Problems

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Total results21,150 problems

Allowed swapsHard9
Union-find, Implementation +2No attempts yetTime limit6sMemory limit512 MB
Judgeable
Appropriate Coordinate MapHard9
Geometry, Greedy +1No attempts yetTime limit5sMemory limit512 MB
Judgeable
Game MovesHard9
Dynamic programming, Backtracking +1No attempts yetTime limit1sMemory limit512 MB
Judgeable
Jumping ImpalaHard9
Binary search, Graph +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Mobile Network BandwidthHard9
Graph, Greedy +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Blue ForestHard9
Geometry, Graph +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Magical Mystery Knight's TourHard9
Backtracking, Brute force +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Sequence and queries 12Hard9
Segment tree, Hash map +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
British MenuHard9
Graph, Dynamic programming +2No attempts yetTime limit5sMemory limit1024 MB
Judgeable
Driving in OptimistanHard9
Tree, Greedy +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Triple treeHard9
Math, Number theory +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Geohash GridHard9
Divide and conquer, Tree +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Hangar HurdlesHard9
Union-find, BFS +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Risky LotteryHard9
Game theory, Probability +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
ConferenceHard9
Graph, Union-find +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
HackerHard9
Segment tree, Hash map +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
AcrobatHard9
Graph, Bit manipulation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Mole TunnelsHard9
Tree, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Large Ping Pong TournamentHard9
Greedy, Sorting +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
EggscavationHard9
Geometry, Prefix sum +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
LegendsHard9
Graph, Divide and conquer +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
PiratesHard9
Greedy, Dynamic programming +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
MinerHard9
Geometry, Binary search +2No attempts yetTime limit1.5sMemory limit512 MB
Judgeable
Cactus giftHard9
Dynamic programming, Tree +2No attempts yetTime limit1.5sMemory limit512 MB
Judgeable
Robotic Cow HerdHard9
Heap, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Function and QueriesHard9
Dynamic programming, Divide and conquer +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Unlucky 89Hard9
Number theory, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Find the SequenceHard9
Number theory, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Soldiers (Large)Hard9
Game theory, Dynamic programming +1No attempts yetTime limit5sMemory limit512 MB
Judgeable
Clash Royale (Large)Hard9
Dynamic programming, Greedy +1No attempts yetTime limit20sMemory limit512 MB
Judgeable
Map Reduce (Large)Hard9
BFS, Graph +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
The Gardener of Seville (Large)Hard9
Implementation, Simulation +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
RonaldHard9
Graph, Bit manipulation +2No attempts yetTime limit1sMemory limit64 MB
Judgeable
The Kingdom of JOIOIHard9
Binary search, Greedy +2No attempts yetTime limit4sMemory limit256 MB
Judgeable
RopeHard9
Dynamic programming, Divide and conquer +2No attempts yetTime limit2.5sMemory limit256 MB
Judgeable
Rides 2Hard9
Segment tree, Sorting +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Distinct Substring QueriesHard9
String, String matching +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Building a Tall BarnHard9
Greedy, Heap +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Incremental Double Free StringsHard9
Combinatorics, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Maximum Color CliqueHard9
Graph, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Bracket PathsHard9
Tree, Divide and conquer +2No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Switch GrassHard9
Graph, Shortest path +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
The Enormous SequenceHard9
Math, Number theory +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Tarot Sham BoastHard9
String matching, Probability +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Shifty GridHard9
Simulation, Implementation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Rolling the BottleHard9
Geometry, Sorting +2No attempts yetTime limit2.5sMemory limit512 MB
Judgeable
Largest window sumHard9
Greedy, Prefix sum +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Minimum Cycle MeanHard9
Dynamic programming, Graph +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
PseudoknotHard9
String, String matching +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Creating Fake NewsHard9
Math, Graph +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Fashion ShowHard9
Greedy, Graph +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Slate Modern (Large)Hard9
Graph, Shortest path +2No attempts yetTime limit80sMemory limit512 MB
Judgeable
Omnicircumnavigation (Large)Hard9
Geometry, Math +2No attempts yetTime limit120sMemory limit512 MB
Judgeable
Stack Management (Small)Hard9
Game theory, Simulation +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Sequence and TransformationHard9
Combinatorics, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Expected value of the greatest common divisorHard9
Probability, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Polynomial and QueriesHard9
Number theory, Divide and conquer +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
NPM998244353 (Hard)Hard9
Combinatorics, Dynamic programming +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Counting multiples with a bounded digit sumHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Smallest unreachable subsequence sumHard9
Segment tree, Greedy +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Good triples of pathsHard9
Combinatorics, Tree +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Strongly MatchableHard9
Graph, Math +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Equivalent DeformationHard9
Geometry, Implementation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
LeapfrogHard9
Number theory, Math +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Fractal TreeHard9
Tree, Recursion +2No attempts yetTime limit7sMemory limit512 MB
Judgeable
Arranging tilesHard9
Dynamic programming, Geometry +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
CratersHard9
Geometry, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Enlarging EnthusiasmHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Treasure MapHard9
Graph, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Jupiter Rock Paper ScissorsHard9
Game theory, Implementation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
IntuidiffHard9
String matching, Greedy +2No attempts yetTime limit7sMemory limit512 MB
Judgeable
Crazy RotationsHard9
String matching, Combinatorics +2No attempts yetTime limit15sMemory limit512 MB
Judgeable
GCD SumHard9
Number theory, Greedy +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
SkiingHard9
Geometry, Greedy +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Restaurant BribesHard9
Graph, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
One-Way StreetsHard9
Graph, DFS +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
Intrinsic IntervalHard9
Segment tree, Stack +1No attempts yetTime limit3sMemory limit512 MB
Judgeable
Lunar LandscapeHard9
Geometry, Sorting +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Journey from Petersburg to MoscowHard9
Graph, Shortest path +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Laminar FamilyHard9
Tree, DFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
ToysHard9
Combinatorics, Number theory +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Workbook AlgorithmsHard9
Combinatorics, Graph +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Secret AgentHard9
Graph, Geometry +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
GarageHard9
Segment tree, Number theory +2No attempts yetTime limit4sMemory limit256 MB
Judgeable
Counting CyclesHard9
Graph, DFS +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
LeadersHard9
Game theory, Dynamic programming +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Disco Dance DebacleHard9
Graph, Greedy +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Imelda's Shopping SpreeHard9
Segment tree, Array +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Majestic Gourmet UniversityHard9
Graph, BFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
KabobsHard9
Dynamic programming, String +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Vera and Love TrianglesHard9
Combinatorics, Number theory +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
DramaHard9
Combinatorics, Dynamic programming +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Push a BoxHard9
Graph, BFS +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
L-th K-th numberHard9
Binary search, Array +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
GardenerHard9
Segment tree, Binary search +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
Revenge of the Broken DoorHard9
Graph, Shortest path +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
Revenge of the Endless BFSHard9
Graph, BFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Conveyor BeltHard9
Math, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Pipe Fitter and the Fierce DogsHard9
Dynamic programming, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Blocks 2Hard9
Combinatorics, Dynamic programming +2No attempts yetTime limit1sMemory limit256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Allowed swapsMaintain an array under swaps and union operations, answering whether it can be sorted and counting pairs of clouds whose merge would fix both.	Hard9	Union-findImplementation+2	No attempts yet	6s	512 MB	Judgeable
Appropriate Coordinate MapGiven N points, choose a ring through all of them and endpoints A, B so the two legs are monotone in the projection onto AB, maximizing the smallest gap in that projection.	Hard9	GeometryGreedy+1	No attempts yet	5s	512 MB	Judgeable
Game MovesGiven a reachable 2048 board and its score, find the minimum number of moves that could have produced that state, using the merge rules and random tile births.	Hard9	Dynamic programmingBacktracking+1	No attempts yet	1s	512 MB	Judgeable
Jumping ImpalaGiven a lake, a central island, and S unit rocks, find the minimum leap distance letting Vlad reach the island and return twice without landing on any rock twice.	Hard9	Binary searchGraph+2	No attempts yet	8s	512 MB	Judgeable
Mobile Network BandwidthGiven a graph whose edge capacities are polynomials in x, output the max-flow polynomial from node 1 to node N for large x.	Hard9	GraphGreedy+2	No attempts yet	8s	512 MB	Judgeable
Blue ForestGiven several planar floor maps that may be rigid-motion duplicates, unify matching maps, merge their warp gates, then find the shortest route from entrance to exit.	Hard9	GeometryGraph+2	No attempts yet	8s	512 MB	Judgeable
Magical Mystery Knight's TourFill the missing numbers so the 8x8 board becomes a semi-magical knight's tour with equal row and column sums, choosing the lexicographically smallest completion.	Hard9	BacktrackingBrute force+2	No attempts yet	2s	512 MB	Judgeable
Sequence and queries 12Maintain a dynamic sequence under point updates, deletions, and insertions, answering range queries for distinct count and the sum of triple products of distinct values.	Hard9	Segment treeHash map+2	No attempts yet	2s	512 MB	Judgeable
British MenuGiven a directed graph where every cycle witnesses a repeat within at most four intervening dishes, find the longest simple path (no repeated vertex).	Hard9	GraphDynamic programming+2	No attempts yet	5s	1024 MB	Judgeable
Driving in OptimistanGiven the pairwise distances among n port towns that lie on a tree, reconstruct the tree, place integer-kilometre signs along every edge, and output the average distance over all sign pairs as a reduced fraction.	Hard9	TreeGreedy+1	No attempts yet	2s	512 MB	Judgeable
Triple treeGenerate triples (a,b,c) satisfying a^2+b^2+c^2 = k(ab+bc+ca)+1 by two sweep operations from (1,k,k+k^2), then greedily print triples whose numbers are all new.	Hard9	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Geohash GridFor a rectilinear polygon inside a 2^n by 2^n grid, answer up to 1e5 queries asking the smallest cell count of a union of at most t geohash intervals covering it.	Hard9	Divide and conquerTree+2	No attempts yet	5s	512 MB	Judgeable
Hangar HurdlesGiven an n by n grid of blocked and empty cells, answer q queries asking for the largest centered square crate that can slide between two empty cells.	Hard9	Union-findBFS+2	No attempts yet	8s	512 MB	Judgeable
Risky LotteryFind the unique symmetric Nash equilibrium mixed strategy for a lottery where the winner is the player holding the smallest number written exactly once, and print each pick probability to five decimals.	Hard9	Game theoryProbability+2	No attempts yet	2s	512 MB	Judgeable
ConferenceGiven M daily pairwise meetings among N people (first K are scientists), find the latest creation day for each invention so a journalist still learns it, then report which journalists learn anything and each invention's first journalist.	Hard9	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
HackerSimulate substring comparisons, substring copy from a fixed string, and range letter-increment operations on a mutable string of length N.	Hard9	Segment treeHash map+2	No attempts yet	4s	512 MB	Judgeable
AcrobatGiven a bipartite multigraph between two sets of N assistants, each rope may be swapped (i,j)->(j,i) at most once; find the minimum swaps so the edges form an Eulerian circuit, or report -1.	Hard9	GraphBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Mole TunnelsOn a binary-heap-shaped tree, each newly woken mole (in a fixed order) must be assigned to a hole with remaining food capacity, minimizing total walking distance; report the minimum for every prefix k.	Hard9	TreeGreedy+2	No attempts yet	2s	512 MB	Judgeable
Large Ping Pong TournamentGiven the total points each of 2^N players scored in a knockout ping pong tournament, decide if Dudu, who always wins ties, could have been champion.	Hard9	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
EggscavationGiven up to 100000 shell species (each in at most 4 cells) and egg insertions, answer queries for the probability that a random K x K scoop covers at least V species and no egg.	Hard9	GeometryPrefix sum+2	No attempts yet	10s	512 MB	Judgeable
LegendsGiven a connected graph, decide whether it can be built from one of five small starting graphs using edge additions, isolated-vertex additions, and vertex splits (each split adds a new vertex adjacent to the old one).	Hard9	GraphDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
PiratesFor every prefix of pirates, compute the oldest pirate's share under the stated voting and tie-breaking rules.	Hard9	GreedyDynamic programming+2	No attempts yet	10s	512 MB	Judgeable
MinerFor each lamp position above a polyline mine floor, find the reachable floor interval lit without crossing the floor.	Hard9	GeometryBinary search+2	No attempts yet	1.5s	512 MB	Judgeable
Cactus giftIn a cactus graph with up to 4000 vertices, count directed simple paths of each length 1 to N, modulo 1e9+7.	Hard9	Dynamic programmingTree+2	No attempts yet	1.5s	512 MB	Judgeable
Robotic Cow HerdEach robot picks one model per location, and all K robots must differ somewhere; find the minimum total cost of K distinct robots.	Hard9	HeapGreedy+2	No attempts yet	2s	512 MB	Judgeable
Function and QueriesGiven an array and a recurrence f(i,j)=min(f(i-1,j),f(i-1,j-1))+a_j, answer up to 1e5 offline queries for f(x,y).	Hard9	Dynamic programmingDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Unlucky 89Average the circumferences of all integer right triangles whose hypotenuse is k*sqrt(89) with k up to n, printed as exact mixed numbers in an ASCII box.	Hard9	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
Find the SequenceGiven B, decide whether there exist distinct integers A_i > 1 such that A_i^{B_i} is divisible by the product of all the other A_j.	Hard9	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
Soldiers (Large)Two players alternately pick soldiers, each new pick must beat all previous picks in attack or in defense; decide if the first player can end up with strictly more picks.	Hard9	Game theoryDynamic programming+1	No attempts yet	5s	512 MB	Judgeable
Clash Royale (Large)Pick 8 of N cards and spend at most M coins on upgrades to maximize the total attack power of the chosen deck.	Hard9	Dynamic programmingGreedy+1	No attempts yet	20s	512 MB	Judgeable
Map Reduce (Large)Each query asks whether walls can be removed so the shortest S-to-F path equals D, and if so reports the deterministic greedy removal order's final map.	Hard9	BFSGraph+2	No attempts yet	5s	512 MB	Judgeable
The Gardener of Seville (Large)Fill an R by C grid with slash or backslash hedges so that paired border courtiers connect through disjoint corridors, choosing the lexicographically smallest valid maze or reporting IMPOSSIBLE.	Hard9	ImplementationSimulation+2	No attempts yet	5s	512 MB	Judgeable
RonaldGiven a graph on N vertices, a move toggles all edges incident to one chosen vertex; decide whether the complete graph is reachable.	Hard9	GraphBit manipulation+2	No attempts yet	1s	64 MB	Judgeable
The Kingdom of JOIOIPartition an H by W grid into two connected regions whose row and column slices are contiguous, minimizing the larger altitude range within either region.	Hard9	Binary searchGreedy+2	No attempts yet	4s	256 MB	Judgeable
RopeA rope of N unit cords with colors is repeatedly folded in half, paying the thickness of cords whose colors are changed, until length 2; for each color report the minimum total cost to end with a cord of that color.	Hard9	Dynamic programmingDivide and conquer+2	No attempts yet	2.5s	256 MB	Judgeable
Rides 2Each day one child grows by 1 or 2, and we must report how many of Q fixed child-pair and ride triples become valid that day.	Hard9	Segment treeSorting+2	No attempts yet	2s	256 MB	Judgeable
Distinct Substring QueriesMaintain a string under push-back and pop-front operations, reporting the number of distinct substrings after each of up to a million queries.	Hard9	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
Building a Tall BarnAssign K cows to N ordered floors, each with work a_i, so each floor gets at least one cow; minimize the sum of a_i/c_i over valid allocations, rounded to nearest integer.	Hard9	GreedyHeap+2	No attempts yet	2s	512 MB	Judgeable
Incremental Double Free StringsFind the nth string of length k(k+1)/2 that uses one letter j times for each j up to k and has no two equal adjacent letters, in alphabetical order.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Maximum Color CliqueGiven a complete graph whose every cycle has two adjacent same-color edges, sum over all nonempty node subsets the size of the largest same-color clique inside each subset, modulo 1e9+7.	Hard9	GraphCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Bracket PathsGiven a tree with '(' or ')' on each node, count ordered pairs (a,b) whose path string w_{a,b} is a properly matched bracket expression.	Hard9	TreeDivide and conquer+2	No attempts yet	3s	1024 MB	Judgeable
Switch GrassA weighted connected graph has a color at each vertex; after each of Q point color updates, report the shortest distance between two vertices of different colors.	Hard9	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
The Enormous SequenceDefine a_n by summing every nonempty subset sum of the first n-1 terms, then answer queries about gcd, 2-adic valuation of lcm, prefix sums, or a single term for various starting values.	Hard9	MathNumber theory+2	No attempts yet	2s	128 MB	Judgeable
Tarot Sham BoastGiven up to 10 equal-length strings over {R,P,S} and a length n random string, sort the strings by the probability each occurs as a contiguous block.	Hard9	String matchingProbability+2	No attempts yet	2s	512 MB	Judgeable
Shifty GridApply a fixed two-phase procedure of cyclic row and column shifts to sort a permutation grid into row-major order, following the exact TURN steps given.	Hard9	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Rolling the BottleGiven a convex polygon as a bottle base and a water volume, find the minimum and maximum number of sides of the water region as the bottle rolls.	Hard9	GeometrySorting+2	No attempts yet	2.5s	512 MB	Judgeable
Largest window sumFor every window length K, find the largest possible sum of a length-K window over all non-negative arrays that satisfy each given length bound.	Hard9	GreedyPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Minimum Cycle MeanGiven a weighted simple digraph, find the minimum mean weight over all simple directed cycles, or 0 0 if no cycle exists, and output it as a reduced fraction.	Hard9	Dynamic programmingGraph+2	No attempts yet	2s	512 MB	Judgeable
PseudoknotFind the largest t such that the string splits into u v z^R u^R y z with \|u\|>=t and \|z\|>=t, or report -1 if no such split exists.	Hard9	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
Creating Fake NewsFind one story vector satisfying n linear equations, then the minimum number of starting people whose reach covers all n people.	Hard9	MathGraph+1	No attempts yet	2s	512 MB	Judgeable
Fashion ShowPlace models on an N by N grid (or upgrade existing ones) so every shared row or column has a plus and every shared diagonal has an x, maximizing style points.	Hard9	GreedyGraph+2	No attempts yet	5s	512 MB	Judgeable
Slate Modern (Large)Fill a huge R by C grid with positive integers so adjacent cells differ by at most D, matching N fixed cells, maximizing the total sum or reporting impossibility.	Hard9	GraphShortest path+2	No attempts yet	80s	512 MB	Judgeable
Omnicircumnavigation (Large)Given points on a unit sphere joined in order by shortest arcs, decide whether the closed path meets every great circle.	Hard9	GeometryMath+2	No attempts yet	120s	512 MB	Judgeable
Stack Management (Small)Decide whether a solitaire game on 2 to 4 short stacks of cards can be reduced to at most one card per stack using two allowed moves.	Hard9	Game theorySimulation+2	No attempts yet	5s	512 MB	Judgeable
Sequence and TransformationCount length-n sequences with entries in [1,m] whose image after applying a min-based affine transformation k times has the given max-minus-min value.	Hard9	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Expected value of the greatest common divisorEach of K values is chosen uniformly from its own interval; find the expected gcd of the K chosen numbers as a fraction mod 1e9+7.	Hard9	ProbabilityMath+2	No attempts yet	2s	512 MB	Judgeable
Polynomial and QueriesEvaluate a degree-N polynomial with integer coefficients at K given points, all modulo the prime 786433, with N and K up to 250000.	Hard9	Number theoryDivide and conquer+2	No attempts yet	10s	512 MB	Judgeable
NPM998244353 (Hard)For every digit-sum cap from 0 to MM, count length-N digit strings divisible by P, modulo 998244353.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	5s	512 MB	Judgeable
Counting multiples with a bounded digit sumCount length-N digit strings divisible by P with digit sum at most M, for every M up to the limit, modulo 998244353.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Smallest unreachable subsequence sumFor each subarray, find the smallest non-negative integer that no subsequence sums to.	Hard9	Segment treeGreedy+1	No attempts yet	2s	512 MB	Judgeable
Good triples of pathsCount triples of simple paths in a tree that are either node-disjoint or pairwise intersecting, modulo 1e9+7.	Hard9	CombinatoricsTree+2	No attempts yet	2s	512 MB	Judgeable
Strongly MatchableDecide whether an even-order graph admits a perfect bipartite matching for every balanced partition of its vertices.	Hard9	GraphMath+2	No attempts yet	3s	512 MB	Judgeable
Equivalent DeformationGiven two equal-area triangles, find the minimum number of vertex-sliding operations that map the first exactly onto the second.	Hard9	GeometryImplementation+2	No attempts yet	2s	512 MB	Judgeable
LeapfrogGiven up to 40 frogs, each starting at x_i with prime jump d_i, find the smallest position where the number of frogs that land there is largest.	Hard9	Number theoryMath+1	No attempts yet	2s	512 MB	Judgeable
Fractal TreeFor a recursively defined fractal tree F_k, answer queries giving the distance between two DFS-labeled vertices.	Hard9	TreeRecursion+2	No attempts yet	7s	512 MB	Judgeable
Arranging tilesGiven up to 14 convex tiles of equal height with cut corners, find the ordering and horizontal placement that minimizes the total frame width when packed side by side.	Hard9	Dynamic programmingGeometry+2	No attempts yet	1s	1024 MB	Judgeable
CratersFind the shortest single closed fence that surrounds all circles at distance 10 or more, given each crater's center and radius.	Hard9	GeometryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Enlarging EnthusiasmCount the distinct final rankings achievable when positive point bonuses summing to x are announced in increasing order, with the lead changing hands each time.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Treasure MapOn a weighted undirected graph, gold decays each day at every mine; starting at mine 1 with forced moves, maximize total gold collected before stopping.	Hard9	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Jupiter Rock Paper ScissorsEach player crops a length-k substring, Alice morphs one block, then the play phase awards 2/1/1 points by who reaches m round wins first; report the optimal outcome.	Hard9	Game theoryImplementation+2	No attempts yet	2s	512 MB	Judgeable
IntuidiffFind the minimum number of blocks, each a substring of the first string or a single new character, whose concatenation equals the second string.	Hard9	String matchingGreedy+2	No attempts yet	7s	512 MB	Judgeable
Crazy RotationsGiven a row of coloured lights, find the smallest rotation amount that can appear at position p in a non-decreasing sequence of rotation craziness values.	Hard9	String matchingCombinatorics+2	No attempts yet	15s	512 MB	Judgeable
GCD SumFor each k from 1 to n, split a multiset of n numbers into k nonempty groups to maximize the sum of the groups' gcds. n is up to 500000 and each value up to 10^12.	Hard9	Number theoryGreedy+2	No attempts yet	2s	1024 MB	Judgeable
SkiingFind the shortest polygonal path from S down to F that crosses n horizontal gates in top-to-bottom order, and output its breakpoints.	Hard9	GeometryGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Restaurant BribesGiven a friendship graph and a list of k people to bribe, choose a real bribe for each so the total restaurant revenue minus bribe money is maximized, and print the answer as an exact reduced fraction.	Hard9	GraphMath+2	No attempts yet	2s	512 MB	Judgeable
One-Way StreetsGiven an undirected multigraph and required reachable pairs, decide for each edge whether every valid orientation matches the input direction (R), the reverse (L), or both are possible (B).	Hard9	GraphDFS+2	No attempts yet	3s	256 MB	Judgeable
Intrinsic IntervalFor each query range in a permutation, find the smallest subarray containing it whose values form a set of consecutive integers.	Hard9	Segment treeStack+1	No attempts yet	3s	512 MB	Judgeable
Lunar LandscapeCompute the total area covered by axis-aligned squares and 45-degree rotated squares, counting overlaps once.	Hard9	GeometrySorting+1	No attempts yet	2s	512 MB	Judgeable
Journey from Petersburg to MoscowFind the minimum cost path from city 1 to city n where only the k most expensive edges of the path are paid for, or all edges if the path has k or fewer.	Hard9	GraphShortest path+2	No attempts yet	3s	512 MB	Judgeable
Laminar FamilyGiven an undirected tree and f vertex sets, each a simple path, decide whether the family of paths is laminar.	Hard9	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
ToysCount the number of distinct toys formed by strings joining n evenly spaced clamps on one disc to m on another, where rotating each disc independently gives the same toy, modulo 1,000,000,007.	Hard9	CombinatoricsNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Workbook AlgorithmsCount the number of undirected graphs X on N vertices whose number of permutations P satisfying G(P)=X lies between l and r, modulo 1e9+7.	Hard9	CombinatoricsGraph+2	No attempts yet	1s	512 MB	Judgeable
Secret AgentGiven a planar straight-line graph (castle walls) where crossing a wall costs its height, find the minimum cost to travel between successive query points, starting from infinity.	Hard9	GraphGeometry+2	No attempts yet	2s	512 MB	Judgeable
GarageMaintain a sequence under point updates, and for each range query count subarrays whose elements share a common divisor greater than 1.	Hard9	Segment treeNumber theory+2	No attempts yet	4s	256 MB	Judgeable
Counting CyclesA connected undirected graph with n vertices and at most n+15 edges is given; count all simple cycles, where a simple cycle is a connected subgraph with every degree exactly two.	Hard9	GraphDFS+2	No attempts yet	4s	512 MB	Judgeable
LeadersAnimals in a circle alternately raise a running number by 1 to K; whoever is forced to say M loses, and we find the winner of every start position.	Hard9	Game theoryDynamic programming+2	No attempts yet	3s	512 MB	Judgeable
Disco Dance DebacleGiven a grid where some cells are unlit (unions of rectangles), find the fewest cell states to flip so that a set of alternating row-column dances can cover all lit cells, each dance starting and ending on the same cell with different first and last feet.	Hard9	GraphGreedy+2	No attempts yet	5s	512 MB	Judgeable
Imelda's Shopping SpreeMaintain a sequence of prices under range-add and range-reverse, and after each update output the number of contiguous segments whose values are strictly increasing.	Hard9	Segment treeArray+2	No attempts yet	5s	512 MB	Judgeable
Majestic Gourmet UniversityGiven proposed FC and IC lab slots with teacher conflicts, seat limits, and timing rules, choose a valid set of labs using the fewest distinct starting days.	Hard9	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
KabobsCount length-K strings over the given alphabet that satisfy all substring-implication rules of the form b>e, modulo 10^7.	Hard9	Dynamic programmingString+2	No attempts yet	5s	512 MB	Judgeable
Vera and Love TrianglesFor each pair of friends, a crush direction is set by the parity of the bit-count of a modular power expression; count cyclic triples.	Hard9	CombinatoricsNumber theory+2	No attempts yet	2s	256 MB	Judgeable
DramaCount the number of valid pyramid colourings of an H by N grid with exactly N black cells, modulo 10^9+7.	Hard9	CombinatoricsDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
Push a BoxGiven a grid with Bessie and a pushable box, decide for each queried cell whether the box can reach it.	Hard9	GraphBFS+1	No attempts yet	2s	512 MB	Judgeable
L-th K-th numberGiven N cards, take the K-th smallest value of every contiguous block of length at least K, then report the L-th smallest of all those values.	Hard9	Binary searchArray+2	No attempts yet	2s	512 MB	Judgeable
GardenerMaintain N gardens under plantings, range deletions of plants taller than h, and range count queries, all with time-dependent growth.	Hard9	Segment treeBinary search+2	No attempts yet	3s	128 MB	Judgeable
Revenge of the Broken DoorAn adversary hides one edge under construction; the traveler learns about an edge only upon reaching its endpoint and must minimize the worst-case distance from S to T.	Hard9	GraphShortest path+2	No attempts yet	10s	512 MB	Judgeable
Revenge of the Endless BFSDecide whether a buggy BFS that forgets visited vertices ever terminates on a given directed graph, and if so output the loop count modulo 1e9+7.	Hard9	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Conveyor BeltAfter each of Q delivery requests (a, b, p) is added, report the minimum time to finish all tasks, given plates arrive one per second and each plate carries one product.	Hard9	MathGreedy+2	No attempts yet	2s	512 MB	Judgeable
Pipe Fitter and the Fierce DogsIn a grid where every odd row and column holds a house, cover all houses with downhill chains, minimizing the cost of pipes through dog blocks, using at most K chains.	Hard9	Dynamic programmingGreedy+2	No attempts yet	2s	512 MB	Judgeable
Blocks 2Count the ways to tile an N x M rectangle with rotated k x N blocks (k=1..N), modulo 1999, where M can be as large as 10^10.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	1s	256 MB	Judgeable