to replace with LeetCode link soon... 2.2j, Bit Manipulation variant of Leetcode 2220; manual check this time 0 2.0
lc3370 to replace with LeetCode link soon... 2.2j, Bit Manipulation try all 2^i-1 for i in [0..10] 0 2.0
lc0043 to replace with LeetCode link soon... 2.2k, Big Integer, Easier basic Big Integer multiplication; programming-skills 0 4.0
lc0415 to replace with LeetCode link soon... 2.2k, Big Integer, Easier basic Big Integer addition 0 2.0
lc0989 to replace with LeetCode link soon... 2.2k, Big Integer, Easier basic Big Integer addition 0 2.0
lc2259 to replace with LeetCode link soon... 2.2l, Big Integer, Harder we can use Big Integer technique to solve this 0 2.0
lc0071 to replace with LeetCode link soon... 2.2m, Stack complex stack simulation; top-interview-150 0 4.0
lc0345 to replace with LeetCode link soon... 2.2m, Stack we can use stack for this; leetcode-75 0 2.0
lc0394 to replace with LeetCode link soon... 2.2m, Stack more complex stack simulation; leetcode-75; top-100-liked 0 4.0
lc0682 to replace with LeetCode link soon... 2.2m, Stack stack simulation; programming-skills 0 2.0
lc0735 to replace with LeetCode link soon... 2.2m, Stack stack simulation; leetcode-75 0 4.0
lc0844 to replace with LeetCode link soon... 2.2m, Stack stack simulation 0 2.0
lc0917 to replace with LeetCode link soon... 2.2m, Stack stack simulation 0 2.0
lc1598 to replace with LeetCode link soon... 2.2m, Stack stack simulation; output last stack size 0 2.0
lc0020 to replace with LeetCode link soon... 2.2n, Stack-based Problems bracket matching; stack; top-100-liked; top-interview-150 0 2.0
lc0032 to replace with LeetCode link soon... 2.2n, Stack-based Problems advanced bracket matching variant; top-100-liked 0 6.0
lc0084 to replace with LeetCode link soon... 2.2n, Stack-based Problems difficult O(n) solution with monotonic increasing stack; top-100-liked 0 6.0
lc0150 to replace with LeetCode link soon... 2.2n, Stack-based Problems classic postfix calculator; top-interview-150 0 4.0
lc0155 to replace with LeetCode link soon... 2.2n, Stack-based Problems monotonic non-increasing stack; top-100-liked; top-interview-150 0 4.0
lc0224 to replace with LeetCode link soon... 2.2n, Stack-based Problems infix-to-postfix and postfix calculator; top-interview-150 0 6.0
lc0739 to replace with LeetCode link soon... 2.2n, Stack-based Problems process right-to-left; monotonic non-increasing stack (temp, day); leetcode-75; top-100-liked 0 4.0
lc0901 to replace with LeetCode link soon... 2.2n, Stack-based Problems process left-to-right (each day); monotonic non-increasing stack (price, days_increasing); leetcode-75 0 4.0
lc0946 to replace with LeetCode link soon... 2.2n, Stack-based Problems need understanding of stack LIFO behavior 0 4.0
lc1021 to replace with LeetCode link soon... 2.2n, Stack-based Problems keep counter of open bracket; skip when counter is zero (the outermost layer) 0 2.0
lc1047 to replace with LeetCode link soon... 2.2n, Stack-based Problems bracket matching variant 0 2.0
lc1381 to replace with LeetCode link soon... 2.2n, Stack-based Problems need to edit the underlying array (bottom k) of the stack 0 4.0
lc2390 to replace with LeetCode link soon... 2.2n, Stack-based Problems bracket matching variant; leetcode-75 0 4.0
lc3174 to replace with LeetCode link soon... 2.2n, Stack-based Problems bracket matching variant; match a digit with closest non-digit; LIFO; stack 0 2.0
lc0232 to replace with LeetCode link soon... 2.2o, List/Queue/Deque the interesting implementation of queue with two stacks: in-stack and out-stack 0 2.0
lc0362 to replace with LeetCode link soon... 2.2o, List/Queue/Deque PREMIUM - hint hidden 0 4.0
lc0622 to replace with LeetCode link soon... 2.2o, List/Queue/Deque the interesting implementation of circular queue 0 4.0
lc0649 to replace with LeetCode link soon... 2.2o, List/Queue/Deque queue simulation; reading comprehension; leetcode-75 0 4.0
lc0933 to replace with LeetCode link soon... 2.2o, List/Queue/Deque queue simulation; leetcode-75 0 2.0
lc0011 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers two pointers, l=0, r=n-1; we can always move the shorter pointer inside; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0026 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers we can use two pointers to maintain a growing window of unique elements; top-interview-150 0 2.0
lc0080 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers just a small update compared to LC 0026; top-interview-150 0 4.0
lc0167 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers two pointers: leftmost and rightmost; top-interview-150 0 4.0
lc0283 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers two pointers: leftmost zero and cur; programming-skills; leetcode-75; top-100-liked 0 2.0
lc0392 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers variant of merge of Merge sort; leetcode-75; top-interview-150 0 2.0
lc1023 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers for each query; do two pointers between query and pattern strings 0 4.0
lc1437 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers two pointers: prev_1 and cur 0 2.0
lc1768 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers variant of merge of Merge sort; programming-skills; leetcode-75 0 2.0
lc2090 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers 2 pointers: l and r (2*k indices away); slide both pointers together 0 4.0
lc2562 to replace with LeetCode link soon... 2.2p, 1D Array, Two Pointers two pointers: left and right; move inwards 0 2.0
lc0003 to replace with LeetCode link soon... 2.2q, Sliding Window increase char freq when extending; reduce window size if duplicate is seen; top-100-liked; top-interview-150 0 4.0
lc0076 to replace with LeetCode link soon... 2.2q, Sliding Window maintain character frequencies as we slide the window; top-100-liked; top-interview-150 0 6.0
lc0209 to replace with LeetCode link soon... 2.2q, Sliding Window add each Integer into window; reduce window if its sum exceeds target; keep the smallest window size; top-interview-150 0 4.0
lc0239 to replace with LeetCode link soon... 2.2q, Sliding Window similar to Kattis - sound; sliding window; deque; top-100-liked 0 6.0
lc0346 to replace with LeetCode link soon... 2.2q, Sliding Window PREMIUM - hint hidden 0 2.0
lc0438 to replace with LeetCode link soon... 2.2q, Sliding Window maintain character frequencies as we slide the window; top-100-liked 0 4.0
lc0643 to replace with LeetCode link soon... 2.2q, Sliding Window slide the window of size k; keep the max; divide by k; leetcode-75 0 2.0
lc1004 to replace with LeetCode link soon... 2.2q, Sliding Window decide window adjustment if 1 vs 0; keep the largest window size; leetcode-75 0 4.0
lc1343 to replace with LeetCode link soon... 2.2q, Sliding Window slide the window of size k; check window's average against threshold 0 4.0
lc1456 to replace with LeetCode link soon... 2.2q, Sliding Window slide the window of size k; adjust number of vowel within the window as we slide; keep the max; leetcode-75 0 4.0
lc1493 to replace with LeetCode link soon... 2.2q, Sliding Window similar to LC 1004; leetcode-75 0 4.0
lc0002 to replace with LeetCode link soon... 2.2r, Linked List Exercises simple problem but in reverse SLL mode; programming-skills; top-100-liked; top-interview-150 0 4.0
lc0019 to replace with LeetCode link soon... 2.2r, Linked List Exercises recurse until tail; count n steps when backtrack; skip the node; top-100-liked; top-interview-150 0 4.0
lc0021 to replace with LeetCode link soon... 2.2r, Linked List Exercises merge of merge sort in linked list way; programming-skills; top-100-liked; top-interview-150 0 2.0
lc0024 to replace with LeetCode link soon... 2.2r, Linked List Exercises deal with special cases of 0 or 1 vertex; then use three pointers strategy; top-100-liked 0 4.0
lc0025 to replace with LeetCode link soon... 2.2r, Linked List Exercises easier if we use O(n) array as an intermediate data structure; top-100-liked; top-interview-150 0 6.0
lc0061 to replace with LeetCode link soon... 2.2r, Linked List Exercises make it circular for easier manipulation; top-interview-150 0 4.0
lc0082 to replace with LeetCode link soon... 2.2r, Linked List Exercises use three pointers; top-interview-150 0 4.0
lc0083 to replace with LeetCode link soon... 2.2r, Linked List Exercises two adjacent pointers strategy 0 2.0
lc0086 to replace with LeetCode link soon... 2.2r, Linked List Exercises split the list into lt and geq; at the end, restitch and return; top-interview-150 0 4.0
lc0092 to replace with LeetCode link soon... 2.2r, Linked List Exercises recurse and unwind; just do; top-interview-150 0 4.0
lc0138 to replace with LeetCode link soon... 2.2r, Linked List Exercises not the intended solution: use Python copy.deepcopy; top-100-liked; top-interview-150 0 4.0
lc0148 to replace with LeetCode link soon... 2.2r, Linked List Exercises not the intended solution: convert SLL to array; sort the array; re-create sorted SLL; top-100-liked; top-interview-150 0 4.0
lc0160 to replace with LeetCode link soon... 2.2r, Linked List Exercises compute length n and m of list A and B; advance the shorter one, if needed; then compare the rest; top-100-liked 0 2.0
lc0203 to replace with LeetCode link soon... 2.2r, Linked List Exercises one pass; skip over nodes to be removed 0 2.0
lc0206 to replace with LeetCode link soon... 2.2r, Linked List Exercises classic SLL reversal task; programming-skills; leetcode-75; top-100-liked 0 2.0
lc0234 to replace with LeetCode link soon... 2.2r, Linked List Exercises use recursion; as it unwinds, compare the values of leftmost and rightmost pointers; top-100-liked 0 2.0
lc0328 to replace with LeetCode link soon... 2.2r, Linked List Exercises two pointers: even/odd; stitch the tail of odd pointer with the head of even pointer; leetcode-75 0 4.0
lc0445 to replace with LeetCode link soon... 2.2r, Linked List Exercises like LC0002; but need to use two stacks; programming-skills 0 4.0
lc0876 to replace with LeetCode link soon... 2.2r, Linked List Exercises two pointers; normal vs twice faster 0 2.0
lc1290 to replace with LeetCode link soon... 2.2r, Linked List Exercises traverse the SLL and convert the bits 0 2.0
lc1721 to replace with LeetCode link soon... 2.2r, Linked List Exercises two pointers: head and tail; move inwards k-1 times; swap 0 4.0
lc2058 to replace with LeetCode link soon... 2.2r, Linked List Exercises three pointers: pre, cur, nxt 0 4.0
lc2095 to replace with LeetCode link soon... 2.2r, Linked List Exercises first pass to count n; second pass to go to the middle vertex and to skip it; leetcode-75 0 4.0
lc2130 to replace with LeetCode link soon... 2.2r, Linked List Exercises use recursion; as it unwinds, sum the values of leftmost and rightmost pointers; leetcode-75 0 4.0
lc2807 to replace with LeetCode link soon... 2.2r, Linked List Exercises two adjacent pointers; gcd 0 4.0
lc0023 to replace with LeetCode link soon... 2.3a, Priority Queue extract next min (+ list i); enqueue next min from list i; construct output; top-100-liked; top-interview-150 0 6.0
lc0215 to replace with LeetCode link soon... 2.3a, Priority Queue use Python heapq nlargest library; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0264 to replace with LeetCode link soon... 2.3a, Priority Queue min PQ simulation; if x is the current smallest; add 2x, 3x, and 5x into min PQ, if they are not seen before 0 4.0
lc0373 to replace with LeetCode link soon... 2.3a, Priority Queue repeat k times: enqueue next from nums1 and next from nums2; avoid duplicate with set 0 4.0
lc1046 to replace with LeetCode link soon... 2.3a, Priority Queue simple max PQ simulation 0 2.0
lc1845 to replace with LeetCode link soon... 2.3a, Priority Queue min PQ simulation; initially put 1 to n 0 4.0
lc1962 to replace with LeetCode link soon... 2.3a, Priority Queue max PQ simulation 0 4.0
lc2335 to replace with LeetCode link soon... 2.3a, Priority Queue max PQ simulation 0 2.0
lc2336 to replace with LeetCode link soon... 2.3a, Priority Queue min PQ simulation; up to 1000 calls involving [1..1000]; avoid duplicates; leetcode-75 0 4.0
lc2462 to replace with LeetCode link soon... 2.3a, Priority Queue min PQ simulation; two pointers: i=0 and j=n-1; move inwards; leetcode-75 0 4.0
lc2530 to replace with LeetCode link soon... 2.3a, Priority Queue max PQ simulation 0 4.0
lc2558 to replace with LeetCode link soon... 2.3a, Priority Queue max PQ simulation 0 2.0
lc3066 to replace with LeetCode link soon... 2.3a, Priority Queue min PQ simulation 0 4.0
lc0383 to replace with LeetCode link soon... 2.3b, DAT, ASCII two DATs ('a'..'z'); check for all 'a'..'z'; top-interview-150 0 2.0
lc0387 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter 0 2.0
lc0389 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); programming-skills 0 2.0
lc0748 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter 0 2.0
lc0771 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('A'..'Z' and 'a'..'z'); simple check 0 2.0
lc1160 to replace with LeetCode link soon... 2.3b, DAT, ASCII use two DATs ('a'..'z'); compare 0 2.0
lc1189 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); per `balloon', we need 1 'ban' and 2 'lo' 0 2.0
lc1624 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); simple check 0 2.0
lc1629 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); simple check 0 2.0
lc1832 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); check if all freq are non-zero 0 2.0
lc1897 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter 0 2.0
lc1935 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); Boolean (broken or not) 0 2.0
lc1941 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter 0 2.0
lc2068 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter; simple check 0 2.0
lc2186 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter; add absolute differences 0 4.0
lc2278 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); simple 0 2.0
lc2287 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter; check 0 2.0
lc2351 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); find the first with freq 2 0 2.0
lc2399 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); remember first occurrence 0 2.0
lc2405 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); has this char been seen? 0 4.0
lc3039 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); counter; find max f; check with new counter 0 4.0
lc3121 to replace with LeetCode link soon... 2.3b, DAT, ASCII two DATs ('a'..'z'); last_lower and first_upper; check 0 4.0
lc3146 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ('a'..'z'); map character to index 0 2.0
lc3442 to replace with LeetCode link soon... 2.3b, DAT, ASCII DAT ['a'..'z']; split even/odd; sort 0 2.0
lc0379 to replace with LeetCode link soon... 2.3c, DAT, Others PREMIUM - hint hidden 0 4.0
lc0645 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..10000]; find key with freq 2 (repeated) and 0 (missing) 0 2.0
lc0788 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..9]; map digit to its rotation or NIL; 0 4.0
lc0869 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..9]; compare digit frequency of n with all powers of 2 up to 2^30 0 4.0
lc0961 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..10000]; find key with freq n 0 2.0
lc1357 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..200] for price of each product; remember customer count; simulate 0 4.0
lc1748 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..100]; counter; sum i if frequency of i is 1 0 2.0
lc1854 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1950..2050]; counter; find earliest year with max freq 0 2.0
lc1893 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..50] Booleans; 0 2.0
lc2190 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..1000]; do as asked 0 2.0
lc2206 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..500]; counter; check even frequencies 0 2.0
lc2283 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..9]; counter; do as asked 0 2.0
lc2341 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..100]; trivial after frequencies of each integers are known 0 2.0
lc2357 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..100]; counter; count number of distinct positive numbers 0 2.0
lc2409 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..365]; mark Alice and Bob days in Rome; count freq 2 0 2.0
lc2491 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..1000]; sort the skills; use DAT to help 0 4.0
lc2570 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..1000]; sum the values 0 2.0
lc2682 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..50]; counter; identify freq 0s 0 2.0
lc2729 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..9]; counter; do as asked 0 2.0
lc2784 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..200]; check as asked 0 2.0
lc2965 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..2500]; counter; check as required 0 2.0
lc3005 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..100]; counter; do as asked 0 2.0
lc3046 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..100]; frequency difference at most two 0 2.0
lc3158 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [1..50]; xor those with freq = 2 0 2.0
lc3238 to replace with LeetCode link soon... 2.3c, DAT, Others 2D DAT n x [0..10]; counter 0 2.0
lc3289 to replace with LeetCode link soon... 2.3c, DAT, Others DAT [0..100]; find two keys with freq = 2 0 2.0
lc0349 to replace with LeetCode link soon... 2.3d, Hash Table (set), E set (no duplicate) intersection 0 2.0
lc0500 to replace with LeetCode link soon... 2.3d, Hash Table (set), E simulate; use 3 sets of chars (one per row) to speed-up 0 2.0
lc0575 to replace with LeetCode link soon... 2.3d, Hash Table (set), E min of n/2 vs number of different candy types 0 2.0
lc0929 to replace with LeetCode link soon... 2.3d, Hash Table (set), E string processing; put to set; set size 0 2.0
lc2215 to replace with LeetCode link soon... 2.3d, Hash Table (set), E use set for fast tests; leetcode-75 0 2.0
lc2441 to replace with LeetCode link soon... 2.3d, Hash Table (set), E turn nums into a set; then do a complete search test 0 2.0
lc2442 to replace with LeetCode link soon... 2.3d, Hash Table (set), E simulate; add to set; report set size 0 4.0
lc3295 to replace with LeetCode link soon... 2.3d, Hash Table (set), E convert bannedWords list to set for faster lookup; then just check all string in message 0 4.0
lc0128 to replace with LeetCode link soon... 2.3e, Hash Table (set), H create set of nums; keep checking if val+1 also exists in num; avoid recomputation; top-100-liked; top-interview-150 0 4.0
lc0205 to replace with LeetCode link soon... 2.3f, Hash Table (map), E mapper and reverse mapper from char to another char; top-interview-150 0 2.0
lc0290 to replace with LeetCode link soon... 2.3f, Hash Table (map), E mapper and reverse mapper from char to string; top-interview-150 0 2.0
lc0359 to replace with LeetCode link soon... 2.3f, Hash Table (map), E PREMIUM - hint hidden 0 2.0
lc0535 to replace with LeetCode link soon... 2.3f, Hash Table (map), E simple mapper from longUrl to shortUrl and back 0 4.0
lc0594 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter; then it is simple 0 2.0
lc0884 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter for all tokens in s1 and s2; do as asked 0 2.0
lc1207 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter and set (to test for uniqueness); leetcode-75 0 2.0
lc1287 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter and test 0 2.0
lc1346 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter and check; special case with 0 as its double is also 0 (its frequency must be at least 2) 0 2.0
lc1394 to replace with LeetCode link soon... 2.3f, Hash Table (map), E use Counter; find key == value 0 2.0
lc1679 to replace with LeetCode link soon... 2.3f, Hash Table (map), E frequency Counter; pairings; leetcode-75 0 4.0
lc0137 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) not intended solution: use Counter 0 4.0
lc0170 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) PREMIUM - hint hidden 0 2.0
lc0347 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) use Counter to count frequency; sort by frequencies; top k; top-100-liked 0 4.0
lc0448 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) Counter; find freq 0s 0 2.0
lc0540 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) non-intended Counter solution; O(n) time and O(n) space 0 4.0
lc0697 to replace with LeetCode link soon... 2.3g, Hash Table (Counter) Counter; max; find candidates; compare rightmost-leftmost indices of each candidate 0 2.0
lc0139 to replace with LeetCode link soon... 2.3h, Hash Table (map), H s: (i); t: try each word in dictionary; top-100-liked; top-interview-150 0 4.0
lc0146 to replace with LeetCode link soon... 2.3h, Hash Table (map), H combination of two hashtables (mapper; last_used) and queue of events; top-100-liked; top-interview-150 0 4.0
lc0677 to replace with LeetCode link soon... 2.3h, Hash Table (map), H hash all the prefixes of key; becareful with the overwrite requirement 0 4.0
lc0819 to replace with LeetCode link soon... 2.3h, Hash Table (map), H clean up the paragraph; frequency counter of strings; report the most common 0 2.0
lc0981 to replace with LeetCode link soon... 2.3h, Hash Table (map), H hash string to sorted list of (timestamps, values); binary search 0 4.0
lc1002 to replace with LeetCode link soon... 2.3h, Hash Table (map), H Python Counter intersection (to handle duplicates) 0 2.0
lc0056 to replace with LeetCode link soon... 2.3i, Balanced BST (set) maintain set of intervals using bBST (set); do quick merging of intervals; top-100-liked; top-interview-150 0 4.0
lc0057 to replace with LeetCode link soon... 2.3i, Balanced BST (set) very similar to LC 0056; top-interview-150 0 4.0
lc0295 to replace with LeetCode link soon... 2.3k, Order Statistics Tree dynamic median selection; pb_ds; similar to Kattis - continousmedian; top-100-liked; top-interview-150 0 6.0
lc0094 to replace with LeetCode link soon... 2.3l, BT Exercises, E simulate inorder traversal; top-100-liked 0 2.0
lc0100 to replace with LeetCode link soon... 2.3l, BT Exercises, E recursive check; top-interview-150 0 2.0
lc0101 to replace with LeetCode link soon... 2.3l, BT Exercises, E two pointers; check if the mirror traversal are identical; top-100-liked; top-interview-150 0 2.0
lc0104 to replace with LeetCode link soon... 2.3l, BT Exercises, E recursive height check; leetcode-75; top-100-liked; top-interview-150 0 2.0
lc0110 to replace with LeetCode link soon... 2.3l, BT Exercises, E for each vertex, check its height of left and right subtrees and compare 0 2.0
lc0112 to replace with LeetCode link soon... 2.3l, BT Exercises, E recursive preorder check; top-interview-150 0 2.0
lc0114 to replace with LeetCode link soon... 2.3l, BT Exercises, E preorder traversal; reconstruct answer as requested; top-100-liked; top-interview-150 0 4.0
lc0129 to replace with LeetCode link soon... 2.3l, BT Exercises, E preorder; process leaves; top-interview-150 0 4.0
lc0144 to replace with LeetCode link soon... 2.3l, BT Exercises, E simulate preorder traversal 0 2.0
lc0145 to replace with LeetCode link soon... 2.3l, BT Exercises, E simulate postorder traversal 0 2.0
lc0173 to replace with LeetCode link soon... 2.3l, BT Exercises, E do inorder traversal; convert into array; keep current next index of array 0 4.0
lc0222 to replace with LeetCode link soon... 2.3l, BT Exercises, E go to the rightmost vertex; if it has a left child, go left once; top-interview-150 0 2.0
lc0226 to replace with LeetCode link soon... 2.3l, BT Exercises, E swap left and right pointers, recursively; top-100-liked; top-interview-150 0 2.0
lc0235 to replace with LeetCode link soon... 2.3l, BT Exercises, E can be solved with LC 0236 solution too 0 4.0
lc0236 to replace with LeetCode link soon... 2.3l, BT Exercises, E find the first vertex using postorder where both p and q are seen; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0257 to replace with LeetCode link soon... 2.3l, BT Exercises, E preorder traversal; remember the paths 0 2.0
lc0298 to replace with LeetCode link soon... 2.3l, BT Exercises, E PREMIUM - hint hidden 0 4.0
lc0366 to replace with LeetCode link soon... 2.3l, BT Exercises, E PREMIUM - hint hidden 0 4.0
lc0437 to replace with LeetCode link soon... 2.3l, BT Exercises, E for each vertex, run preorder traversal; check if the path sum equals to target; leetcode-75; top-100-liked 0 4.0
lc0543 to replace with LeetCode link soon... 2.3l, BT Exercises, E n is small enough; take the maximum sum of height of left+right subtrees, for all subtrees; top-100-liked 0 2.0
lc0559 to replace with LeetCode link soon... 2.3l, BT Exercises, E compute the height of n-ary tree 0 2.0
lc0563 to replace with LeetCode link soon... 2.3l, BT Exercises, E modify postorder traversal a bit to compute the tilt 0 2.0
lc0572 to replace with LeetCode link soon... 2.3l, BT Exercises, E n is small enough; for each subtree of root, we can test if it is an identical tree with subroot 0 2.0
lc0589 to replace with LeetCode link soon... 2.3l, BT Exercises, E extension of LC 0144; on n-ary tree 0 2.0
lc0590 to replace with LeetCode link soon... 2.3l, BT Exercises, E extension of LC 0145; on n-ary tree 0 2.0
lc0654 to replace with LeetCode link soon... 2.3l, BT Exercises, E find the location of the max; recursively build the binary tree 0 4.0
lc0671 to replace with LeetCode link soon... 2.3l, BT Exercises, E preorder; just do as asked 0 2.0
lc0814 to replace with LeetCode link soon... 2.3l, BT Exercises, E do postorder traversal; if the subtree has all zeroes; remove it 0 4.0
lc0872 to replace with LeetCode link soon... 2.3l, BT Exercises, E run inorder traversals on both trees; picking only the leaves; compare them; leetcode-75 0 2.0
lc0965 to replace with LeetCode link soon... 2.3l, BT Exercises, E recursive check if all values in the tree is the same 0 2.0
lc0988 to replace with LeetCode link soon... 2.3l, BT Exercises, E preorder; keep path; reverse 0 4.0
lc0993 to replace with LeetCode link soon... 2.3l, BT Exercises, E customize binary tree traversal to also compute depth 0 2.0
lc1372 to replace with LeetCode link soon... 2.3l, BT Exercises, E modified preorder traversal; reset counter if same direction; add counter if zig-zag-ing; leetcode-75 0 4.0
lc1379 to replace with LeetCode link soon... 2.3l, BT Exercises, E run inorder traversal on both trees simultaneously 0 2.0
lc1448 to replace with LeetCode link soon... 2.3l, BT Exercises, E modified preorder traversal; keep the largest along the way; leetcode-75 0 4.0
lc2236 to replace with LeetCode link soon... 2.3l, BT Exercises, E trivial check 0 2.0
lc2265 to replace with LeetCode link soon... 2.3l, BT Exercises, E n is small enough; for each subtree of root, compute sum of values and number of vertices in that subtree 0 4.0
lc2331 to replace with LeetCode link soon... 2.3l, BT Exercises, E postorder custom traversal on Boolean binary tree 0 2.0
lc0098 to replace with LeetCode link soon... 2.3m, BST Exercises recursive BST property validator; top-100-liked; top-interview-150 0 4.0
lc0108 to replace with LeetCode link soon... 2.3m, BST Exercises recursively insert the median of the sorted array; top-100-liked; top-interview-150 0 2.0
lc0230 to replace with LeetCode link soon... 2.3m, BST Exercises inorder traversal; report the k-th element; top-100-liked; top-interview-150 0 4.0
lc0255 to replace with LeetCode link soon... 2.3m, BST Exercises PREMIUM - hint hidden 0 4.0
lc0285 to replace with LeetCode link soon... 2.3m, BST Exercises PREMIUM - hint hidden 0 4.0
lc0333 to replace with LeetCode link soon... 2.3m, BST Exercises PREMIUM - hint hidden 0 4.0
lc0426 to replace with LeetCode link soon... 2.3m, BST Exercises PREMIUM - hint hidden 0 4.0
lc0450 to replace with LeetCode link soon... 2.3m, BST Exercises code BST deletion sub-cases; leetcode-75 0 4.0
lc0501 to replace with LeetCode link soon... 2.3m, BST Exercises run inorder traversal; use Counter; output the mode(s) 0 2.0
lc0530 to replace with LeetCode link soon... 2.3m, BST Exercises the min gap is between successive elements during inorder traversal; same as LC 0783; top-interview-150 0 2.0
lc0700 to replace with LeetCode link soon... 2.3m, BST Exercises the classic BST search process; leetcode-75 0 2.0
lc0783 to replace with LeetCode link soon... 2.3m, BST Exercises the minimum gap is between successive elements found during inorder traversal; same as LC 0530 0 2.0
lc0897 to replace with LeetCode link soon... 2.3m, BST Exercises create new skewed BST using inorder traversal of original BST 0 2.0
lc0938 to replace with LeetCode link soon... 2.3m, BST Exercises customize inorder traversal of BST 0 2.0
lc1038 to replace with LeetCode link soon... 2.3m, BST Exercises run reverse Inorder traversal; cumulative sum 0 4.0
lc0175 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0176 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0177 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0178 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0180 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0181 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0182 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0183 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0184 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0196 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0197 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0511 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0512 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0534 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0550 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0570 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0574 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0577 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0578 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0580 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0584 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0586 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0595 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0596 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0597 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0603 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0607 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0608 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0610 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0613 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0614 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc0619 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0620 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0627 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1045 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1050 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1068 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1069 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1070 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1075 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1076 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1077 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1082 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1083 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1084 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1107 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1112 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1113 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1126 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1132 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1141 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1142 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1148 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1149 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1173 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1174 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1179 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1193 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1204 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1211 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1241 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1251 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1270 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1280 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1294 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1303 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1308 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1322 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1327 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1341 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1350 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1378 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1393 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1407 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1421 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1435 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1445 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1468 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1484 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1495 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1511 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1517 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1527 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1543 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1555 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1565 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1571 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1581 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1587 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1607 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1623 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1633 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1661 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1667 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1677 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1683 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1693 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1699 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1729 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1731 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1741 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1757 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1777 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1783 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1789 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1795 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1809 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1821 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1831 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1853 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1873 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1890 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1934 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc1939 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1965 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc1978 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2026 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2066 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc2072 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2082 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2205 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2230 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2298 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc2329 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2339 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2356 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2372 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc2377 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2480 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2504 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2668 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2669 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2687 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2837 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2853 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2985 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2987 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc2988 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc2989 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc2990 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3051 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3053 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3054 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc3055 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc3059 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3150 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3172 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3198 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3204 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 4.0
lc3246 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3358 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3415 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3436 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3465 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3570 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc3642 to replace with LeetCode link soon... 2.3z, SQL SQL - hint hidden 0 2.0
lc0133 to replace with LeetCode link soon... 2.4a, Graph Data Structures clone AL; use hashtable to ensure we only create each node once; top-interview-150 0 4.0
lc1615 to replace with LeetCode link soon... 2.4a, Graph Data Structures network rank of (u, v) = degree[u] + degree[v] - has_edge(u, v); try all pairs 0 4.0
lc0253 to replace with LeetCode link soon... 2.4c, Tree-related DS PREMIUM - hint hidden 0 4.0
lc0052 to replace with LeetCode link soon... 3.2a, Pre-calculate-able pre-calculate answers for n = 1 to 9; top-interview-150 0 6.0
lc2698 to replace with LeetCode link soon... 3.2a, Pre-calculate-able the list of punishment numbers under 1000 is small 0 4.0
lc0496 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E O(nm) is possible 0 2.0
lc0796 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all possible shifts; 2 nested loops 0 2.0
lc1288 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 4.0
lc1385 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc1475 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc1512 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc1909 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E O(n^2) solution is possible 0 2.0
lc2006 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc2023 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 4.0
lc2221 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E just do as asked; 2 nested loops; like bottom-up Pascal's triangle construction 0 4.0
lc2451 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E get O(n) difference array for each string; try each one, find one that is different 0 2.0
lc2643 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E for each row; sum the row; keep running max 0 2.0
lc2744 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc2815 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc2824 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc2903 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc2932 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs, 2 nested loops 0 2.0
lc2947 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E O(n^2) solution is possible 0 4.0
lc2960 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E simulation; 2 nested loops 0 2.0
lc3033 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E do O(mn) pass to get the max of each column first; then do another O(mn) pass to fill in the matrix 0 2.0
lc3034 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E O(nm) solution is possible 0 4.0
lc3083 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all substrings of length 2; check if it is in the reverse of s 0 2.0
lc3162 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs; 2 nested loops 0 2.0
lc3184 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E 2 nested loops 0 2.0
lc3264 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E O(kn) operations; just do as asked 0 2.0
lc3304 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E just simulate the process; small constraints 0 2.0
lc3477 to replace with LeetCode link soon... 3.2b, Iterative (Two Loops), E try all pairs 0 2.0
lc0477 to replace with LeetCode link soon... 3.2c, Iterative (Two Loops), H do not do O(n^2); do O(31 * n) 0 4.0
lc1769 to replace with LeetCode link soon... 3.2c, Iterative (Two Loops), H 2 nested loops; only swap indices with '1' 0 4.0
lc0599 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; plus another short loop to compare two strings 0 2.0
lc0670 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all possible digit swaps; plus another O(n) loop 0 4.0
lc1409 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E just do as asked 0 4.0
lc1534 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc1588 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc1790 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc1995 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 4 nested loops 0 2.0
lc2062 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all substrings; plus another O(n) checks 0 2.0
lc2452 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 4.0
lc2475 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc2760 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops solution is still acceptable 0 2.0
lc2873 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc2908 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E 3 nested loops 0 2.0
lc2913 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; additional O(n) distinct count checks 0 2.0
lc2928 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; DAT [0..100] 0 2.0
lc3090 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; additional O(n) frequency checks 0 2.0
lc3258 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; additional O(n) 0/1 frequency checks 0 2.0
lc3364 to replace with LeetCode link soon... 3.2d, Three+ Nested Loops, E try all pairs; additional O(n) to sum subarray 0 2.0
lc2352 to replace with LeetCode link soon... 3.2e, Three+ Nested Loops, H 3 nested loops solution is still acceptable; leetcode-75 0 4.0
lc2428 to replace with LeetCode link soon... 3.2e, Three+ Nested Loops, H 3 nested loops; be careful with 2D matrix indexing 0 4.0
lc0031 to replace with LeetCode link soon... 3.2f, Iterative (Permutation) C++ next_permutation; top-100-liked 0 4.0
lc0046 to replace with LeetCode link soon... 3.2f, Iterative (Permutation) C++ next_permutation from sorted to reverse-sorted permutations; top-100-liked; top-interview-150 0 4.0
lc0047 to replace with LeetCode link soon... 3.2f, Iterative (Permutation) standard C++ next_permutation 0 4.0
lc1947 to replace with LeetCode link soon... 3.2f, Iterative (Permutation) try all permutations 0 4.0
lc3309 to replace with LeetCode link soon... 3.2f, Iterative (Permutation) try all permutations 0 4.0
lc0077 to replace with LeetCode link soon... 3.2g, Iterative (Combination) standard nCk; use itertools.combinations; top-interview-150 0 4.0
lc0078 to replace with LeetCode link soon... 3.2g, Iterative (Combination) use Python itertools.combinations; top-100-liked 0 4.0
lc0401 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all possible bitmasks; 4 bits for H, 6 bits for M 0 2.0
lc0784 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all possible bitmasks; each letter can be in UPPER or lower cases 0 4.0
lc1079 to replace with LeetCode link soon... 3.2g, Iterative (Combination) combo of iterative bitmask and next_permutation 0 4.0
lc1286 to replace with LeetCode link soon... 3.2g, Iterative (Combination) generate all possible combinations upfront; advance iterator as asked 0 4.0
lc1863 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all possible subsets 0 2.0
lc1980 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all subsets 0 4.0
lc2094 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all 3 digits combination and their permutations 0 2.0
lc2597 to replace with LeetCode link soon... 3.2g, Iterative (Combination) try all possible subsets of nums; then do O(n^2) checks 0 4.0
lc3483 to replace with LeetCode link soon... 3.2g, Iterative (Combination) similar to LC 2094 0 2.0
lc2843 to replace with LeetCode link soon... 3.2h, Try All Answers create helper function is_symmetric; try all numbers between low..high 0 2.0
lc1317 to replace with LeetCode link soon... 3.2i, Math Simulation, E just do as asked 0 2.0
lc1518 to replace with LeetCode link soon... 3.2i, Math Simulation, E interesting simulation problem; similar to UVa 10346 0 2.0
lc1539 to replace with LeetCode link soon... 3.2i, Math Simulation, E try all possible answer between [1..2000] 0 2.0
lc1646 to replace with LeetCode link soon... 3.2i, Math Simulation, E generate the array as asked 0 2.0
lc1823 to replace with LeetCode link soon... 3.2i, Math Simulation, E use Josephus formula 0 4.0
lc2176 to replace with LeetCode link soon... 3.2i, Math Simulation, E try all (i, j) pairs and test 0 2.0
lc2269 to replace with LeetCode link soon... 3.2i, Math Simulation, E simple math simulation 0 2.0
lc2427 to replace with LeetCode link soon... 3.2i, Math Simulation, E try all x; a and b are small 0 2.0
lc2443 to replace with LeetCode link soon... 3.2i, Math Simulation, E simple math simulation 0 4.0
lc2520 to replace with LeetCode link soon... 3.2i, Math Simulation, E simple math simulation 0 2.0
lc2553 to replace with LeetCode link soon... 3.2i, Math Simulation, E simulate; there are at most 6 digits per integer 0 2.0
lc2566 to replace with LeetCode link soon... 3.2i, Math Simulation, E try all possible digit remapppings 0 2.0
lc2644 to replace with LeetCode link soon... 3.2i, Math Simulation, E simple math simulation 0 2.0
lc3100 to replace with LeetCode link soon... 3.2i, Math Simulation, E interesting simulation problem; similar to UVa 10346 0 4.0
lc3200 to replace with LeetCode link soon... 3.2i, Math Simulation, E simulate the max if we start with red first versus blue first 0 2.0
lc3345 to replace with LeetCode link soon... 3.2i, Math Simulation, E simulate; t is only up to 10 0 2.0
lc0970 to replace with LeetCode link soon... 3.2j, Math Simulation, M the values of x^i or y^j will grow fast; search space is small 0 4.0
lc1535 to replace with LeetCode link soon... 3.2j, Math Simulation, M simulate as asked; special case when k ≥ n 0 4.0
lc1860 to replace with LeetCode link soon... 3.2j, Math Simulation, M simulate the memory leak; at most 50K steps 0 4.0
lc3179 to replace with LeetCode link soon... 3.2j, Math Simulation, M O(kn); just simulate as asked 0 4.0
lc3487 to replace with LeetCode link soon... 3.2j, Math Simulation, M check values in range [1..100]; special case involving 0s or negatives 0 2.0
lc0017 to replace with LeetCode link soon... 3.2m, Backtracking, Easier classic backtracking; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0039 to replace with LeetCode link soon... 3.2m, Backtracking, Easier generate answers with backtracking; top-100-liked; top-interview-150 0 4.0
lc0051 to replace with LeetCode link soon... 3.2m, Backtracking, Easier classic n-queens; backtrack; similar to UVa 00750; top-100-liked 0 6.0
lc0386 to replace with LeetCode link soon... 3.2m, Backtracking, Easier generate the lexicographic order via recursive backtracking 0 4.0
lc0491 to replace with LeetCode link soon... 3.2m, Backtracking, Easier backtrack; output distinct answers 0 4.0
lc0797 to replace with LeetCode link soon... 3.2m, Backtracking, Easier backtrack to enumerate all paths on DAG 0 4.0
lc0967 to replace with LeetCode link soon... 3.2m, Backtracking, Easier backtrack; digit by digit 0 4.0
lc1291 to replace with LeetCode link soon... 3.2m, Backtracking, Easier backtrack; generate the required integers 0 4.0
lc3211 to replace with LeetCode link soon... 3.2m, Backtracking, Easier simple backtracking 0 4.0
lc0022 to replace with LeetCode link soon... 3.2n, Backtracking, Harder s: (cur_o, o_used); t: add an open or add a close (if cur_o > 0); top-100-liked; top-interview-150 0 4.0
lc0216 to replace with LeetCode link soon... 3.2n, Backtracking, Harder backtracking; bitmask; generate solutions; leetcode-75 0 4.0
lc1780 to replace with LeetCode link soon... 3.2n, Backtracking, Harder notice that 3^15 > 10^7; backtrack on this small search space 0 4.0
lc0033 to replace with LeetCode link soon... 3.3a, Binary Search custom binary search on a special sorted array; top-100-liked; top-interview-150 0 4.0
lc0034 to replace with LeetCode link soon... 3.3a, Binary Search lower_bound and upper_bound; top-100-liked; top-interview-150 0 4.0
lc0035 to replace with LeetCode link soon... 3.3a, Binary Search basic lower_bound; top-100-liked; top-interview-150 0 2.0
lc0074 to replace with LeetCode link soon... 3.3a, Binary Search binary search variant on a special 2D grid; top-100-liked; top-interview-150 0 4.0
lc0162 to replace with LeetCode link soon... 3.3a, Binary Search interesting binary-search modification; leetcode-75; top-interview-150 0 4.0
lc0243 to replace with LeetCode link soon... 3.3a, Binary Search PREMIUM - hint hidden 0 2.0
lc0244 to replace with LeetCode link soon... 3.3a, Binary Search PREMIUM - hint hidden 0 4.0
lc0374 to replace with LeetCode link soon... 3.3a, Binary Search classic binary search task; leetcode-75 0 2.0
lc0506 to replace with LeetCode link soon... 3.3a, Binary Search we can sort the scores and use binary searches per query; alternative solution exists 0 2.0
lc0704 to replace with LeetCode link soon... 3.3a, Binary Search as the problem name implies 0 2.0
lc0744 to replace with LeetCode link soon... 3.3a, Binary Search we can do bisect_right; alternative solution exists 0 2.0
lc0849 to replace with LeetCode link soon... 3.3a, Binary Search combination of linear search and binary search 0 4.0
lc0852 to replace with LeetCode link soon... 3.3a, Binary Search interesting binary search modification on a 'mountain' array 0 4.0
lc1331 to replace with LeetCode link soon... 3.3a, Binary Search sort; lower_bound per query 0 2.0
lc1365 to replace with LeetCode link soon... 3.3a, Binary Search sort; binary search per query 0 2.0
lc1887 to replace with LeetCode link soon... 3.3a, Binary Search sort distinct elements of nums; use binary searches 0 4.0
lc2389 to replace with LeetCode link soon... 3.3a, Binary Search sort; prefix sum; binary searches 0 2.0
lc0069 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + square check; top-interview-150 0 2.0
lc0274 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + simple check; top-interview-150 0 4.0
lc0275 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + check citations 0 4.0
lc0278 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + API isBadVersion check 0 2.0
lc0367 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + square check; similar to LC 0069 0 2.0
lc0441 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + sum of Arithmetic Progression 0 2.0
lc0875 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + simulation check; leetcode-75 0 4.0
lc1011 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + simulate load 0 4.0
lc2560 to replace with LeetCode link soon... 3.3b, Bisection and BSTA, E BSTA + simulate robbery 0 4.0
lc1901 to replace with LeetCode link soon... 3.3c, Ternary Search & Others extension of LC 0162 on 2D grid 0 4.0
lc2293 to replace with LeetCode link soon... 3.3c, Ternary Search & Others simulate the game; n halves each level 0 2.0
lc0455 to replace with LeetCode link soon... 3.4a, Greedy (Classical) sort; greedy bipartite matching 0 2.0
lc1024 to replace with LeetCode link soon... 3.4a, Greedy (Classical) similar to Kattis - grass 0 4.0
lc2037 to replace with LeetCode link soon... 3.4a, Greedy (Classical) sort; greedy bipartite matching 0 2.0
lc2224 to replace with LeetCode link soon... 3.4a, Greedy (Classical) Coin-Change variant; min 'coins' to make up the difference of minutes between current and correct; but [60, 15, 5, 1] ad... 0 2.0
lc2410 to replace with LeetCode link soon... 3.4a, Greedy (Classical) sort; greedy bipartite matching 0 4.0
lc2592 to replace with LeetCode link soon... 3.4a, Greedy (Classical) sort; greedy bipartite matching 0 4.0
lc3111 to replace with LeetCode link soon... 3.4a, Greedy (Classical) interval covering variant 0 4.0
lc0561 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort non-decreasing; take every even indices 0 2.0
lc0628 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort nums; then just 2 possible cases 0 2.0
lc1005 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort; negate the smallest negatives first; ignore any excess k > 1; for the last one, negate the smallest 0 2.0
lc1403 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort nums in non-increasing order; then a simple greedy strategy emerges 0 2.0
lc1481 to replace with LeetCode link soon... 3.4b, Involving Sorting, E count the frequencies of each Integer; sort the Integers from least to most frequent 0 4.0
lc1561 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort piles from max to min coins 0 4.0
lc1710 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-increasing numberOfUnitsPerBox 0 2.0
lc1833 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing costs 0 4.0
lc1877 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the nums first 0 4.0
lc1913 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort; use the last and first two 0 2.0
lc1936 to replace with LeetCode link soon... 3.4b, Involving Sorting, E rungs are already sorted; if needed, place new rung at the highest possible point after last used rung 0 4.0
lc2126 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing mass 0 4.0
lc2144 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the cost in non-increasing order 0 2.0
lc2160 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the 4 digits; report AC+BD 0 2.0
lc2279 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing gaps 0 4.0
lc2294 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing nums 0 4.0
lc2358 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing grades 0 4.0
lc2578 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the digits; a bit more general than LC 2160 0 2.0
lc2587 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-increasing nums 0 4.0
lc2706 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the prices 0 2.0
lc2966 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-decreasing nums 0 4.0
lc3074 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort the capacities in non-increasing order 0 2.0
lc3075 to replace with LeetCode link soon... 3.4b, Involving Sorting, E sort by non-increasing happiness 0 4.0
lc0435 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-decreasing endpoints; greedy; leetcode-75 0 4.0
lc0452 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-decreasing endpoints; greedy; leetcode-75; top-interview-150 0 4.0
lc0881 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort people by non-dec weights; two pointers: lightest+heaviest; greedy 0 4.0
lc1090 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-increasing values 0 4.0
lc1282 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-decreasing size, keep the original indices 0 4.0
lc2895 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort tasks by non-increasing order and processor time by non-decreasing order 0 4.0
lc3301 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-increasing maximum height 0 4.0
lc3572 to replace with LeetCode link soon... 3.4c, Involving Sorting, M sort by non-increasing (y, x) pairs 0 4.0
lc0055 to replace with LeetCode link soon... 3.4d, Involving Sorting, H for each reachable i, greedily extend the furthest jump, if we can; top-100-liked; top-interview-150 0 4.0
lc0502 to replace with LeetCode link soon... 3.4e, Involving PQ sort projects by non-decreasing capital; greedily take next project within our current capital with highest profit; use ... 0 6.0
lc1792 to replace with LeetCode link soon... 3.4e, Involving PQ add one brilliant student to the class with highest max ratio increase; use max PQ 0 4.0
lc2208 to replace with LeetCode link soon... 3.4e, Involving PQ greedily halve the largest; use max PQ 0 4.0
lc2542 to replace with LeetCode link soon... 3.4e, Involving PQ sort (nums2[i], nums1[i]) by non-increasing nums2; maintain min PQ of nums1; keep largest k; leetcode-75 0 4.0
lc0860 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier use 10+5 before 5+5+5; programming-skills 0 2.0
lc1221 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier count L and R from left to right; as soon as they are balanced, greedily increase answer counter by one 0 2.0
lc1323 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier replace the leftmost (most significant) 6 (if any), with 9 0 2.0
lc2078 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier two cases: leftmost with i or i with rightmost (different colors) 0 2.0
lc2829 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier greedy construction; use set to denote numbers to skip 0 4.0
lc3014 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier greedy; 8,8,8,2 keys to 1,2,3,4 keypresses, respectively 0 2.0
lc3402 to replace with LeetCode link soon... 3.4f, Non-Classical, Easier if needed; raise value of a grid as minimally as possible 0 2.0
lc0763 to replace with LeetCode link soon... 3.4g, Non-Classical, Harder DAT last occurence of ('a'..'z'); one-pass greedy solution is possible; top-100-liked 0 4.0
lc0053 to replace with LeetCode link soon... 3.5a, 1D Range Sum Kadane's; special case for all negatives; top-100-liked; top-interview-150 0 4.0
lc0121 to replace with LeetCode link soon... 3.5a, 1D Range Sum Kadane's algorithm on the difference of prices; top-100-liked; top-interview-150 0 2.0
lc0303 to replace with LeetCode link soon... 3.5a, 1D Range Sum very basic prefix sum problem 0 2.0
lc0560 to replace with LeetCode link soon... 3.5a, 1D Range Sum O(n^2) is still possible with prefix-sum range sum DP speedup; top-100-liked 0 4.0
lc1299 to replace with LeetCode link soon... 3.5a, 1D Range Sum process suffixes from the right 0 2.0
lc1310 to replace with LeetCode link soon... 3.5a, 1D Range Sum prefix XOR variant 0 4.0
lc1480 to replace with LeetCode link soon... 3.5a, 1D Range Sum very basic prefix sum problem 0 2.0
lc1508 to replace with LeetCode link soon... 3.5a, 1D Range Sum prefix sum; try all O(n^2) subarray sums; sort; get the answer 0 4.0
lc1749 to replace with LeetCode link soon... 3.5a, 1D Range Sum Kadane's twice: normal one and most negative one; pick the larger 0 4.0
lc1800 to replace with LeetCode link soon... 3.5a, 1D Range Sum Kadane's variant; reset when equal or descending 0 2.0
lc2606 to replace with LeetCode link soon... 3.5a, 1D Range Sum we can transform this problem into max 1D range sum; Kadane's 0 4.0
lc3105 to replace with LeetCode link soon... 3.5a, 1D Range Sum extension of LC 1800 0 2.0
lc3432 to replace with LeetCode link soon... 3.5a, 1D Range Sum once we have prefix sum; we can try all possible partitioning 0 2.0
lc3546 to replace with LeetCode link soon... 3.5a, 1D Range Sum this problem can be solved with prefix sum; transpose matrix to simplify col to row issue 0 4.0
lc0085 to replace with LeetCode link soon... 3.5b, 2D Range Sum after penalising the 0s heavily, this is just max 2D range sum 0 6.0
lc0221 to replace with LeetCode link soon... 3.5b, 2D Range Sum 2D Range Sum; complete search all (r, c) with length s; see if it is a square; top-interview-150 0 4.0
lc0300 to replace with LeetCode link soon... 3.5c, LIS classic LIS problem; top-100-liked; top-interview-150 0 4.0
lc0334 to replace with LeetCode link soon... 3.5c, LIS LIS problem with a very small tweak; leetcode-75 0 4.0
lc0646 to replace with LeetCode link soon... 3.5c, LIS LIS problem; this time comparing pairs 0 4.0
lc0673 to replace with LeetCode link soon... 3.5c, LIS counting version of LIS 0 4.0
lc0377 to replace with LeetCode link soon... 3.5d, 0-1 KNAPSACK/SS counting version of SUBSET-SUM 0 4.0
lc0416 to replace with LeetCode link soon... 3.5d, 0-1 KNAPSACK/SS classic Subset-Sum; top-100-liked 0 4.0
lc0474 to replace with LeetCode link soon... 3.5d, 0-1 KNAPSACK/SS Knapsack; skip or take a string 0 4.0
lc0322 to replace with LeetCode link soon... 3.5e, COIN-CHANGE COIN-CHANGE; top-100-liked; top-interview-150 0 4.0
lc0518 to replace with LeetCode link soon... 3.5e, COIN-CHANGE Coin-Change; the counting variant 0 4.0
lc0279 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (n); t: try all perfect numbers ≤ n; top-100-liked 0 4.0
lc0397 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (n); t: just do as asked; memoize 0 4.0
lc0746 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (i); t: to (i+1) or (i+2); Fibonacci variant; leetcode-75 0 2.0
lc2110 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E there is a DP solution and alternative solution 0 4.0
lc2310 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (num); t: try all values in [1..num] that ends with k 0 4.0
lc2900 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (i); t: try all possible next group; print solution 0 2.0
lc3147 to replace with LeetCode link soon... 3.5g, Non-Classical, 1D, E s: (i); t: jump k indices away 0 4.0
lc0122 to replace with LeetCode link soon... 3.5i, DP level 2 similar to LC 0174, but without transaction fee; top-interview-150 0 4.0
lc0309 to replace with LeetCode link soon... 3.5i, DP level 2 similar to LC 0174, but with one day cooldown after sell 0 4.0
lc0714 to replace with LeetCode link soon... 3.5i, DP level 2 s: (own, i); t: skip day i or sell if own/buy if not; leetcode-75 0 4.0
lc0200 to replace with LeetCode link soon... 4.2a, Finding CCs count number of CCs on a 2D grid; top-100-liked; top-interview-150 0 4.0
lc0261 to replace with LeetCode link soon... 4.2a, Finding CCs PREMIUM - hint hidden 0 4.0
lc0323 to replace with LeetCode link soon... 4.2a, Finding CCs PREMIUM - hint hidden 0 4.0
lc0547 to replace with LeetCode link soon... 4.2a, Finding CCs count number of CCs; leetcode-75 0 4.0
lc0695 to replace with LeetCode link soon... 4.2a, Finding CCs find CC with the maximum size on this grid 0 4.0
lc0733 to replace with LeetCode link soon... 4.2b, Flood Fill, Easier basic flood fill problem 0 2.0
lc0529 to replace with LeetCode link soon... 4.2c, Flood Fill, Harder Minesweeper simulation; harder floodfill variant 0 4.0
lc1254 to replace with LeetCode link soon... 4.2c, Flood Fill, Harder flood fill; avoiding borders 0 4.0
lc0210 to replace with LeetCode link soon... 4.2d, Topological Sort cycle check; compute toposort if acyclic; top-interview-150 0 4.0
lc0207 to replace with LeetCode link soon... 4.2e, Graph Properties Check is the directed graph acyclic?; top-100-liked; top-interview-150 0 4.0
lc0785 to replace with LeetCode link soon... 4.2e, Graph Properties Check check if the undirected graph is bipartite 0 4.0
lc0886 to replace with LeetCode link soon... 4.2e, Graph Properties Check standard bipartite checker 0 4.0
lc0339 to replace with LeetCode link soon... 4.2h, Really Ad Hoc PREMIUM - hint hidden 0 4.0
lc0364 to replace with LeetCode link soon... 4.2h, Really Ad Hoc PREMIUM - hint hidden 0 4.0
lc0399 to replace with LeetCode link soon... 4.2h, Really Ad Hoc creative directed weighted graph modeling; traversal from C to D; leetcode-75; top-interview-150 0 4.0
lc0684 to replace with LeetCode link soon... 4.2h, Really Ad Hoc try each edge from the last to the first; reachability tests 0 4.0
lc0841 to replace with LeetCode link soon... 4.2h, Really Ad Hoc DFS/BFS from 0; see if all rooms are visited; leetcode-75 0 4.0
lc1971 to replace with LeetCode link soon... 4.2h, Really Ad Hoc basic reachability test 0 2.0
lc3528 to replace with LeetCode link soon... 4.2h, Really Ad Hoc custom directed graph traversal 0 4.0
lc1584 to replace with LeetCode link soon... 4.3a, MST, Standard basic MST problem 0 4.0
lc0045 to replace with LeetCode link soon... 4.4a, SSSP, BFS, Easier this can be modeled as unweighted SSSP problem; BFS from 0 to n-1; top-100-liked; top-interview-150 0 4.0
lc0286 to replace with LeetCode link soon... 4.4a, SSSP, BFS, Easier PREMIUM - hint hidden 0 4.0
lc0417 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium multi-sources BFS on grid graph twice 0 4.0
lc0542 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium MSSP on grid; start from all zero cells; identical with LC 1765 0 4.0
lc0909 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium BFS; model the snakes/ladders correctly; top-interview-150 0 4.0
lc0994 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium multi-source BFS on grid; leetcode-75; top-100-liked 0 4.0
lc1091 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium SSSP from top-left to bottom-right of a 2D grid; BFS; 8 directions 0 4.0
lc1162 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium MSSP; grid; BFS; special cases with all zeros or all ones 0 4.0
lc1765 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium MSSP on grid; start from all water cells; identical with LC 0542 0 4.0
lc1926 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium BFS on grid; stop at border (that is not source); leetcode-75 0 4.0
lc3286 to replace with LeetCode link soon... 4.4b, SSSP, BFS, Medium 0/1-weighted SSSP on grid; BFS+deque 0 4.0
lc2596 to replace with LeetCode link soon... 4.4c, Knight Moves, BFS standard knight tour; BFS; 8 directions 0 4.0
lc0743 to replace with LeetCode link soon... 4.4h, SSSP, Bellman-Ford SSSP on a small directed weighted graph 0 4.0
lc1334 to replace with LeetCode link soon... 4.5a, APSP, Standard get APSP information using Floyd-Warshall; compute reachability; get the answer 0 4.0
lc0064 to replace with LeetCode link soon... 4.6a, S/Longest Paths on DAG basic SSSP on DAG; top-100-liked; top-interview-150 0 4.0
lc0120 to replace with LeetCode link soon... 4.6a, S/Longest Paths on DAG SSSP on DAG; top-interview-150 0 4.0
lc0329 to replace with LeetCode link soon... 4.6a, S/Longest Paths on DAG find LONGEST-PATH in an implicit DAG; DP 0 6.0
lc0931 to replace with LeetCode link soon... 4.6a, S/Longest Paths on DAG SSSP on implicit DAG; can only go down 0 4.0
lc2684 to replace with LeetCode link soon... 4.6a, S/Longest Paths on DAG find LONGEST-PATH in implicit DAG 0 4.0
lc0062 to replace with LeetCode link soon... 4.6b, Counting Paths, Easier counting paths; DAG; leetcode-75; top-100-liked 0 4.0
lc0063 to replace with LeetCode link soon... 4.6b, Counting Paths, Easier counting paths in DAG with some obstacles; top-interview-150 0 4.0
lc0091 to replace with LeetCode link soon... 4.6b, Counting Paths, Easier counting paths on implicit DAG; single digit that is not 0 or [10..19] or [20..26] 0 4.0
lc1641 to replace with LeetCode link soon... 4.6b, Counting Paths, Easier s: (i, last); counting paths on implicit DAG 0 4.0
lc0690 to replace with LeetCode link soon... 4.6d, Tree custom traversal of a tree from a given source 0 4.0
lc1466 to replace with LeetCode link soon... 4.6d, Tree create undirected tree; traverse from the root 0 to identify the answers; leetcode-75 0 4.0
lc2204 to replace with LeetCode link soon... 4.6d, Tree PREMIUM - hint hidden 0 6.0
lc0102 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; expand frontier; top-100-liked; top-interview-150 0 4.0
lc0103 to replace with LeetCode link soon... 4.6g, BT Exercises, H like LC0102, just zig-zag; top-interview-150 0 4.0
lc0105 to replace with LeetCode link soon... 4.6g, BT Exercises, H frontmost of preorder is the root; use it to split the inorder traversal; top-100-liked; top-interview-150 0 4.0
lc0106 to replace with LeetCode link soon... 4.6g, BT Exercises, H the back of postorder is the root; use it to split the inorder traversal; top-interview-150 0 4.0
lc0107 to replace with LeetCode link soon... 4.6g, BT Exercises, H like LC0102, just in reverse order 0 4.0
lc0111 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS until there is a leaf 0 2.0
lc0116 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; level-order traversal; connect vertices on the same level; top-interview-150 0 4.0
lc0117 to replace with LeetCode link soon... 4.6g, BT Exercises, H identical with LC 0116 0 4.0
lc0124 to replace with LeetCode link soon... 4.6g, BT Exercises, H diameter of a rooted binary tree; top-100-liked; top-interview-150 0 6.0
lc0199 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; last item per level; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0429 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS on n-ary tree 0 4.0
lc0513 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; first element in last level 0 4.0
lc0515 to replace with LeetCode link soon... 4.6g, BT Exercises, H just a small edit from LC 0513 0 4.0
lc0637 to replace with LeetCode link soon... 4.6g, BT Exercises, H like LC0102, just compute the average per level; top-interview-150 0 2.0
lc1161 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; max level sum; leetcode-75 0 4.0
lc1302 to replace with LeetCode link soon... 4.6g, BT Exercises, H like LC0102, sum the values of last level 0 4.0
lc1609 to replace with LeetCode link soon... 4.6g, BT Exercises, H BFS; with custom ordering rules 0 4.0
lc0908 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier the formula involves max and min of nums 0 2.0
lc1523 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier simple formula; inclusion-exclusion; programming-skills 0 2.0
lc1716 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier involve a bit of sum of arithmetic progression 0 2.0
lc2413 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier a simple number theory; n or 2n 0 2.0
lc2656 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier get simple formula involving max(nums) 0 2.0
lc2833 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier get simple formula involving number of 'L', 'R', and '_' 0 2.0
lc2980 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier just check if there are at least two even numbers in nums 0 2.0
lc3513 to replace with LeetCode link soon... 5.2a, Finding Formula, Easier there is a simple pattern 0 4.0
lc0781 to replace with LeetCode link soon... 5.2b, Finding Formula, Harder count the answer frequencies; for each answer k, group the rabbits into size k+1 0 4.0
lc2929 to replace with LeetCode link soon... 5.2b, Finding Formula, Harder get formula to be able to solve this in O(n) 0 4.0
lc0067 to replace with LeetCode link soon... 5.2c, Base Number Conversion convert a and b from bin to dec; add them; convert back; programming-skills; top-interview-150 0 2.0
lc0168 to replace with LeetCode link soon... 5.2c, Base Number Conversion reverse of LC 0171; decimal to base 26 0 2.0
lc0171 to replace with LeetCode link soon... 5.2c, Base Number Conversion reverse of LC 0168; base 26 to decimal 0 2.0
lc0190 to replace with LeetCode link soon... 5.2c, Base Number Conversion dec to bin; reverse; bin to dec; top-interview-150 0 2.0
lc0405 to replace with LeetCode link soon... 5.2c, Base Number Conversion dec to hex conversion; use two's complement for negatives 0 2.0
lc0504 to replace with LeetCode link soon... 5.2c, Base Number Conversion dec to base 7 0 2.0
lc0868 to replace with LeetCode link soon... 5.2c, Base Number Conversion dec to bin; compute the required answer 0 2.0
lc3280 to replace with LeetCode link soon... 5.2c, Base Number Conversion convert yyyy-mm-dd in decimal to binary 0 2.0
lc2595 to replace with LeetCode link soon... 5.2d, Base Number Variants convert n from base 10 to 2; process 0 2.0
lc3099 to replace with LeetCode link soon... 5.2e, Number Systems/Seqs compute sum of digits; check as asked 0 2.0
lc0231 to replace with LeetCode link soon... 5.2f, Log, Exp, Pow n ≤ 0 is False; log2 and exp test 0 2.0
lc0326 to replace with LeetCode link soon... 5.2f, Log, Exp, Pow n = 0 is False; log3 and exp test 0 2.0
lc0342 to replace with LeetCode link soon... 5.2f, Log, Exp, Pow n = 0 is False; log4 and exp test 0 2.0
lc0598 to replace with LeetCode link soon... 5.2j, Really Ad Hoc keep the largest upper-left rectangle size 0 2.0
lc0204 to replace with LeetCode link soon... 5.3a, Prime Numbers basic Sieve of Eratosthenes 0 4.0
lc3115 to replace with LeetCode link soon... 5.3a, Prime Numbers precompute small primes under 100; find leftmost/rightmost prime(s) 0 4.0
lc2614 to replace with LeetCode link soon... 5.3b, (Prob) Prime Testing check primes (Java isProbablePrime works) along the diagonals 0 2.0
lc0914 to replace with LeetCode link soon... 5.3f, GCD and/or LCM gcd of the frequencies of each distinct cards 0 2.0
lc1979 to replace with LeetCode link soon... 5.3f, GCD and/or LCM just compute gcd(min(nums), max(nums)) 0 2.0
lc2447 to replace with LeetCode link soon... 5.3f, GCD and/or LCM when computing GCD; stop as soon as it is lower than k 0 4.0
lc2470 to replace with LeetCode link soon... 5.3f, GCD and/or LCM when computing LCM; stop as soon as it is greater than k 0 4.0
lc2748 to replace with LeetCode link soon... 5.3f, GCD and/or LCM complete search; coprime (gcd) tests 0 2.0
lc3411 to replace with LeetCode link soon... 5.3f, GCD and/or LCM complete search; compute product, GCD, and LCM of all subarrays 0 2.0
lc1006 to replace with LeetCode link soon... 5.3g, Factorial O(n) modified factorial-style computation 0 4.0
lc0172 to replace with LeetCode link soon... 5.3h, Working with PFs count number of prime factor 5; top-interview-150 0 4.0
lc0263 to replace with LeetCode link soon... 5.3h, Working with PFs take out all prime factors 2, 3, 5 from n; is n = 1? 0 2.0
lc2761 to replace with LeetCode link soon... 5.3h, Working with PFs sieve up to 1000; do prime tests 0 4.0
lc0492 to replace with LeetCode link soon... 5.3k, Divisibility Test divisibility tests 0 2.0
lc0507 to replace with LeetCode link soon... 5.3k, Divisibility Test divisibility tests 0 2.0
lc1492 to replace with LeetCode link soon... 5.3k, Divisibility Test get all the factors; sort; return the k-th factor 0 4.0
lc1952 to replace with LeetCode link soon... 5.3k, Divisibility Test divisibility test up to sqrt of n 0 2.0
lc0070 to replace with LeetCode link soon... 5.4a, Fibonacci Numbers basically compute Fib(n+1); DP; top-100-liked; top-interview-150 0 2.0
lc0509 to replace with LeetCode link soon... 5.4a, Fibonacci Numbers basic Fibonacci; DP 0 2.0
lc1137 to replace with LeetCode link soon... 5.4a, Fibonacci Numbers basic Tribonacci; DP; leetcode-75 0 2.0
lc1414 to replace with LeetCode link soon... 5.4a, Fibonacci Numbers generate Fn up to n = 44; use greedy (use largest Fn ≤ current k) 0 4.0
lc0118 to replace with LeetCode link soon... 5.4b, Binomial Coefficients basic bottom-up DP to generate Pascal's triangle; top-100-liked 0 2.0
lc0119 to replace with LeetCode link soon... 5.4b, Binomial Coefficients use space-saving trick; consider last two rows of the bottom-up DP 0 2.0
lc0096 to replace with LeetCode link soon... 5.4c, Catalan Numbers Catalan numbers; pre-calculateable 1 to 19 0 4.0
lc1010 to replace with LeetCode link soon... 5.4d, Others, Easier count number of songs with the same length (modulo 60); a bit of combinatorics 0 4.0
lc1128 to replace with LeetCode link soon... 5.4d, Others, Easier treat [a, b] and [b, a] as the same; count freq of each distinct domino; C(freq, 2) per distinct domino 0 2.0
lc1175 to replace with LeetCode link soon... 5.4d, Others, Easier let k be number of primes up to n; output k! * (n-k)!, mod 10^9+7 0 2.0
lc2125 to replace with LeetCode link soon... 5.4d, Others, Easier multiply the number of 1s between successive rows 0 4.0
lc3084 to replace with LeetCode link soon... 5.4d, Others, Easier let k be number of times c appears in s; output C(k, 1) + C(k, 2) 0 4.0
lc3185 to replace with LeetCode link soon... 5.4d, Others, Easier count frequencies modulo 24; a bit of simple combinatorics 0 4.0
lc0141 to replace with LeetCode link soon... 5.6a, Cycle Finding Floyd's cycle-finding on SLL; top-100-liked; top-interview-150 0 2.0
lc0142 to replace with LeetCode link soon... 5.6a, Cycle Finding Floyd's cycle-finding on SLL; also find μ; top-100-liked 0 4.0
lc0202 to replace with LeetCode link soon... 5.6a, Cycle Finding use hash table to record seen numbers; top-interview-150 0 2.0
lc0287 to replace with LeetCode link soon... 5.6a, Cycle Finding find μ, start of the cycle; Floyd's cycle-finding algorithm; popularized by Joma Tech YouTube video; top-100-liked 0 4.0
lc0957 to replace with LeetCode link soon... 5.6a, Cycle Finding cycle finding is needed as n can be very large 0 4.0
lc2582 to replace with LeetCode link soon... 5.6a, Cycle Finding compute simple formula involving a bit of modulo; same as LC 3178 0 2.0
lc3178 to replace with LeetCode link soon... 5.6a, Cycle Finding compute simple formula involving a bit of modulo; same as LC 2582 0 2.0
lc0292 to replace with LeetCode link soon... 5.7a, Game Theory (Basic) simple game; short formula 0 2.0
lc3222 to replace with LeetCode link soon... 5.7a, Game Theory (Basic) 115 = 1x75 + 4x10; no other way; simulate 0 2.0
lc3360 to replace with LeetCode link soon... 5.7a, Game Theory (Basic) simulate the process to determine the winner 0 2.0
lc0050 to replace with LeetCode link soon... 5.8a, Matrix Power D&C exponentiation; programming-skills; top-interview-150 0 4.0
lc0372 to replace with LeetCode link soon... 5.8a, Matrix Power D&C modular exponentiation 0 4.0
lc2961 to replace with LeetCode link soon... 5.8a, Matrix Power use D&C modular exponentiation twice 0 4.0
lc0014 to replace with LeetCode link soon... 6.2e, String Comparison complete search; try each prefix; see if it all strings start with it; top-interview-150 0 2.0
lc1961 to replace with LeetCode link soon... 6.2e, String Comparison compare the concatenation of first k strings of words with s 0 2.0
lc3042 to replace with LeetCode link soon... 6.2e, String Comparison complete search; see if a word both starts and ends with another word 0 2.0
lc0459 to replace with LeetCode link soon... 6.2f, Really Ad Hoc complete search; test repeated substring; programming-skills 0 2.0
lc0890 to replace with LeetCode link soon... 6.2f, Really Ad Hoc custom matching; map each word to appropriate index (signature); compare signatures 0 4.0
lc2734 to replace with LeetCode link soon... 6.2f, Really Ad Hoc ad hoc string processing 0 4.0
lc2937 to replace with LeetCode link soon... 6.2f, Really Ad Hoc make the 3 strings equal to their LCPs 0 2.0
lc0072 to replace with LeetCode link soon... 6.3a, DP String, Classic classic; DP; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc1035 to replace with LeetCode link soon... 6.3a, DP String, Classic just a rewording of classic LCS problem 0 4.0
lc1092 to replace with LeetCode link soon... 6.3a, DP String, Classic SCS; very similar to Kattis - nafnagift 0 6.0
lc1143 to replace with LeetCode link soon... 6.3a, DP String, Classic classic; DP; leetcode-75; top-100-liked 0 4.0
lc0097 to replace with LeetCode link soon... 6.3b, DP String, Non Classic s: (i, j); k is derived from i+j; t: use a[i] or b[i] next; top-interview-150 0 4.0
lc0028 to replace with LeetCode link soon... 6.4a, String Matching simple string matching; programming-skills; top-interview-150 0 2.0
lc0161 to replace with LeetCode link soon... 6.4a, String Matching PREMIUM - hint hidden 0 4.0
lc0686 to replace with LeetCode link soon... 6.4a, String Matching observation: you do not have to repeat a too many times 0 4.0
lc1408 to replace with LeetCode link soon... 6.4a, String Matching complete search and string matching combo 0 2.0
lc1668 to replace with LeetCode link soon... 6.4a, String Matching complete search; (short) string matching tests 0 2.0
lc1967 to replace with LeetCode link soon... 6.4a, String Matching simple string matching task 0 2.0
lc2264 to replace with LeetCode link soon... 6.4a, String Matching string matching up to 10x: ['999', '888', ..., '000'] 0 2.0
lc0079 to replace with LeetCode link soon... 6.4b, String Matching, 2D 2D grid; backtracking; top-100-liked; top-interview-150 0 4.0
lc0208 to replace with LeetCode link soon... 6.5a, Trie Trie implementation; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0648 to replace with LeetCode link soon... 6.5a, Trie use Trie to speed-up the identification of the shortest root for each derivative 0 4.0
lc1268 to replace with LeetCode link soon... 6.5a, Trie use Trie to speed-up the search process; leetcode-75 0 4.0
lc2416 to replace with LeetCode link soon... 6.5a, Trie we can use Trie or frequency Counter of each prefixes 0 6.0
lc1044 to replace with LeetCode link soon... 6.5b, Suffix Tree/Array classic Longest Repeated Substring problem; solvable with Suffix Array 0 6.0
lc0187 to replace with LeetCode link soon... 6.6a, String Hashing classic rolling hash task; maintain hash of 10-characters substring as the window slides 0 4.0
lc3271 to replace with LeetCode link soon... 6.6a, String Hashing divide the string into k equal-length substrings; hash them 0 4.0
lc0049 to replace with LeetCode link soon... 6.7a, Anagram hash each string to the sorted version of those strings; top-100-liked; top-interview-150 0 4.0
lc0242 to replace with LeetCode link soon... 6.7a, Anagram sort s and t; compare; programming-skills; top-interview-150 0 2.0
lc1347 to replace with LeetCode link soon... 6.7a, Anagram count character frequencies; simple calculation 0 4.0
lc2273 to replace with LeetCode link soon... 6.7a, Anagram one pass; check the sorted version of adjacent words 0 2.0
lc0009 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) compare x (read as string) and its reverse; top-interview-150 0 2.0
lc0125 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) parse input; reverse; compare; top-interview-150 0 2.0
lc0131 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) backtracking; many palindrome checks of short strings; top-100-liked 0 4.0
lc0647 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) complete search all substrings plus DP isPalindrome(l, r) speedup 0 4.0
lc0680 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) s: (l, r, num_del); recursive check 0 2.0
lc1332 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) three cases: s is a palindrome; s contains only 'a' or only 'b'; s contains both 0 2.0
lc1457 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) preorder traversal; at most one is odd 0 4.0
lc2108 to replace with LeetCode link soon... 6.7b, Palindrome (Checking) check isPalindrome of each string 0 2.0
lc0005 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) s: (i, j); t: check isPal(i+1, j-1); print solution; top-100-liked; top-interview-150 0 4.0
lc0409 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) count character frequencies; even cases are easy; odd cases need a small observation 0 2.0
lc0516 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) slightly easier than LC 0005 0 4.0
lc1312 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) s: (i, j); t: first/last char match vs mismatch; O(n^2) DP 0 6.0
lc2697 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) two pointers: l=0, r=n-1; compare (take the smaller one if mismatch) and move inwards 0 2.0
lc3239 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) check per row; transpose the matrix so we can check rows again (for columns) 0 4.0
lc3517 to replace with LeetCode link soon... 6.7c, Palindrome (Generating) sort the first half; middle (if odd); and reverse sort the second half 0 4.0
lc0973 to replace with LeetCode link soon... 7.2a, Points sort points by non-decreasing Euclidean distances 0 4.0
lc1037 to replace with LeetCode link soon... 7.2a, Points check if three points are distinct and not collinear 0 2.0
lc1232 to replace with LeetCode link soon... 7.2a, Points check if all other points are collinear with the line defined by the first two points; programming-skills 0 2.0
lc1779 to replace with LeetCode link soon... 7.2a, Points check all points as per requirement 0 2.0
lc1828 to replace with LeetCode link soon... 7.2c, Circles for each circle query, check how many points are inside; O(QN) 0 4.0
lc2481 to replace with LeetCode link soon... 7.2c, Circles three cases: when n = 1, n is even, or n is odd 0 2.0
lc1925 to replace with LeetCode link soon... 7.2d, Triangles (Trig) Pythagorean triples; complete search 0 2.0
lc3024 to replace with LeetCode link soon... 7.2d, Triangles (Trig) determine type of given triangle; case analysis 0 2.0
lc0836 to replace with LeetCode link soon... 7.2f, Quadrilaterals set rec2 as reference point; simple case analysis of where rec1 is vs rec2 0 2.0
lc1725 to replace with LeetCode link soon... 7.2f, Quadrilaterals largest square out of a rectangle lxw has length = min(l, w); check all rectangles 0 2.0
lc3000 to replace with LeetCode link soon... 7.2f, Quadrilaterals diagonal of a rectangle lxw has length = hypot(l, w); check all rectangles 0 2.0
lc0587 to replace with LeetCode link soon... 7.3a, Polygon, Easier Convex Hull; collinear allowed 0 6.0
lc0433 to replace with LeetCode link soon... 8.2b, State-Space, BFS, E unweighted SSSP; BFS; s: (8-char-gene); t: as described; top-interview-150 0 4.0
lc0126 to replace with LeetCode link soon... 8.2c, State-Space, BFS, H map string to indices; BFS on state-space graph; backtrack 0 6.0
lc0127 to replace with LeetCode link soon... 8.2c, State-Space, BFS, H like LC 0126; without backtracking; top-interview-150 0 6.0
lc0123 to replace with LeetCode link soon... 8.3a, DP level 3 like LC 0188; larger n; but k at most 2; top-interview-150 0 6.0
lc0152 to replace with LeetCode link soon... 8.3a, DP level 3 clever 1 pass DP solution; keep cur-min and cur-max so far; top-100-liked 0 4.0
lc0188 to replace with LeetCode link soon... 8.3a, DP level 3 s: (i, own, k_left); t: skip or buy/sell; also consider k_left; top-interview-150 0 6.0
lc0790 to replace with LeetCode link soon... 8.3b, DP level 4 s: (n, got_hole); t: depends whether there is a hole (due to a Triomino) or not; simple profile DP; leetcode-75 0 4.0
lc3530 to replace with LeetCode link soon... 8.3d, DP with Bitmask s: (mult, mask); t: go to unprocessed vertex if the topological order is not violated 0 6.0
lc0015 to replace with LeetCode link soon... 8.6b, NP-hard/C, small, H one possible way is to hash all numbers and try all-pairs; avoid duplicates; top-100-liked; top-interview-150 0 4.0
lc0198 to replace with LeetCode link soon... 8.6c, NP-hard/C, special, E MWIS; on line graph; simple DP; leetcode-75; top-100-liked; top-interview-150 0 4.0
lc0213 to replace with LeetCode link soon... 8.6c, NP-hard/C, special, E MWIS; on circular line graph; DP variant 0 4.0
lc0256 to replace with LeetCode link soon... 8.6c, NP-hard/C, special, E PREMIUM - hint hidden 0 4.0
lc0265 to replace with LeetCode link soon... 8.6c, NP-hard/C, special, E PREMIUM - hint hidden 0 6.0
lc0337 to replace with LeetCode link soon... 8.6c, NP-hard/C, special, E MWIS; on tree; DP 0 4.0
lc0149 to replace with LeetCode link soon... 8.7e, Geometry+CS identical with UVa 11227; top-interview-150 0 6.0
lc0812 to replace with LeetCode link soon... 8.7e, Geometry+CS try all 3 points; compute triangle area; keep the largest 0 2.0
lc0976 to replace with LeetCode link soon... 8.7f, Geometry+Other sort nums in non-increasing order; do triangle inequality checks; programming-skills 0 2.0
lc0789 to replace with LeetCode link soon... 8.7h, Mathematics+Other compute SSSP with Manhattan distance; see if my shortest is shorter than the fastest ghost 0 4.0
lc1071 to replace with LeetCode link soon... 8.7h, Mathematics+Other divisibility; on string; leetcode-75 0 2.0
lc2300 to replace with LeetCode link soon... 8.7k, Three++ Components, E sort potions; try all spells and BSTA each time; leetcode-75 0 4.0
lc0296 to replace with LeetCode link soon... 9.grad, Gradient Descent PREMIUM - hint hidden 0 6.0
lc0969 to replace with LeetCode link soon... 9.panc, Pancake Sorting the easier form of Pancake Sorting; flip largest to top (index 1), then to target; at most 2*n flips 0 4.0
lc0169 to replace with LeetCode link soon... 9.rand, Randomized Algo try a random number and see if it is the majority element, repeat; top-100-liked; top-interview-150 0 2.0
lc0229 to replace with LeetCode link soon... 9.rand, Randomized Algo pick a random value; see if appears > floor(n/3) times; at most two; a few tries 0 4.0
lc0398 to replace with LeetCode link soon... 9.rand, Randomized Algo separate chaining; record indices of each value; randomly return a valid index 0 4.0
lc0519 to replace with LeetCode link soon... 9.rand, Randomized Algo randomly pick (r, c) inside the grid; repeat if it has been taken 0 4.0

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