Problems

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Total results21,289 problems

Keyboard QueriesHard8
Union-find, String matching +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
GomGom and TetrisHard8
Game theory, Bit manipulation +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
AND vs ORHard8
Bit manipulation, Divide and conquer +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Card GameHard8
Game theory, Dynamic programming +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Frog JumpHard8
Intervals, Binary search +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Linear RegressionHard8
Geometry, Binary search +1No attempts yetTime limit5sMemory limit1024 MB
Judgeable
Longest SubstringHard8
String matching, TreeNo attempts yetTime limit5sMemory limit1024 MB
Judgeable
SubsetMexHard8
Greedy, Dynamic programming +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Lego WallHard8
Combinatorics, Dynamic programming +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Take On MemeHard8
Tree, Geometry +1No attempts yetTime limit4sMemory limit1024 MB
Judgeable
Unbroken Spirit 2Hard8
Greedy, Heap +1No attempts yetTime limit1.5sMemory limit1024 MB
Judgeable
Faster Than LightHard8
Geometry, Sorting +1No attempts yetTime limit10sMemory limit1024 MB
Judgeable
MortgageHard8
Prefix sum, Divide and conquer +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Silver TreeHard8
Tree, Math +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Winter Forest and the Magic FlameHard8
Tree, Greedy +1No attempts yetTime limit1.5sMemory limit512 MB
Judgeable
Expected length of the minimum cycleHard8
Combinatorics, MathNo attempts yetTime limit2sMemory limit1024 MB
Judgeable
TicketsHard8
Tree, Divide and conquer +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Simple Math ProblemHard8
Combinatorics, Math +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
BinCoinHard8
Tree, Probability +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
DominoesHard8
Graph, DFS +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Game of QuestionsHard8
Dynamic programming, Bit manipulation +1No attempts yetTime limit5sMemory limit1024 MB
Judgeable
AibohphobiAHard8
Graph, DFS +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Balanced Seesaw ArrayHard8
Segment tree, Math +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
InvitationHard8
Combinatorics, Sorting +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Under Construction ForeverHard8
Graph, Dynamic programming +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
KnightmareHard8
Segment tree, Sorting +1No attempts yetTime limit5sMemory limit1024 MB
Judgeable
Gold RushHard8
Divide and conquer, Dynamic programming +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Knight Moves: Black EditionHard8
Math, ImplementationNo attempts yetTime limit1sMemory limit1024 MB
Judgeable
DeCSS 3Hard8
Backtracking, Bit manipulation +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
DeCSS 4Hard8
Bit manipulation, Brute force +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
DeCSS 5Hard8
Brute force, Math +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
DeCSS 7Hard8
Bit manipulation, Math +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
NeboderiHard8
Sliding window, Number theory +1No attempts yetTime limit2.5sMemory limit1024 MB
Judgeable
LampiceHard8
Prefix sum, Dynamic programming +1No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Expected Cycle SizeHard8
Probability, Combinatorics +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
FoldingHard8
String matching, Math +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
MFP: Most Fluctuated PlayerHard8
Segment tree, Sorting +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Qarentheziz SequenceHard8
Segment tree, String +1No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Sequence and Queries 41Hard8
Segment tree, Dynamic programmingNo attempts yetTime limit5sMemory limit1024 MB
Judgeable
PalindromeHard8
String matching, Two pointers +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
TennisHard8
Dynamic programming, Math +1No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Team SelectionHard9
Divide and conquer, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Good NumbersHard9
Combinatorics, Math +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
DominoesHard9
Graph, Combinatorics +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Folded Paper PaintingHard9
Geometry, Simulation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Cactus Graph AutomorphismsHard9
Tree, Combinatorics +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Diameter of a CactusHard9
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Coloring RectanglesHard9
Geometry, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Goal CelebrationHard9
Geometry, Sorting +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Admiral Yi Sun-sinHard9
Union-find, Tree +2No attempts yetTime limit1.216sMemory limit512 MB
Judgeable
Robot ArmHard9
Geometry, Intervals +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
Queen and Two KingsHard9
Game theory, BFS +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Wake Up!Hard9
Geometry, Divide and conquer +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
ShotHard9
Segment tree, Binary search +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Coprime Products from Six IndicesHard9
Number theory, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Matrix SwapsHard9
Graph, Shortest path +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Hyungtaek's Candy BagsHard9
Combinatorics, Number theory +1No attempts yetTime limit5sMemory limit128 MB
Judgeable
Shom LanguageHard9
Graph, Combinatorics +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
All Closed-Walk LengthsHard9
Graph, Matrix +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Maximum Matching in an Almost Bipartite GraphHard9
Graph, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Small SquaresHard9
Game theory, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Pro Gamer YoungsikHard9
Dynamic programming, Greedy +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
District PartitioningHard9
Binary search, Greedy +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Choosing PointsHard9
Geometry, Combinatorics +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
WoodpeckersHard9
Tree, Graph +2No attempts yetTime limit10sMemory limit128 MB
Judgeable
Shom CodeHard9
Trie, BFS +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Counting Multiples by Divisor CountHard9
Number theory, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Domino TilingHard9
Graph, BFS +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
Travel GuideHard9
Brute force, Binary search +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Candy JarsHard9
Greedy, Bit manipulation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
OrchardHard9
Geometry, Matrix +2No attempts yetTime limit2sMemory limit64 MB
Judgeable
CowboysHard9
Game theory, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Hangul-Missing NumbersHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Mail CarrierHard9
Graph, Greedy +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
FenceHard9
Geometry, Sorting +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Matrix and Fibonacci SumHard9
Matrix, Math +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Square and PointsHard9
Geometry, Math +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Hard MatchingHard9
String matching, Prefix sum +2No attempts yetTime limit30sMemory limit1536 MB
Judgeable
Tree RotationHard9
Tree, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Hyeonju's Pizza ShopHard9
Greedy, Segment tree +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Roller CoasterHard9
Dynamic programming, Graph +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
MoleHard9
Tree, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Beautiful ArchipelagoHard9
Union-find, Hash map +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
FPSHard9
Combinatorics, Math +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
Waiting for the DogHard9
Geometry, Shortest path +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Standard ProblemHard9
Segment tree, Divide and conquer +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
Paper FoldingHard9
Simulation, Greedy +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Chip RoutingHard9
Dynamic programming, Greedy +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
BEARsHard9
Graph, Game theory +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
L GameHard9
Game theory, Brute force +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Farm and FactoryHard9
Shortest path, Graph +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
BeastsHard9
Geometry, Binary search +1No attempts yetTime limit3sMemory limit128 MB
Judgeable
Casting SpellsHard9
String matching, String +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Fields and FarmersHard9
Geometry, Combinatorics +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Hanging HatsHard9
Geometry, Segment tree +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
Gates of LogicHard9
Simulation, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Origami Axiom Six: Counting FoldsHard9
Geometry, Math +1No attempts yetTime limit1sMemory limit512 MB
Judgeable
AsteroidsHard9
Geometry, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Exclusive Access 2Hard9
Graph, Combinatorics +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Grand Theft Auto WheelHard9
Geometry, Simulation +1No attempts yetTime limit3sMemory limit256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Keyboard QueriesGiven palindrome facts about substrings of S, decide whether two substrings must be equal, cannot be equal, or remain undetermined.	Hard8	Union-findString matching+1	No attempts yet	1s	1024 MB	Judgeable
GomGom and TetrisTwo players alternately place Tetris pieces or 1x1 blocks on an N by M board to maximize their own score, and the task is to decide the winner with a 0.5 first-player penalty.	Hard8	Game theoryBit manipulation+1	No attempts yet	2s	1024 MB	Judgeable
AND vs ORFor each query range, sum the positive values of (first AND last) minus the OR of the inner elements over all subarrays, modulo 1000000007.	Hard8	Bit manipulationDivide and conquer+1	No attempts yet	2s	1024 MB	Judgeable
Card GameAlice and Bob alternately pick a card on an N by M grid and remove its connected diagonal run by color. Determine whether the first player wins.	Hard8	Game theoryDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Frog JumpGiven n closed intervals and a sequence of k target intervals, find the total jump length the frog pays while visiting the targets in order from interval 1.	Hard8	IntervalsBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Linear RegressionRemove k points, then find a line that minimizes the largest vertical distance to the remaining points, and print that distance.	Hard8	GeometryBinary search+1	No attempts yet	5s	1024 MB	Judgeable
Longest SubstringFor each k from 1 to n, find the longest substring that occurs exactly k times and allows the most non-overlapping occurrences, then print the lengths.	Hard8	String matchingTree	No attempts yet	5s	1024 MB	Judgeable
SubsetMexGiven the counts f_i of each value below n in a multiset, find the fewest subset-and-mex operations needed to insert n.	Hard8	GreedyDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Lego WallCount the connected, hole-free walls of width w and height h built from 1x1x1 and 2x1x1 bricks, modulo 1000000007.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
Take On MemeGiven a rooted vote tree where each child's (x, y) vector is added or subtracted at every node, find the largest squared length the root can reach.	Hard8	TreeGeometry+1	No attempts yet	4s	1024 MB	Judgeable
Unbroken Spirit 2For each prefix of N dragons with growth D_i and start height H_i, find the max total height a thief can cut with one arrow per day.	Hard8	GreedyHeap+1	No attempts yet	1.5s	1024 MB	Judgeable
Faster Than LightGiven n non-overlapping axis-aligned rectangles, decide whether a single infinite line touches every one of them.	Hard8	GeometrySorting+1	No attempts yet	10s	1024 MB	Judgeable
MortgageGiven monthly incomes and several loan intervals, find for each interval the largest equal payment that can be covered month by month using only money saved inside that interval.	Hard8	Prefix sumDivide and conquer+1	No attempts yet	3s	1024 MB	Judgeable
Silver TreeGiven K, H, and query pairs of keys, find the path length between the two blue nodes holding each pair in a silver tree, or -1 if a key is missing.	Hard8	TreeMath+1	No attempts yet	2s	512 MB	Judgeable
Winter Forest and the Magic FlameGiven a weighted tree rooted at village 1, find the smallest possible farthest distance from the root after shortening edges within a magic budget B, for each query.	Hard8	TreeGreedy+1	No attempts yet	1.5s	512 MB	Judgeable
Expected length of the minimum cycleGiven N and a prime P, find the expected length of the shortest cycle in a random permutation of 1 to N, modulo P as a reduced fraction.	Hard8	CombinatoricsMath	No attempts yet	2s	1024 MB	Judgeable
TicketsGiven a tree of cities and ticket types that reach any city within k train rides for a fixed price, find the cheapest way from each query city to city 1.	Hard8	TreeDivide and conquer+1	No attempts yet	3s	1024 MB	Judgeable
Simple Math ProblemGiven N, K, and X, find the X-th lexicographically smallest length-K array over 1 to N that uses every value and balances each i-1 count around every i.	Hard8	CombinatoricsMath+1	No attempts yet	1s	256 MB	Judgeable
BinCoinGiven k random signing sequences from a full binary tree, restore each employee's direct superior in that tree.	Hard8	TreeProbability+1	No attempts yet	3s	1024 MB	Judgeable
DominoesCount the pairs of free cells that, once both are blocked, leave the grid with no full domino tiling, capped at 1000000.	Hard8	GraphDFS+1	No attempts yet	3s	1024 MB	Judgeable
Game of QuestionsGiven n questions answered correctly or not by m participants, find the probability that participant 1 is the last one left after all questions are asked in a random order.	Hard8	Dynamic programmingBit manipulation+1	No attempts yet	5s	1024 MB	Judgeable
AibohphobiAFind the longest walk from (0, 0) to (M-1, N-1) that visits each query cell and has no palindromic substring, or report -1 or -2.	Hard8	GraphDFS+1	No attempts yet	3s	1024 MB	Judgeable
Balanced Seesaw ArrayGiven an array with range add and range assign updates, answer whether a queried subarray is a balanced seesaw array.	Hard8	Segment treeMath+1	No attempts yet	3s	1024 MB	Judgeable
InvitationCount the groups of k leaders whose availability intervals share a common time slot, for every k from 1 to n, modulo 998244353.	Hard8	CombinatoricsSorting+1	No attempts yet	3s	1024 MB	Judgeable
Under Construction ForeverGiven a connected graph of buildings with costs, find the fewest buildings left after leaf-absorbing reconstructions, the minimum cost for that count, and the number of ways modulo 1,000,000,007.	Hard8	GraphDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
KnightmareCount the squares attacked by at least k knights, where each knight's reach is a symmetric set of offsets determined by its a and b values.	Hard8	Segment treeSorting+1	No attempts yet	5s	1024 MB	Judgeable
Gold RushCount the distinct win-loss records possible in an n-player single-elimination bracket with best-of-k matches, modulo 1,000,003.	Hard8	Divide and conquerDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Knight Moves: Black EditionGiven an N by N board with N up to 1e15, find the fewest knight moves between two cells.	Hard8	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
DeCSS 3Given a partially known CSS keystream, find one 42-bit key whose two LFSRs and carry rule reproduce every known byte.	Hard8	BacktrackingBit manipulation+1	No attempts yet	1s	1024 MB	Judgeable
DeCSS 4Given a partially known CSS key stream where unknown bytes are -1, find a 42-bit key that reproduces every known byte.	Hard8	Bit manipulationBrute force+1	No attempts yet	1s	1024 MB	Judgeable
DeCSS 5Given a partly known CSS keystream, find one 42-bit key whose two LFSRs reproduce every known byte.	Hard8	Brute forceMath+1	No attempts yet	1s	1024 MB	Judgeable
DeCSS 7Given a partly known CSS keystream built from two LFSRs with a carry bit, find any 42-bit key that reproduces the known bytes.	Hard8	Bit manipulationMath+2	No attempts yet	1s	1024 MB	Judgeable
NeboderiFind the largest product of the GCD and the sum over any contiguous block of at least k skyscrapers, with up to 10^6 heights.	Hard8	Sliding windowNumber theory+1	No attempts yet	2.5s	1024 MB	Judgeable
LampiceCount axis-aligned rectangles with integer corners on an n by m terrace where, for each colour, both lamps are inside or both are outside.	Hard8	Prefix sumDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
Expected Cycle SizeGiven a permutation pattern where 0 is a wildcard, output for each index the expected cycle size over all random permutations matching the pattern, modulo 998244353.	Hard8	ProbabilityCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
FoldingGiven a string, count the foldings whose fold positions form an arithmetic set and where every pile holds only one letter.	Hard8	String matchingMath+1	No attempts yet	2s	1024 MB	Judgeable
MFP: Most Fluctuated PlayerGiven Q point updates to N players, find each player's total coins, where coins are the absolute change in point rank after each update.	Hard8	Segment treeSorting+1	No attempts yet	2s	1024 MB	Judgeable
Qarentheziz SequenceGiven a parentheses string with range flips, find for each query the fewest end insertions and adjacent swaps needed to make a substring balanced.	Hard8	Segment treeString+1	No attempts yet	2s	1024 MB	Judgeable
Sequence and Queries 41Given an array, process range updates that set each A_i to max(A_i, x) and queries for the maximum subarray sum inside a range, floored at 0.	Hard8	Segment treeDynamic programming	No attempts yet	5s	1024 MB	Judgeable
PalindromeGiven N numbers with fixed digit lengths, find the fewest elements to replace so their concatenation becomes a palindrome.	Hard8	String matchingTwo pointers+1	No attempts yet	1s	1024 MB	Judgeable
TennisFind the sum of costs over all n-ball sequences whose weight sum mod w is at most x, where cost is the count of balls with weight at most y raised to the power k.	Hard8	Dynamic programmingMath+1	No attempts yet	1s	1024 MB	Judgeable
Team SelectionSplit N players into two equal teams so the difference between the captains' total scores is minimized, choosing the lexicographically smallest assignment.	Hard9	Divide and conquerDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Good NumbersGiven a set S of forbidden integers, rank positive integers by how many good intervals (ranges containing only non-S values) contain each one, then print the first n.	Hard9	CombinatoricsMath+2	No attempts yet	2s	128 MB	Judgeable
DominoesCount how many ways a given set of dominoes can be partitioned into one or more edge-disjoint cycles using every piece exactly once.	Hard9	GraphCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Folded Paper PaintingSimulate K rounds of folding a W by H rectangle along a vertical line and several horizontal folds, painting one rectangle each round through all layers, and report the unpainted area at the end.	Hard9	GeometrySimulation+2	No attempts yet	2s	128 MB	Judgeable
Cactus Graph AutomorphismsCount automorphisms modulo 1e9+3 of a given vertex cactus graph with up to 200 vertices.	Hard9	TreeCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Diameter of a CactusGiven a cactus graph (each edge in at most one cycle), compute the maximum shortest-path distance between any two vertices.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Coloring RectanglesGiven N rectangles, choose exactly K of them to maximize the total visible union area under a max-index-wins overlap rule, picking the lexicographically smallest tie-break.	Hard9	GeometryDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Goal CelebrationGiven a point inside a field with polygonal obstacles, find the farthest boundary point reachable by a straight segment that avoids the obstacles' interiors.	Hard9	GeometrySorting+2	No attempts yet	2s	128 MB	Judgeable
Admiral Yi Sun-sinMaintain a dynamic graph of national roads (union-find) and acyclic expressways (link-cut style tree), updating region comfort values tied to region 1's component and answering path/sum queries online.	Hard9	Union-findTree+2	No attempts yet	1.216s	512 MB	Judgeable
Robot ArmGiven a rectilinear factory polygon and five candidate fixed points, decide for each whether an L-shaped two-segment robot arm confined to the polygon can reach every interior point.	Hard9	GeometryIntervals+2	No attempts yet	5s	128 MB	Judgeable
Queen and Two KingsGiven a queen and two kings on a 100x100 board playing optimally, compute the minimum number of queen moves needed to capture either king.	Hard9	Game theoryBFS+2	No attempts yet	2s	128 MB	Judgeable
Wake Up!Count the distinct points where any two of up to 20,000 line segments intersect, using an efficient computational geometry sweep.	Hard9	GeometryDivide and conquer+2	No attempts yet	1s	128 MB	Judgeable
ShotGiven columns of black/gray/white cans stacked in fixed color order, repeatedly shoot a height to remove one layer from every tall-enough column and report the collapsing score after each shot.	Hard9	Segment treeBinary search+2	No attempts yet	2s	256 MB	Judgeable
Coprime Products from Six IndicesGiven N integers, count ordered 6-tuples of indices whose three pairwise products mod 359999 = 599*601 have gcd 1, modulo 1e9+7.	Hard9	Number theoryCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Matrix SwapsGiven binary matrices A and B and a per-cell swap-count limit matrix C, find the minimum number of adjacent (including diagonal) cell swaps to turn A into B, or report impossibility.	Hard9	GraphShortest path+2	No attempts yet	2s	128 MB	Judgeable
Hyungtaek's Candy BagsGiven N, find the maximum sum-free subset size of {1,...,N}, count all such maximum subsets, and print every one of them.	Hard9	CombinatoricsNumber theory+1	No attempts yet	5s	128 MB	Judgeable
Shom LanguageGiven a sentence with alternating uppercase and lowercase letters, find the minimum number of distinct two-letter words needed to rebuild it via overlapping placements.	Hard9	GraphCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
All Closed-Walk LengthsGiven a directed graph, decide for every length x whether a closed walk of that length exists, then print the eventually periodic 0/1 sequence in its shortest prefix-plus-period notation.	Hard9	GraphMatrix+2	No attempts yet	2s	128 MB	Judgeable
Maximum Matching in an Almost Bipartite GraphCompute the maximum matching size in a graph formed by two paths (A and B) joined by up to 50 extra cross edges.	Hard9	GraphDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Small SquaresDetermine the winner of an optimal-play coloring game on a grid where players color 1x1 or restricted 2x2 squares, using Sprague-Grundy analysis.	Hard9	Game theoryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Pro Gamer YoungsikGiven time and resource budgets, compute the maximum number of top-tier units obtainable from a chain of unit upgrades where each unit can repeatedly spawn the next type.	Hard9	Dynamic programmingGreedy+2	No attempts yet	2s	128 MB	Judgeable
District PartitioningPick X horizontal and Y vertical dividing roads from an (n+1)x(m+1) population grid so the maximum population of any resulting block is minimized.	Hard9	Binary searchGreedy+2	No attempts yet	2s	128 MB	Judgeable
Choosing PointsGiven up to 1000 planar points, find the largest subset where every line through two chosen points also passes through a third chosen point, or report -1 if impossible.	Hard9	GeometryCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
WoodpeckersCount ways to place N woodpeckers into two height-ordered trees so every visiting pair lands in different trees and their connecting segments never cross, modulo K.	Hard9	TreeGraph+2	No attempts yet	10s	128 MB	Judgeable
Shom CodeGiven binary codes assigned to up to 26 letters, find the minimum length of a binary string decodable as three or more distinct letter sequences, or -1 if none exists.	Hard9	TrieBFS+2	No attempts yet	2s	128 MB	Judgeable
Counting Multiples by Divisor CountGiven N up to 10^18, count positive integers X that are multiples of N and have exactly N divisors, or report infinitely many.	Hard9	Number theoryCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Domino TilingFind the lexicographically smallest way to tile an N by M grid with dominoes while respecting forbidden borders between certain adjacent cells, or report impossibility.	Hard9	GraphBFS+2	No attempts yet	5s	128 MB	Judgeable
Travel GuideFind the minimum time for a guide starting at the origin to intercept N moving tourists in some order and send them home, then return herself.	Hard9	Brute forceBinary search+2	No attempts yet	2s	128 MB	Judgeable
Candy JarsGiven N jars holding consecutive candy counts starting at K, find the minimum number of subset-subtraction operations needed to empty every jar and print the operations.	Hard9	GreedyBit manipulation+2	No attempts yet	2s	128 MB	Judgeable
OrchardGiven up to 2500 non-overlapping colored rectangles, find the maximum area axis-aligned rectangle fully covered by orchards of one fruit type.	Hard9	GeometryMatrix+2	No attempts yet	2s	64 MB	Judgeable
CowboysGiven N cowboys shooting in turns with hit probabilities and optimal target choice under strategic play, compute each cowboy's probability of being the sole survivor.	Hard9	Game theoryDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Hangul-Missing NumbersGiven which Hangul letters are forbidden, find the N-th positive integer up to 10^52-1 whose Korean numeral representation avoids all forbidden jamo, using digit DP over decomposed syllables.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Mail CarrierFind an Euler tour of a multigraph that maximizes the sum of w[i] minus \|k - w[i]\| over the traversal order of edges, then print the resulting vertex sequence.	Hard9	GraphGreedy+1	No attempts yet	2s	128 MB	Judgeable
FenceGiven a square field with 4N fence posts and up to 30000 convex polygonal rocks blocking sight lines, count how many posts are visible from a given viewpoint using angular occlusion by polygon silhouettes.	Hard9	GeometrySorting+1	No attempts yet	2s	128 MB	Judgeable
Matrix and Fibonacci SumCompute the sum of Fibonacci numbers with linearly growing indices times increasing powers of a K×K matrix, modulo a prime, for N up to 10^1000.	Hard9	MatrixMath+2	No attempts yet	5s	512 MB	Judgeable
Square and PointsGiven points inside a unit square with 4 fixed corners, find where to move the points to minimize the Steiner-tree-like minimum spanning length, then among those optimal configurations minimize total movement of points.	Hard9	GeometryMath+1	No attempts yet	2s	128 MB	Judgeable
Hard MatchingGiven a text sequence and two number patterns, count positions where consecutive-sum grouping matches each pattern, then find the smallest glue value x maximizing matches of the concatenated pattern with x inserted between them and report that match count.	Hard9	String matchingPrefix sum+2	No attempts yet	30s	1536 MB	Judgeable
Tree RotationCompute the minimum number of restricted tree rotations (at the root or root's right child) to transform one 0-2 binary tree's shape into another and output a valid rotation sequence.	Hard9	TreeGraph+2	No attempts yet	1s	128 MB	Judgeable
Hyeonju's Pizza ShopGiven jobs with desired completion times and processing times on a single machine, compute the maximum total tip (sum of signed lateness against desired times) after each of many update operations that change a job's parameters, requiring an efficient dynamic scheduling data structure.	Hard9	GreedySegment tree+1	No attempts yet	2s	128 MB	Judgeable
Roller CoasterFind a self-avoiding path from top-left to bottom-right on a grid up to 1000x1000 that maximizes the sum of visited cells' joy values.	Hard9	Dynamic programmingGraph+1	No attempts yet	1s	256 MB	Judgeable
MoleGiven a tree, remove one edge and add one edge (keeping it connected) to minimize the tree's diameter, and output the resulting diameter with the edges swapped.	Hard9	TreeGraph+2	No attempts yet	1s	128 MB	Judgeable
Beautiful ArchipelagoFor each queried sea level, count unordered pairs of islands (connected land regions after flooding) that are translation-equivalent in shape, over up to 1000x1000 grid and 100000 queries.	Hard9	Union-findHash map+1	No attempts yet	2s	128 MB	Judgeable
FPSGiven N players and Q candidate additions, count ways to pick K bots with distinct speeds/ranges each dominated by some human, modulo 10009.	Hard9	CombinatoricsMath+2	No attempts yet	5s	128 MB	Judgeable
Waiting for the DogGiven rectangular obstacles, entrance, exit, and a waiting time, compute the total area of points whose shortest-path distances from both entrance and exit sum to at most a bound, in an L1-like grid metric with obstacles.	Hard9	GeometryShortest path+2	No attempts yet	1s	256 MB	Judgeable
Standard ProblemGiven a 0/1 grid, answer up to a million offline queries for the largest all-zero rectangle confined to a specified row range.	Hard9	Segment treeDivide and conquer+2	No attempts yet	3s	128 MB	Judgeable
Paper FoldingGiven a colored paper strip, determine the sequence of folds that minimizes final length while respecting a color-matching constraint on folded layers.	Hard9	SimulationGreedy+1	No attempts yet	1s	128 MB	Judgeable
Chip RoutingAssign each marked point on a square chip a direction toward a side so that drawn segments never cross or pass through other points, minimizing the total segment length.	Hard9	Dynamic programmingGreedy+2	No attempts yet	1s	128 MB	Judgeable
BEARsDetermine the maximum guaranteed Chebyshev distance from the origin that a pursuer can force an evader to maintain on an infinite grid graph, given blocked main-street edges, using a game-theoretic reachability argument.	Hard9	GraphGame theory+2	No attempts yet	1s	128 MB	Judgeable
L GameGiven a 4x4 L-Game board, determine if the player to move has a forced win, output the lexicographically smallest winning resulting board, or report draw/loss under perfect play.	Hard9	Game theoryBrute force+2	No attempts yet	1s	128 MB	Judgeable
Farm and FactoryGiven a weighted graph with two special nodes, choose non-negative toll values for new edges from a virtual capital so every shortest path to farm and factory avoids it, minimizing average distance to all cities, expressed as an exact fraction.	Hard9	Shortest pathGraph+2	No attempts yet	5s	128 MB	Judgeable
BeastsGiven lines splitting the plane, compute the exact squared minimum distance as a reduced fraction between two convex regions containing two extremely distant fixed points, bounded by half-planes determined for each side.	Hard9	GeometryBinary search+1	No attempts yet	3s	128 MB	Judgeable
Casting SpellsGiven a string, find the maximum length of a substring of the form ww^R w w^R (a palindrome ww^R followed immediately by itself) across up to 40 large test cases.	Hard9	String matchingString+2	No attempts yet	1s	128 MB	Judgeable
Fields and FarmersGiven initial unit-square fields, count subsets whose repeated convex-hull-based expansion yields the same final parcel as the full set, modulo 1e9+7.	Hard9	GeometryCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Hanging HatsSimulate mages hanging triangular hats on a wall, tracking nail visibility and expulsion under coverage rules that require an advanced geometric data structure.	Hard9	GeometrySegment tree+2	No attempts yet	3s	128 MB	Judgeable
Gates of LogicParse an ASCII-art diagram of logic gates and wires with grid tracing rules (junctions, crossings, negation, ports) and compute values propagated to every named output.	Hard9	SimulationGraph+2	No attempts yet	1s	128 MB	Judgeable
Origami Axiom Six: Counting FoldsGiven two point-line pairs, count the distinct fold lines (common tangents of two parabolas) satisfying Huzita's sixth origami axiom for up to 20000 test cases.	Hard9	GeometryMath+1	No attempts yet	1s	512 MB	Judgeable
AsteroidsGiven two convex polyhedra, find rotations and a touching translation that minimize the distance between their centers of mass without overlap.	Hard9	GeometryMath+1	No attempts yet	1s	128 MB	Judgeable
Exclusive Access 2Given process-resource pairs, choose lock acquisition order per process to avoid deadlock while minimizing the longest alternating wait chain, over at most 15 resource labels.	Hard9	GraphCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Grand Theft Auto WheelGiven star-shaped polar polygons for a bolt hole and several wrench lugs, determine which wrenches can be inserted but cannot fully rotate inside the bolt hole.	Hard9	GeometrySimulation+1	No attempts yet	3s	256 MB	Judgeable