Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,164 problems

Immigration
Hard8
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Reachable Sequences
Hard8
Combinatorics, Bit manipulation+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Physics
Hard8
Math, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Array and Operations
Hard8
Segment tree, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Value of the Array
Hard8
Combinatorics, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pruefsumme
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Vier
Hard8
Hash map, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Weltall
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Robots
Hard8
Graph, BFS+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Triangles
Hard8
Geometry, Hash map+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
XOR Tree
Hard8
Tree, Game theory
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Friends and Berries - 2
Hard8
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Easy Homework
Hard8
Number theory, Matrix+1
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Intersection is Not Allowed!
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Circles
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Eel and Grid
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cups and Beans
Hard8
Game theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sublime Marathon
Hard8
Tree, DFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Length String
Hard8
String, Math+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Function Reconstruction
Hard8
Graph, Combinatorics+2
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Mixture
Hard8
Geometry, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Triangulation
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2.5s
Memory limit
256 MB
Judgeable
Drought (Large)
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Urban Blight
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Swapping Seats
Hard8
Greedy, Sliding window+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Game with Grundy
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fancy Fence
Hard8
Stack, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Chess Rush
Hard8
Matrix, Math+1
No attempts yet
Time limit
2.3s
Memory limit
64 MB
Judgeable
Superpermutations
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flexible Segments
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Drawing
Hard8
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fraction Paradox
Hard8
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Shushpanchiks and the Cinema
Hard8
Math, Intervals+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cipher Breaking
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Strange Exhibit
Hard8
Implementation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Planet Nine
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Linearization
Hard8
Bit manipulation, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Equal Maximums
Hard8
Array, Stack+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Koosaga's problem
Hard8
Graph, BFS+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
«Exclusive or» Strikes Back
Hard8
Bit manipulation, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Speeding
Hard8
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Machine Learning
Hard8
Bit manipulation, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Broken Line 04
Hard8
Sorting, Greedy+2
No attempts yet
Time limit
0.1s
Memory limit
512 MB
Judgeable
Broken Line 05
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
0.1s
Memory limit
512 MB
Judgeable
Broken Line 08
Hard8
Sorting, Greedy+2
No attempts yet
Time limit
0.1s
Memory limit
512 MB
Judgeable
Painting Squares
Hard8
String, Combinatorics+2
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Carnival Tickets
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Counting Mushrooms
Hard8
Implementation, Math+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sea Battle
Hard8
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Turtles in the Pond
Hard8
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Painting the Fence
Hard8
Greedy, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rotating Plate
Hard8
Geometry, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Advertisement Matching
Hard8
Math, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
LCS 8
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Min-hashing
Hard8
Graph, Simulation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Remote Control
Hard8
Simulation, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Steel Slicing 2
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bit String
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Broken Tiles
Hard8
Binary search, Greedy+1
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Counting the Number of Trees
Hard8
Dynamic programming, Tree+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Toy Train
Hard8
Graph, Game theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cup of Jamshid
Hard8
Bit manipulation, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Card Shuffle
Hard8
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Vista 1
Hard8
Geometry, Greedy+2
No attempts yet
Time limit
0.1s
Memory limit
128 MB
Judgeable
Vista 2
Hard8
Geometry, Greedy+2
No attempts yet
Time limit
0.1s
Memory limit
128 MB
Judgeable
Vista 7
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
0.1s
Memory limit
128 MB
Judgeable
Hero Loves Powers of Two! Hero Loves Powers of Two!
Hard8
Bit manipulation, Greedy+2
No attempts yet
Time limit
2.2s
Memory limit
222 MB
Judgeable
Imprecise Computer
Hard8
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Switches
Hard8
Math, Matrix+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bubble Bubble
Hard8
Sorting, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Icpcan Alphabet
Hard8
Dynamic programming, Brute force+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Nunchucks Shop
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Make Numbers
Hard8
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Critical Structures
Hard8
Graph, DFS+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Save lives or money
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Bad-hash students
Hard8
Math, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Dance of Divisibility
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Interactivity
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Machine Gun
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Phone Friends
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
SPC Cake
Hard8
Geometry, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The Second Part
Hard8
Geometry, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Classic Quarantine
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bidirectional Code
Hard8
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sail Shreds - 1
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds - 2
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds 4
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds - 6
Hard8
Geometry, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds - 7
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds - 8
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sail Shreds
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Squares and Cubes
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Old Book
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
🎵I hate you, hate you, I hate you so much, don't come near me, stop pestering me🎵 - 2
Hard8
Sorting, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Radium Mining
Hard8
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bender
Hard8
Brute force, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Kaisa - Survival
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Vlak
Hard8
Trie, Game theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Strange Strings
Hard8
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
CCTV Control
Hard8
Array, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
ImmigrationPeter moves along the x-axis while tracking an object whose velocity changes n times; find the maximum absolute angular speed of his gaze from time t0 onward.	Hard8	GeometryMath+2	No attempts yet	2s	256 MB	Judgeable
Reachable SequencesCount ordered pairs of permutations (i, j) where a^(i) can be reached from a^(j) by repeatedly swapping an out-of-order pair.	Hard8	CombinatoricsBit manipulation+1	No attempts yet	4s	512 MB	Judgeable
PhysicsBalls move on a line with acceleration tied to speed, collide elastically, and each query asks for the k-th smallest velocity at time t.	Hard8	MathSorting+2	No attempts yet	1s	512 MB	Judgeable
Array and OperationsMaintain an array under range add, range floor-square-root, and range sum queries, printing each sum.	Hard8	Segment treeBinary search+2	No attempts yet	1s	512 MB	Judgeable
Value of the ArrayFor each k from 1 to n, sum over all non-empty subsequences the sum of their min(size, k) largest elements, modulo 998244353.	Hard8	CombinatoricsSorting+2	No attempts yet	1s	512 MB	Judgeable
PruefsummeGiven n and m, build matrices p and q for a checksum that detects any single-digit change or adjacent swap, or report that none exists.	Hard8	MathNumber theory+1	No attempts yet	2s	256 MB	Judgeable
VierGiven a random permutation, find two distinct unordered pairs with equal sums of indices and equal sums of permutation values, both modulo n.	Hard8	Hash mapMath+2	No attempts yet	2s	256 MB	Judgeable
WeltallFind the d-th lexicographic permutation of 1..n that has exactly k fixed points.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	4s	256 MB	Judgeable
RobotsFind a number k such that after k nondeterministic moves, every robot is surely in one of the first b strongholds, or report -1 if none exists.	Hard8	GraphBFS+2	No attempts yet	10s	256 MB	Judgeable
TrianglesGiven up to 2000 distinct points, count right triangles formed by three of the points whose area falls in the inclusive range [A, B].	Hard8	GeometryHash map+2	No attempts yet	10s	256 MB	Judgeable
XOR TreeGiven a tree whose edges have multiplicities, decide for each query pair S and T whether Alice can force a path between them in H.	Hard8	TreeGame theory	No attempts yet	2s	256 MB	Judgeable
Friends and Berries - 2Given n points in the plane, find all pairs u, v such that every other point w lies in the closed disk with diameter uv.	Hard8	GeometryMath	No attempts yet	2s	256 MB	Judgeable
Easy HomeworkCount the indices n in [L, R] where f(n) mod p equals x, for the sequence f(0)=0, f(1)=1, f(n)=A·f(n-1)+f(n-2).	Hard8	Number theoryMatrix+1	No attempts yet	1.5s	256 MB	Judgeable
Intersection is Not Allowed!Count the ways to route K non-crossing monotone paths from fixed top squares to fixed bottom squares on an N by N board, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	256 MB	Judgeable
CirclesGiven N circles that all pass through the origin, count the lattice points lying inside or on at least one of the circles.	Hard8	GeometrySorting+1	No attempts yet	1s	256 MB	Judgeable
Eel and GridAn eel on a toroidal H by W grid walks right or down, painting cells, until it returns to a painted cell; count Hamiltonian-style walks that cover every cell and end at (0,0).	Hard8	CombinatoricsMath+1	No attempts yet	1s	256 MB	Judgeable
Cups and BeansBeans sit in cups 1 through N-1, each with a move limit C_i; players alternate sliding one bean to a lower cup and whoever cannot move loses. Decide the winner.	Hard8	Game theoryDynamic programming+2	No attempts yet	1s	256 MB	Judgeable
Sublime MarathonGiven a tree with N intersections, count the ways to add exactly two roads so that some two intersections are joined by three internally disjoint paths.	Hard8	TreeDFS+1	No attempts yet	2s	512 MB	Judgeable
Length StringGiven a and b, output the length string of length a times 10 to the power b, printing only the first 17 characters when that length is at least 21.	Hard8	StringMath+1	No attempts yet	3s	1024 MB	Judgeable
Function ReconstructionGiven the full reachability matrix of a functional graph on N nodes, count the number of functions f consistent with it, modulo 1e9+7.	Hard8	GraphCombinatorics+2	No attempts yet	1.5s	1024 MB	Judgeable
MixtureAfter each add or remove of a bottle, find the fewest shelf bottles whose nonnegative combination gives the target salt:pepper:garlic ratio, or 0 if none exists.	Hard8	GeometrySegment tree+1	No attempts yet	2s	256 MB	Judgeable
TriangulationCount, over all triangulations of a regular N-gon with a proper red/blue coloring, the total number of red triangles, modulo 998244353.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2.5s	256 MB	Judgeable
Drought (Large)Maximize the sum of a_i minus the sum of b_j over nonnegative reals a and b subject to a_i - b_j <= c_ij, then round the answer to the nearest integer.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Urban BlightGiven points and weighted segments, find a horizontal line whose intersection with the segments maximizes the total weight of segments it touches.	Hard8	GeometrySorting+2	No attempts yet	2s	1024 MB	Judgeable
Swapping SeatsGiven a circular string of A, B, C, find the minimum number of seat swaps needed so each letter forms one contiguous block.	Hard8	GreedySliding window+2	No attempts yet	2s	512 MB	Judgeable
A Game with GrundyFor each i from 0 to N, count integer x positions with L <= x <= R that lie strictly inside at most i of N triangular visibility wedges.	Hard8	GeometrySorting+2	No attempts yet	1s	512 MB	Judgeable
Fancy FenceCount axis-aligned integer rectangles lying on a histogram of N sections with heights h_i and widths w_i, modulo 1e9+7.	Hard8	StackDivide and conquer+2	No attempts yet	1s	32 MB	Judgeable
Chess RushFind the minimum number of moves and the count of shortest paths for a piece going from a column in row 1 to a target column in row R.	Hard8	MatrixMath+1	No attempts yet	2.3s	64 MB	Judgeable
SuperpermutationsGiven a permutation of 1 to n, find the position where it starts in the superpermutation s_n built by Dima's insertion process, modulo 1e9+7.	Hard8	CombinatoricsMath+1	No attempts yet	1s	512 MB	Judgeable
Flexible SegmentsFor each n up to 10000, decide whether some n consecutive positive integers admit a +1/-1 choice per element preserving the product, and output the start and signs.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
DrawingPaint exactly a_ij cells in each 4x4 block of a wraparound grid so that the painted cells and the unpainted cells are each connected.	Hard8	ImplementationMath	No attempts yet	1s	512 MB	Judgeable
Fraction ParadoxGiven k irreducible fractions, choose four distinct ones forming two pairs with a at most b and c at most d, maximizing (a+c)/(b+d) minus (e+g)/(f+h). Print their indices.	Hard8	SortingGreedy+1	No attempts yet	1s	512 MB	Judgeable
Shushpanchiks and the CinemaGiven an n by n grid with m blocked seats, choose k consecutive free seats in one row minimizing the sum of Manhattan distances to a target seat.	Hard8	MathIntervals+2	No attempts yet	2s	512 MB	Judgeable
Cipher BreakingOutput a press sequence of at most 2n! buttons so that every permutation of 1..n appears as a contiguous block, for n up to 9.	Hard8	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
A Strange ExhibitGiven the inversion counts of every window of length k in an unknown permutation of 1..n, reconstruct any valid permutation.	Hard8	ImplementationGreedy+2	No attempts yet	2s	512 MB	Judgeable
Planet NineDecide whether a register can go from a to b using operations that add 9x and operations that delete leading digits, all of which are 1.	Hard8	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
LinearizationFor each query substring whose length is a power of two, find the minimum number of contiguous flips that make it a parity-of-AND pattern; the answer reduces to half the number of adjacent differing pairs after an XOR derivative.	Hard8	Bit manipulationPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Equal MaximumsCount quadruples of indices i<=j<k<=l where the maximum of a[i..j] equals the maximum of a[k..l], modulo 1e9+7, for n up to 100000.	Hard8	ArrayStack+2	No attempts yet	1s	512 MB	Judgeable
Koosaga's problemCount the edge subsets of size at most two that make the connected graph bipartite, where no smaller removal set also works.	Hard8	GraphBFS+1	No attempts yet	2s	1024 MB	Judgeable
«Exclusive or» Strikes BackFor each query with a and n up to 1e18, find the smallest non-negative b such that a xor b is divisible by n.	Hard8	Bit manipulationNumber theory+2	No attempts yet	2s	512 MB	Judgeable
SpeedingGiven n road segments with speed limits and lengths, plus m speeding ranges with fines, find for each car the maximum fine guaranteed from its entry and exit times.	Hard8	Binary searchGreedy+2	No attempts yet	2s	512 MB	Judgeable
Machine LearningCount length-n arrays with values from 0 to k where each value is a submask of every later value, and the given index pairs must differ, modulo 1e9+7.	Hard8	Bit manipulationCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Broken Line 04Construct an axis-aligned broken line starting at the origin that passes through every given dot, minimizing the number of segments for partial credit.	Hard8	SortingGreedy+2	No attempts yet	0.1s	512 MB	Judgeable
Broken Line 05Given n points with distinct x and y coordinates, build a horizontal/vertical polyline from the origin covering all points, minimizing the number of segments.	Hard8	GreedySorting+2	No attempts yet	0.1s	512 MB	Judgeable
Broken Line 08Output-only task: build a horizontal and vertical broken line from the origin that touches every given dot, minimizing the number of segments for partial score.	Hard8	SortingGreedy+2	No attempts yet	0.1s	512 MB	Judgeable
Painting SquaresPaint squares black or white and choose the smallest k so that the color pattern in any window of length k, together with whether it runs off the row, always identifies the window's start.	Hard8	StringCombinatorics+2	No attempts yet	4s	1024 MB	Judgeable
Carnival TicketsGiven n sorted lists (n even), choose k disjoint transversal sets of one element per list to maximize the sum over rounds of the minimized total absolute deviation from a best center b.	Hard8	GreedySorting+2	No attempts yet	2s	1024 MB	Judgeable
Counting MushroomsGiven that mushroom 0 is species A, use a machine that counts adjacent differing pairs in a queried row to determine how many of the n mushrooms are species A.	Hard8	ImplementationMath+2	No attempts yet	2s	1024 MB	Judgeable
Sea BattleTwo fleets of point ships move on an infinite grid at periodic step intervals; find the earliest step at which any ship from one fleet shares a cell with any ship from the other, or -1.	Hard8	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Turtles in the PondGiven a growing connected set of grid cells, after each insertion decide whether every pair can be joined by a path that uses only two fixed directions of movement.	Hard8	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
Painting the FenceGiven n segment lengths on a cyclic fence of k boards, order the painters and place each segment to maximize the minimum number of boards each painter is first to paint.	Hard8	GreedyBinary search+2	No attempts yet	2s	512 MB	Judgeable
Rotating PlateGiven a simple polygon pinned at its first vertex, find for each of m external points the maximum clockwise and counterclockwise rotation before the polygon hits that point.	Hard8	GeometryBinary search+2	No attempts yet	2s	512 MB	Judgeable
Advertisement MatchingAfter each update, check whether all ads can be delivered so that no recipient gets two ads from the same advertiser.	Hard8	MathCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
LCS 8Count the length-N uppercase strings T whose LCS with S is at least N minus K, modulo 1e9+7, where K is at most 3.	Hard8	Dynamic programmingString+1	No attempts yet	3s	1024 MB	Judgeable
Min-hashingGiven a graph with a distinct label per node, repeatedly replace each node's value by the minimum value among its neighbors and find the largest number of node pairs sharing a value at any iteration.	Hard8	GraphSimulation+2	No attempts yet	1s	1024 MB	Judgeable
Remote ControlGiven one blocked cell at the origin and a fixed command string of N moves, find the final cell for each of Q starting positions.	Hard8	SimulationPrefix sum+2	No attempts yet	2s	1024 MB	Judgeable
Steel Slicing 2Given a histogon of width N made from two mirrored histograms, find the fewest axis-parallel cuts that split it into rectangles.	Hard8	GeometryGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Bit StringCount bit strings of length n that contain P1 as a substring but avoid P2, modulo 1,000,000,007.	Hard8	Dynamic programmingString matching+2	No attempts yet	1.5s	1024 MB	Judgeable
Broken TilesGiven a rectangle split by a monotone rectilinear curve, find the largest possible minimum side length among rectangles from a rectangular cut of both pieces.	Hard8	Binary searchGreedy+1	No attempts yet	0.5s	512 MB	Judgeable
Counting the Number of TreesCount, modulo 1e9+7, the binary search trees on keys 1..N that the insertion procedure can produce with height at most K.	Hard8	Dynamic programmingTree+2	No attempts yet	2s	256 MB	Judgeable
Toy TrainOn a directed graph with charging stations, two players alternately fix the outgoing edge of each newly visited vertex; decide for every start whether Arezou can force the train to keep moving forever.	Hard8	GraphGame theory+2	No attempts yet	2s	512 MB	Judgeable
Cup of JamshidFind a hidden point in a square using queries that return \|x-p\| XOR \|y-q\| for chosen points, staying within a query budget.	Hard8	Bit manipulationBinary search+2	No attempts yet	1s	512 MB	Judgeable
Card ShuffleGiven an odd deck size N and positions A and B, find the shortest sequence of X and Y shuffles that moves the card at position A to position B.	Hard8	ImplementationMath+2	No attempts yet	1s	256 MB	Judgeable
Vista 1Given up to a million points in the plane, output a cyclic tour that visits every point once and returns to the start, judged by total Euclidean length.	Hard8	GeometryGreedy+2	No attempts yet	0.1s	128 MB	Judgeable
Vista 2Given up to a million points in the plane, output a cyclic tour visiting every point whose total Euclidean length is at most a constant factor times the optimal tour.	Hard8	GeometryGreedy+2	No attempts yet	0.1s	128 MB	Judgeable
Vista 7Given up to 1,000,000 points in the plane, find a closed tour visiting every point once, with the total Euclidean length kept short.	Hard8	GeometryGreedy+1	No attempts yet	0.1s	128 MB	Judgeable
Hero Loves Powers of Two! Hero Loves Powers of Two!Given up to 2.2M numbers, delete at most one, represent the rest as sums of distinct powers of two, XOR the resulting exponent sets, and print twice the maximum XOR value.	Hard8	Bit manipulationGreedy+2	No attempts yet	2.2s	222 MB	Judgeable
Imprecise ComputerGiven n and a sequence of n nonnegative integers, decide whether it can be the difference sequence of a double round-robin tournament played on {1,...,n} where each comparison may be answered arbitrarily when the two numbers differ by one.	Hard8	GreedyMath+1	No attempts yet	1s	512 MB	Judgeable
SwitchesGiven an N by N 0/1 matrix linking switches to lights, decide whether each light can be lit alone, and if so print the switches to press for every light.	Hard8	MathMatrix+2	No attempts yet	1s	512 MB	Judgeable
Bubble BubbleFor each index, replace that one element with any real number and report the minimum number of adjacent swaps bubble sort needs to sort the resulting array.	Hard8	SortingPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Icpcan AlphabetCount the total orders on n letters that make two nested min/max expressions evaluate to the same letter.	Hard8	Dynamic programmingBrute force+2	No attempts yet	3s	512 MB	Judgeable
Nunchucks ShopGiven n and k, find the minimum number of binary strings of length n such that every length-n binary string pair with total k ones can be formed by joining two stored sticks, each usable in either orientation.	Hard8	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Make NumbersGiven four digits, count how many distinct non-negative integers can be formed by concatenating the digits in any grouping and order with +, -, and × under standard precedence.	Hard8	Brute forceImplementation+2	No attempts yet	1s	512 MB	Judgeable
Critical StructuresGiven a connected undirected graph, count articulation points and bridges, group edges into biconnected components, and report the component count divided by the largest component size in lowest terms.	Hard8	GraphDFS+2	No attempts yet	3s	1024 MB	Judgeable
Save lives or moneyPick which gates to open so the flooded area is at least Area, saving the most residents and then losing the least money.	Hard8	TreeDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
Bad-hash studentsGiven n, k1, and alpha, count how many distinct cells the broken probe sequence k_i = k1 + alpha*k_{i-1}^2 mod n visits before it repeats.	Hard8	MathNumber theory+2	No attempts yet	5s	512 MB	Judgeable
Dance of DivisibilityCount the ways to perform K rotation moves between two circles of N dancers so that every couple's age sum has the same remainder mod M, modulo 1e9+7.	Hard8	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
InteractivityCount the minimum-size query sets that determine every node value in a rooted tree whose internal nodes are sums of their children, modulo 1e9+7.	Hard8	TreeDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
Machine GunFor each query, find all enemies inside a right-facing angular wedge and evaluate a polynomial hash of their sorted indices; queries are forced online and the total number of hits is bounded.	Hard8	GeometrySorting+2	No attempts yet	2s	512 MB	Judgeable
Phone FriendsCount ordered distributions of K identical candies to N friends where each friend gets between m and M candies, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
SPC CakeChoose two lattice points A and B on the right and top edges with Manhattan distance L from the origin's corner rays, maximizing the total area of axis-aligned chocolates left uncut inside the wedge.	Hard8	GeometryPrefix sum+2	No attempts yet	1s	1024 MB	Judgeable
The Second PartGiven n distinct points, find the minimum possible ratio of Manhattan distance to Euclidean distance over all pairs of points.	Hard8	GeometryDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
Classic QuarantineGiven a masked and unmasked count and n guests each with a mask threshold, find the minimum and maximum possible masked count after all guests enter in any order.	Hard8	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Bidirectional CodeGiven n up to 10^18, express it as a sum of at most 10 palindromic numbers and output the count and the palindromes.	Hard8	MathGreedy+2	No attempts yet	1s	512 MB	Judgeable
Sail Shreds - 1Place N triangles by translation only, without rotation, so they exactly tile an X by Y rectangle, and output the new position of each triangle's vertex A.	Hard8	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Sail Shreds - 2Translate each given triangle, without rotation, so that the triangles tile an X by Y rectangle with no overlap, and output the new position of each vertex A.	Hard8	GeometrySorting+1	No attempts yet	2s	512 MB	Judgeable
Sail Shreds 4Translate each triangle without rotation so that the triangles exactly tile an X by Y rectangle, with no overlaps and no part outside.	Hard8	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Sail Shreds - 6Place N triangles into an X by Y rectangle without rotating them so they tile it exactly, then output the new position of each triangle's vertex A.	Hard8	GeometryImplementation+1	No attempts yet	2s	512 MB	Judgeable
Sail Shreds - 7Place N triangles on an X by Y rectangle without rotating them so they tile it with no overlaps, then print the new position of vertex A for each triangle.	Hard8	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Sail Shreds - 8Translate each triangular shred without rotation so that the shreds tile the X by Y rectangle exactly, with no overlaps and nothing outside the sail.	Hard8	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Sail ShredsTranslate each triangle without rotation so that the shreds tile an X by Y rectangle exactly, with no overlaps and nothing outside the rectangle.	Hard8	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Squares and CubesCount pairs of natural numbers x, y with a <= x^2 <= b, a <= y^3 <= b, and \|x^2 - y^3\| <= k, for a, b, k up to 10^18.	Hard8	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Old BookGiven that the first k pages are illustrations and the page numbers on text pages sum to s, find the minimum possible number of illustrations in the book.	Hard8	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
🎵I hate you, hate you, I hate you so much, don't come near me, stop pestering me🎵 - 2Given K non-overlapping axis-aligned rectangles (holes) and a square of side L, find the maximum number of rectangles fully covered by some placement of the square.	Hard8	SortingTwo pointers+2	No attempts yet	1s	1024 MB	Judgeable
Radium MiningGiven a grid of distinct values, count cells that are the maximum in both their row and column after each update that only increases a cell's value.	Hard8	ArrayImplementation+2	No attempts yet	1s	512 MB	Judgeable
BenderChoose parameters a, b, c of a linear congruential sequence so that n swaps of adjacent cups move the ball from position r to position l, or report Impossible.	Hard8	Brute forceImplementation+2	No attempts yet	2s	512 MB	Judgeable
Kaisa - SurvivalGiven a rooted tree, take the LCA of every ordered pair of vertices (including x=y), collect all N^2 results into one multiset, sort it, then print the sum of values at odd and even positions.	Hard8	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
VlakTwo players alternately append letters so the growing word stays a prefix of a word in the mover's own song; decide who wins under optimal play.	Hard8	TrieGame theory+2	No attempts yet	1s	512 MB	Judgeable
Strange StringsGiven a string s, count the number of distinct substrings t such that the set of substrings of t equals the set of subsequences of t.	Hard8	StringHash map+2	No attempts yet	1s	512 MB	Judgeable
CCTV ControlGiven an n by m grid of 1s and 2s that can be cyclically shifted in rows and columns, maximize the number of 2x2 blocks whose four cells all match.	Hard8	ArrayImplementation+2	No attempts yet	2s	512 MB	Judgeable