Competitive Programming

Methods to Solve (2000-present)

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

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You can now sort these problems based on Distinct ACcepted Users (DACU) column.
Generally, problems with high DACU are the easier problems.
Note that we only update DACU column manually when we first entered the hint (thus an outdated data).

As Kattis users, you can also sort these problems based Kattis points (usually correlated with DACU but not always).
Generally, problems with low Kattis points are the easier problems.
Note that we only update Point column manually (not a live data).

For Kattis and Google Chrome users, install Kattis Hint Giver created by one of my student Lin Si Jie that integrates this page directly with Kattis problems pages (Kattis has major UI/UX upgrade on early Jun 2022, Si Jie has updated this tool and added 'spoiler blur' so users can decide when to be spoiled; but Kattis changes its UI again by end 2023 so this feature is now broken again)
(Almost) all of the easiest 1097 problems (range: [1.1..3.3] points, average at 2.2 points) have hints and solving them all gives you 1097*~2.2 ≥ 2413.4 total Kattis points — The Lower Bound of Programming Contests in the 2020s year 2024.
Tips: You may want to occasionally 'Remove 'Kattis Hint Giver' from Chrome' and re-'Add it back to Chrome' to manually sync this Methods to Solve content with the local cache.

Kattis Problem Title CP4 Hint DACU Point
baloni baloni 2.2a, 1D Array, Medium clever use of 1D histogram array to decompose the shots as per requirement 689 3.5
downtime downtime 2.2a, 1D Array, Medium 1D array; use Fenwick Tree-like operation for Range Update Point Query 1068 3.2
erase erase 2.2a, 1D Array, Medium if N is odd, the second line has to be the inverse of the first; if N is even, both lines have to be the same 2166 1.6
fluortanten fluortanten 2.2a, 1D Array, Medium remove Bjorn first; then do O(n) pass to check where is Bjorn's optimal position 181 3.1
greedilyincreasing greedilyincreasing 2.2a, 1D Array, Medium just 1D array manipulation; this is not the DP-LIS problem 1151 1.9
jollyjumpers jollyjumpers 2.2a, 1D Array, Medium 1D Boolean flags to check [1..n-1]; also available at UVa 10038 - Jolly Jumpers 413 3.4
rankproblem rankproblem 2.2a, 1D Array, Medium list (array) manipulation problem 120 2.8
trackingshares trackingshares 2.2a, 1D Array, Medium keep track of the shares in small arrays and simulate 73 2.2
astro astro 2.2b, 1D Array, Harder use large Boolean array 115 4.3
charged charged 2.2b, 1D Array, Harder convoluted problem statement; ignore E and F; for each cell, compute sum of Vs using rx/ry; convert the value of each ce... 61 1.8
crashingrobots crashingrobots 2.2b, 1D Array, Harder just simulate the x/y/direction of the N robots 107 4.6
divideby100 divideby100 2.2b, 1D Array, Harder big 1D character array processing; be careful 557 4.2
flippingpatties flippingpatties 2.2b, 1D Array, Harder use 1D int array of size 43 201; at each time t, we need one cook (hand) at time t-2d (to start), t-d (to flip), ... 116 2.4
inverteddeck inverteddeck 2.2b, 1D Array, Harder can we sort the array with just one contiguous swap?; compress duplicates; use sentinel so that we only check /&bsol... 203 3.7
keypad keypad 2.2b, 1D Array, Harder 2D array manipulation 200 3.3
mastermind mastermind 2.2b, 1D Array, Harder 1D array manipulation to count r and s 446 2.4
physicalmusic physicalmusic 2.2b, 1D Array, Harder a reading comprehension problem to come up with a simple algorithm to determine the answer 168 5.5
piperotation piperotation 2.2b, 1D Array, Harder use 1D Boolean array to check if cell (r, c) needs to be connected from the top (r-1) or left (c-1) and pass information... 50 2.6
pivot pivot 2.2b, 1D Array, Harder static range min/max query problem; special condition allows this problem to be solvable in O(n) using help of 1D arrays 1723 3.2
queens queens 2.2b, 1D Array, Harder simple N queens verifier program; use several 1D Boolean arrays to help do this check in O(N) 725 3.3
rockband rockband 2.2b, 1D Array, Harder interesting usage of 1D array to simplify the solution; a bit of sorting to arrange the output 194 3.9
traffic traffic 2.2b, 1D Array, Harder just simulate the movement of the car for 'longer than 10^6', analyze the required bound 233 4.1
upsanddownsofinvesting upsanddownsofinvesting 2.2b, 1D Array, Harder simplify by a factor of two by realizing that peaks and valleys are symmetrical 147 3.6
compromise compromise 2.2c, 2D Array, Easier 2D array manipulation; take the majority bits of each column; output either 0 or 1 for ties 363 2.2
epigdanceoff epigdanceoff 2.2c, 2D Array, Easier count number of CCs on 2D grid; simpler solution exists: count the number of blank columns plus one 505 1.9
fastestavailableroute fastestavailableroute 2.2c, 2D Array, Easier count the number of dots in a 2D grid; scale up by a factor of s 126 2.5
flowshop flowshop 2.2c, 2D Array, Easier interesting 2D array manipulation 392 2.5
guesswho guesswho 2.2c, 2D Array, Easier 2D and 1D array; simulate and eliminate impossible candidates 197 1.6
imageprocessing imageprocessing 2.2c, 2D Array, Easier interesting 2D array manipulation 344 2.1
laegdyfirlandinu laegdyfirlandinu 2.2c, 2D Array, Easier easy 2D array check 208 1.6
laptopstickers laptopstickers 2.2c, 2D Array, Easier 2D array manipulation 318 2.5
moderatepace moderatepace 2.2c, 2D Array, Easier sort each column; take the middle one 272 1.6
mylla2 mylla2 2.2c, 2D Array, Easier simple 3x3 grid manipulation 247 1.6
nineknights nineknights 2.2c, 2D Array, Easier 2D array checks; 8 directions 881 1.9
patchwork patchwork 2.2c, 2D Array, Easier tedious 2D grid manipulation 109 2.0
prjonamynstur prjonamynstur 2.2c, 2D Array, Easier process-2d-grid-on-the-fly 395 1.5
rulen rulen 2.2c, 2D Array, Easier bitmask application; follow the instructions 59 2.9
starbattles1 starbattles1 2.2c, 2D Array, Easier simple 2D array checks; use delta row/col technique to simplify the implementation 189 3.1
thisaintyourgrandpascheckerboard thisaintyourgrandpaschecke... 2.2c, 2D Array, Easier simple 2D array manipulation 578 1.6
vemvinner vemvinner 2.2c, 2D Array, Easier small 3x3 array checks 408 2.1
2048 2048 2.2d, 2D Array, Harder just a 2D array manipulation problem; utilize symmetry using 90 degrees rotation(s) to reduce 4 cases into 1 3150 2.1
apples apples 2.2d, 2D Array, Harder 2D array manipulation; gravity simulation 439 3.6
falcondive falcondive 2.2d, 2D Array, Harder 2D array manipulation; translation vector of the Falcon 64 2.8
flagquiz flagquiz 2.2d, 2D Array, Harder array of array of strings; be careful; duplicates may exists 167 3.7
funhouse funhouse 2.2d, 2D Array, Harder 2D array manipulation; note the direction update 700 2.0
huntthewumpus huntthewumpus 2.2d, 2D Array, Harder tedious 2D array simulation 215 2.2
prva prva 2.2d, 2D Array, Harder 2D array manipulation; check vertically and horizontally 756 1.7
rings2 rings2 2.2d, 2D Array, Harder more challenging 2D array manipulation; special output formatting style 385 3.8
tetris tetris 2.2d, 2D Array, Harder actually 3D pattern array to simulate various shape positions 322 1.8
waterworld waterworld 2.2d, 2D Array, Harder reading comprehension problem; compute average of a 2D array 68 2.2
basicprogramming2 basicprogramming2 2.2e, Sorting, Easier a nice problem about basic sorting applications 189 3.4
classfieldtrip classfieldtrip 2.2e, Sorting, Easier just sort the characters 1019 1.3
closingtheloop closingtheloop 2.2e, Sorting, Easier sort first 1415 1.6
cups cups 2.2e, Sorting, Easier a bit of string parsing; sort 2987 1.5
height height 2.2e, Sorting, Easier insertion sort simulation 899 2.0
judging judging 2.2e, Sorting, Easier sort DOM judge and Kattis outputs; then do the O(n) merge procedure of mergesort to count common outputs 1183 2.5
magictrick magictrick 2.2e, Sorting, Easier can if all chars are unique or cannot otherwise; either sort s then check adjacent characters or use set to eliminate du... 1605 1.3
mjehuric mjehuric 2.2e, Sorting, Easier a direct simulation of a bubble sort algorithm 1349 1.6
musicaltrees musicaltrees 2.2e, Sorting, Easier sort p and t; then just simulate as asked with Boolean array 23 2.8
nothanks nothanks 2.2e, Sorting, Easier sort; then linear pass to check adjacent sorted elements 441 2.4
sidewayssorting sidewayssorting 2.2e, Sorting, Easier stable_sort or sort multi-fields of columns of a 2D array; ignore case 857 2.0
stokigalistor stokigalistor 2.2e, Sorting, Easier compare original list with its sorted version 537 2.2
addemup addemup 2.2f, Sorting, Harder create a helper function to read digits upside down; add all possibilities; sort; then use fast O(n) target pair solutio... 338 4.4
booking booking 2.2f, Sorting, Harder 2 events per booking (need room and release room); convert to minutes; be careful of leap year on 2016; sort the events;... 164 5.4
chartingprogress chartingprogress 2.2f, Sorting, Harder sort using modified comparison function (by column); transpose the input 757 2.2
classy classy 2.2f, Sorting, Harder sort using modified comparison function; a bit of string parsing/tokenization 1633 4.5
dirtydriving dirtydriving 2.2f, Sorting, Harder sort; find max - derive the formula; reading comprehension problem 279 2.1
dyslectionary dyslectionary 2.2f, Sorting, Harder sort the reverse of original string; output formatting 775 3.4
gearchanging gearchanging 2.2f, Sorting, Harder generate all O(N*M) possible gear ratios; sort; check consecutive ratios (it is ok to have duplicates) 161 3.2
includescoring includescoring 2.2f, Sorting, Harder sort; custom comparison function, tedious 342 3.7
lawnmower lawnmower 2.2f, Sorting, Harder sort and check if Guido covers all land (end-to-end and side-to-side); also available at UVa 12269 - Land Mower 448 2.1
longswaps longswaps 2.2f, Sorting, Harder observation: if k ≤ n/2, output 'Yes'; otherwise the middle chars at s[n-k..k-1] cannot move; sort s and compare the ... 172 3.3
musicyourway musicyourway 2.2f, Sorting, Harder stable_sort; custom comparison function 404 2.4
sortofsorting sortofsorting 2.2f, Sorting, Harder stable_sort or sort multi-fields 2667 2.2
statues statues 2.2f, Sorting, Harder sort distinct statue heights; test all 4 possible diagonal placements, pick the min 106 2.8
zipfsong zipfsong 2.2f, Sorting, Harder sort; custom comparison function; zipf law 209 4.5
bread bread 2.2g, Special Sorting inversion count; hard to derive 249 5.0
excursion excursion 2.2g, Special Sorting inversion index; requires O(n log n) merge sort 387 4.3
froshweek froshweek 2.2g, Special Sorting requires O(n log n) merge sort; 64-bit integer; also available at UVa 11858 - Frosh Week 694 5.6
gamenight gamenight 2.2g, Special Sorting Counting Sort is a subproblem; count frequency of A/B/Cs; complete search AA..ABB..BCC..C or AA..ACC..CBB..B 70 2.8
mali mali 2.2g, Special Sorting Counting Sort two arrays; greedy matching largest+smallest at that point 97 5.1
sort sort 2.2g, Special Sorting Counting Sort variant 318 2.3
ultraquicksort ultraquicksort 2.2g, Special Sorting requires O(n log n) merge sort; also available at UVa 10810 - Ultra Quicksort 180 5.2
bracketmatching bracketmatching 2.2j, Stack bracket matching; stack 1172 1.7
dream dream 2.2j, Stack stack simulation; reading comprehension problem, need other fast DS for mapping strings to indices 219 6.4
evenup evenup 2.2j, Stack use stack to solve this problem 1273 2.7
pairingsocks pairingsocks 2.2j, Stack simulation using two stacks; just do as asked 556 3.0
restaurant restaurant 2.2j, Stack simulation with stack-based concept; drop plates at stack 2 (LIFO); use move 2-$gt;1 to reverse order; take from stack 1... 364 4.5
reversebinary reversebinary 2.2j, Stack decimal to binary; reverse it; binary to decimal 7144 1.5
symmetricorder symmetricorder 2.2j, Stack use stack to help reverse even-indexed names 3584 1.5
thegrandadventure thegrandadventure 2.2j, Stack stack simulation 348 2.0
throwns throwns 2.2j, Stack use stack of egg positions to help with the undo operation; be careful of corner cases involving modulo operation 1091 2.6
bracketsequence bracketsequence 2.2k, Stack-based Problems bracket matching variant; stack; push a pair of (+ result, * result) for each '('; pop topmost pair for each ')'; operat... 100 5.5
bungeebuilder bungeebuilder 2.2k, Stack-based Problems clever usage of stack; linear pass; bracket (mountain) matching variant 83 3.3
circuitmath circuitmath 2.2k, Stack-based Problems postfix calculator problem 918 2.4
delimitersoup delimitersoup 2.2k, Stack-based Problems bracket matching; stack 382 1.9
backspace backspace 2.2l, List/Queue/Deque we can use deque (or vector) to help solve this problem 2517 3.0
ferryloading3 ferryloading3 2.2l, List/Queue/Deque simulation with queue; also available at UVa 10901 - Ferry Loading III 368 3.6
ferryloading4 ferryloading4 2.2l, List/Queue/Deque simulation with queue; also available at UVa 11034 - Ferry Loading IV 703 3.6
foosball foosball 2.2l, List/Queue/Deque queue simulation; tedious 186 3.7
integerlists integerlists 2.2l, List/Queue/Deque use deque for fast deletion from front (normal) & back (reversed list); use stack to reverse the final list if it is... 882 4.8
joinstrings joinstrings 2.2l, List/Queue/Deque all '+' operations must be O(1) 959 4.1
lyklagangriti lyklagangriti 2.2l, List/Queue/Deque use list and its iterator; very similar to Kattis - sim 114 2.7
server server 2.2l, List/Queue/Deque one first come first serve pass; we can use queue although overkill 3331 1.9
sim sim 2.2l, List/Queue/Deque use list and its iterator 99 2.0
teque teque 2.2l, List/Queue/Deque all operations must be O(1) 766 3.3
trendingtopic trendingtopic 2.2l, List/Queue/Deque use queue of length 7 to maintain words in the past 7 days, unordered_map to count frequencies, sort to format the outpu... 181 5.8
alehouse alehouse 2.3a, Priority Queue discretize the events; PQ simulation 223 4.6
clinic clinic 2.3a, Priority Queue interesting PQ simulation; reverse thinking; project to time 0 165 3.0
guessthedatastructure guessthedatastructure 2.3a, Priority Queue stack, queue, and priority_queue; also available at UVa 11995 - I Can Guess ... 2148 2.5
heap heap 2.3a, Priority Queue basic Binary (Max) Heap implementation task 11 5.8
janeeyre janeeyre 2.3a, Priority Queue simulate Anna's reading behavior with PQ; the input parsing is tedious 79 4.8
jugglingpatterns jugglingpatterns 2.3a, Priority Queue PQ simulation; reading comprehension 48 6.3
knigsoftheforest knigsoftheforest 2.3a, Priority Queue PQ simulation after sorting the entries by year 184 3.6
numbertree numbertree 2.3a, Priority Queue not a direct priority queue problem, but the indexing strategy is similar to binary heap indexing 1760 2.1
pharmacy pharmacy 2.3a, Priority Queue simulation with PQ (time) and 2 normal queues (in-store vs remote) 118 3.4
rationalsequence2 rationalsequence2 2.3a, Priority Queue the L/R pattern can be easily derived and indexing strategy is similar to binary heap indexing 1388 1.5
rationalsequence3 rationalsequence3 2.3a, Priority Queue the reverse problem of rationalsequence2 587 1.8
stockprices stockprices 2.3a, Priority Queue PQ simulation; both max and min PQ 109 3.7
alphabetspam alphabetspam 2.3b, DAT, ASCII count the frequencies of lowercase, uppercase, and whitespace characters 3902 1.4
cyclicalperiods cyclicalperiods 2.3b, DAT, ASCII DAT of last occurrence of 26 chars [`a`..`z`], keep the running max 112 3.0
keyboardd keyboardd 2.3b, DAT, ASCII frequency counting of A-Zs and spaces 92 2.0
quickbrownfox quickbrownfox 2.3b, DAT, ASCII pangram; frequency counting of 26 alphabets 4433 1.6
soundex soundex 2.3b, DAT, ASCII DAT for soundex A-Z code mapping; also available at UVa 10260 - Soundex 106 2.9
bladra bladra 2.3c, DAT, Others DAT of frequencies of size k; find min 324 2.0
bookingaroom bookingaroom 2.3c, DAT, Others only 100 rooms; use 1D Boolean array 2849 1.7
busnumbers busnumbers 2.3c, DAT, Others only 1000 bus numbers; use 1D Boolean array 2776 2.4
dontbefake dontbefake 2.3c, DAT, Others it is sufficient to use DAT of size 86400 to get the required answers efficiently 100 2.9
freefood freefood 2.3c, DAT, Others only 365 days in a year 1965 1.5
hardware hardware 2.3c, DAT, Others parsing is tedious; count the frequency of digits 244 2.0
heimavinna heimavinna 2.3c, DAT, Others DAT of 1000 problems 431 1.4
princesspeach princesspeach 2.3c, DAT, Others DAT; linear pass 839 2.1
relocation relocation 2.3c, DAT, Others just use DAT 1112 1.5
simone simone 2.3c, DAT, Others DAT to count frequencies of [1..K] 106 1.6
bard bard 2.3d, Hash Table (set) use one unordered_set per villager; simulate the singing process 637 2.6
boatparts boatparts 2.3d, Hash Table (set) use unordered_set 1398 1.6
cd cd 2.3d, Hash Table (set) unordered_set is faster than set here; or use modified merge as the input is sorted; also available at UVa 11849 - CD 3176 5.3
deduplicatingfiles deduplicatingfiles 2.3d, Hash Table (set) use vector to store the strings; unordered_set to store unique strings; and complete search to compare the n^2 hash code... 583 4.4
engineeringenglish engineeringenglish 2.3d, Hash Table (set) use unordered_set to remember duplicated words; transform to lowercase 1627 2.2
esej esej 2.3d, Hash Table (set) use unordered_set to prevent duplicate 509 3.3
everywhere everywhere 2.3d, Hash Table (set) use unordered_set 7015 1.4
greetingcard greetingcard 2.3d, Hash Table (set) use unordered_set; good question; major hint: only 12 neighbors 607 4.9
icpcawards icpcawards 2.3d, Hash Table (set) use unordered_set; print first 12 distinct Universities (and their first teams) 2167 1.4
icpcrecordmatching icpcrecordmatching 2.3d, Hash Table (set) string processing; set of emails/names; sort the output 111 4.2
iwannabe iwannabe 2.3d, Hash Table (set) sort Pokenoms based on each stat; pick top K ids and put in an unordered_set; report final size of unordered_set 739 2.5
keywords keywords 2.3d, Hash Table (set) pre-process the strings; put inside unordered_set; report final size 349 2.3
knotknowledge knotknowledge 2.3d, Hash Table (set) simple set difference problem 890 1.5
nodup nodup 2.3d, Hash Table (set) use unordered_set; string 3564 1.3
oddmanout oddmanout 2.3d, Hash Table (set) use unordered_set to find and eliminate pairs 4450 1.5
pizzahawaii pizzahawaii 2.3d, Hash Table (set) use Python to help with (unordered) set intersection and difference operations 335 2.6
proofs proofs 2.3d, Hash Table (set) parsing; use unordered_set to store past conclusions; a few corner cases 48 2.4
securedoors securedoors 2.3d, Hash Table (set) use unordered_set to keep track of the people 2108 1.8
shiritori shiritori 2.3d, Hash Table (set) linear pass; use unordered_set to keep track of words that have been called 295 2.9
shoppinglist shoppinglist 2.3d, Hash Table (set) simple set intersection problem 16 4.4
shoppinglisteasy shoppinglisteasy 2.3d, Hash Table (set) see Kattis - shoppinglist 23 3.4
thoringtest thoringtest 2.3d, Hash Table (set) lowercase all inputs; see if all words are known by Thore; use set 38 2.8
tripodometer tripodometer 2.3d, Hash Table (set) let s = sum(d); subtract s by each d_i; keep the answers in a set; sort 185 2.1
upprodun upprodun 2.3d, Hash Table (set) not really a Hash Table problem but uses Hash Table concept; the number of teams in each room is the 'load factor' of th... 197 1.9
variabelnamn variabelnamn 2.3d, Hash Table (set) hash table (set) and DAT simulation 411 3.0
whatdoesthefoxsay whatdoesthefoxsay 2.3d, Hash Table (set) use unordered_set to record excluded sounds 2578 2.1
babelfish babelfish 2.3e, Hash Table (map), E a pure dictionary problem; use unordered_map; also available at UVa 10282 - Babelfish 2835 2.3
candystore candystore 2.3e, Hash Table (map), E we can use hash table; but easier solution exists 447 1.5
competitivearcadebasketball competitivearcadebasketbal... 2.3e, Hash Table (map), E use unordered_map 209 2.8
conformity conformity 2.3e, Hash Table (map), E use unordered_map to count frequencies of the sorted permutations of 5 ids; also available at UVa 11286 - Conformity 1100 1.9
costumecontest costumecontest 2.3e, Hash Table (map), E use unordered_map to map frequency of each category; get the minimum one; print output lexicographically 532 2.0
election2 election2 2.3e, Hash Table (map), E frequency counting; be careful of tie breaker 166 2.4
gandalfsspell gandalfsspell 2.3e, Hash Table (map), E map string to char and char to string 86 2.5
grandpabernie grandpabernie 2.3e, Hash Table (map), E use unordered_map plus (sorted) vector 1065 3.2
haypoints haypoints 2.3e, Hash Table (map), E use unordered_map to deal with Hay Points dictionary; also available at UVa 10295 - Hay Points 1055 2.0
marko marko 2.3e, Hash Table (map), E frequency counting with unordered_map 495 1.9
metaprogramming metaprogramming 2.3e, Hash Table (map), E use unordered_map; somewhat similar with Kattis - addingwords 820 2.4
nicknames nicknames 2.3e, Hash Table (map), E use unordered_map of frequency of prefixes 364 3.3
pakethanterare pakethanterare 2.3e, Hash Table (map), E map package name to version number 454 2.0
pencilcrayons pencilcrayons 2.3e, Hash Table (map), E for each box, count number of element > 1 (offset -1) 384 1.5
planets2 planets2 2.3e, Hash Table (map), E map species name to planet name; frequency counting 106 3.5
recount recount 2.3e, Hash Table (map), E use map; frequency counting 1163 2.0
rollcall rollcall 2.3e, Hash Table (map), E use unordered_map to count frequency; sort 530 2.4
streetsahead streetsahead 2.3e, Hash Table (map), E map street name to linear indices; find the absolute differences of the indices per query 438 2.1
toktik toktik 2.3e, Hash Table (map), E standard frequency counter problem with hash table 451 1.5
variablearithmetic variablearithmetic 2.3e, Hash Table (map), E use unordered_map as mapper 394 2.6
addingwords addingwords 2.3f, Hash Table (map), H use unordered_map 1880 3.9
awkwardparty awkwardparty 2.3f, Hash Table (map), H use unordered_map to running max and running min; report the largest difference 611 3.0
basicinterpreter basicinterpreter 2.3f, Hash Table (map), H the harder version of Kattis - variablearithmetic; tedious; be careful; print string inside double quotes verbatim 152 6.7
bokforing bokforing 2.3f, Hash Table (map), H use unordered_map to map index to value; for each 'RESTART', clear the hash table in 'faster than O(N)' (amortized) and ... 493 3.8
conversationlog conversationlog 2.3f, Hash Table (map), H use combo DS: unordered_map, set, plus (sorted) vector 507 2.8
iforaneye iforaneye 2.3f, Hash Table (map), H use unordered_map to map the various rules mentioned in the problem description; tedious 143 5.0
kaploeb kaploeb 2.3f, Hash Table (map), H hash the total time and lap count of each start number; sort at the end 899 2.3
magicalcows magicalcows 2.3f, Hash Table (map), H use unordered_map of farm size to frequency; small simulation; but since C is small, we can also use DAT 257 4.6
minorsetback minorsetback 2.3f, Hash Table (map), H use unordered_map of string to another unordered_map of int to string; need a bit of music theory to solve the problem; ... 147 3.6
parallelanalysis parallelanalysis 2.3f, Hash Table (map), H reading comprehension; use unordered_map to map memory address to last time it is written 80 4.8
recenice recenice 2.3f, Hash Table (map), H use unordered_map to prepare pronunciation of [1..999]; precalculate the answer afterwards using another unordered_map 225 3.1
snowflakes snowflakes 2.3f, Hash Table (map), H use unordered_map to record the occurrence index of a certain snowflake size; use this to determine the answer in linear... 404 4.4
bst bst 2.3g, Balanced BST (set) simulate special BST [1..N] insertions using set 449 7.3
caching caching 2.3g, Balanced BST (set) combo ds (unordered_map and set) 210 5.8
candydivision candydivision 2.3g, Balanced BST (set) complete search from 1 to sqrt(N); insert all divisors into set for automatic sorting and elimination of duplicates 702 3.4
compoundwords compoundwords 2.3g, Balanced BST (set) use set extensively; iterator 1807 1.7
coursescheduling coursescheduling 2.3g, Balanced BST (set) keep (ordered) set of courses and (unordered) map of course to students taking the course 40 3.1
ministryofmagic ministryofmagic 2.3g, Balanced BST (set) simulate directly, use of queue and set (PQ with update key/increase key; use STL set) 63 6.0
missinggnomes missinggnomes 2.3g, Balanced BST (set) use set to keep ordered list of missing gnomes 659 2.6
orphanbackups orphanbackups 2.3g, Balanced BST (set) use set for auto sorting 94 6.2
palindromicpassword palindromicpassword 2.3g, Balanced BST (set) there are not more than 900 3-digits number; generate all and store them in a (sorted) set; find ceil and floor of input... 431 3.3
raceday raceday 2.3g, Balanced BST (set) use combo of map; multiset (the most important part for the rankings); and unordered_map 184 3.8
raidteams raidteams 2.3g, Balanced BST (set) use more than one PQs that can support erase operation 75 3.5
administrativeproblems administrativeproblems 2.3h, Balanced BST (map) use several maps as the output (of spy names) has to be sorted; be careful of corner cases 194 6.3
baconeggsandspam baconeggsandspam 2.3h, Balanced BST (map) use map; sort 1712 1.6
cakeymccakeface cakeymccakeface 2.3h, Balanced BST (map) map differences to frequencies; return the one with maximum frequency and if ties, the smallest difference 197 3.8
doctorkattis doctorkattis 2.3h, Balanced BST (map) Max Priority Queue with frequent (increaseKey) updates; use map 114 4.7
fantasydraft fantasydraft 2.3h, Balanced BST (map) use map to keep ordering; simulate; need to erase 111 4.0
fodelsedagsmemorisering fodelsedagsmemorisering 2.3h, Balanced BST (map) use map; sorted output 289 1.8
hardwoodspecies hardwoodspecies 2.3h, Balanced BST (map) use map; sorted output; also available at UVa 10226 - Hardwood Species 378 2.7
kattissquest kattissquest 2.3h, Balanced BST (map) use map of priority queues; other solutions exist 834 3.1
maeting maeting 2.3h, Balanced BST (map) map name to frequencies; sort in non-increasing order 433 1.6
notamused notamused 2.3h, Balanced BST (map) use map; sorted output 601 2.0
opensource opensource 2.3h, Balanced BST (map) use map and set to check previous strings; order needed; also available at UVa 11239 - Open Source 291 3.3
problemclassification problemclassification 2.3h, Balanced BST (map) mapper; frequency counting 345 3.1
srednji srednji 2.3h, Balanced BST (map) go left and right of B; use fast data structure like map to help determine the result fast 164 4.1
warehouse warehouse 2.3h, Balanced BST (map) use unordered_map and multimap 920 2.1
zoo zoo 2.3h, Balanced BST (map) parsing; keep last token; tolower; frequency counting with map; order needed 1499 1.7
babynames babynames 2.3i, Order Statistics Tree dynamic rank problem; use two pb_ds 87 5.5
continuousmedian continuousmedian 2.3i, Order Statistics Tree dynamic selection problem; specifically the median values; pb_ds helps 140 3.9
cookieselection cookieselection 2.3i, Order Statistics Tree map large integers to up to 600K integers; use pb_ds or Fenwick Tree and the select(median) operation of Fenwick Tree 923 4.3
gcpc gcpc 2.3i, Order Statistics Tree dynamic rank problem; pb_ds helps 876 5.3
abinitio abinitio 2.4a, Graph Data Structures combo: EL input, AM as working graph DS, AL output (in hash format); all operations must be O(V) or better 104 7.3
alphabetanimals alphabetanimals 2.4a, Graph Data Structures somewhat an Adjacency List data structure 478 3.4
chopwood chopwood 2.4a, Graph Data Structures Prüfer sequence; use priority_queue 258 3.5
cutthenegativity cutthenegativity 2.4a, Graph Data Structures AM to EL conversion 1213 1.4
flyingsafely flyingsafely 2.4a, Graph Data Structures trivial solution exists 1421 1.7
hermits hermits 2.4a, Graph Data Structures a simple Graph Data Structure application question 98 3.2
illuminatispotti illuminatispotti 2.4a, Graph Data Structures store the graph in an Adjacency Matrix; O(N^3) try-all possible triangles 30 4.3
popularitycontest popularitycontest 2.4a, Graph Data Structures a simple graph DS problem 107 2.0
railroad railroad 2.4a, Graph Data Structures do as asked; graph DS modification; bypass vertices with degree 2 95 6.3
traveltheskies traveltheskies 2.4a, Graph Data Structures (graph) DS manipulation; an array of ALs (one per each day); simulate the number of people day by day 188 3.2
tripplanning tripplanning 2.4a, Graph Data Structures use unordered_map to map bidirectional edges into 1-based indices; simulate the linear journey 232 2.4
weakvertices weakvertices 2.4a, Graph Data Structures graph edge existence checks 1775 1.5
8queens 8queens 3.2b, Iterative (Two Loops) classic 8-Queens problem; write a checker 2385 3.2
antiarithmetic antiarithmetic 3.2b, Iterative (Two Loops) 2 nested loops with pruning can still pass the time limit; compare this with UVa 11129; also available at UVa 10730 - An... 195 7.3
bestrelayteam bestrelayteam 3.2b, Iterative (Two Loops) sort runners based on flying start times; brute force first runner and pick top 3 other flying start runners 1420 1.9
bikegears bikegears 3.2b, Iterative (Two Loops) 2D nested loops; sort the output 185 5.4
blackfriday blackfriday 3.2b, Iterative (Two Loops) 2D nested loops; frequency counting 2384 2.2
closestsums closestsums 3.2b, Iterative (Two Loops) sort and then do O(n^2) pairings; also available at UVa 10487 - Closest Sums 1105 2.9
codeguessing codeguessing 3.2b, Iterative (Two Loops) try all possible two digits for Bob 154 2.1
countdoubles countdoubles 3.2b, Iterative (Two Loops) try all contiguous subarrays of m elements 311 2.0
erosionfilter erosionfilter 3.2b, Iterative (Two Loops) for each Ai, just try a few indices around it 93 4.6
golombrulers golombrulers 3.2b, Iterative (Two Loops) 2D nested loops; additional 1D loops for checking 297 3.2
kafkaesque kafkaesque 3.2b, Iterative (Two Loops) 2D nested loops; simple 293 1.7
largesthoarding largesthoarding 3.2b, Iterative (Two Loops) 2D nested loops; try all possible heights and try all N skycrapers 149 3.7
liga liga 3.2b, Iterative (Two Loops) 2D nested loops; interesting logic game; each team is independent; if number played and number loss both not defined, as... 71 6.1
majstor majstor 3.2b, Iterative (Two Loops) for the second output line; just try each of 'S', 'P', or 'R' at every round and take the max 101 1.9
mathtrade mathtrade 3.2b, Iterative (Two Loops) just try all starting point and simulate 241 3.3
missingnumber missingnumber 3.2b, Iterative (Two Loops) rolling prefix tests; doable with just 2D nested loops 387 3.3
peg peg 3.2b, Iterative (Two Loops) 2D nested loops; try all possible moves 931 1.8
pet pet 3.2b, Iterative (Two Loops) very simple 2D nested loops problem 7932 1.4
putovanje putovanje 3.2b, Iterative (Two Loops) clever problem with hint that masks possible brute force solution; just use 2D nested loops 413 2.5
reduction reduction 3.2b, Iterative (Two Loops) 2 nested loops; with sorting; also available at UVa 10670 - Work Reduction 119 5.8
register register 3.2b, Iterative (Two Loops) clever problem with hint that masks possible brute force solution; just use 2D nested loops 583 2.1
smoothiestand smoothiestand 3.2b, Iterative (Two Loops) simple 2D nested loops 195 3.0
straights straights 3.2b, Iterative (Two Loops) 2 nested loops with pruning 227 3.3
summertrip summertrip 3.2b, Iterative (Two Loops) 3 loops TLE; clever 2D nested loops; try all possible ending index i; use DAT to remember the latest lowest starting ind... 632 2.4
telephones telephones 3.2b, Iterative (Two Loops) brute force; check intervals; also available at UVa 12205 - Happy Telephones 302 2.6
tourdefrance tourdefrance 3.2b, Iterative (Two Loops) brute force plus sorting; also available at UVa 11242 - Tour de France 354 2.7
whogoesthere whogoesthere 3.2b, Iterative (Two Loops) small n and m; just simulate the process with 2D nested loop 157 4.1
busskortet busskortet 3.2c, Three+ Nested Loops, E try all possible 500, 200, and 100 to ensure correctness 704 3.0
cinemaseating cinemaseating 3.2c, Three+ Nested Loops, E 3 nested loops; O(8*R*C); with a small DAT for frequency counter 68 2.5
cudoviste cudoviste 3.2c, Three+ Nested Loops, E 4 nested loops; the inner loops is just 2x2; 5 possibilities of crushed cars; skip 2x2 area that contains building 1194 1.4
fourdierolls fourdierolls 3.2c, Three+ Nested Loops, E 4 nested loops 243 2.6
mathhomework mathhomework 3.2c, Three+ Nested Loops, E 3 nested loops 257 2.1
namnsdag namnsdag 3.2c, Three+ Nested Loops, E 3 nested loops 60 2.0
npuzzle npuzzle 3.2c, Three+ Nested Loops, E 4 nested loops; easy 683 2.2
patuljci patuljci 3.2c, Three+ Nested Loops, E 3 nested loops; n = 9 1123 1.8
radir radir 3.2c, Three+ Nested Loops, E 3 nested loops; never drop any card 70 3.1
restaurantopening restaurantopening 3.2c, Three+ Nested Loops, E 4 nested loops 307 1.9
safehouses safehouses 3.2c, Three+ Nested Loops, E 4 nested loops 261 3.1
set set 3.2c, Three+ Nested Loops, E 4 nested loops; easy 364 1.8
triangledrama triangledrama 3.2c, Three+ Nested Loops, E try all O(N^3) triplets 46 2.5
firefly firefly 3.3a, Binary Search sort stalactites vs stalagmites separately; brute force height; binary search the obstacles hit 323 4.0
massivecardgame massivecardgame 3.3a, Binary Search sort once upfront; upperbound-lowerbound per query 803 3.0
outofsorts outofsorts 3.3a, Binary Search do O(log n) binary searches on unsorted array n times 107 3.7
roompainting roompainting 3.3a, Binary Search sort the cans at shop (can be used more than once); use lower_bound for what Joe needs at shop 416 3.8
synchronizinglists synchronizinglists 3.3a, Binary Search sort and lower_bound 2130 1.5
bootstrappingnumber bootstrappingnumber 3.3b, Bisection and BSTA, E BSTA+exponent 144 2.4
carefulascent carefulascent 3.3b, Bisection and BSTA, E BSTA + Physics simulation 558 1.8
financialplanning financialplanning 3.3b, Bisection and BSTA, E BSTA + observation 108 3.5
freeweights freeweights 3.3b, Bisection and BSTA, E BSTA + simulation; Mathematical observation 356 4.5
hindex hindex 3.3b, Bisection and BSTA, E BSTA + another binary search 460 3.3
htoo htoo 3.3b, Bisection and BSTA, E BSTA + simulation; use DAT 200 2.4
monk monk 3.3b, Bisection and BSTA, E BSTA + simulation; cool 86 3.3
slalom2 slalom2 3.3b, Bisection and BSTA, E BSTA + Physics simulation; also available at UVa 11627 - Slalom 43 5.4
smallschedule smallschedule 3.3b, Bisection and BSTA, E BSTA + greedy or math 302 3.1
speed speed 3.3b, Bisection and BSTA, E LA 8043 - WorldFinals RapidCity17; BSTA + Physics; also available at UVa 01753 - Need for Speed 955 3.2
suspensionbridges suspensionbridges 3.3b, Bisection and BSTA, E BSTA + Maths; be careful of precision error 409 4.6
svada svada 3.3b, Bisection and BSTA, E BSTA + simulation; process the two types of monkeys separately 144 3.5
taxing taxing 3.3b, Bisection and BSTA, E BSTA + simulation; use double; be careful of precision errors 143 4.7
acm2 acm2 3.4b, Involving Sorting, E greedy; sorting 790 2.6
akcija akcija 3.4b, Involving Sorting, E greedy; sorting 2658 2.0
aprizenoonecanwin aprizenoonecanwin 3.4b, Involving Sorting, E greedy; sorting 790 2.5
cocktail cocktail 3.4b, Involving Sorting, E sort; greedy 1191 2.9
fallingapart fallingapart 3.4b, Involving Sorting, E greedy; sorting 1011 1.6
fridge fridge 3.4b, Involving Sorting, E greedy; sorting 429 3.1
gettowork gettowork 3.4b, Involving Sorting, E greedy; sorting 255 2.2
help help 3.4b, Involving Sorting, E greedy; sorting 60 7.5
hotsprings hotsprings 3.4b, Involving Sorting, E greedy; sorting 86 1.9
icpcteamselection icpcteamselection 3.4b, Involving Sorting, E greedy; sorting 586 3.0
linesperhour linesperhour 3.4b, Involving Sorting, E sort; greedy 595 1.7
minimumscalar minimumscalar 3.4b, Involving Sorting, E greedy; sorting 1202 2.3
pikemaneasy pikemaneasy 3.4b, Involving Sorting, E greedy; sorting 473 3.5
pizzubestun pizzubestun 3.4b, Involving Sorting, E sort; greedy every two indices; a bit different between odd and even n 323 2.2
planetaris planetaris 3.4b, Involving Sorting, E greedy; sorting 143 2.8
plantingtrees plantingtrees 3.4b, Involving Sorting, E greedy; sorting 3462 2.0
redistribution redistribution 3.4b, Involving Sorting, E greedy; sorting 537 2.0
sangbok sangbok 3.4b, Involving Sorting, E sort; greedy 200 1.9
shopaholic shopaholic 3.4b, Involving Sorting, E greedy; sorting 959 2.4
stadiljus stadiljus 3.4b, Involving Sorting, E sort; greedy 315 2.2
standings standings 3.4b, Involving Sorting, E greedy; sorting 329 4.1
textmessaging textmessaging 3.4b, Involving Sorting, E greedy; sorting 222 2.9
toflur toflur 3.4b, Involving Sorting, E greedy; sorting 178 2.5
universityzoning universityzoning 3.4b, Involving Sorting, E greedy; sorting; use Manhattan distance to compute distances 122 2.5
woodcutting woodcutting 3.4b, Involving Sorting, E greedy; sorting 572 3.1
annoyedcoworkers annoyedcoworkers 3.4d, Involving PQ greedy PQ simulation 429 3.2
arraysmoothening arraysmoothening 3.4d, Involving PQ greedy PQ simulation 1291 2.6
ballotboxes ballotboxes 3.4d, Involving PQ greedy; priority queue 776 4.4
canvas canvas 3.4d, Involving PQ greedy; priority queue 214 3.5
entertainmentbox entertainmentbox 3.4d, Involving PQ sort; greedy simulation; Priority Queue with update key (we can use multiset) 274 6.0
vegetables vegetables 3.4d, Involving PQ greedy; priority queue 347 3.4
workstations workstations 3.4d, Involving PQ greedy; priority queue 1110 3.6
cartrouble cartrouble 4.2a, Finding CCs graph traversal on forward and reverse graphs 106 4.4
daceydice daceydice 4.2a, Finding CCs reachability test of a state-space graph; s: (r, c, where_is_five) 171 3.5
dominoes2 dominoes2 4.2a, Finding CCs unlike UVa 11504, we treat SCCs as CCs; also available at UVa 11518 - Dominos 2 599 3.3
moneymatters moneymatters 4.2a, Finding CCs see if the sum of vertex weights of each CC = 0 990 3.1
pearwise pearwise 4.2a, Finding CCs clever problem wording; can be reduced into basic graph traversal 159 3.7
reachableroads reachableroads 4.2a, Finding CCs report number of CC-1 892 2.1
sailingfriends sailingfriends 4.2a, Finding CCs find number of CCs without any boat in a medium-sized undirected graph 293 2.5
securitybadge securitybadge 4.2a, Finding CCs reachability test; clever idea to compress ids 87 6.6
skyislands skyislands 4.2a, Finding CCs reachability test 37 2.1
terraces terraces 4.2a, Finding CCs group cells with similar height together; if it cannot flow to any other component with lower height, add the size of th... 339 3.6
wheresmyinternet wheresmyinternet 4.2a, Finding CCs check connectivity to vertex 1 1716 3.7
amoebas amoebas 4.2b, Flood Fill, Easier easy floodfill 1079 1.8
countingstars countingstars 4.2b, Flood Fill, Easier basic flood fill problem; count CCs 1494 2.7
floodit floodit 4.2b, Flood Fill, Easier multiple calls of flood fill tests 74 2.9
fontan fontan 4.2b, Flood Fill, Easier modified multi-sources BFS/floodfill 101 2.2
gold gold 4.2b, Flood Fill, Easier flood fill with extra blocking constraint; also available at UVa 11561 - Getting Gold 735 2.2
wheresmywaterfall wheresmywaterfall 4.2b, Flood Fill, Easier identical with Kattis - fontan 230 3.0
brexit brexit 4.2d, Topological Sort toposort; chain reaction; modified Kahn's algorithm 826 3.6
brexitnegotiations brexitnegotiations 4.2d, Topological Sort toposort with modified Kahn's algorithm; greedy 270 4.8
builddeps builddeps 4.2d, Topological Sort the graph is acyclic; toposort with DFS from the changed file 626 4.7
collapse collapse 4.2d, Topological Sort similar with Kattis - brexit 77 5.8
conservation conservation 4.2d, Topological Sort modified Kahn's algorithm; greedily process all steps in a certain lab before alternating to the other lab 133 4.2
curveknights curveknights 4.2d, Topological Sort input is a DAG; multi-sources, find toposort; propagate using topological order 46 3.3
digicomp2 digicomp2 4.2d, Topological Sort toposort helps avoid TLE; do not simulate the process n times as n can be as big as 10^18 288 5.9
grapevine grapevine 4.2d, Topological Sort BFS variant; like Kahn's algorithm, only propagate from a person once his/her skepticism level is cleared; be careful wi... 84 6.4
managingpackaging managingpackaging 4.2d, Topological Sort if the graph is cyclic, output 'cannot be ordered'; otherwise, find the lexicographically smallest topological order 128 5.9
pickupsticks pickupsticks 4.2d, Topological Sort cycle check + toposort if DAG; also available at item UVa 11686 - Pick up sticks 373 4.7
amanda amanda 4.2e, Graph Properties Check add edge only among airports where only one end point has lounge; bicolouring/bipartite check; pick colour with smaller ... 368 5.2
ballsandneedles ballsandneedles 4.2e, Graph Properties Check cycle check on 2 similar graphs; easier solution exists 161 3.2
breakingbad breakingbad 4.2e, Graph Properties Check check if we can decompose the vertices into two disjoint sets; bipartite graph check 643 4.2
hoppers hoppers 4.2e, Graph Properties Check the answer is number of CC-1 if there is at least one non-bipartite component in the graph; or number of CC otherwise 234 3.9
molekule molekule 4.2e, Graph Properties Check undirected tree is also Bipartite/bi-colorable; bi-color it with 0 and 1; direct all edges from 0 to 1 (or vice versa) 175 3.5
pubs pubs 4.2e, Graph Properties Check isolated vertex has no solution; this is actually not a bipartite graph check; we can do alternate labeling of vertices ... 216 3.5
runningmom runningmom 4.2e, Graph Properties Check find a cycle in a directed graph 591 3.8
torn2pieces torn2pieces 4.2e, Graph Properties Check construct graph from strings; traversal from source to target; reachability check; print path 1115 3.6
ads ads 4.2h, Really Ad Hoc modified traversal; can we reach an illegal character from a frame - remove that ads once 218 5.1
brickwall brickwall 4.2h, Really Ad Hoc s: (n1, n2, n3); number of type 1/2/3 bricks used so far; max is (c1, c2, c3); prefix sum to check if a position has a b... 91 5.1
connectn connectn 4.2h, Really Ad Hoc ad hoc straight-line (implicit) graph traversal 397 3.1
droppingdirections droppingdirections 4.2h, Really Ad Hoc modified graph: a vertex is (origin intersection id, intersection id); modified DFS from vertices leading to goal; count... 87 3.5
faultyrobot faultyrobot 4.2h, Really Ad Hoc interesting graph traversal variant 182 4.5
promotions promotions 4.2h, Really Ad Hoc modified DFS; special graph; DAG; also available at UVa 13015 - Promotions 129 5.5
silueta silueta 4.2h, Really Ad Hoc 2D grid processing initially; modified DFS to count perimeter of polygon in grid 37 5.3
succession succession 4.2h, Really Ad Hoc (upwards) traversal of family DAG; use unordered_maps; make the founder has very large starting blood to avoid fraction 165 3.1
buttonbashing buttonbashing 4.4a, SSSP, BFS, Easier very similar to UVa 12160 728 3.4
elevatortrouble elevatortrouble 4.4a, SSSP, BFS, Easier s: (cur_level); only 1M floors; go up/down; BFS 362 3.1
grid grid 4.4a, SSSP, BFS, Easier modified BFS with step size multiplier 1026 2.8
horror horror 4.4a, SSSP, BFS, Easier SSSP from all sources = horror movies; report lowest ID with the highest unweighted SSSP distance 500 3.3
interplanetarytunnels interplanetarytunnels 4.4a, SSSP, BFS, Easier simple BFS from pa; output dist[pb]/2 (round up) 273 2.2
modulosolitaire modulosolitaire 4.4a, SSSP, BFS, Easier s: (cur_sj); try all n (n ≤ 10) possible moves; BFS 286 3.0
onaveragetheyrepurple onaveragetheyrepurple 4.4a, SSSP, BFS, Easier reading comprehension; the answer is just unweighted SSSP from 1 to N, minus one; BFS 518 3.1
spiral spiral 4.4a, SSSP, BFS, Easier generate the 2D 100x100 spiraling grid first; involving small primes; BFS 148 3.5
wettiles wettiles 4.4a, SSSP, BFS, Easier multi-sources BFS; limited flood fill or unweighted SSSP limited to step T 227 3.6
grasshopper grasshopper 4.4c, Knight Moves BFS on implicit Knight jump graph 136 4.0
hidingplaces hidingplaces 4.4c, Knight Moves SSSP from (r, c); find cells with max distance; print 607 1.9
knightjump knightjump 4.4c, Knight Moves unweighted SSSP from the cell that contains 'K' to (1, 1) using Knight jump movements; avoid '#' cells 292 2.5
flowerytrails flowerytrails 4.4d, SSSP, Dijkstra, Easier Dijkstra's; record predecessor graph as there can be multiple shortest paths; also available at UVa 12878 - Flowery Trai... 305 3.9
george george 4.4d, SSSP, Dijkstra, Easier not easy, rating deceptive: Dijkstra's but with a few constraints; some roads are blocked at certain timings; similar wi... 205 2.0
getshorty getshorty 4.4d, SSSP, Dijkstra, Easier log(f) when f in [0..1] is negative; log(f1 * f2 * ... * fn) = log(f1) + log(f2) + ... + log(fn); longest path; use max... 1572 3.4
hopscotch50 hopscotch50 4.4d, SSSP, Dijkstra, Easier MSSP from all 1s; implicit weighted graph; stop at first cell with value k 200 2.3
shortestpath1 shortestpath1 4.4d, SSSP, Dijkstra, Easier very standard Dijkstra's problem 1470 3.5
shortestpath2 shortestpath2 4.4d, SSSP, Dijkstra, Easier Dijkstra's with modification; edges only available periodically; be careful with P = 0 case 423 3.9
subway2 subway2 4.4d, SSSP, Dijkstra, Easier use basic geometry skill to build the weighted graph; then run Dijkstra's; also available at UVa 10389 - Subway 70 5.9
texassummers texassummers 4.4d, SSSP, Dijkstra, Easier Dijkstra's; complete weighted graph; print path 97 4.0
crosscountry crosscountry 4.4f, SSSP, -ve weight medium complete graph with N ≤ 1000; Bellman-Ford can still pass (or use Dijkstra's) 217 3.0
hauntedgraveyard hauntedgraveyard 4.4f, SSSP, -ve weight Bellman-Ford; negative cycle check needed 95 8.2
shortestpath3 shortestpath3 4.4f, SSSP, -ve weight Bellman-Ford; do DFS/BFS from vertices that are part of any negative cycle 524 5.1
xyzzy xyzzy 4.4f, SSSP, -ve weight check 'positive' cycle; check connectedness; also available at UVa 10557 152 6.7
ecoins ecoins 8.2b, State-Space, BFS, E s: (conventional-value, infotechnological-value); BFS; also available at UVa 10306 - e-Coins 169 4.6
flipfive flipfive 8.2b, State-Space, BFS, E s: (bitmask); only 2^9 = 512 grid configurations; BFS 621 2.7
hydrasheads hydrasheads 8.2b, State-Space, BFS, E s: (cur_H, cur_T); BFS; but easier solution exists 551 1.7
illiteracy illiteracy 8.2b, State-Space, BFS, E s: (string); 6 different transition rules; BFS 126 2.9
safe safe 8.2b, State-Space, BFS, E s: (convert 3x3 grid into a base 4 integer); BFS 181 3.0
bigtruck bigtruck 8.2d, State-Space, Dijkstra s: (city, items_picked); use Dijkstra's 1144 3.2
bumped bumped 8.2d, State-Space, Dijkstra s: (city, has_use_free_ticket); use Dijkstra's 545 4.4
destinationunknown destinationunknown 8.2d, State-Space, Dijkstra use Dijkstra's twice; one normally; one with s: (point, has_edge_g_h_used); compare the results 101 5.6
justpassingthrough justpassingthrough 8.2d, State-Space, Dijkstra s: (r, c, n_left); Dijkstra's/SSSP on DAG 92 5.1
kitchen kitchen 8.2d, State-Space, Dijkstra s: (volume_of_the_n_cups); t: try all possible pourings; use Dijkstra's 152 3.5
quantum quantum 8.2d, State-Space, Dijkstra s: (bitmask); t: all of the nop operations; use Dijkstra's 82 3.3
rainbowroadrace rainbowroadrace 8.2d, State-Space, Dijkstra s: (pos, bitmask_of_7_colors); use Dijkstra's 101 2.9
treasure treasure 8.2d, State-Space, Dijkstra s: (day, k_left, cur_r, cur_c); use Dijkstra's 118 8.0
xentopia xentopia 8.2d, State-Space, Dijkstra s: (u, k1_used, k2_used); use Dijkstra's 184 4.6

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