Interview core

Mediums from real onsites

Under construction

Still being built. Things may change

Total results3,435 problems

High-Rise BuildingsMedium5
Geometry, Brute force +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
CocktailMedium5
Tree, DFS +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
LampsMedium5
Hash map, String +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
DiceMedium5
Implementation, Greedy +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Lexicographically Largest SortMedium5
Greedy, Array +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Unknown SentenceMedium5
Dynamic programming, String +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
HotelMedium5
Dynamic programming, MathNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Maximum SumMedium5
Greedy, Math +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
PrefixMedium5
Trie, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Tree DiameterMedium5
Tree, DFS +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
ExerciseMedium5
Greedy, Simulation +1No attempts yetTime limit2sMemory limit16 MB
Judgeable
PartyMedium5
Shortest path, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Farm ManagementMedium5
BFS, DFS +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Good NumbersMedium5
Two pointers, Array +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
DictionaryMedium5
Combinatorics, Greedy +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Wall-Breaking MazeMedium5
BFS, Shortest path +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
K-th NumberMedium5
Binary search, MathNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Run, HongjunMedium5
Sliding window, Queue +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
X and KMedium5
Bit manipulation, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Hopping FrogMedium5
BFS, Graph +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Fixed-Length Reversal SortMedium5
BFS, Graph +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Tangled Electric WiresMedium5
Dynamic programming, Binary search +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Watering FieldsMedium5
Minimum spanning tree, Graph +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Paper FoldingMedium5
Two pointers, Simulation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Woodcutter DasomMedium5
Brute force, Simulation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Sunday Morning DateMedium5
Shortest path, BFS +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
DuelMedium5
Greedy, Sorting +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Shortest Path Through Required VerticesMedium5
Shortest path, Graph +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
String ExchangeMedium5
Sliding window, String +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Sejun and Sebi's WarMedium5
Greedy, Simulation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Triangle SubsequenceMedium5
Sorting, Two pointers +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
World ConquestMedium5
Binary search, Greedy +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Roads of the Northern CountryMedium5
Tree, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Counting Crossing EdgesMedium5
Sorting, Divide and conquer +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
New Year PartyMedium5
Dynamic programming, Tree +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Making the Best TeamMedium5
Dynamic programming, Greedy +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Sungji's Birthday PartyMedium5
Greedy, Sorting +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Running MedianMedium5
Heap, Sorting +1No attempts yetTime limit0.1sMemory limit128 MB
Judgeable
Captain DasomMedium5
Dynamic programming, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Number GameMedium5
Dynamic programming, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Labels Without a Forbidden DigitMedium5
Math, Combinatorics +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Making a PalindromeMedium5
Dynamic programming, Array +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Power Strip SchedulingMedium5
Greedy, Simulation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Candidate RecommendationMedium5
Simulation, Hash map +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Number GroupingMedium5
Greedy, Sorting +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
TilingMedium5
Dynamic programming, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Maal GatheringMedium5
BFS, Shortest path +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Balanced LineupMedium5
Prefix sum, Hash map +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Sorting the BookshelfMedium5
Dynamic programming, Array +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Word ExtensionMedium5
Dynamic programming, String +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Lexicographically Smallest Valid SequenceMedium5
Greedy, ArrayNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Stacking BoxesMedium5
Simulation, Array +1No attempts yetTime limit3sMemory limit128 MB
Judgeable
Coin DistributionMedium5
Dynamic programming, ArrayNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Chemistry ExperimentMedium5
Binary search, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Prime PathMedium5
BFS, Graph +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
CheersMedium5
Dynamic programming, IntervalsNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Safe Squares on a ChessboardMedium5
Simulation, Implementation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Products of PrimesMedium5
Heap, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Minimum Transfer RouteMedium5
BFS, Graph +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
SemitoneMedium5
Simulation, Implementation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
OmokMedium5
Simulation, Implementation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Bug on a TreeMedium5
Tree, Dynamic programming +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
AntsMedium5
Simulation, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Bulbs and SwitchesMedium5
Greedy, Simulation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Building a BridgeMedium5
BFS, Array +1No attempts yetTime limit2sMemory limit192 MB
Judgeable
Wine TastingMedium5
Dynamic programmingNo attempts yetTime limit2sMemory limit128 MB
Judgeable
In-Flight Meal TripMedium5
Dynamic programming, GraphNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Similar WordsMedium5
String, Sorting +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Field Mouse EscapeMedium5
Graph, Greedy +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Move by Breaking One WallMedium5
BFS, Graph +1No attempts yetTime limit2sMemory limit192 MB
Judgeable
Checking CausalityMedium5
Graph, Topological sort +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Team FormationMedium5
Dynamic programming, Array +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Plum TreeMedium5
Dynamic programmingNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Tree Height and WidthMedium5
Tree, BFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Recover Tree PreorderMedium5
Tree, Recursion +1No attempts yetTime limit5sMemory limit128 MB
Judgeable
SequenceMedium5
Backtracking, Combinatorics +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Theater SeatsMedium5
Dynamic programming, Combinatorics +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Buying JewelsMedium5
Dynamic programming, Array +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Tree CuttingMedium5
Tree, Dynamic programming +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Pipe CuttingMedium5
Greedy, SortingNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Height OrderMedium5
Graph, DFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Three SolutionsMedium5
Two pointers, Sorting +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Brotherly Field DivisionMedium5
Dynamic programming, Brute force +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Inequality SignsMedium5
Backtracking, Greedy +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
ParameciaMedium5
Dynamic programming, Simulation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Electric WiresMedium5
Dynamic programming, Binary search +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Colored Paper 3Medium5
Array, Brute force +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Folding a Tape MeasureMedium5
Simulation, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Crossing the Stone BridgesMedium5
Dynamic programming, StringNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Number BeadsMedium5
Binary search, Greedy +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Finding the Middle MarbleMedium5
Graph, DFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Stable GroupMedium5
Union-find, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Making a MazeMedium5
BFS, Shortest path +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Glass BallsMedium5
Dynamic programming, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Running MediansMedium5
Heap, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Cup HolderMedium5
Greedy, String +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Dongjun's GameMedium5
Greedy, Array +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Observing Two StarsMedium5
Number theory, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Trimming StringsMedium5
Binary search, String +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Array Not Divisible by ThreeMedium5
Greedy, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
High-Rise BuildingsGiven the heights of N buildings in a row, find the maximum number of other buildings visible in a straight line of sight from any single building.	Medium5	GeometryBrute force+2	No attempts yet	2s	128 MB	Judgeable
CocktailGiven a tree of N ingredients linked by N-1 known mass ratios, compute the smallest positive integer masses that satisfy every ratio.	Medium5	TreeDFS+2	No attempts yet	2s	128 MB	Judgeable
LampsGiven an N by M lamp grid where pressing a column switch exactly K times total flips columns, find the max number of rows that end up fully lit.	Medium5	Hash mapString+2	No attempts yet	2s	128 MB	Judgeable
DiceGiven a die net and N, stack N^3 dice into an N x N x N cube and minimize the sum of numbers on the five visible faces.	Medium5	ImplementationGreedy+2	No attempts yet	2s	128 MB	Judgeable
Lexicographically Largest SortGiven a distinct-integer array and a budget of at most S adjacent swaps, output the lexicographically largest array reachable within that swap budget.	Medium5	GreedyArray+1	No attempts yet	2s	128 MB	Judgeable
Unknown SentencePartition a sentence into segments that are anagrams of given words, minimizing total letters moved from their original word positions.	Medium5	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
HotelGiven advertising costs and customer gains for up to 20 cities with unlimited repeats, find the minimum total cost to gain at least C new customers.	Medium5	Dynamic programmingMath	No attempts yet	2s	128 MB	Judgeable
Maximum SumAssign digits 0-9 to letters A-J that encode N numbers so that the sum of the numbers is maximized while no number has a leading zero.	Medium5	GreedyMath+2	No attempts yet	2s	128 MB	Judgeable
PrefixGiven up to 50 words, find the largest subset where no word is a prefix of another, using a trie and tree DP.	Medium5	TrieDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Tree DiameterGiven a weighted tree with up to 100,000 vertices, compute the diameter as the maximum distance between any two vertices.	Medium5	TreeDFS+2	No attempts yet	2s	256 MB	Judgeable
ExerciseSimulate a pulse that rises by T when exercising and falls by R when resting (bounded between m and M) to find the minimum minutes needed to accumulate N exercise minutes, or report impossibility.	Medium5	GreedySimulation+1	No attempts yet	2s	16 MB	Judgeable
PartyGiven a directed weighted graph, compute for each village the round-trip shortest time to a fixed village X and return the maximum over all villages.	Medium5	Shortest pathGraph+1	No attempts yet	1s	128 MB	Judgeable
Farm ManagementCount 8-directionally connected groups of equal-height cells in a grid where every outside neighbor is strictly lower.	Medium5	BFSDFS+2	No attempts yet	2s	128 MB	Judgeable
Good NumbersGiven N integers, count how many of them equal the sum of two other numbers at two different positions in the sequence.	Medium5	Two pointersArray+1	No attempts yet	2s	256 MB	Judgeable
DictionaryConstruct the K-th lexicographically smallest string made of N 'a's and M 'z's using combinatorial counting, or report -1 if K exceeds the total count.	Medium5	CombinatoricsGreedy+1	No attempts yet	2s	128 MB	Judgeable
Wall-Breaking MazeFind the minimum number of walls to break on a grid path from the top-left to the bottom-right room, moving through 4 directions.	Medium5	BFSShortest path+1	No attempts yet	1s	128 MB	Judgeable
K-th NumberFind the k-th smallest value in the N x N multiplication table using binary search with a counting function.	Medium5	Binary searchMath	No attempts yet	2s	128 MB	Judgeable
Run, HongjunGiven N billboard intensities and a sight range M, output the maximum intensity within a sliding window of size 2M-1 for each valid position.	Medium5	Sliding windowQueue+1	No attempts yet	2s	256 MB	Judgeable
X and KGiven X and K, find the K-th smallest positive integer Y such that X+Y equals X OR Y, which requires placing K's bits into the zero-bit positions of X.	Medium5	Bit manipulationMath+1	No attempts yet	2s	128 MB	Judgeable
Hopping FrogFind the minimum number of jumps for a frog moving between numbered stones, where each stone's value dictates allowed jump distances as multiples.	Medium5	BFSGraph+1	No attempts yet	2s	128 MB	Judgeable
Fixed-Length Reversal SortGiven a permutation of up to 8 numbers, find the minimum number of fixed-length K reversals needed to sort it, or report impossibility.	Medium5	BFSGraph+2	No attempts yet	2s	128 MB	Judgeable
Tangled Electric WiresGiven a matching between left and right poles, find the minimum number of wires to cut so no two remaining wires cross, which reduces to computing N minus the longest increasing subsequence.	Medium5	Dynamic programmingBinary search+1	No attempts yet	1s	128 MB	Judgeable
Watering FieldsGiven well-digging costs per field and pairwise pipe-connection costs, compute the minimum total cost to give every field water using an MST-style approach with a virtual water source.	Medium5	Minimum spanning treeGraph+1	No attempts yet	2s	128 MB	Judgeable
Paper FoldingDecide whether a strip of N labeled cells can be folded so the stack reads 1 to N from top to bottom, checking labels against the shrinking strip's two ends.	Medium5	Two pointersSimulation+1	No attempts yet	2s	128 MB	Judgeable
Woodcutter DasomChoose a single cut length for all logs to maximize total profit from selling equal-length pieces after subtracting per-cut costs.	Medium5	Brute forceSimulation+1	No attempts yet	2s	128 MB	Judgeable
Sunday Morning DateFind a grid path from S to F that first minimizes the number of trash cells stepped on, then minimizes clean cells adjacent to trash along that path.	Medium5	Shortest pathBFS+2	No attempts yet	2s	128 MB	Judgeable
DuelMatch N Team A fighters against N Team B fighters to maximize points, where a win scores 2, a tie scores 1, and a loss scores 0.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
Shortest Path Through Required VerticesGiven a weighted undirected graph, find the shortest path from vertex 1 to vertex N that must pass through two specified vertices.	Medium5	Shortest pathGraph+1	No attempts yet	1s	256 MB	Judgeable
String ExchangeGiven a circular string of a's and b's, find the minimum number of swaps to make all a's form one consecutive block.	Medium5	Sliding windowString+2	No attempts yet	2s	128 MB	Judgeable
Sejun and Sebi's WarGiven two armies whose weakest soldier dies each round (ties killing Sebi's soldier first), determine which side's soldier survives last.	Medium5	GreedySimulation+2	No attempts yet	2s	128 MB	Judgeable
Triangle SubsequenceGiven a sequence, find the longest subsequence where every triple of elements satisfies the triangle inequality.	Medium5	SortingTwo pointers+1	No attempts yet	2s	128 MB	Judgeable
World ConquestGiven population counts for N countries, find the maximum number of size-K groups where each group's members come from distinct countries.	Medium5	Binary searchGreedy+1	No attempts yet	2s	128 MB	Judgeable
Roads of the Northern CountryGiven the edges of a weighted tree of up to 10,000 cities, compute the length of the tree's diameter (the longest path between two nodes).	Medium5	TreeGraph+2	No attempts yet	1s	128 MB	Judgeable
Counting Crossing EdgesGiven M cross edges between two labeled vertex sets of size N, count how many unordered pairs of edges cross each other.	Medium5	SortingDivide and conquer+2	No attempts yet	2s	128 MB	Judgeable
New Year PartyPick a maximum-score guest list from a company tree so no employee and their direct manager both attend, computed with and without the root.	Medium5	Dynamic programmingTree+1	No attempts yet	2s	128 MB	Judgeable
Making the Best TeamChoose 15 players for white and 15 for black from a list of up to 1000 players to maximize the total ability sum.	Medium5	Dynamic programmingGreedy+1	No attempts yet	1s	128 MB	Judgeable
Sungji's Birthday PartyGiven N students each requiring a minimum number of other attendees to be satisfied, find the smallest group of students that can be invited so every invited student's requirement is met.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
Running MedianGiven integers one by one, output the running median (lower of the two middles when count is even) after each insertion.	Medium5	HeapSorting+1	No attempts yet	0.1s	128 MB	Judgeable
Captain DasomGiven N cannonballs, find the minimum number of tetrahedral-number piles whose sizes sum exactly to N using unbounded coin-change style DP.	Medium5	Dynamic programmingMath+1	No attempts yet	2s	128 MB	Judgeable
Number GameGiven a set of numbers including 1 and a limit K, find the first integer that cannot be formed using at most K chosen numbers, then decide the game winner by turn parity.	Medium5	Dynamic programmingMath+1	No attempts yet	2s	128 MB	Judgeable
Labels Without a Forbidden DigitGiven N and a forbidden digit L, find the N-th smallest positive integer whose decimal digits never contain L.	Medium5	MathCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Making a PalindromeFind the minimum number of integers to insert into a sequence so it becomes a palindrome, using interval or LCS-based dynamic programming.	Medium5	Dynamic programmingArray+1	No attempts yet	2s	128 MB	Judgeable
Power Strip SchedulingSimulate plugging devices into a strip with N outlets and, when full, evict the device whose next use is farthest away (or never used again), counting total unplugs.	Medium5	GreedySimulation+1	No attempts yet	2s	128 MB	Judgeable
Candidate RecommendationSimulate N photo frames where each recommendation either updates a displayed student's count or evicts the least-recommended, longest-displayed student to show the new one.	Medium5	SimulationHash map+2	No attempts yet	2s	128 MB	Judgeable
Number GroupingGiven N integers, decide which pairs to multiply instead of add so that the resulting total sum is maximized.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
TilingCount the number of ways to tile a 2×n rectangle using 2×1 and 2×2 tiles for multiple values of n up to 250.	Medium5	Dynamic programmingMath+1	No attempts yet	1s	128 MB	Judgeable
Maal GatheringGiven a grid with K-Maal pieces that jump up to K knight moves per turn, find the minimum total moves to gather all pieces on one square.	Medium5	BFSShortest path+2	No attempts yet	2s	128 MB	Judgeable
Balanced LineupGiven fans sorted by x-coordinate with a gender bit each, find the longest contiguous segment that has an equal number of men and women.	Medium5	Prefix sumHash map+2	No attempts yet	2s	256 MB	Judgeable
Sorting the BookshelfFind the minimum number of single-book relocations needed to sort a permutation of N books into increasing order.	Medium5	Dynamic programmingArray+1	No attempts yet	2s	128 MB	Judgeable
Word ExtensionGiven a dictionary and a starting 3-letter word, find the longest word reachable by repeatedly inserting one letter such that each intermediate word exists in the dictionary.	Medium5	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
Lexicographically Smallest Valid SequenceGiven a permutation S, construct the lexicographically smallest permutation T where each element differs from the corresponding S element by at most 1.	Medium5	GreedyArray	No attempts yet	1s	128 MB	Judgeable
Stacking BoxesSimulate stacking N axis-aligned boxes at given footprints using a 2D max-height map and report the final maximum height.	Medium5	SimulationArray+1	No attempts yet	3s	128 MB	Judgeable
Coin DistributionGiven several coin denominations with counts, decide for three test cases whether the coins can be split into two subsets of equal total value.	Medium5	Dynamic programmingArray	No attempts yet	2s	128 MB	Judgeable
Chemistry ExperimentDecide whether M mg of solution can be split into positive integer amounts per reagent so every reagent's linear gas formula a_i*x+b_i gives the same value, and output that value or 0.	Medium5	Binary searchMath+1	No attempts yet	2s	128 MB	Judgeable
Prime PathFind the minimum number of single-digit changes to transform one four-digit prime into another, keeping every intermediate number a four-digit prime, using BFS on the graph of primes.	Medium5	BFSGraph+1	No attempts yet	2s	256 MB	Judgeable
CheersGiven N people around a circle each drinking a cola brand, find the maximum number of non-crossing pairs connecting people with the same brand.	Medium5	Dynamic programmingIntervals	No attempts yet	2s	128 MB	Judgeable
Safe Squares on a ChessboardGiven a chessboard with queens, knights, and pawns, count squares that no queen or knight attacks, treating all pieces as movement blockers.	Medium5	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
Products of PrimesFind the N-th smallest number that can be formed as a product of one or more (with repetition) of K given distinct primes, using a heap-based merge.	Medium5	HeapMath+1	No attempts yet	2s	128 MB	Judgeable
Minimum Transfer RouteGiven several subway lines as sequences of stations, compute the minimum number of transfers to travel between two given stations using BFS over lines.	Medium5	BFSGraph+1	No attempts yet	1s	256 MB	Judgeable
SemitoneGiven a sequence of semitone moves, determine which of the 7 white-key starting notes keep every intermediate step on a white key and report each valid start/end note pair.	Medium5	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
OmokSimulate placing stones in given order on a 19x19 Gomoku board and find the first move that creates exactly 5 in a row (not 6+) for its color.	Medium5	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
Bug on a TreeGiven a tree with fruit values on vertices, find the maximum sum path (simple path) and its smallest-numbered starting endpoint.	Medium5	TreeDynamic programming+1	No attempts yet	2s	128 MB	Judgeable
AntsSimulate ants that reverse on collision by treating collisions as pass-throughs, then track identities to find which numbered ant falls off last and when.	Medium5	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Bulbs and SwitchesGiven current and target bulb states, determine the minimum number of switch presses (each flipping a small neighborhood) needed, or -1 if impossible.	Medium5	GreedySimulation+1	No attempts yet	2s	128 MB	Judgeable
Building a BridgeGiven a grid of land and sea, find the shortest straight sea-cell bridge connecting two different islands.	Medium5	BFSArray+1	No attempts yet	2s	192 MB	Judgeable
Wine TastingPick numbers from a sequence maximizing sum while never selecting three consecutive elements.	Medium5	Dynamic programming	No attempts yet	2s	128 MB	Judgeable
In-Flight Meal TripFind the maximum-score path from city 1 to city N using at most M cities, moving only to strictly increasing city numbers along available flights.	Medium5	Dynamic programmingGraph	No attempts yet	2s	128 MB	Judgeable
Similar WordsGiven up to 20,000 distinct words, find the pair with the longest common prefix, breaking ties by input order.	Medium5	StringSorting+1	No attempts yet	2s	128 MB	Judgeable
Field Mouse EscapeGiven mouse and tunnel coordinates plus a max travel distance, compute the minimum number of mice that cannot be matched to a distinct tunnel using bipartite matching.	Medium5	GraphGreedy+1	No attempts yet	2s	128 MB	Judgeable
Move by Breaking One WallFind the shortest path in a grid from top-left to bottom-right where you may break at most one wall along the way.	Medium5	BFSGraph+1	No attempts yet	2s	192 MB	Judgeable
Checking CausalityGiven send/receive events across computers with local clocks, detect whether the induced ordering constraints form a cycle indicating a causality violation.	Medium5	GraphTopological sort+1	No attempts yet	1s	128 MB	Judgeable
Team FormationPartition an age-ordered score sequence into contiguous groups to maximize the sum of each group's max-minus-min score.	Medium5	Dynamic programmingArray+1	No attempts yet	2s	128 MB	Judgeable
Plum TreeGiven a sequence of falling trees over T seconds, find the max plums caught starting at tree 1 with at most W moves between trees.	Medium5	Dynamic programming	No attempts yet	2s	128 MB	Judgeable
Tree Height and WidthGiven a binary tree's parent-child structure, place nodes on a grid by binary tree layout rules and find the level with the maximum column width, breaking ties by smallest level.	Medium5	TreeBFS+1	No attempts yet	2s	128 MB	Judgeable
Recover Tree PreorderGiven a tree's inorder and postorder sequences, reconstruct the tree and output its preorder traversal.	Medium5	TreeRecursion+1	No attempts yet	5s	128 MB	Judgeable
SequenceFind the K-th lexicographically smallest non-decreasing sequence of N positive integers summing to M.	Medium5	BacktrackingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Theater SeatsCount permutations where each ticket holder sits in their own or adjacent seat, with VIP seats fixed and splitting the row into independent segments counted by a Fibonacci-like recurrence.	Medium5	Dynamic programmingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Buying JewelsFor each of n rows pick a contiguous non-empty subarray maximizing summed total value, breaking ties by fewest jewels then lexicographically smallest index sequence.	Medium5	Dynamic programmingArray+1	No attempts yet	2s	128 MB	Judgeable
Tree CuttingGiven a tree with n vertices, find the minimum number of edges to cut so some resulting piece has exactly m vertices, or report impossibility.	Medium5	TreeDynamic programming+1	No attempts yet	2s	128 MB	Judgeable
Pipe CuttingGiven M long pipes and N required short pipe lengths, compute the maximum number of short pipes that can be cut from the long pipes.	Medium5	GreedySorting	No attempts yet	2s	128 MB	Judgeable
Height OrderGiven pairwise shorter-than relations between students, count how many students have their exact height rank fully determined by transitivity.	Medium5	GraphDFS+1	No attempts yet	1s	128 MB	Judgeable
Three SolutionsGiven up to 5000 distinct integers, find three distinct values whose sum is closest to zero, using sorting and two-pointer scanning.	Medium5	Two pointersSorting+1	No attempts yet	1s	256 MB	Judgeable
Brotherly Field DivisionChoose a non-decreasing staircase cut across N columns of an N x N grid to minimize the harvest difference between the two regions, and output one such cut.	Medium5	Dynamic programmingBrute force+1	No attempts yet	1s	256 MB	Judgeable
Inequality SignsGiven a sequence of < and > signs, place k+1 distinct digits 0-9 to satisfy all comparisons and output the lexicographically largest and smallest resulting digit strings.	Medium5	BacktrackingGreedy+1	No attempts yet	1s	256 MB	Judgeable
ParameciaSimulate a population where each individual matures, reproduces daily within an age window, dies at a fixed age, and count survivors on day N modulo 1000.	Medium5	Dynamic programmingSimulation+1	No attempts yet	1s	128 MB	Judgeable
Electric WiresGiven wires connecting positions on two poles, find the minimum removals so remaining wires never cross, equivalent to n minus the longest increasing subsequence.	Medium5	Dynamic programmingBinary search+1	No attempts yet	1s	128 MB	Judgeable
Colored Paper 3Given up to 100 aligned black 10x10 squares on a 100x100 grid, find the maximum area axis-aligned all-black rectangle.	Medium5	ArrayBrute force+1	No attempts yet	1s	128 MB	Judgeable
Folding a Tape MeasureSimulate folding a tape at marked positions for red, blue, then yellow dot pairs, tracking coordinate transformations and final folded length.	Medium5	SimulationMath+1	No attempts yet	1s	128 MB	Judgeable
Crossing the Stone BridgesCount ways to match a scroll string to positions across two parallel bridge strings, alternating bridges and strictly increasing positions.	Medium5	Dynamic programmingString	No attempts yet	1s	128 MB	Judgeable
Number BeadsSplit an ordered array into M contiguous groups to minimize the largest group sum, then output that value and the group sizes.	Medium5	Binary searchGreedy+1	No attempts yet	1s	128 MB	Judgeable
Finding the Middle MarbleGiven pairwise heavier-than relations among N odd marbles, count marbles that must be eliminated as the possible median using transitive closure of the order.	Medium5	GraphDFS+1	No attempts yet	1s	128 MB	Judgeable
Stable GroupGiven a like/dislike matrix, decide if people can be partitioned into groups (size at least 2) where members like each other within groups and dislike each other across groups, and output that partition.	Medium5	Union-findGraph+1	No attempts yet	1s	128 MB	Judgeable
Making a MazeFind the minimum number of black cells to convert to white so a path exists from top-left to bottom-right of an n x n grid, using 0-1 BFS or Dijkstra.	Medium5	BFSShortest path+1	No attempts yet	1s	128 MB	Judgeable
Glass BallsGiven B balls and M floors, compute the minimum number of drops needed to guarantee finding the critical breaking floor in the worst case.	Medium5	Dynamic programmingMath+1	No attempts yet	1s	128 MB	Judgeable
Running MediansGiven a sequence read one number at a time, output the running median every time an odd number of elements have been read.	Medium5	HeapImplementation	No attempts yet	1s	128 MB	Judgeable
Cup HolderGiven a seat row with regular seats and adjacent couple-seat pairs that lack a middle cup holder, compute the maximum number of people who can access a cup holder, matching people to holders one per holder.	Medium5	GreedyString+1	No attempts yet	1s	128 MB	Judgeable
Dongjun's GameGiven N level scores, find the minimum total decrease needed to make the sequence strictly increasing while all scores stay positive.	Medium5	GreedyArray+1	No attempts yet	1s	128 MB	Judgeable
Observing Two StarsGiven start times and periods of two blinking stars, find the earliest simultaneous blink time and weekday, or report it never happens.	Medium5	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
Trimming StringsFind how many top rows can be removed one at a time from a grid while all column strings (read top to bottom) remain pairwise distinct.	Medium5	Binary searchString+1	No attempts yet	1s	256 MB	Judgeable
Array Not Divisible by ThreeRearrange an array so no two adjacent elements sum to a multiple of 3, or report impossibility.	Medium5	GreedyMath+1	No attempts yet	1s	128 MB	Judgeable