cho.sh

Problems

Pick a problem and write your solution in the built-in editor. The judge runs it against real test cases while you watch, and the wider archive is open to read whenever you like.

Total results1,020 problems
TitleLevelTopicsSolvedTime limitMemory limitJudge
The Perfect SymmetryGiven a set of distinct integer points, decide whether it has a center of symmetry and, if so, print that center to one decimal place.Medium5Hash mapGeometry+2No attempts yet1s128 MBJudgeable
Spies Like UsGiven a bipartite graph, decide whether any two vertices on the same side share at most one common neighbor on the other side.Medium5GraphHash map+2No attempts yet2s512 MBJudgeable
Degrees of SeparationMaintain a friendship graph under edge insertions and deletions, and answer queries about friend counts, friends-of-friends counts, and shortest-path distance between two people.Medium5GraphBFS+2No attempts yet1s128 MBJudgeable
SnowflakesGiven up to 100,000 snowflakes of six arm lengths each, find whether two are identical under cyclic rotation or reversal.Medium5Hash mapString+2No attempts yet1s128 MBJudgeable
ScribbleGiven seven tiles with letter values and a dictionary of up to 100000 words, find the highest-scoring dictionary word formable from the tiles, or 0 if none is.Medium5StringHash map+2No attempts yet1s128 MBJudgeable
SpamCount trigram frequencies in sample spam and non-spam messages, then classify each test message by which sample it matches more closely under the cosine similarity measure.Medium5StringHash map+2No attempts yet1s128 MBJudgeable
ChocolateGiven an M by N grid of labels, decide whether every label occupies exactly one solid axis-aligned rectangle.Medium5MatrixImplementation+1No attempts yet1s1024 MBJudgeable
Dynamic Declaration Language (DDL)Simulate a tiny language with dynamic variable declarations, jumps, and increments, printing a repeated-declaration or undeclared-reference error each time one occurs.Medium5SimulationImplementation+2No attempts yet1s128 MBJudgeable
Spell CheckerGiven a dictionary and query words, mark each query correct, or list dictionary words reachable by one deletion, replacement, or insertion.Medium5StringHash map+2No attempts yet1s128 MBJudgeable
CocktailsSimulate Angelo's cocktail mixing rules, track each cocktail's counts, and print the top ten by count then recipe-book order with computed prices.Medium5SimulationHash map+2No attempts yet1s128 MBJudgeable
Reconstructing Binary TreesGiven the pre-order and in-order traversals of a binary tree with distinct labels, print its post-order traversal or report that no tree matches.Medium5TreeRecursion+2No attempts yet1s128 MBJudgeable
Random GapGiven a linear congruential generator, find the largest gap between neighboring distinct values the sequence produces.Medium5SimulationHash map+2No attempts yet4s128 MBJudgeable
Binary WitchGiven a binary string, predict the next L digits by matching suffixes of length 13 down to 1 against earlier occurrences, using the rightmost match.Medium5StringString matching+2No attempts yet1s128 MBJudgeable
BalanceGiven weights, split some into two equal-sum disjoint groups; find the largest weight that can be the heaviest used one.Medium5Dynamic programmingSorting+2No attempts yet3s128 MBJudgeable
RepetitionsGiven up to five lowercase words of length at most 2000, find the length of the longest substring that appears as a contiguous fragment in every word.Medium5StringBinary search+2No attempts yet3s128 MBJudgeable
Paper StripFind the longest contiguous block of numbers that adds up to exactly s, or print BRAK when none exists.Medium5Hash mapPrefix sumNo attempts yet1s128 MBJudgeable
RadiotelegraphGiven n integers and at most w changes to any values, find the longest run of equal numbers achievable.Medium5Sliding windowHash mapNo attempts yet1s128 MBJudgeable
Domino TilesCount pip frequencies to find the two odd endpoints of the domino chain, or report ambiguity when the chain can start anywhere.Medium5GraphHash mapNo attempts yet1s128 MBJudgeable
Poetry with an AsteriskCount for each one-asterisk query how many dictionary words start with its prefix and end with its suffix without overlap.Medium5Hash mapStringNo attempts yet5s128 MBJudgeable
Word Translation LookupGiven pairs of directly translated words, list every target-language word linked to each query word through translation chains.Medium5Union-findHash map+1No attempts yet12s128 MBJudgeable
MCSCount every length-k substring of a DNA string by its letter composition and report the size of the largest group.Medium5Sliding windowHash mapNo attempts yet5s128 MBJudgeable
SymmetryDecide whether the given dots mirror exactly across some vertical line, printing YES or NO for each test case.Medium5Hash mapGeometry+1No attempts yet1s128 MBJudgeable
RankingsPlayers accumulate points through updates and each query asks for the current rank of one player among up to 100000 players.Medium5Segment treeSorting+1No attempts yet3s128 MBJudgeable
SpaceCount, for each test case, the pairs of up to 100000 points whose Euclidean distance is strictly less than d.Medium5Hash mapGeometryNo attempts yet1s128 MBJudgeable
Call Me Back, Please!Read call records with start times and durations and list every pair of numbers with opposite-direction calls that fit in one 24-hour window.Medium5Two pointersHash map+2No attempts yet1s128 MBJudgeable
Cracking the CodeGiven a plaintext and ciphertext candidates under a substitution cipher, keep every consistent match and decrypt X, printing '?' for ambiguous letters.Medium5String matchingBrute force+1No attempts yet2s128 MBJudgeable
Decimal Representation LengthFor each n, report the longest decimal writing among all fractions a/b with a and b from 1 to n, where the count includes digits, the point, and parentheses.Medium5SimulationHash map+2No attempts yet1s128 MBJudgeable
Encrypted passwordDecide whether the original password's letters can be rearranged to match a contiguous block inside the encrypted password.Medium5Sliding windowHash map+1No attempts yet2s128 MBJudgeable
Joe is learning to speakTrack every word block up to length n from known sentences and ask about each unknown word and each new sentence with an unseen block.Medium5Hash mapSliding window+1No attempts yet3s128 MBJudgeable
Trending TopicMaintain word counts over a rolling 7-day window and answer each top N query in frequency order with ties included.Medium5Sliding windowHash map+1No attempts yet1s128 MBJudgeable
SMS PollNormalize phone formats to identify each sender, keep only the earliest valid vote per sender, and print truncated percentages and participant count.Medium5StringHash map+1No attempts yet1s128 MBJudgeable
Find the MarblesGiven up to 99 distinct integer points per test case, report the largest number of points that lie on one straight line.Medium5GeometryHash mapNo attempts yet1s128 MBJudgeable
Alike TablesDecide whether two tables with distinct entries match after any row and column reorderings.Medium5Hash mapMatrixNo attempts yet1s128 MBJudgeable
ChorusFor each lyric, find its longest repeated substring and list which songs contain each query as a substring of it.Medium5String matchingBinary search+1No attempts yet1s128 MBJudgeable
Fair PhotographyAfter sorting cows by position, find the widest interval with equal numbers of G and H cows, where single-breed intervals also count.Medium5Prefix sumHash map+1No attempts yet1s128 MBJudgeable
Gondola sequence checkDecide whether n observed gondola numbers could appear as consecutive passings on a circle where broken gondolas are replaced in order by numbered spares.Medium5SimulationHash map+1No attempts yet1s256 MBJudgeable
Gondola ReplacementGiven the n cars seen on a circular gondola line, find one possible order of breakdowns that explains the observed numbers.Medium5SortingHash mapNo attempts yet1s256 MBJudgeable
Distinct Subarray GCDsCount the distinct GCD values taken over all contiguous subarrays for each test case.Medium5Number theoryDynamic programming+1No attempts yet5s256 MBJudgeable
Hexagonal colonyChoose hexagonal cell blocks so the exposed wall windows house at least P people with the fewest blocks.Medium5GreedyGeometry+2No attempts yet1s256 MBJudgeable
Top 25 Poll ComparisonSplit two rankings of the same teams into the smallest consecutive groups that hold the same teams and print each size.Medium5GreedyHash mapNo attempts yet10s256 MBJudgeable
Mushroom tractorMushrooms appear one per second, and the goal is the earliest second when some row, column, or diagonal contains at least K of them.Medium5Hash mapMathNo attempts yet2s32 MBJudgeable
Cow Routing IIFind the cheapest fare from city A to city B using at most two ordered flight routes, paying each used route full fare.Medium5Brute forceHash mapNo attempts yet1s256 MBJudgeable
Color BallsFor each ball, add up the sizes of all strictly smaller balls with a different color.Medium5SortingPrefix sum+1No attempts yet1s256 MBJudgeable
DimensionsConvert defined units and evaluate each expression, printing results in SI base units or Incompatible for mismatched dimensions.Medium5ImplementationHash map+1No attempts yet1s256 MBJudgeable
Goblin Garden GuardsCount how many of up to 100000 points remain uncovered by 20000 sprinkler circles of radius at most 100.Medium5GeometryHash mapNo attempts yet3s256 MBJudgeable
Number of distinct substringsCount how many different contiguous substrings appear in a lowercase string of length up to 1000.Medium5String matchingHash map+1No attempts yet1s512 MBJudgeable
Pyro TubesFor each value in a sorted list, count larger list values whose 18-bit patterns differ in at most two bits.Medium5Bit manipulationHash mapNo attempts yet13s256 MBJudgeable
Fraction to Repeating DecimalWrite each given fraction as its decimal form with the shortest nonrepeating part and the repeating block in parentheses.Medium5Hash mapMath+1No attempts yet1s256 MBJudgeable
A Strange SequenceYou get the first N terms, each later term equals the count of distinct values before it, and you must output the Mth term.Medium5SimulationHash map+1No attempts yet1s64 MBJudgeable
Mr. Kim's Grocery Store (Small)Given the sorted pile of 2N mixed normal and discounted price tags, recover the N sale prices.Medium5GreedyHash map+1No attempts yet5s512 MBJudgeable
Kim Incheon's Grocery Store (Large)Given 2N sorted tags that pair N sale prices with regular prices at 4/3 of each sale price, recover the N sale tags.Medium5GreedyHash map+1No attempts yet5s512 MBJudgeable
Robot Rock Band (Small)Count quadruples with one element from each of four lists whose bitwise XOR equals K.Medium5Hash mapBrute forceNo attempts yet5s512 MBJudgeable
Robot Rock Band (Large)Count quadruples with one element from each of four lists whose bitwise XOR equals K.Medium5Hash mapBit manipulationNo attempts yet7s512 MBJudgeable
Equal Subset Sums (Small)For each set of 20 distinct numbers, print two different non-empty subsets with equal sum in code order, or Impossible.Medium5Brute forceHash mapNo attempts yet5s512 MBJudgeable
Equal SumsGiven up to 20 distinct numbers, print the two lexicographically smallest distinct subsets that share the smallest repeated sum, or Impossible.Medium5Brute forceHash map+1No attempts yet20s512 MBJudgeable
Recycled Numbers (Large)Count pairs n < m in [A, B] with equal digits where m is a rotation of n with no leading zero, counting each pair once.Medium5StringBrute force+1No attempts yet5s512 MBJudgeable
N-dimensional travelGiven a walk on an N-dimensional integer grid as a list of coordinate indices and signs, decide whether all visited points, including start and end, are distinct.Medium5Hash mapImplementation+2No attempts yet2s512 MBJudgeable
Nice PairsCount pairs (x, y) with A <= x < y <= B where y is a rotation of x's digits (a suffix moved to the front), counting duplicates only once.Medium5StringMath+2No attempts yet2s512 MBJudgeable
Turning A into BGiven two equal-length uppercase strings A and B, find the minimum number of moves that bring a chosen character to the front of A so that A becomes B, or -1 if impossible.Medium5StringGreedy+2No attempts yet2s512 MBJudgeable
Intervals of Unique NumbersCount pairs (i, j) where the subarray from i to j has all distinct values, with N up to 100000.Medium5Two pointersSliding window+2No attempts yet1s32 MBJudgeable
DwarvesGiven strict size comparisons between named dwarves, decide whether the statements are mutually consistent.Medium5GraphTopological sort+2No attempts yet2s512 MBJudgeable
Minimum SwapsGiven permutations A and B, find the minimum number of swaps within A that turn it into B.Medium5ArrayHash map+2No attempts yet1s64 MBJudgeable
Memory MatchGiven the history of a Memory match game, find how many pairs you can guarantee scoring on the current turn.Medium5SimulationHash map+1No attempts yet5s512 MBJudgeable
Hidden AnagramsGiven two lowercase strings s1 and s2, find the maximum length of a substring of s1 that is an anagram of some substring of s2.Medium5Hash mapString+2No attempts yet10s512 MBJudgeable
Number of arithmetic triplesCount index triples i < j < k where the three values A_i, A_j, A_k form an arithmetic progression.Medium5Hash mapMathNo attempts yet3s512 MBJudgeable
Rouba-MonteSimulate a card game where players draw, steal montes, and discard mismatches; report the winners by monte size.Medium5SimulationImplementation+2No attempts yet1s512 MBJudgeable
Command HistoryGiven a sequence of positions in a command history, simulate running each command by the nearest occurrence and total the up-arrow presses needed.Medium5ArrayHash map+2No attempts yet1s512 MBJudgeable
Chinese ClassicsGiven letters with returning marks (Re marks and numbered jump marks), simulate the reading rules and print the order in which letters are read.Medium5SimulationImplementation+1No attempts yet8s512 MBJudgeable
Cities and StatesGiven up to 200,000 cities with names and two-letter state codes, count unordered pairs whose first two name letters match the other city's state code and vice versa, with different states.Medium5Hash mapString+2No attempts yet2s512 MBJudgeable
Arithmetic and Geometric SequencesCount integers from 1 to u that lie in an arithmetic sequence or a geometric sequence, counting overlaps only once.Medium5MathHash map+2No attempts yet2s512 MBJudgeable
Codejamon Cipher (Small)For each enciphered string, count the sentences of vocabulary words whose letter multisets concatenate to it, modulo 1e9+7.Medium5Dynamic programmingHash map+1No attempts yet5s512 MBJudgeable
Phone Number Riddle (Small)Given a shuffled string formed from the English words of a phone number's digits, recover the digits, which are guaranteed to be in ascending order.Medium5StringHash map+2No attempts yet5s512 MBJudgeable
Phone Number Riddle (Large)A shuffled concatenation of the English words for a phone number's digits is given; recover the digits, which are in ascending order.Medium5StringHash map+2No attempts yet5s512 MBJudgeable
PasswordsCount ordered pairs of distinct passwords where one string is a substring of the other, treating the passwords as a multiset of short strings.Medium5String matchingHash map+1No attempts yet1s64 MBJudgeable
Killer SudokuRead a 19 by 37 ASCII diagram of a Killer Sudoku grid plus one sum per cage, and report OK or NotOK for all constraints.Medium5ImplementationSimulation+2No attempts yet1s512 MBJudgeable
Easy QuestGiven a sequence of gifts (+type), costs (-type), and unicorns (0), decide if every cost can be paid and choose the lexicographically smallest item type for each unicorn.Medium5GreedyImplementation+2No attempts yet3s512 MBJudgeable
Cakey McCakeFaceGiven sorted entry and exit timestamps, find the smallest nonnegative time difference d that maximizes how many entry times t satisfy t + d is an exit time.Medium5Hash mapArray+2No attempts yet7s512 MBJudgeable
Counting the closest pair sumsGiven n integers and a target v, count how many index pairs have a sum whose distance from v is as small as possible.Medium5SortingTwo pointers+2No attempts yet2s512 MBJudgeable
Martian DNAGiven a string over K symbols and minimum counts for R of them, find the length of the shortest contiguous substring meeting all the quotas, or report impossible.Medium5Sliding windowArray+2No attempts yet2s1024 MBJudgeable
Rotating SushiOn a circular belt of N sushi plates, find the maximum number of distinct kinds in any k consecutive plates, counting the coupon kind c once more if it is not already present.Medium5Sliding windowTwo pointers+2No attempts yet1s512 MBJudgeable
Longest Consecutive SubsequenceGiven an integer sequence, find the longest subsequence whose values form an arithmetic run with common difference 1, keeping the original order.Medium5Dynamic programmingHash map+1No attempts yet2s256 MBJudgeable
Pants On FireGiven n true statements of the form "a are worse than b" that form a partial order, classify each of m queries as Fact, Alternative Fact, or Pants on Fire by transitive reachability.Medium5GraphDFS+2No attempts yet2s512 MBJudgeable
Life on a TorusSimulate Conway's Life on a wrapped 8x8 torus and find the smallest repeat period reached after any transient.Medium5SimulationHash map+1No attempts yet2s512 MBJudgeable
Magic WeaponCount triples of details, one per color, where the red number's first and last digits match the green's last digit and the blue's first digit, and all three model numbers differ.Medium5CombinatoricsMath+2No attempts yet2s512 MBJudgeable
H to OCount each atom's total from the input formula multiplied by k and from the output formula, then divide each element's counts to find the smallest quotient, the output count.Medium5StringHash map+2No attempts yet1s512 MBJudgeable
Building a FieldGiven N points on a circle with arc lengths between consecutive points, decide whether four trees are the vertices of some rectangle.Medium5Hash mapGeometry+2No attempts yet2s512 MBJudgeable
Email DestructionGiven n, k and k distinct shuffled email subjects of repeated 'Re: ' prefixes plus letters, decide whether exactly n emails could have existed before deletion.Medium5StringHash map+1No attempts yet3s512 MBJudgeable
Surface Area of CubesGiven an A x B x C block of unit cubes with N cubes removed (including interior ones), compute the total surface area including surfaces of interior cavities.Medium5Hash mapMath+2No attempts yet5s512 MBJudgeable
SiblingsGiven each woman's mother as an index, count pairs of women who share the same mother across several data sets.Medium5Hash mapSorting+1No attempts yet2s512 MBJudgeable
JuniorGiven names in birth order with optional junior or iii suffixes, count people who have no earlier possible parent under the naming rules, which is the number of families.Medium5Hash mapString+1No attempts yet2s512 MBJudgeable
String GuessingGiven all 2N-2 prefixes and suffixes of a hidden string, recover the string and label each input line as prefix or suffix in order.Medium5StringHash map+2No attempts yet2s512 MBJudgeable
Divide by 3, Multiply by 2Given a shuffled copy B of the sequence produced by a divide-by-3, multiply-by-2 game, reconstruct the original order A.Medium5GraphDFS+2No attempts yet2s512 MBJudgeable
Frequency-Greater Next ElementFor each position, find the nearest value to its right whose total frequency in the array exceeds the frequency of the current element, or -1 if none exists.Medium5StackHash map+2No attempts yet1s512 MBJudgeable
Analogue ClusterGiven n vertices with widths and c edges, recolor the fewest vertices so every edge joins equal widths, per connected component.Medium5GraphGreedy+2No attempts yet1s512 MBJudgeable
What Does UNIST Stand For?Count ways to pick a prefix of each of N words so the concatenation spells UNIST, modulo 1e9+7.Medium5Dynamic programmingString+2No attempts yet1s512 MBJudgeable
Fantasy DraftSimulate a snake-free fantasy draft where each owner repeatedly takes the best available player on their own preference list, falling back to the previous year's ranking.Medium5SimulationHash map+2No attempts yet2s512 MBJudgeable
TypoGiven a dictionary of unique words, print each word that becomes another dictionary word after deleting exactly one character, in input order.Medium5Hash mapString+2No attempts yet6s512 MBJudgeable
Keyboards in ConcertGiven n keyboards, the sets of notes each can play, and the note sequence of a tune, find the minimum number of keyboard switches needed to play the whole tune.Medium5Dynamic programmingHash map+2No attempts yet1s512 MBJudgeable
Alphabet AnimalsGiven the previous animal and a list of unused names, pick a playable name that leaves the next player with no valid move, preferring that over any playable name.Medium5Hash mapImplementation+2No attempts yet2s512 MBJudgeable
Managing DifficultiesCount triples of increasing indices i < j < k where a[j] - a[i] equals a[k] - a[j], so a[i] + a[k] = 2*a[j].Medium5Hash mapCombinatorics+2No attempts yet2s512 MBJudgeable