Problems

Pick a problem, code in the editor, and watch the judge run real test cases. The archive is open to browse

Under construction

Still being built. Things may change

Total results29,416 problems

Binary Strings
Hard8
Math, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Witcher Potion
Hard8
Brute force, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sky Tax
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Printing Press
Hard8
Dynamic programming, Graph+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Expected Number of Connected Components
Hard8
Probability, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sequence and Queries 13
Hard8
Segment tree, Linked list+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
gcd(n, k) = 1
Hard8
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 14
Hard8
Array, Sorting+2
No attempts yet
Time limit
5s
Memory limit
1536 MB
Judgeable
Arranging Hat
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Gotta Nudge 'Em All
Hard8
Greedy, Sliding window+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Zoltan
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Flyswatter placements
Hard8
Geometry, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Bipartite Blanket
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Invisible Integers
Hard8
Backtracking, DFS+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Passwords
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Power towers
Hard8
Number theory, Recursion+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lefkaritika
Hard8
Array, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cruise
Hard8
Geometry, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Contest Strategy
Hard8
Combinatorics, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Shopping
Hard8
Array, Segment tree+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Demilitarized Zone
Hard8
Intervals, Sorting+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Binary Code
Hard8
Trie, Greedy+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Delight for a Cat
Hard8
Dynamic programming, Sliding window+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Game on Graph
Hard8
Graph, Game theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Jenga Boom
Hard8
Geometry, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Kids Designing Kids
Hard8
Implementation, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Solar Flight
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
15s
Memory limit
512 MB
Judgeable
Timpani Retuning
Hard8
Binary search, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Data Structure
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Field Trip
Hard8
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Zombie Apocalypse
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
K-th good string
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Broadcast Tower Offers
Hard8
Stack, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The divisibility game
Hard8
Game theory, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fence
Hard8
Math, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Maximum Bitwise OR by Window Length
Hard8
Bit manipulation, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
K representatives on a line
Hard8
Dynamic programming, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bitstock
Hard8
Greedy, Tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Quadrilateral blanket
Hard8
Geometry, Brute force+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Substring appearing twice
Hard8
String, Binary search+2
No attempts yet
Time limit
6s
Memory limit
128 MB
Judgeable
Beautiful Paths
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Walk
Hard8
Divide and conquer, Recursion+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sort
Hard8
Probability, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
XOR
Hard8
Graph, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ivoization
Hard8
Sorting, Prefix sum+2
No attempts yet
Time limit
1.5s
Memory limit
128 MB
Judgeable
Zvonimir
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Aggressor
Hard8
Game theory, Combinatorics+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Painting Squares
Hard8
Geometry, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Permutations that contain a word
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Restaurant Recommendations
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Truffles
Hard8
Geometry, Prefix sum+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Virus
Hard8
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Trips
Hard8
Graph, Combinatorics+1
No attempts yet
Time limit
0.5s
Memory limit
128 MB
Judgeable
Electricity
Hard8
Geometry, Binary search+1
No attempts yet
Time limit
1.5s
Memory limit
128 MB
Judgeable
Samtris
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Matches
Hard8
Graph, Union-find+1
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Median filter
Hard8
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Scout Gatherings
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Maxplus
Hard8
Math, Matrix+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Frogs
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Particles
Hard8
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
5s
Memory limit
64 MB
Judgeable
Switches
Hard8
Bit manipulation, Brute force+1
No attempts yet
Time limit
10s
Memory limit
64 MB
Judgeable
RSA factorization proof
Hard8
Bit manipulation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Triangle regions
Hard8
Geometry, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Titteop Land
Hard8
Dynamic programming, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Möbius Strip
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Expression
Hard8
Implementation, Recursion+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rahyab
Hard8
Graph, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Skeletons
Hard8
Graph, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sticks and Carrots
Hard8
Geometry, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Son of Durin
Hard8
BFS, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Function
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Divisor Roads
Hard8
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Reconstruct the progressions
Hard8
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Rhyme
Hard8
String, Trie+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Osmosmjerka
Hard8
Math, String matching+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Assigning jobs 2
Hard8
Greedy, Math+1
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
The Lazy Postman
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Splitting Game Levels
Hard8
Dynamic programming, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Beautiful Graph
Hard8
Graph, Minimum spanning tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Wolves 2
Hard8
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Coprime Neighbors
Hard8
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String array
Hard8
String matching, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Nice Array
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
I Teach Sweeping
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
f(X) = A + X + B + X + C
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Road Construction
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Block stacking
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Product of Two Numbers 2
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cutting edges one at a time
Hard8
Graph, Minimum spanning tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Company Culture 4
Hard8
Tree, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Beautiful Numbers (Large)
Hard8
Number theory, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sorting Array (Large)
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
30s
Memory limit
512 MB
Judgeable
Stretch Rope (Large)
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
30s
Memory limit
512 MB
Judgeable
Monster Path (Large)
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Safe Squares (Large)
Hard8
Array, Dynamic programming+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sherlock and Permutation Sorting (Large)
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Imbalance Obviation
Hard8
Greedy, Implementation+2
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Integeregex (Large)
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Gallery of Pillars (Small)
Hard8
Geometry, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Binary StringsCount binary strings whose length lies in [L, R], is a multiple of K, and contains no two adjacent 1s, modulo 1e9+7.	Hard8	MathCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Witcher PotionGiven up to 8 potions with energy and toxicity, determine how many identical monsters Geralt can beat given energy, poison, and time rules.	Hard8	Brute forceSimulation+2	No attempts yet	1s	512 MB	Judgeable
Sky TaxOn a tree with a moving capital, each vertex answers for all vertices whose path to the capital passes through it; move the capital or query a vertex's count.	Hard8	TreeDFS+2	No attempts yet	1s	512 MB	Judgeable
Printing PressGiven a DAG of book-ordering constraints, choose how many days to shorten each book so all finish within X, minimizing printing plus shortening cost.	Hard8	Dynamic programmingGraph+2	No attempts yet	10s	512 MB	Judgeable
Expected Number of Connected ComponentsFor each node i with inclusion probability P_i, find the expected number of connected components of the subgraph where two selected nodes are adjacent when gcd > 1, then print E times 100^N mod 1e9+7.	Hard8	ProbabilityMath+2	No attempts yet	5s	512 MB	Judgeable
Sequence and Queries 13Maintain an array under range add, range multiply, and range assign modulo 1e9+7, answering range sum queries.	Hard8	Segment treeLinked list+2	No attempts yet	2s	512 MB	Judgeable
gcd(n, k) = 1Given n up to 10^18, count how many k in [1, n] satisfy gcd(n, k) = 1, that is, compute Euler's totient function of n.	Hard8	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 14For each query on a subarray, take the distinct values, sort them, and report the k-th smallest, with each query depending on the previous answer.	Hard8	ArraySorting+2	No attempts yet	5s	1536 MB	Judgeable
Arranging HatEach of n m-digit strings may have individual digits rewritten; find the minimum number of digit changes so the sequence becomes nondecreasing.	Hard8	Dynamic programmingGreedy+2	No attempts yet	5s	512 MB	Judgeable
Gotta Nudge 'Em AllChoose one 30-minute window for a double-XP bonus, catch every Nudgemon already logged, and maximize XP from evolutions inside that window.	Hard8	GreedySliding window+1	No attempts yet	3s	512 MB	Judgeable
ZoltanCero builds a deque by placing each array element on the left or right in order; over all 2^(N-1) builds, find the longest strictly increasing subsequence length and the total number of subsequences attaining it, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	32 MB	Judgeable
Flyswatter placementsCount the integer translations of a fixed polygon that keep it inside an axis-aligned rectangle and avoid all given points, including points on the boundary.	Hard8	GeometryPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
Bipartite BlanketCount vertex subsets of a weighted bipartite graph whose total weight is at least t and that some matching covers completely.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	3s	512 MB	Judgeable
Invisible IntegersGiven up to 10 hints, each a walk order of distinct digits 1 to 9, find the shortest hidden integer sequence that can produce every hint.	Hard8	BacktrackingDFS+2	No attempts yet	5s	512 MB	Judgeable
PasswordsCount length A to B alphanumeric passwords with mixed case and a digit that avoid blacklist substrings, where digits can stand in for similar letters.	Hard8	Dynamic programmingString matching+2	No attempts yet	2s	512 MB	Judgeable
Power towersGiven lists of positive integers, compute each power tower modulo M, where the tower can be astronomically large.	Hard8	Number theoryRecursion+2	No attempts yet	2s	512 MB	Judgeable
LefkaritikaGiven a grid with blocked points, count the maximum number of axis-aligned square items of any side length that can be placed without covering blocked points, respecting placement order and same-size non-overlap rules.	Hard8	ArrayDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
CruiseChoose a closed polygonal cruise from Piraeus through the islands so that collected point value divided by route length is maximized.	Hard8	GeometryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Contest StrategySum the contest penalty over all n! read orders, where after reading k problems you always solve the read-but-unsolved problem with the smallest solving time.	Hard8	CombinatoricsGreedy+2	No attempts yet	2s	512 MB	Judgeable
ShoppingGiven an array of prices and a sequence of queries (money, l, r), simulate a shopper who spends as much as possible at each product from l to r and report the leftover money.	Hard8	ArraySegment tree+2	No attempts yet	5s	512 MB	Judgeable
Demilitarized ZoneFor each protected point, count how many starting mines eventually trigger a blast covering it, given chain reactions over intervals.	Hard8	IntervalsSorting+2	No attempts yet	3s	256 MB	Judgeable
Binary CodeEach of n binary words has at most one unreadable bit; decide whether the ?s can be filled so no word is a prefix of another.	Hard8	TrieGreedy+2	No attempts yet	2s	2048 MB	Judgeable
Delight for a CatChoose sleep or eat each hour to maximize total delight, with at least ms sleep and me eat hours in every window of k consecutive hours.	Hard8	Dynamic programmingSliding window+2	No attempts yet	2s	512 MB	Judgeable
Game on GraphOn a directed graph, Gennady prefers an endless game over winning and Georgiy prefers winning over everything but an endless game; report the outcome (W, L, D) for every start vertex and both first players.	Hard8	GraphGame theory+2	No attempts yet	2s	512 MB	Judgeable
Jenga BoomSimulate removals from a Jenga-like tower and report whether it falls, and at which removal, when a level's center of mass leaves the convex hull of the blocks still supporting it.	Hard8	GeometrySimulation+2	No attempts yet	2s	512 MB	Judgeable
Kids Designing KidsGiven three grid pictures, find the translation of the second that makes the XOR of the first two match the third, up to translation.	Hard8	ImplementationString matching+2	No attempts yet	2s	512 MB	Judgeable
Solar FlightFor a line segment query, find the maximum total intercept-weight above a given ray over all x in a length-K window.	Hard8	GeometrySorting+2	No attempts yet	15s	512 MB	Judgeable
Timpani RetuningChoose tunings for up to 4 ordered drums before each of N notes so the shortest retuning interval time is maximized; output that time rounded to two decimals.	Hard8	Binary searchDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Data StructureGiven M required cells in a triangular pyramid with N up to 1e9, find the minimum number of filled cells so that every filled cell has both supporting cells below it filled.	Hard8	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Field TripGiven a graph where each vertex has degree at most 2, delete edges so that the remaining components are cliques of size exactly K, maximizing total covered vertices then minimizing deletions.	Hard8	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
Zombie ApocalypseGiven up to 2000 zombie cells on an N by M grid with Chebyshev distance spreading, count how many cells end up at level Q.	Hard8	GeometrySorting+2	No attempts yet	2s	512 MB	Judgeable
K-th good stringGiven a bracket string S, list the distinct good strings that appear as subsequences in lexicographic order and print the K-th one.	Hard8	Dynamic programmingString+1	No attempts yet	2s	512 MB	Judgeable
Broadcast Tower OffersFor each offered tower height, find the best position along a row of buildings and report how many buildings to its west can receive its westward signal.	Hard8	StackSorting+2	No attempts yet	2s	512 MB	Judgeable
The divisibility gameTwo players alternately delete numbers from a set; decide whether X can force the remaining sum to be divisible by P after exactly K deletions.	Hard8	Game theoryCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
FenceSum x! times y! over all unit cells inside an axis-aligned polygon, modulo 1e9+7, with coordinates up to 1e9.	Hard8	MathPrefix sum+2	No attempts yet	3s	512 MB	Judgeable
Maximum Bitwise OR by Window LengthFor each window length K from 1 to N, output the maximum bitwise OR over all K consecutive elements of the array.	Hard8	Bit manipulationDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
K representatives on a lineFor each K from 1 to N, place K real points on a line to minimize the total distance to all given points.	Hard8	Dynamic programmingDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
BitstockGiven share prices, income rates, and a support forest where each owned share can subsidize its children at half price, find the minimum time until income reaches P per second.	Hard8	GreedyTree+2	No attempts yet	1s	128 MB	Judgeable
Quadrilateral blanketGiven N points and an area limit L, pick four points forming a simple quadrilateral with area at most L, maximizing that area.	Hard8	GeometryBrute force+2	No attempts yet	5s	128 MB	Judgeable
Substring appearing twiceGiven a string and at most K letter replacements, maximize the length of the longest substring that occurs at two different starting positions, allowing overlap.	Hard8	StringBinary search+2	No attempts yet	6s	128 MB	Judgeable
Beautiful PathsOn a tree with capitals 1 and 2, sum over all pairs of cities of the minimum distance-to-nearest-capital along their path.	Hard8	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
WalkA fractal tiling is built by repeated splits; given a start cell and a walk, report for each move whether he crossed between tiles.	Hard8	Divide and conquerRecursion+2	No attempts yet	2s	512 MB	Judgeable
SortFor an array of at most 8 elements, compute the expected number of random-swap steps until sorted for two different swap schemes.	Hard8	ProbabilityDynamic programming+1	No attempts yet	2s	128 MB	Judgeable
XORIn a connected weighted graph where a ride's cost is the XOR of its edge lengths and edges may repeat, answer queries for the minimum cost between two vertices.	Hard8	GraphBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
IvoizationSum the Ivoization values of every K by K submatrix, where Ivoization is the pairwise absolute-difference sum of all K^2 entries, modulo 10007.	Hard8	SortingPrefix sum+2	No attempts yet	1.5s	128 MB	Judgeable
ZvonimirFind the minimum number of operations (type one letter, or copy a contiguous block of already typed text and append it) to produce string X.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
AggressorFor every split of N countries into aggressors and peaceful, decide the winner of the tank game under optimal play, then count Mirko's and Slavko's wins.	Hard8	Game theoryCombinatorics+1	No attempts yet	5s	128 MB	Judgeable
Painting SquaresAn infinite canvas starts white; each step picks the largest monochrome axis-aligned square of side at most D centered at a given point and flips its color. Find the final black area.	Hard8	GeometryDivide and conquer+2	No attempts yet	1s	128 MB	Judgeable
Permutations that contain a wordCount distinct permutations of A that contain B as a contiguous substring, modulo 10007.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Restaurant RecommendationsRestaurants recommend each other through a favorite digraph; find the cheapest cost to visit exactly k restaurants for every k, where each step's price depends on whether the recommender is a favorite of the current restaurant.	Hard8	GraphDynamic programming+2	No attempts yet	3s	128 MB	Judgeable
TrufflesGiven a grid of per-meter values, compute for each of M slanted lines the weighted length integral of the line through the grid, rounded to five decimals.	Hard8	GeometryPrefix sum+1	No attempts yet	3s	128 MB	Judgeable
VirusFind the rational point (X, Y, Z) closest to the origin satisfying N linear inequalities in three variables, or report that none exists.	Hard8	GeometryMath+1	No attempts yet	1s	128 MB	Judgeable
TripsCount assignments of N people to two trips, each internally a clique, at least A and B people, covering everyone, modulo 10007.	Hard8	GraphCombinatorics+1	No attempts yet	0.5s	128 MB	Judgeable
ElectricityPlace a power plant at an integer intersection minimizing the sum over axis-aligned rectangles of the Manhattan distance to the nearest rectangle corner.	Hard8	GeometryBinary search+1	No attempts yet	1.5s	128 MB	Judgeable
SamtrisGiven N marked cells in a 7-column grid, find the fewest 3x1 bars (vertical or horizontal) that can be dropped so all marked cells end up covered.	Hard8	Dynamic programmingGreedy+2	No attempts yet	5s	128 MB	Judgeable
MatchesGiven a spanning tree drawn on a grid of tokens with matches, count the ways to remove one match and add another so the graph stays a valid crossing-free spanning tree.	Hard8	GraphUnion-find+1	No attempts yet	1.5s	256 MB	Judgeable
Median filterGiven a piecewise-linear integer signal by its corner points, output the corners of its median-filtered signal of width 2d+1.	Hard8	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Scout GatheringsOn a tree, support adding a member at a city and querying the sum of weighted distances from all members to the current gathering city, which moves along edges.	Hard8	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
MaxplusGiven 3x3 integer matrices A and C, find the entrywise-largest integer matrix B with A (max-plus) B = C, or report that none exists.	Hard8	MathMatrix+2	No attempts yet	1s	128 MB	Judgeable
FrogsFrogs of type d land on pads d, 2d, 3d, ... stopping at the first pad with no other frog; find the farthest occupied pad for each type.	Hard8	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
ParticlesCount functions from N chambers to themselves such that applying the function K times returns every element to its start, modulo M.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	5s	64 MB	Judgeable
SwitchesChoose a subset and order of switches to press so the cost of hand-fixing the remaining closed barns (morning) or open barns (evening) is minimized.	Hard8	Bit manipulationBrute force+1	No attempts yet	10s	64 MB	Judgeable
RSA factorization proofGiven up to 100000 moduli built from at most 36 shared primes, find the minimum set of primes whose removal leaves each modulus as 1 or a prime.	Hard8	Bit manipulationGreedy+2	No attempts yet	2s	64 MB	Judgeable
Triangle regionsGiven N points with no three collinear, count for each v how many triangles formed by three points contain exactly v other points strictly inside.	Hard8	GeometryCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Titteop LandPartition the line into K consecutive groups so the sum of pairwise awkwardness inside every group is minimized.	Hard8	Dynamic programmingDivide and conquer+1	No attempts yet	2s	512 MB	Judgeable
Möbius StripDecide if repeated thirds-cuts of paper strips can make two given multisets of half-twist counts agree on every type.	Hard8	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
ExpressionParse a two-dimensional rendering of nested fractions, additions, multiplications, and divisions, then print the reduced value as a fraction.	Hard8	ImplementationRecursion+2	No attempts yet	2s	512 MB	Judgeable
RahyabAssign C unit flows from M to T in a directed graph so no flow can unilaterally reroute to pay less, minimizing the sum over flows of the square of their max edge load.	Hard8	GraphGreedy+2	No attempts yet	2s	512 MB	Judgeable
SkeletonsFor each directed graph, decide whether some positive real t lets every possible perfect matching of skeletons to targets be realized by walks of length exactly t.	Hard8	GraphNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Sticks and CarrotsChoose a subset of at least three vertices of a convex polygon so every carrot lies strictly inside the new polygon, minimizing its area.	Hard8	GeometryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Son of DurinGiven a grid with walls, teleport pads, and up to 15 coin caves, find the most gold collectible within L moves and P teleports.	Hard8	BFSDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
FunctionCount functions on {1..n} whose eventual image (the set of values reached after iterating long enough) has size exactly k, modulo 1e9+7.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Divisor RoadsA one-way road runs from X to Y when some A_i divides X and B_i divides Y; find the shortest distance from S to T.	Hard8	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Reconstruct the progressionsGiven K listed values in [A,B], find the smallest set of positive step sizes whose multiples in [A,B] hit exactly those values.	Hard8	Number theoryMath+2	No attempts yet	2s	128 MB	Judgeable
RhymeGiven N distinct words, find the longest sequence using each word at most once where consecutive words rhyme: their longest common suffix has length at least the longer word's length minus one.	Hard8	StringTrie+2	No attempts yet	1s	256 MB	Judgeable
OsmosmjerkaGiven a letter block tiled infinitely in all directions, pick a random start square and one of 8 directions twice, and report the probability that the two read words of length K match, as a reduced fraction.	Hard8	MathString matching+2	No attempts yet	4s	256 MB	Judgeable
Assigning jobs 2Given an N by N cost matrix, assign each of N people to a distinct job so the total cost is minimum.	Hard8	GreedyMath+1	No attempts yet	0.5s	512 MB	Judgeable
The Lazy PostmanGiven a directed weighted graph on n cities, find the minimum total distance of a walk with exactly n cities visited in sequence (n-1 moves), where the same city may repeat.	Hard8	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Splitting Game LevelsPartition n levels into k consecutive groups to minimize the expected total time of a random coin-draw process, and print it to six decimals.	Hard8	Dynamic programmingDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Beautiful GraphOver all complete graphs on N vertices whose edges cost 1 or 2, sum the number of minimum spanning trees that are paths (every degree at most 2).	Hard8	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Wolves 2Count binary strings of length N in which every given interval contains at most two ones, modulo 1e9+7.	Hard8	Dynamic programmingPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Coprime NeighborsGiven a set of up to 50 distinct integers, insert the fewest new distinct positive integers so that consecutive values in sorted order are coprime.	Hard8	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
String arrayCount strings S of length 1 to W such that the repeated periodic filling of X matches the given patch F at the fixed offset.	Hard8	String matchingNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Nice ArrayCount ways to fill the erased cells of an N by N array so that every permutation's diagonal sum is equal, modulo 1e9+7.	Hard8	CombinatoricsMath+1	No attempts yet	2s	512 MB	Judgeable
I Teach SweepingGiven segments in the first quadrant, find a line through the origin that intersects the most segments and report that count.	Hard8	GeometrySorting+1	No attempts yet	2s	512 MB	Judgeable
f(X) = A + X + B + X + CCount occurrences of pattern F in the K-fold string expansion f(X)=A+X+B+X+C applied to S, modulo 1e9+7.	Hard8	String matchingDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Road ConstructionCount the ways to place exactly M undirected edges among N houses, each edge joining houses at distance at most K, so that every house has even degree, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Block stackingCount structures built on one 1x1xw base block using unlimited 1x1x1, 1x1x2, and 1x1x3 blocks with height at most h, where long blocks need both ends supported.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Product of Two Numbers 2Given a, b, c, choose positive A, B, C with A*B=C minimizing \|A-a\|+\|B-b\|+\|C-c\|.	Hard8	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Cutting edges one at a timeDelete edges of a weighted undirected graph one by one so that the total weight removed before s and t get disconnected is as large as possible.	Hard8	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Company Culture 4On a rooted tree, praise spreads downward from an employee to all descendants or upward to all ancestors, the direction flips over time, and queries ask for an employee's accumulated praise.	Hard8	TreePrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Beautiful Numbers (Large)For each N up to 1e18, find the base B that writes N with all digits 1, preferring the base that gives the most 1 digits.	Hard8	Number theoryMath+2	No attempts yet	5s	512 MB	Judgeable
Sorting Array (Large)Given a permutation of 1..N and a limit P, partition it into contiguous blocks, sort each, then reorder at most P blocks by swaps; maximize the number of blocks.	Hard8	GreedySorting+2	No attempts yet	30s	512 MB	Judgeable
Stretch Rope (Large)Given N rubber bands with stretch ranges [A_i, B_i] and prices, pick a subset whose summed range contains L at minimum total cost within budget M.	Hard8	Dynamic programmingGreedy+2	No attempts yet	30s	512 MB	Judgeable
Monster Path (Large)Walk exactly S steps on a grid, catching each cell's monster with probability P or Q on first visit, to maximize the expected number caught.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	5s	512 MB	Judgeable
Safe Squares (Large)Count all grid-aligned square regions of any size that contain no monster, given a sparse set of at most K monster cells on an R by C board.	Hard8	ArrayDynamic programming+2	No attempts yet	5s	512 MB	Judgeable
Sherlock and Permutation Sorting (Large)For each N and modulus M, sum f(p)^2 over all permutations of 1..N, where f(p) is the maximum number of blocks that can be sorted independently; output the sum mod M.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	10s	512 MB	Judgeable
Imbalance ObviationAssign each marble L or R so the pan difference stays within 1 during insertion in order and during a given removal permutation; output the lexicographically smallest assignment.	Hard8	GreedyImplementation+2	No attempts yet	20s	1024 MB	Judgeable
Integeregex (Large)Count integers in [A, B] whose decimal form (no leading zeros) matches a small regular expression over digits.	Hard8	Dynamic programmingString+2	No attempts yet	5s	512 MB	Judgeable
Gallery of Pillars (Small)Count the pillars in an N by N grid that are visible from the corner viewpoint, given identical circular pillars of radius R whose centers sit at cell centers.	Hard8	GeometryNumber theory+2	No attempts yet	5s	512 MB	Judgeable