Problems

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Total results29,197 problems

Maximize the Minimum
Hard8
Binary search, Dynamic programming+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Fischer's Chess Guessing Game
Hard8
Combinatorics, Implementation
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Graph Cuts
Hard8
Graph, Hash map+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Poor Students
Hard8
Shortest path, Graph+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Crossing the Border
Hard8
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
15s
Memory limit
2048 MB
Judgeable
Fortune Wheel
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Jumping Lights
Hard8
Tree, BFS+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Abstract
Hard8
Graph, Topological sort+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Fast Debugger
Hard8
Bit manipulation, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Data Structures Master
Hard8
Segment tree, Sorting+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Poisonous Labyrinth
Hard8
Tree, DFS+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Lost Table
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
A Tree Game
Hard8
Tree, Game theory+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Generating the Sequence
Hard8
Number theory, Bit manipulation+1
No attempts yet
Time limit
10s
Memory limit
2048 MB
Judgeable
Interesting Words
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Festival Decorating
Hard8
Math, Array
No attempts yet
Time limit
9s
Memory limit
2048 MB
Judgeable
Comedy's Not Omnipotent
Hard8
Array, Bit manipulation+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Palindrome Strings
Hard8
String matching, String
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Count the Orders
Hard8
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Simple Math Problem
Hard8
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Neutral Spectator
Hard8
Binary search, Geometry+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Old Solution Methods
Hard8
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Immensely Long Expressions
Hard8
Dynamic programming, Probability+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Sending Substrings
Hard8
String matching, String+1
No attempts yet
Time limit
6s
Memory limit
2048 MB
Judgeable
Cat Tour
Hard8
Graph, Shortest path
No attempts yet
Time limit
0.5s
Memory limit
2048 MB
Judgeable
Sequences, Queries, and Probability 2
Hard8
Probability, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
What Should You Say When You See Trees Burning?
Hard8
Tree, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sum Sequence
Hard8
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
\mathtt{MatKor} \oplus \mathtt{AlKor} = \mathtt{MatAl}
Hard8
Prefix sum, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Caterpillar and Tree
Hard8
Tree, Graph+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Reachable Pairs
Hard8
Graph, Union-find
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Team Selection
Hard9
Divide and conquer, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Good Numbers
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Dominoes
Hard9
Graph, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Folded Paper Painting
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Cactus Graph Automorphisms
Hard9
Tree, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Diameter of a Cactus
Hard9
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Coloring Rectangles
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Goal Celebration
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Admiral Yi Sun-sin
Hard9
Union-find, Tree+2
No attempts yet
Time limit
1.216s
Memory limit
512 MB
Judgeable
Robot Arm
Hard9
Geometry, Intervals+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Queen and Two Kings
Hard9
Game theory, BFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Wake Up!
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Shot
Hard9
Segment tree, Binary search+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Coprime Products from Six Indices
Hard9
Number theory, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Matrix Swaps
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hyungtaek's Candy Bags
Hard9
Combinatorics, Number theory+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Shom Language
Hard9
Graph, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
All Closed-Walk Lengths
Hard9
Graph, Matrix+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Maximum Matching in an Almost Bipartite Graph
Hard9
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Small Squares
Hard9
Game theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pro Gamer Youngsik
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
District Partitioning
Hard9
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Choosing Points
Hard9
Geometry, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Woodpeckers
Hard9
Tree, Graph+2
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Shom Code
Hard9
Trie, BFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Counting Multiples by Divisor Count
Hard9
Number theory, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Domino Tiling
Hard9
Graph, BFS+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Travel Guide
Hard9
Brute force, Binary search+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Candy Jars
Hard9
Greedy, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Orchard
Hard9
Geometry, Matrix+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Cowboys
Hard9
Game theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hangul-Missing Numbers
Hard9
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mail Carrier
Hard9
Graph, Greedy+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Fence
Hard9
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Matrix and Fibonacci Sum
Hard9
Matrix, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Square and Points
Hard9
Geometry, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hard Matching
Hard9
String matching, Prefix sum+2
No attempts yet
Time limit
30s
Memory limit
1536 MB
Judgeable
Tree Rotation
Hard9
Tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hyeonju's Pizza Shop
Hard9
Greedy, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Roller Coaster
Hard9
Dynamic programming, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Mole
Hard9
Tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Beautiful Archipelago
Hard9
Union-find, Hash map+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
FPS
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Waiting for the Dog
Hard9
Geometry, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Standard Problem
Hard9
Segment tree, Divide and conquer+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Paper Folding
Hard9
Simulation, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Chip Routing
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
BEARs
Hard9
Graph, Game theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
L Game
Hard9
Game theory, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Farm and Factory
Hard9
Shortest path, Graph+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Beasts
Hard9
Geometry, Binary search+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Casting Spells
Hard9
String matching, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fields and Farmers
Hard9
Geometry, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hanging Hats
Hard9
Geometry, Segment tree+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Gates of Logic
Hard9
Simulation, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Origami Axiom Six: Counting Folds
Hard9
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Asteroids
Hard9
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Exclusive Access 2
Hard9
Graph, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grand Theft Auto Wheel
Hard9
Geometry, Simulation+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Fibonacci Base
Hard9
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ground Works
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
K’ak’-u-pakal and the Maya Script
Hard9
Recursion, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fool's Game
Hard9
Game theory, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Room Assignments
Hard9
Graph, Union-find+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tantrix
Hard9
Simulation, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Road Planner
Hard9
Graph, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
RSA Factorization
Hard9
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Moon of Valencia
Hard9
Backtracking, DFS+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cubic Colonies
Hard9
Geometry, Graph+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Maximize the MinimumGiven two arrays with per-element removal costs, find the largest possible minimum gap \|a_i - b_j\| across the remaining elements when total removal cost is at most s.	Hard8	Binary searchDynamic programming+1	No attempts yet	4s	2048 MB	Judgeable
Fischer's Chess Guessing GameJill picks one of the 960 Fischer Random starting positions, and Jack must identify it in at most six guesses, each returning how many white pieces match.	Hard8	CombinatoricsImplementation	No attempts yet	2s	2048 MB	Judgeable
Graph CutsMaintain a vertex set U under insertions and deletions, and for each query remove one edge with exactly one endpoint in U, or report 0 if none exists.	Hard8	GraphHash map+1	No attempts yet	4s	2048 MB	Judgeable
Poor StudentsAssign each of n students to one of k exams so that exam j gets at most a_j students, minimizing the total frustration c[i][j].	Hard8	Shortest pathGraph+1	No attempts yet	4s	2048 MB	Judgeable
Crossing the BorderPack n weighted items into knapsacks of capacity W so that the sum of each knapsack's maximum tax is minimal, and count the optimal packings.	Hard8	Dynamic programmingBit manipulation+1	No attempts yet	15s	2048 MB	Judgeable
Fortune WheelGiven a wheel with n sectors, a start sector x, and K power spins, find the minimum expected number of spins to land on sector 0, as an irreducible fraction.	Hard8	Dynamic programmingMath+2	No attempts yet	1s	2048 MB	Judgeable
Jumping LightsGiven a tree, process queries that mark or unmark a vertex and a global step that marks each vertex with a marked neighbor, printing the marked count after each query.	Hard8	TreeBFS+1	No attempts yet	3s	2048 MB	Judgeable
AbstractValues in a DAG pass along edges each second, and the sink keeps half of its own value. Find the first moment all values reach 0, modulo 998244353.	Hard8	GraphTopological sort+2	No attempts yet	2s	2048 MB	Judgeable
Fast DebuggerGiven a program of bitwise instructions on four 8-bit registers with nested repeat blocks, find the register values after the first k instructions.	Hard8	Bit manipulationDivide and conquer+1	No attempts yet	1s	2048 MB	Judgeable
Data Structures MasterAfter each append to A, B, or C, output the sum over all triples (x from A, y from B, z from C) of the max of a between min and max of x, y, z, mod 998244353.	Hard8	Segment treeSorting+1	No attempts yet	2s	2048 MB	Judgeable
Poisonous LabyrinthGiven a weighted tree with m pairs of poison vials, find the start vertex that minimizes the distance needed to cure all poisons and return to it.	Hard8	TreeDFS+1	No attempts yet	3s	2048 MB	Judgeable
Lost TableCount the n by m tables of positive integers whose row maxima are a and column maxima are b, modulo 1e9+7.	Hard8	CombinatoricsMath+1	No attempts yet	2s	2048 MB	Judgeable
A Tree GameGiven a tree, decide whether Little I can move a chip from vertex 1 to a leaf (degree 1) while Little J closes one open edge per round. Print 1 if I wins, else 0.	Hard8	TreeGame theory+1	No attempts yet	1s	2048 MB	Judgeable
Generating the SequenceGiven an array of odd numbers, add an even value to a range and query the product of a range modulo 2^20.	Hard8	Number theoryBit manipulation+1	No attempts yet	10s	2048 MB	Judgeable
Interesting WordsCount the ordered sequences of given words whose concatenation is a palindrome of exact length L, modulo 1e9+7.	Hard8	Dynamic programmingString matching+1	No attempts yet	3s	2048 MB	Judgeable
Festival DecoratingFor each distance d, find the lowest-index lamp that has a lamp at x plus d with a different color, or print 0 if none exists.	Hard8	MathArray	No attempts yet	9s	2048 MB	Judgeable
Comedy's Not OmnipotentRecover a random hidden binary sequence of length n using subset-sum queries, with fewer than n/2 queries and total query size at most 3n.	Hard8	ArrayBit manipulation+1	No attempts yet	4s	2048 MB	Judgeable
Palindrome StringsGiven a string S and query strings t, count the pairs (l, r) for which t followed by S[l..r] is a palindrome.	Hard8	String matchingString	No attempts yet	2s	2048 MB	Judgeable
Count the OrdersPlace n distinct integers on a circle to maximize the sum of adjacent absolute differences, then count the arrangements that reach that maximum modulo 1e9+7.	Hard8	SortingGreedy+1	No attempts yet	1s	2048 MB	Judgeable
Simple Math ProblemGiven positive integers m and n, compute a double sum of squared binomial products modulo 998244353 for up to 100000 test cases.	Hard8	CombinatoricsMath	No attempts yet	1s	2048 MB	Judgeable
Neutral SpectatorEach query picks x consecutive good mages and y consecutive evil mages, and asks for the largest possible minimum of (a_i + c_j) / (b_i + d_j) over all cross pairs.	Hard8	Binary searchGeometry+1	No attempts yet	2s	2048 MB	Judgeable
Old Solution MethodsThree lines through fixed points A, B, C are rotated by a common angle, and the task is to find the largest area of the triangle formed by their pairwise intersections.	Hard8	GeometryMath+1	No attempts yet	1s	2048 MB	Judgeable
Immensely Long ExpressionsFor each odd length n, find the expected value of a uniformly random valid arithmetic expression of that length, modulo 998244353.	Hard8	Dynamic programmingProbability+1	No attempts yet	1s	2048 MB	Judgeable
Sending SubstringsGiven team names, count over all ordered pairs of different teams the distinct substrings that both names contain, summed over every pair.	Hard8	String matchingString+1	No attempts yet	6s	2048 MB	Judgeable
Cat TourFind the shortest closed walk that crosses every one-way cat street in its direction and never reuses a street, or report -1.	Hard8	GraphShortest path	No attempts yet	0.5s	2048 MB	Judgeable
Sequences, Queries, and Probability 2Given M random operations on a sequence, find the expected ratio of the final sum or product to the initial one, modulo 1e9+7.	Hard8	ProbabilityMath+1	No attempts yet	1s	1024 MB	Judgeable
What Should You Say When You See Trees Burning?Each vertex starts with its own index as weight. Each query cyclically shifts the weights on the a-b path by k and prints the XOR of that path.	Hard8	TreeImplementation+1	No attempts yet	2s	1024 MB	Judgeable
Sum SequenceFor a given M, decide for each query N whether N appears in the sequence B_M formed by repeatedly summing the M smallest unused positive integers.	Hard8	MathNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
\mathtt{MatKor} \oplus \mathtt{AlKor} = \mathtt{MatAl}Heat pieces with tent-shaped rises of height N so every adjacent temperature gap is at most M, minimizing the number of heating steps.	Hard8	Prefix sumGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Caterpillar and TreeFor each query, decide whether a caterpillar on a tree can move its head and tail from h and t to the queried vertices h' and t'.	Hard8	TreeGraph+1	No attempts yet	5s	1024 MB	Judgeable
Reachable PairsGiven an undirected graph and a binary string, count the reachable node pairs before each step, where a 1 removes the node and joins its neighbors and a 0 just removes it.	Hard8	GraphUnion-find	No attempts yet	2s	2048 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
Fibonacci BaseGiven N up to 10^15, count how many '1' characters appear among the first N characters of the string formed by concatenating Zeckendorf (Fibonacci base) representations of 1,2,3,... in order.	Hard9	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Ground WorksSimulate water filling inside the region enclosed by a rotated Hilbert curve fractal against a tilted ground line, accounting for trapped air pockets, and output the flooded area to four decimals.	Hard9	GeometrySimulation+2	No attempts yet	3s	256 MB	Judgeable
K’ak’-u-pakal and the Maya ScriptParse a recursive grammar for Maya glyph compositions and render a minimal-size ASCII-art box layout respecting horizontal/vertical grouping and bracket-doubling size rules.	Hard9	RecursionString+2	No attempts yet	1s	128 MB	Judgeable
Fool's GameSimulate the full two-player card game 'Fool' with optimal play from both sides and determine which player ultimately wins.	Hard9	Game theoryDFS+2	No attempts yet	1s	128 MB	Judgeable
Room AssignmentsGiven n-1 inventors' two-choice coins forming a graph, pick an edge for the organizer's own coin that maximizes his expected room rating while keeping a perfect assignment possible.	Hard9	GraphUnion-find+1	No attempts yet	1s	128 MB	Judgeable
TantrixSimulate the hexagonal tile game Tantrix and count all legal placements of hand tiles given complex forced-space and controlled-side rules.	Hard9	SimulationGeometry+2	No attempts yet	1s	128 MB	Judgeable
Road PlannerGiven a DAG with linear latency functions per edge, distribute an integer number of cars from source to sink to reach Wardrop (selfish routing) equilibrium and output the floor of the equilibrium travel time.	Hard9	GraphMath+1	No attempts yet	1s	128 MB	Judgeable
RSA FactorizationGiven a huge n up to 10^120 and k, find primes p ≤ q with n = p*q and \|q - kp\| bounded by 10^5, requiring advanced factorization insight.	Hard9	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
The Moon of ValenciaGiven a map of places with satisfaction values and walking edges, decide for each query whether a simple path between two nodes exists that fits a time budget and yields a satisfaction sum within 0.1 of a target.	Hard9	BacktrackingDFS+1	No attempts yet	1s	128 MB	Judgeable
Cubic ColoniesGiven a 3x3x3 arrangement of unit cubic blocks (some missing) and two surface points, compute the length of the shortest path on the colony's outer surface between them, allowing passage through zero-width edge or vertex gaps.	Hard9	GeometryGraph+2	No attempts yet	5s	128 MB	Judgeable