Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,152 problems

DeCSS 7
Hard8
Bit manipulation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
DeCSS 9
Hard8
Brute force, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Neboderi
Hard8
Sliding window, Number theory+1
No attempts yet
Time limit
2.5s
Memory limit
1024 MB
Judgeable
Lampice
Hard8
Prefix sum, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Expected Cycle Size
Hard8
Probability, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Folding
Hard8
String matching, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Tennis
Hard8
Dynamic programming, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Quadratic Functions and a Line
Hard8
Geometry, Math+1
No attempts yet
Time limit
0.1s
Memory limit
1024 MB
Judgeable
Maximum Absolute Value of the Product of Interval Sums
Hard8
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Stone Game and Queries
Hard8
Number theory, Math+1
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Card Game
Hard8
Game theory, Graph+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Hilbert Billiards
Hard8
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Permutation
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Carcassonne
Hard8
Matrix, BFS+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Magic Towers
Hard8
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Alps Cable Car 2
Hard8
Dynamic programming, Geometry+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Tea
Hard8
Math, Sorting+1
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Three Roads
Hard8
Graph, DFS+1
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Spanning Trees
Hard8
Number theory, Graph+1
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Kindergarten
Hard8
Graph, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Difference Representations
Hard8
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Water Pipe Game
Hard8
Game theory, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Energy Generation
Hard8
Graph, Geometry
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Greatest Common Divisor
Hard8
Number theory, Math+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
TwoFour
Hard8
Game theory, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Attack Relay
Hard8
Simulation, Geometry+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Projectors
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Expedition to Sirius
Hard8
Sorting, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magnetic Games
Hard8
Implementation, Geometry+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Square Running
Hard8
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Wires Puzzle
Hard8
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Stacking Cups
Hard8
Dynamic programming, Combinatorics
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Jump Rope
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
How Much Money Can Eggs Make?
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
DAGame
Hard8
Game theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Chino's Latte Art
Hard8
Geometry, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Present
Hard8
Number theory, Combinatorics+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Letter Passing
Hard8
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Nice Lines
Hard8
Geometry, Math+1
No attempts yet
Time limit
0.2s
Memory limit
1024 MB
Judgeable
Colorful Tree
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Birthday Gift
Hard8
Dynamic programming, Matrix+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Fishing Game
Hard8
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Chimichangas
Hard8
Math, Dynamic programming+1
No attempts yet
Time limit
0.35s
Memory limit
1024 MB
Judgeable
Euclid
Hard8
Segment tree, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cake Decoration
Hard8
Math, Combinatorics+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Sorting
Hard8
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Game With Numbers
Hard8
Game theory, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pancake Tower
Hard8
Probability, Combinatorics+1
No attempts yet
Time limit
0.7s
Memory limit
1024 MB
Judgeable
Graph Traveler
Hard8
Graph, Union-find+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
K-Convex Hull
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fencing the Sheep
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
UFO in the Sinchon
Hard8
Math, Simulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Making a Good Binary String
Hard8
Prefix sum, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Digits of Unity
Hard8
Bit manipulation, Combinatorics+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Team Formation
Hard8
Geometry, Segment tree+2
No attempts yet
Time limit
6s
Memory limit
1024 MB
Judgeable
Hilbert's Hedge Maze
Hard8
Recursion, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Forming a Team
Hard8
Segment tree, Sorting+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Convex Hull
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Qizz Quzz (Hard)
Hard8
String, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Flipping and cutting (Hard)
Hard8
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Russian Roulette (Hard)
Hard8
Dynamic programming, Probability+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Ferries (Hard)
Hard8
Math, Bit manipulation
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Ultimate magic rectangles (Hard)
Hard8
Math, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Maximum enjoyment
Hard8
Graph, Shortest path+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Exploring the cave
Hard8
Graph, Combinatorics+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Harvesting potatoes
Hard8
Implementation, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Rotate to divide
Hard8
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Klingon High Council Training
Hard8
Game theory, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Counting Cases
Hard8
Number theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Forest Scientist
Hard8
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Operator Party
Hard8
Math, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Cartesian Job
Hard8
Geometry, Probability+1
No attempts yet
Time limit
40s
Memory limit
1024 MB
Judgeable
Bacterial Tactics
Hard8
Game theory, Graph+1
No attempts yet
Time limit
30s
Memory limit
1024 MB
Judgeable
New Elements: Part 1
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Pottery Lottery
Hard8
Probability, Game theory+1
No attempts yet
Time limit
40s
Memory limit
1024 MB
Judgeable
Zillionim
Hard8
Game theory, Math+1
No attempts yet
Time limit
50s
Memory limit
1024 MB
Judgeable
Join the Ranks
Hard8
Math, Implementation
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Recalculating
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Hexacoin Jam
Hard8
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
90s
Memory limit
1024 MB
Judgeable
Bakery
Hard8
Math, Geometry+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Three Similar Chocolates
Hard8
Geometry, Number theory+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Singularity of the Nim
Hard8
Game theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Square Deck 2
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Permutation Cycles and Queries
Hard8
Number theory, Array+1
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Yoon stole something huge
Hard8
Game theory, Graph+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Three People on a Tree
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Good Bitstrings
Hard8
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Shuffled Stones
Hard8
Combinatorics, Math
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Splitting Pairs
Hard8
Game theory, Math+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Lucky Stars Management
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Optimal Quadratic Function
Hard8
Math, Binary search+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Courses
Hard8
Dynamic programming, Combinatorics
No attempts yet
Time limit
15s
Memory limit
1024 MB
Judgeable
Sets May Be Good
Hard8
Math, Matrix+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Record Parity
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
5
Hard8
Dynamic programming, Math
No attempts yet
Time limit
5s
Memory limit
555 MB
Judgeable
Classical Counting Problem
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Classical FFT Problem
Hard8
Combinatorics, Math
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Dominoes
Hard8
Stack, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Stone Taking Game
Hard8
Game theory, Graph+1
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Colored-Dealt
Hard8
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
DeCSS 9Given some known bytes of a CSS keystream from two LFSRs (17 and 25 bits) with a carry, find any 42-bit key that reproduces them.	Hard8	Brute forceMath+1	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
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
Quadratic Functions and a LineGiven N quadratics with leading coefficient 1 or -1, pick the fewest that make every line meet at least one of them, and print their indices or -1.	Hard8	GeometryMath+1	No attempts yet	0.1s	1024 MB	Judgeable
Maximum Absolute Value of the Product of Interval SumsGiven an integer array and at most K non-overlapping intervals, find the maximum absolute value of the product of the interval sums.	Hard8	Dynamic programmingPrefix sum+1	No attempts yet	1s	256 MB	Judgeable
Stone Game and QueriesGiven X, T, and N, find the fewest turns needed to leave the fewest stones, where turn I takes a multiple of X+I of at most (X+I)×T stones.	Hard8	Number theoryMath+1	No attempts yet	1.5s	512 MB	Judgeable
Card GamePlayers alternately discard the opponent's decks, and given the known win and loss pairs, the task is to decide whether Bajtek wins, draws, or loses.	Hard8	Game theoryGraph+1	No attempts yet	2s	1024 MB	Judgeable
Hilbert BilliardsGiven a ball bouncing inside a Hilbert-curve billiard table of size 2n+1, report its integer coordinates at up to 100000 query times.	Hard8	SimulationMath+1	No attempts yet	2s	1024 MB	Judgeable
PermutationFind the k-th lexicographically smallest permutation of length n whose inversion count is exactly half of all pairs, or report NIE if none exists.	Hard8	CombinatoricsMath+1	No attempts yet	1s	1024 MB	Judgeable
CarcassonneCounts the distinct sets of k new tiles that can be added to an n by n board so each new tile touches the tiles placed before it, modulo 1e9+7.	Hard8	MatrixBFS+1	No attempts yet	5s	1024 MB	Judgeable
Magic TowersGiven n mages with two towers each, find the area of points where every movement direction brings you closer to both towers of some mage.	Hard8	GeometryMath	No attempts yet	1s	1024 MB	Judgeable
Alps Cable Car 2Connect the peaks of N triangles from peak 1 to peak N using at most K wires, minimizing the sum of squared wire lengths.	Hard8	Dynamic programmingGeometry+1	No attempts yet	2s	1024 MB	Judgeable
TeaDecide whether splitting and mixing tea can turn each cup's initial temperature into its target temperature while keeping every volume.	Hard8	MathSorting+1	No attempts yet	8s	1024 MB	Judgeable
Three RoadsCount the triples of roads whose removal leaves some pair of cities unable to reach each other in a connected graph.	Hard8	GraphDFS+1	No attempts yet	8s	1024 MB	Judgeable
Spanning TreesCount the spanning trees of a graph where each pair of vertices i and j has gcd(a_i, a_j) parallel edges, modulo 10^9+7.	Hard8	Number theoryGraph+1	No attempts yet	8s	1024 MB	Judgeable
KindergartenCount the proper k-colorings of a graph with n vertices and m edges, for up to 1000 values of k, modulo 1000000007.	Hard8	GraphCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
Difference RepresentationsFor each given positive integer x up to 10^9, find the index pair (p, q) where a_p minus a_q equals x in this doubling and difference-avoiding sequence.	Hard8	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
Water Pipe GameFor each intersection, decide whether the first player wins the game where crews take turns walking along unused road segments.	Hard8	Game theoryGraph+1	No attempts yet	1s	1024 MB	Judgeable
Energy GenerationGiven N towers on a plane, choose each tower's 90-degree orientation to maximize passive energy plus pairwise interaction energy for towers within radius R.	Hard8	GraphGeometry	No attempts yet	1s	1024 MB	Judgeable
Greatest Common DivisorGiven n and queries p, find the p-th pair (x, y) in lexicographic order where Gennady's div-based Euclid finishes and outputs the true gcd.	Hard8	Number theoryMath+1	No attempts yet	5s	1024 MB	Judgeable
TwoFourGiven initial piles of 0 to 4 balls, find the winner of TwoFour under optimal play, where each two-ball pile belongs to whoever last moved it.	Hard8	Game theoryDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Attack RelayGiven N members with positions and view directions, find the total damage each member takes over K chase turns, modulo 998244353.	Hard8	SimulationGeometry+1	No attempts yet	3s	1024 MB	Judgeable
ProjectorsEach projector lights one axis-aligned 90-degree corner of a w by h field; choose the directions that maximize the total lit area.	Hard8	GeometrySorting+1	No attempts yet	1s	1024 MB	Judgeable
Expedition to SiriusGiven players whose experience grows each round by the count of distinct higher levels, answer queries on level count, total gain, or one player's value.	Hard8	SortingPrefix sum+2	No attempts yet	2s	1024 MB	Judgeable
Magnetic GamesGiven the 8-direction compass readings on an n by m grid, find the magnet's cell and the two lines flipped by the anomaly.	Hard8	ImplementationGeometry+1	No attempts yet	1s	1024 MB	Judgeable
Square RunningGiven n runners on concentric lanes around a rectangle, find the earliest second when every runner is in the photographer's row or column, or report -1.	Hard8	Number theoryMath+1	No attempts yet	1s	1024 MB	Judgeable
Wires PuzzleRecover a hidden permutation that maps right wire labels to left wire labels, using exactly three interactive queries that report which left wires share a right-side group.	Hard8	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Stacking CupsCount the valid stacks of exactly N red and blue cups, where each cup on top sits on two neighbors with at least one red, modulo prime P.	Hard8	Dynamic programmingCombinatorics	No attempts yet	2s	1024 MB	Judgeable
Jump RopeWoo-kyung starts at S among N ropes that translate at constant velocity, and the task is to find the fewest rope crossings needed to end off every rope.	Hard8	GeometrySorting+1	No attempts yet	3s	1024 MB	Judgeable
How Much Money Can Eggs Make?Jaewoo drops i eggs on day i for K days, and the task is to sum the highest floor testable each day, modulo 1000000007, with K up to 10^18.	Hard8	CombinatoricsMath+1	No attempts yet	1s	1024 MB	Judgeable
DAGameTwo players take turns moving tokens along DAG edges, and same-colored token pairs move together once they meet. Output the winner under optimal play.	Hard8	Game theoryDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Chino's Latte ArtGiven a simple polygon, decide whether one reflex vertex and one convex vertex form a symmetry axis that splits it into two convex halves.	Hard8	GeometryString matching+1	No attempts yet	1s	1024 MB	Judgeable
PresentGiven K, output the K-th finite set of positive integers that is closed under gcd, counted in Laikan order.	Hard8	Number theoryCombinatorics+1	No attempts yet	4s	1024 MB	Judgeable
Letter PassingGiven a permutation F, find the LCM of its cycle lengths, and the smallest LCM reachable by swapping two entries of F.	Hard8	Number theoryMath+1	No attempts yet	2s	512 MB	Judgeable
Nice LinesRecover the N hidden lines y = a_i x + b_i by querying the sum of distances from a chosen point to all lines, using few queries.	Hard8	GeometryMath+1	No attempts yet	0.2s	1024 MB	Judgeable
Colorful TreeCount the colorings of a rooted tree with k colors where each vertex takes one of its children's colors, and the children use between l_i and r_i colors.	Hard8	TreeDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Birthday GiftCount the decimal numbers with exactly a digits, no two adjacent digits equal, and remainder b mod 225, modulo 1e9+7.	Hard8	Dynamic programmingMatrix+1	No attempts yet	2s	1024 MB	Judgeable
Fishing GameCount the distinct ways three players can pass cards in Fishing until every card is discarded, given their hands after the first discard, modulo 1000000007.	Hard8	Dynamic programmingCombinatorics	No attempts yet	1s	1024 MB	Judgeable
ChimichangasCount the ordered sequences of exactly K calorie values from N types that sum to each queried meal, modulo 2999.	Hard8	MathDynamic programming+1	No attempts yet	0.35s	1024 MB	Judgeable
EuclidAnswer range gcd queries on an array after range updates that add an arithmetic progression to each interval.	Hard8	Segment treeMath	No attempts yet	1s	1024 MB	Judgeable
Cake DecorationCount distinct positive quadruples (dogs, cats, red, blue) with dogs plus cats in [L, R) whose product is at most X but exceeds X when any single count increases by one.	Hard8	MathCombinatorics+1	No attempts yet	10s	1024 MB	Judgeable
SortingCount permutations of N elements whose inversion count exceeds the minimum number of arbitrary swaps (N minus cycles), modulo 999017.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Game With NumbersTwo players alternately delete all array elements divisible by b_i or all not divisible by b_i, and the task is the final sum under optimal play.	Hard8	Game theoryNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Pancake TowerGiven odd N and p/q, find the probability that spoiled pancakes outnumber fresh ones in a chain of N, modulo 998244353.	Hard8	ProbabilityCombinatorics+1	No attempts yet	0.7s	1024 MB	Judgeable
Graph TravelerFor each query start (x, y), count the distinct vertices the walk visits infinitely often, where the next edge depends on the running sum c mod m_i.	Hard8	GraphUnion-find+1	No attempts yet	2s	512 MB	Judgeable
K-Convex HullGiven N distinct points, count how many single points can be removed so that the convex hull of the remaining points has exactly K vertices.	Hard8	GeometrySorting+1	No attempts yet	1s	1024 MB	Judgeable
Fencing the SheepGiven N sheep on an infinite grid, find the fewest unit fences that enclose all sheep in one connected pen, and the smallest pen area with that many fences.	Hard8	GeometrySorting+1	No attempts yet	1s	1024 MB	Judgeable
UFO in the SinchonEach UFO pulls every person one king move per second toward its cell for a set time, and the task is to print final positions after all appearances.	Hard8	MathSimulation+1	No attempts yet	2s	1024 MB	Judgeable
Making a Good Binary StringGiven a binary string, find the fewest character flips so that the shortest intervals covering all 0s and all 1s have equal length.	Hard8	Prefix sumDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Digits of UnityCount n-element sets of distinct integers from 1 to m whose bitwise AND has at least k set bits, modulo 998244353.	Hard8	Bit manipulationCombinatorics+1	No attempts yet	5s	1024 MB	Judgeable
Team FormationFor each query, find the largest (A1[i]+A2[j]) times (B1[i]+B2[j]) over a range of boys i and a range of girls j.	Hard8	GeometrySegment tree+2	No attempts yet	6s	1024 MB	Judgeable
Hilbert's Hedge MazeGiven a hedge maze of order n built from a Hilbert-curve-like string, find the shortest walking distance between two cells.	Hard8	RecursionDivide and conquer+2	No attempts yet	1s	1024 MB	Judgeable
Forming a TeamGiven N points (A_i, B_i) and Q pairs, find for each pair the smallest extra cost a third point adds to their bounding box in both coordinates.	Hard8	Segment treeSorting+1	No attempts yet	3s	1024 MB	Judgeable
Convex HullFor each point, count how many of the other points lie on the convex hull after that point is removed from the set.	Hard8	GeometrySorting+1	No attempts yet	1s	1024 MB	Judgeable
Qizz Quzz (Hard)Given a sequence of labels, find the longest prefix that some set of divisor-to-string rules in a Generalized Fizz Buzz program could produce.	Hard8	StringString matching+1	No attempts yet	1s	1024 MB	Judgeable
Flipping and cutting (Hard)Given circumference c and squared step s, find which pairs make repeated wedge flips return the paper to all black, and the fewest rounds needed.	Hard8	Number theoryMath+1	No attempts yet	1s	1024 MB	Judgeable
Russian Roulette (Hard)Given n players, c chambers, and k passes per empty shot, find the starting seat with the best survival chance and its probability modulo 1000000009.	Hard8	Dynamic programmingProbability+1	No attempts yet	5s	1024 MB	Judgeable
Ferries (Hard)Given car positions a_1 to a_k seen during a trip on 2n cars, find the fewest ferry crossings and an L/R string of ferry types that produces them.	Hard8	MathBit manipulation	No attempts yet	10s	1024 MB	Judgeable
Ultimate magic rectangles (Hard)Count the ways to fill a 3-row, c-column grid with nonnegative integers so every triplet on a line across all three rows sums to s, modulo 10^9 + 9.	Hard8	MathCombinatorics+1	No attempts yet	1s	1024 MB	Judgeable
Maximum enjoymentGiven an undirected graph with link capacities, find the maximum total bandwidth from s to t when each path may use at most L links and shared links cannot exceed capacity.	Hard8	GraphShortest path+1	No attempts yet	10s	1024 MB	Judgeable
Exploring the caveGiven n and d, build a cave with n chambers and labeled one-way tunnels that meets the parameters, or report that no such cave exists.	Hard8	GraphCombinatorics+1	No attempts yet	10s	1024 MB	Judgeable
Harvesting potatoesGiven an r by c field and a per-pass limit d, schedule row and column passes so each cell is harvested once, using the fewest passes and then the lowest difficulty.	Hard8	ImplementationGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Rotate to divideGiven base b and ratio k, find the smallest number whose last digit moved to the front gives exactly 1/k of the original, and output its length and first digit.	Hard8	Number theoryMath	No attempts yet	1s	1024 MB	Judgeable
Klingon High Council TrainingTwo players take turns moving up to K of N ships toward the origin, each move strictly closer, and the task is to find the winner under optimal play.	Hard8	Game theoryNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Counting CasesGiven N rabbits that each pick a value from the set X, count the assignments whose product equals k for every k from 1 to K, modulo 1e9+7.	Hard8	Number theoryDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Forest ScientistGiven N and a list of positions, find the values at those positions in the insertion order that minimizes the weighted energy of the resulting BST.	Hard8	TreeGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Operator PartyStarting from X = 0, apply the operations for multiples of A to F at each step i from 1 to N, in the given priority order, and print the final X.	Hard8	MathBit manipulation+1	No attempts yet	2s	512 MB	Judgeable
The Cartesian JobGiven N rotating lasers with random directions, find the probability that some open time interval exists when no laser touches the segment from (0, 0) to (0, 1000).	Hard8	GeometryProbability+1	No attempts yet	40s	1024 MB	Judgeable
Bacterial TacticsBecca and Terry alternately place H or V colonies on a grid with radioactive cells, and the task is to count Becca's winning first moves or report 0.	Hard8	Game theoryGraph+1	No attempts yet	30s	1024 MB	Judgeable
New Elements: Part 1Given N molecules with Codium and Jamarium atom counts, count the orderings by molecular weight that some pair of positive integer atomic weights can produce.	Hard8	GeometrySorting+1	No attempts yet	20s	1024 MB	Judgeable
Pottery LotteryPlayer 100 gets up to 99 forge or peek actions against 20 vases, then picks one vase for their token so that it ends up as the unique minimum.	Hard8	ProbabilityGame theory+1	No attempts yet	40s	1024 MB	Judgeable
ZillionimGiven a Zillionim position on 10^12 coins where each move removes 10^10 consecutive coins, decide whether you can beat a random-moving AI most of the time.	Hard8	Game theoryMath+1	No attempts yet	50s	1024 MB	Judgeable
Join the RanksGiven R ranks and S suits, find the fewest pile-swap operations that regroup the deck by rank, and output the pile sizes for each operation.	Hard8	MathImplementation	No attempts yet	Not set	1024 MB	Judgeable
RecalculatingGiven repair centers and an L1 radius D, find the fraction of the covered area where the drone's position is uniquely determined by what it sees.	Hard8	GeometrySorting+1	No attempts yet	Not set	1024 MB	Judgeable
Hexacoin JamGiven hexadecimal numbers and a range, find the probability that a random digit permutation followed by a random pair sum lands inside the range.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	90s	1024 MB	Judgeable
BakeryGiven friends' orders and waiting limits, find the fewest oven upgrades that cut cookie and muffin times so every friend is served before leaving.	Hard8	MathGeometry+1	No attempts yet	2s	1024 MB	Judgeable
Three Similar ChocolatesCount integer tuples (a,b,c,d) with b+d < N for which some integer point P on segment AC makes triangles ABP, BDP, and DCP pairwise similar.	Hard8	GeometryNumber theory+1	No attempts yet	3s	1024 MB	Judgeable
Singularity of the NimGiven a staircase game where taking x coins from a step adds x^j coins to each lower step j, decide whether the first or second player wins.	Hard8	Game theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
Square Deck 2Merge N single-card decks so each merge pairs cards with a perfect-square sum, minimizing the product of recorded differences modulo 998244353.	Hard8	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Permutation Cycles and QueriesGiven a permutation A and a huge exponent m, answer queries that swap two entries of A and print the sum of S^m(i) times i.	Hard8	Number theoryArray+1	No attempts yet	7s	512 MB	Judgeable
Yoon stole something hugeGiven a tree with Yoon at vertex a and the two officers at b and c, decide whether Yoon can reach a leaf without being caught.	Hard8	Game theoryGraph+2	No attempts yet	1s	1024 MB	Judgeable
Three People on a TreeCount triples of people on three distinct vertices whose pairwise LCA D is not one of them and whose distances to D sum to K, modulo 998244353.	Hard8	TreeDynamic programming+1	No attempts yet	4s	1024 MB	Judgeable
Good BitstringsGiven A and B, count the prefixes of gen_string(A, B) that also equal gen_string(x, y) for some positive integers x and y.	Hard8	Number theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
Shuffled StonesGiven N and a pair X, Y, count the sequences of 2N stones with longest decreasing subsequence 2 in which X and Y are a pair, modulo 998244353.	Hard8	CombinatoricsMath	No attempts yet	3s	1024 MB	Judgeable
Splitting PairsGiven piles of stones, decide whether Alice wins a Nim variant where each turn removes k piles and splits k others, with k at most half the piles.	Hard8	Game theoryMath+1	No attempts yet	1s	2048 MB	Judgeable
Lucky Stars ManagementGiven a company tree and expected fines E_i, decide whether the values are consistent and, if so, find Bill's minimum possible annual salary.	Hard8	TreeDFS+2	No attempts yet	2s	1024 MB	Judgeable
Optimal Quadratic FunctionGiven N points (x_i, y_i), find the quadratic ax^2+bx+c that minimizes the maximum squared vertical error over all points and print that minimum.	Hard8	MathBinary search+1	No attempts yet	10s	1024 MB	Judgeable
CoursesCount the course sequences with total cost exactly t and total IQ change at least k, for each t from 1 to n, modulo 998244353.	Hard8	Dynamic programmingCombinatorics	No attempts yet	15s	1024 MB	Judgeable
Sets May Be GoodCount the vertex subsets whose induced edge count is even, for a graph with up to 1000 vertices, modulo 998244353.	Hard8	MathMatrix+1	No attempts yet	2s	1024 MB	Judgeable
Record ParityGiven a permutation, find the sum of (-1)^len over all subsequences with exactly k records (left-to-right maxima), modulo 998244353.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	1s	1024 MB	Judgeable
5Given an array of non-negative integers with sum S and at least S/5 ones, count the pairs (k, T) where some subsequence of length k sums to T.	Hard8	Dynamic programmingMath	No attempts yet	5s	555 MB	Judgeable
Classical Counting ProblemCount the distinct sets of p problems that can end up as the top p after m judges each vote for v problems, modulo 998244353.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
Classical FFT ProblemGiven a Young diagram with nondecreasing row widths, find the fewest rooks that cover every cell and count the ways to place them.	Hard8	CombinatoricsMath	No attempts yet	10s	1024 MB	Judgeable
DominoesGiven n dominoes that fall left with heights l_i, find for each starting domino the area of the union of quarter circles that topple.	Hard8	StackDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Stone Taking GameGiven a cycle whose edges hold stones, find for each i the fewest extra stones Jeonghu must add so he wins from at least i starting vertices.	Hard8	Game theoryGraph+1	No attempts yet	0.5s	256 MB	Judgeable
Colored-DealtUsing at most N wreath attempts and only the maximum photo value r + 2g + 3b over rotations, infer the color order of the N flowers Jay places.	Hard8	ImplementationMath+1	No attempts yet	1s	1024 MB	Judgeable