Competitive Programming

Methods to Solve (2000-present)

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

OJ: , Topic: , Quality: , Difficulty:

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Note that we only update DACU column manually when we first entered the hint (thus an outdated data).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+5 Hint DACU Point
carrots carrots 1.4a, One-Liner I/O just print P 15155 1.3
hello hello 1.4a, One-Liner I/O just print "Hello World!" 39217 1.2
thelastproblem thelastproblem 1.4a, One-Liner I/O S can have space(s) 76 1.8
r2 r2 1.4b, I/O + Sequences Only just print 2*S-R1 14929 1.2
conteststruggles conteststruggles 1.4c, Selection Only, 2 Cases simple formula; check if answer in [0..100] 729 2.2
isithalloween isithalloween 1.4c, Selection Only, 2 Cases if-else; 2 cases 3761 1.3
laptopsticker laptopsticker 1.4c, Selection Only, 2 Cases if-else; 2 cases; note: one centimeter for both sides 3329 1.5
moscowdream moscowdream 1.4c, Selection Only, 2 Cases if-else; 2 cases; check n ≥ 3 3902 1.8
vajningsplikt vajningsplikt 1.4c, Selection Only, 2 Cases selection; multiple cases; be careful 788 2.1
grading grading 1.4d, Selection Only, 3+ Cases 6 cases 2744 1.5
onechicken onechicken 1.4d, Selection Only, 3+ Cases 4 cases; piece vs pieces 6464 1.6
provincesandgold provincesandgold 1.4d, Selection Only, 3+ Cases 6 cases 4756 1.4
sith sith 1.4d, Selection Only, 3+ Cases 3 cases 1137 1.6
temperature temperature 1.4d, Selection Only, 3+ Cases 3 cases; derive formula 1776 2.2
testdrive testdrive 1.4d, Selection Only, 3+ Cases 4 cases 848 2.1
different different 1.4e, Repetition Only use abs function per test case 8964 2.3
qaly qaly 1.4e, Repetition Only trivial loop 5955 1.2
tarifa tarifa 1.4e, Repetition Only one pass; array not needed 9768 1.3
timeloop timeloop 1.4e, Repetition Only just print 'num Abracadabra' N times 17170 1.3
eligibility eligibility 1.4f, Multiple TC + Selection 3 cases 1741 1.6
helpaphd helpaphd 1.4f, Multiple TC + Selection 2 cases 2044 1.6
leftbeehind leftbeehind 1.4f, Multiple TC + Selection 4 cases 2014 1.6
oddities oddities 1.4f, Multiple TC + Selection 2 cases 11523 1.3
licensetolaunch licensetolaunch 1.4g, Control Flow, Level 1 easy linear pass 1969 1.4
oddgnome oddgnome 1.4i, Control Flow, Level 3 linear pass 2388 1.6
statistics statistics 1.4i, Control Flow, Level 3 one pass; array not needed 2942 1.7
artichoke artichoke 1.4j, Function LA 7150 - WorldFinals Marrakech15; linear scan; probably one of the easiest WorldFinals problem; also available at UVa 0... 1390 2.8
digits digits 1.4j, Function direct simulation; also available at UVa 11687 - Digits 214 3.5
filip filip 1.4j, Function create a 'reverse string' function; then if-else check 6345 1.3
mia mia 1.4j, Function just if-else check 1136 2.1
acm acm 1.4k, 1D Array, Easier simple simulation; one pass 3526 1.5
cetiri cetiri 1.4k, 1D Array, Easier sort 3 number helps; 3 cases 1165 1.9
lineup lineup 1.4k, 1D Array, Easier sort ascending/descending and compare; or linear pass 3703 1.6
lostlineup lostlineup 1.4k, 1D Array, Easier simple 1D array manipulation 550 1.5
hakkari hakkari 1.4l, 2D Array, Easier find indices of the '*' 659 1.3
batterup batterup 1.4m, Easy easy one loop 4542 1.3
hangingout hangingout 1.4m, Easy simple loop 2218 1.3
hissingmicrophone hissingmicrophone 1.4m, Easy simple loop 7690 1.3
stopwatch stopwatch 1.4m, Easy linear pass; simulation 390 1.3
bossbattle bossbattle 1.4n, Still Easy trick question 1391 1.8
peasoup peasoup 1.4n, Still Easy one linear pass 771 2.4
thanos thanos 1.4n, Still Easy simple simulation; R is at least 2 2503 2.5
vote vote 1.4n, Still Easy follow the requirements 1584 2.2
basicprogramming1 basicprogramming1 1.4o, Medium a nice summative problem for programming examination of a basic programming methodology course 201 4.0
battlesimulation battlesimulation 1.4o, Medium one pass; special check on 3! = 6 possible combinations of 3 combo moves 900 2.8
bitsequalizer bitsequalizer 1.4o, Medium analyzing patterns; also available at UVa 12545 - Bits Equalizer 174 4.5
conundrum conundrum 1.5b, Cipher, Easier simple cipher 5240 1.4
encodedmessage encodedmessage 1.5b, Cipher, Easier simple 2D grid cipher 2316 1.4
t9spelling t9spelling 1.5b, Cipher, Easier similar to (the reverse of) UVa 12896 2425 1.7
anewalphabet anewalphabet 1.5c, Cipher, Medium simple cipher; 26 characters 4154 1.8
piglatin piglatin 1.5c, Cipher, Medium simple; check the vowels that include 'y' and process it 916 2.1
secretmessage secretmessage 1.5c, Cipher, Medium just do as asked; use 2D grid 2866 1.7
tajna tajna 1.5c, Cipher, Medium simple 2D grid cipher 471 2.1
autori autori 1.5d, Input Parsing (Iter) simple string tokenizer problem 11602 1.2
pervasiveheartmonitor pervasiveheartmonitor 1.5d, Input Parsing (Iter) simple parsing; then finding average 950 1.7
timebomb timebomb 1.5d, Input Parsing (Iter) just a tedious input parsing problem; divisibility by 6 1174 1.8
display display 1.5e, Output Formatting, E unordered_map; map a digit -> enlarged 7x5 version 635 2.5
musicalnotation musicalnotation 1.5e, Output Formatting, E simple but tedious 421 2.0
skener skener 1.5e, Output Formatting, E enlarging 2D character array 2067 1.5
ptice ptice 1.5f, Easy, Involving String just a simple simulation 2100 1.5
sevenwonders sevenwonders 1.5f, Easy, Involving String one pass 4776 1.4
yinyangstones yinyangstones 1.5f, Easy, Involving String trick question; just check if number of whites equals to number of blacks 1365 1.8
bela bela 1.6a, Game (Card) simple card scoring problem 3731 1.3
memorymatch memorymatch 1.6a, Game (Card) interesting simulation game; many corner cases 161 4.0
pokerhand pokerhand 1.6a, Game (Card) frequency count; report max 2173 1.4
shuffling shuffling 1.6a, Game (Card) simulate card shuffling operation 218 2.8
chess chess 1.6b, Game (Chess) bishop movements; either impossible, 0, 1, or 2 ways - one of this can be invalid; just use brute force 856 2.9
empleh empleh 1.6b, Game (Chess) the reverse problem of Kattis - helpme 245 1.8
helpme helpme 1.6b, Game (Chess) convert the given chess board into chess notation 302 2.4
connectthedots connectthedots 1.6c, Game (Others), Easier classic children game; output formatting 213 3.6
gamerank gamerank 1.6c, Game (Others), Easier simulate the ranking update process 732 3.9
guessinggame guessinggame 1.6c, Game (Others), Easier use a 1D flag array; also available at UVa 10530 - Guessing Game 684 2.7
battleship battleship 1.6d, Game (Others), Harder simulation; reading comprehension; many corner cases 120 5.4
rockpaperscissors rockpaperscissors 1.6d, Game (Others), Harder count wins and losses; output win average; also available at UVa 10903 - Rock-Paper-Scissors ... 820 3.7
tictactoe2 tictactoe2 1.6d, Game (Others), Harder check validity of Tic Tac Toe game; tricky; also available at UVa 10363 - Tic Tac Toe 167 5.3
turtlemaster turtlemaster 1.6d, Game (Others), Harder interesting board game to teach programming for children; simulation 323 2.9
chopin chopin 1.6e, Real Life, Easier you can learn a bit of music with this problem 823 1.8
compass compass 1.6e, Real Life, Easier your typical smartphone's compass function usually has this small feature 1529 2.0
fizzbuzz fizzbuzz 1.6e, Real Life, Easier actually just about easy divisibility properties 10274 1.3
trainpassengers trainpassengers 1.6e, Real Life, Easier create a verifier; be careful of corner cases 1807 2.1
wertyu wertyu 1.6e, Real Life, Easier use 2D mapper array to simplify the problem; also available at UVa 10082 - WERTYU 768 2.9
beatspread beatspread 1.6f, Real Life, Medium be careful with boundary cases!; also available at UVa 10812 - Beat the Spread 980 2.4
luhnchecksum luhnchecksum 1.6f, Real Life, Medium very similar (~95%) to UVa 11743 836 1.6
toilet toilet 1.6f, Real Life, Medium simulation; be careful of corner cases 1756 2.4
wordcloud wordcloud 1.6f, Real Life, Medium just a simulation; but be careful of corner cases 322 2.4
creditcard creditcard 1.6g, Real Life, Harder real life issue; precision error issue if we do not convert double (with just 2 digits after decimal point) into long lo... 123 6.3
tenis tenis 1.6g, Real Life, Harder Tennis scoring rules; tricky test cases; be careful 78 5.0
friday friday 1.6h, Time, Easier the answer depends on the start day of the month 1059 1.9
justaminute justaminute 1.6h, Time, Easier linear pass; total seconds/(total minutes*60) 1512 1.7
marswindow marswindow 1.6h, Time, Easier simple advancing of year and month by 26 months or 2 years+2 months each; direct formula exists 830 2.0
savingdaylight savingdaylight 1.6h, Time, Easier convert hh:mm to minute; compute difference of ending and starting; then convert minute to hh:mm again 986 2.1
bestbefore bestbefore 1.6i, Time, Harder tedious; 3! = 6 possibilities to check 148 4.0
birthdayboy birthdayboy 1.6i, Time, Harder convert mm-dd into [0..364]; use DAT; find largest gap via brute force 108 4.6
natrij natrij 1.6i, Time, Harder convert hh:mm:ss to seconds; make sure the second time is larger than the first time; corner case: 24:00:00 1136 2.6
timezones timezones 1.6i, Time, Harder follow the description, tedious; also available at UVa 10371 - Time Zones 67 5.3
rimski rimski 1.6j, Roman Numerals to Roman/to Decimal conversion problem; use next permutation to be sure 118 4.5
romanholidays romanholidays 1.6j, Roman Numerals generate and sort the first 1K Roman strings; ''M'' is at index 945; append prefix 'M' for numbers larger than 1K 92 3.6
asciiaddition asciiaddition 1.6k, Time Waster, Easier a+b problem in text format 509 1.9
glitchbot glitchbot 1.6k, Time Waster, Easier O(n^2) simulation; only output one answer 1036 2.0
pachydermpeanutpacking pachydermpeanutpacking 1.6k, Time Waster, Easier time waster; simple one loop simulation 322 1.9
printingcosts printingcosts 1.6k, Time Waster, Easier clear time waster; the hard part is in parsing the costs of each character in the problem description 705 2.2
froggie froggie 1.6l, Time Waster, Harder just a simulation; but many corner cases; S can be 0 296 6.8
functionalfun functionalfun 1.6l, Time Waster, Harder just follow the description; 5 cases; tedious parsing problem; requires a kind of mapper 487 1.9
windows windows 1.6l, Time Waster, Harder LA 7162 - WorldFinals Marrakech15; tedious simulation problem; also available at UVa 01721 - Window Manager 92 7.6

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