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 results29,171 problems

Ones
Hard9
Math, Combinatorics+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Garbage
Hard9
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Periodicity
Hard9
String, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Milk Multidrink
Hard9
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ski Rental
Hard9
Segment tree, Geometry+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Binary Knockout
Hard9
Game theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Spider
Hard9
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Journeys
Hard9
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Computational Biology
Hard9
String, Sorting+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Hard Choice
Hard9
Graph, DFS+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Fragments
Hard9
String matching, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Army Training
Hard9
Geometry, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Blindfold Nim
Hard9
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Quasi-template
Hard9
String matching, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Diamond
Hard9
Geometry, Brute force+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fishes
Hard9
Graph, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Programming Contest
Hard9
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Watchmen
Hard9
Geometry, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Questions
Hard9
Brute force, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Dragon Milkdrinker
Hard9
Probability, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Video Poker
Hard9
Brute force, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Microchips
Hard9
Graph, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fibonacci Word
Hard9
String, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Highways
Hard9
Matrix, Segment tree+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Reconstructing the Convex Polygon
Hard9
Graph, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Manhunt
Hard9
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prefix-Suffixes
Hard9
String matching, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Peaks
Hard9
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Minimum brackets
Hard9
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Highways
Hard9
Tree, DFS+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Palindromic Equivalence
Hard9
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
BARMAN
Hard9
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Godzilla
Hard9
Graph, Union-find+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sets
Hard9
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Most Valuable Tower
Hard9
Number theory, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sequence
Hard9
Math, Binary search+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Genome
Hard9
Greedy, Segment tree+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Land Tax
Hard9
Divide and conquer, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Plot of Land
Hard9
Geometry, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Crystal
Hard9
Math, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Thirsty Ants
Hard9
Simulation, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Multiplication
Hard9
Number theory, Math+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Delivery
Hard9
Graph, Shortest path
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Wombats
Hard9
Segment tree, Shortest path+1
No attempts yet
Time limit
20s
Memory limit
256 MB
Judgeable
Puzzle
Hard9
String matching, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Roof
Hard9
Geometry
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Aquarium Drainage
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Aquarium 3
Hard9
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Möbius Strip
Hard9
Math, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fence Watch
Hard9
Geometry, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mineshaft
Hard9
Geometry, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Anchored Balloon
Hard9
Geometry, Binary search+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Dragon Pattern
Hard9
String matching, Recursion+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Adriatic
Hard9
Graph, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Lonely Mountain
Hard9
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Largest and Smallest Triangle
Hard9
Geometry, Sorting+1
No attempts yet
Time limit
6s
Memory limit
128 MB
Judgeable
It Takes a Village
Hard9
Graph, DFS+2
No attempts yet
Time limit
20s
Memory limit
128 MB
Judgeable
Chain & Co.
Hard9
Geometry, Graph+1
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Cactus Automorphisms
Hard9
Tree, Dynamic programming+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Green Energy
Hard9
Geometry, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Teaching Hazard
Hard9
Number theory, Math+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Recurrence
Hard9
Combinatorics, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Strange Graph
Hard9
Graph
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Even cycle partition of a planar graph
Hard9
Graph, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
GRAD
Hard9
Shortest path, Graph+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Rail Station Recovery
Hard9
Graph, Sorting+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Gondola replacement count
Hard9
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Friend
Hard9
Graph, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
16 MB
Judgeable
Orbit
Hard9
Geometry, Math+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Maximum Transport Profit
Hard9
Tree, Dynamic programming
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Bisecting the Island
Hard9
Geometry, Brute force
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
The Forest of Fangorn
Hard9
Geometry, Graph
No attempts yet
Time limit
3s
Memory limit
64 MB
Judgeable
Cake
Hard9
Segment tree, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Solar Lamps
Hard9
Geometry, Segment tree+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Parking
Hard9
Geometry, Graph+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Sequence Center
Hard9
Math, Binary search
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Museum
Hard9
Graph, Geometry+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Tollgate
Hard9
Shortest path, Graph+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Watering the Bean Plants
Hard9
Geometry, Greedy+1
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Exhibition
Hard9
Dynamic programming, Math+1
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Combinator Expression
Hard9
Dynamic programming, Tree+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Expression and Substring
Hard9
Shortest path, Graph+1
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Growing Orthogonal Spiral
Hard9
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Red and Black Stepping Stones
Hard9
Game theory, Graph+1
No attempts yet
Time limit
9s
Memory limit
256 MB
Judgeable
Pork barrel
Hard9
Minimum spanning tree, Divide and conquer+2
No attempts yet
Time limit
30s
Memory limit
256 MB
Judgeable
Hidden Maze
Hard9
Divide and conquer, Tree+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Tokyo Olympics Center
Hard9
Dynamic programming, Shortest path+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Revenge of Minimum Cost Flow
Hard9
Graph, Shortest path+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Hashigo Sama
Hard9
Dynamic programming, Graph
No attempts yet
Time limit
8s
Memory limit
256 MB
Judgeable
Overwriting Game
Hard9
Probability, Matrix+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Slave to Achievements 2
Hard9
Probability, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Believer in I 2
Hard9
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Followers of I 3
Hard9
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Same Suffix Array
Hard9
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Meeting in the Sierpinski Labyrinth
Hard9
Tree, Divide and conquer+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Tile Cutting
Hard9
Number theory, Math+1
No attempts yet
Time limit
15s
Memory limit
256 MB
Judgeable
Art Gallery
Hard9
Geometry, Shortest path
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Dictionary Survey
Hard9
Trie, Math+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Bulb Puzzle
Hard9
Graph, Backtracking+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Phibonacci
Hard9
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
OnesGiven run lengths of n in binary, output run lengths of the binary form of sks(n), the total UFO count over 1 to n.	Hard9	MathCombinatorics+2	No attempts yet	3s	512 MB	Judgeable
GarbageEach street needs its state flipped or not; a route is a simple cycle, and driving a street flips it. Find the minimum total length of cycles whose symmetric difference equals the set of streets needing a flip.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
PeriodicityFor each name, find the lexicographically smallest bit string of the same length whose set of periods equals the name's set of periods, or XXX if none exists.	Hard9	StringPrefix sum+2	No attempts yet	1s	128 MB	Judgeable
Milk MultidrinkDecide whether a tree with n nodes has a Hamiltonian path from 1 to n where consecutive vertices stay within distance two.	Hard9	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
Ski RentalGiven daily snowfall amounts with point updates, answer queries asking for the maximum average snowfall over a consecutive run starting at a given day, reported as an irreducible fraction.	Hard9	Segment treeGeometry+1	No attempts yet	1s	128 MB	Judgeable
Binary KnockoutA coin game on a line: each coin may double its position or move one step right; the player unable to move loses. Find the k-th value of n where the second player wins.	Hard9	Game theoryMath+1	No attempts yet	1s	128 MB	Judgeable
SpiderA walk on an infinite regular seven-legged web is given as turn directions; count the web nodes strictly inside the closed polygon it traces.	Hard9	GeometryImplementation+1	No attempts yet	1s	128 MB	Judgeable
JourneysGiven m batches, each joining every town in one interval to every town in a disjoint interval, find the shortest path in highway count from town p to all towns.	Hard9	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Computational BiologyFor each query length m, find a length-m word whose every cyclic rotation appears in s, maximizing the total count of those rotations in s.	Hard9	StringSorting+2	No attempts yet	5s	128 MB	Judgeable
Hard ChoiceAfter streets are closed one by one offline, answer for each query whether two edge-disjoint paths still connect the given pair of junctions.	Hard9	GraphDFS+2	No attempts yet	5s	128 MB	Judgeable
FragmentsCount how many times each digit string appears as a contiguous substring across the decimal forms of all numbers in a union of disjoint integer intervals up to 10^18.	Hard9	String matchingDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Army TrainingGiven n points with no three collinear, answer m queries, each a simple clockwise polygon on those points, counting the points strictly inside it.	Hard9	GeometryCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Blindfold NimEach stack size is uniform on [0, a_i]; compute the probability that the first player wins a game of Nim with hidden positions where a player who overshoots a stack loses at once.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Quasi-templateCount the distinct words that, as substrings of v with possibly overhanging copies, can tile across the whole input; report the count and the shortest, lexicographically smallest such word.	Hard9	String matchingString+2	No attempts yet	1s	128 MB	Judgeable
DiamondGiven a convex polyhedron, choose one plane cut so that the two resulting pieces have the largest combined number of faces.	Hard9	GeometryBrute force+1	No attempts yet	2s	512 MB	Judgeable
FishesGroup recorded closed routes into the fewest fish, where two routes can follow on consecutive days if the start cells touch and every point is visible 24 hours earlier.	Hard9	GraphGeometry+2	No attempts yet	2s	512 MB	Judgeable
Programming ContestGiven each participant's skill per topic, decide whether we can choose n tasks (topic and difficulty) so Byteman is the unique winner under solve-count then points ranking.	Hard9	GreedyMath+2	No attempts yet	2s	512 MB	Judgeable
WatchmenCount, for each city gutter, how many Palace gutters a walker can reach while dodging rotating watchers' lines of sight.	Hard9	GeometryGraph+2	No attempts yet	2s	512 MB	Judgeable
QuestionsSimulate a logic puzzle where princes and a sorcerer reason about a system of variable constraints over time; answer what each prince or the sorcerer knows.	Hard9	Brute forceSimulation+2	No attempts yet	1s	128 MB	Judgeable
Dragon MilkdrinkerCompute the probability that the sum of n independent uniform [m, M] yields is strictly less than h, printed truncated to d decimals.	Hard9	ProbabilityMath+2	No attempts yet	1s	128 MB	Judgeable
Video PokerFor a given video poker payout table, count how many of the 2,598,960 dealt hands make the optimal expected-value strategy discard exactly 0, 1, 2, 3, 4, and 5 cards.	Hard9	Brute forceCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
MicrochipsCount directed walks whose edge-impedance product equals I, allowing repeated vertices and edges, and report infinity when infinitely many such walks exist.	Hard9	GraphNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Fibonacci WordCount occurrences of a given binary pattern in the Fibonacci word F_m and count distinct subwords occurring at least that many times, mod 20062006, with m up to 1e9.	Hard9	StringDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
HighwaysMaintain a layered graph where each province has a few cities and highway lane counts change over time, answering route-count queries modulo d after each update.	Hard9	MatrixSegment tree+1	No attempts yet	1s	128 MB	Judgeable
Reconstructing the Convex PolygonGiven all edges and non-crossing diagonals of a convex polygon with shuffled vertex labels, recover the cyclic boundary order, with vertex 1 first and the smallest possible second vertex.	Hard9	GraphImplementation+1	No attempts yet	1s	128 MB	Judgeable
ManhuntGiven a connected undirected graph where the bandit moves to a different city each night, find the minimum number of days for a search schedule that guarantees capture, or report impossibility.	Hard9	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Prefix-SuffixesCount proper borders summed over all substrings of a given lowercase word of length up to 10^5.	Hard9	String matchingString+1	No attempts yet	1s	128 MB	Judgeable
PeaksFor each query, starting from a peak and using only edges up to a difficulty limit, report the k-th highest reachable peak height or -1.	Hard9	GraphUnion-find+2	No attempts yet	2s	128 MB	Judgeable
Minimum bracketsGiven an arithmetic template with holes, delete as many brackets as possible while keeping the same value for every valid assignment of real numbers to the holes.	Hard9	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
HighwaysGiven a tree plus extra highway edges, count for each query (x,y) the main tree path plus alternative single-highway paths that touch the main path only at x and y.	Hard9	TreeDFS+2	No attempts yet	3s	128 MB	Judgeable
Palindromic EquivalenceCount words of the same length that have palindromic substrings at exactly the same positions as the given word.	Hard9	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
BARMANGiven orders m_i of hidden values modulo a hidden n, choose up to 2k range-multiply operations to maximize the worst-case guaranteed order of the final sum.	Hard9	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
GodzillaAfter each of k edge deletions in a directed graph, the task asks for the smallest number of start vertices that reach every vertex.	Hard9	GraphUnion-find+1	No attempts yet	1s	128 MB	Judgeable
SetsGiven n arithmetic-progression sets of multiples of d_i, count elements in their union that share no prime factor with m.	Hard9	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
The Most Valuable TowerFind the largest sum any single tower can reach by swapping top segments between towers of different heights.	Hard9	Number theorySorting+2	No attempts yet	1s	512 MB	Judgeable
SequenceFind the nth term of the nondecreasing sequence where each k appears exactly as many times as the kth term.	Hard9	MathBinary search+1	No attempts yet	1s	512 MB	Judgeable
GenomeBuild the lexicographically smallest sequence that is l adjacent swaps from the first genome and k-l swaps from the second.	Hard9	GreedySegment tree+1	No attempts yet	1s	128 MB	Judgeable
Land TaxChoose a non-empty contiguous row and column range that maximizes combined row and column payments weighted by heights and widths.	Hard9	Divide and conquerGeometry+2	No attempts yet	1s	128 MB	Judgeable
Plot of LandGiven up to 3000 pine points and one million query rectangles, report the convex hull area of the points inside each rectangle.	Hard9	GeometryDivide and conquer+1	No attempts yet	1s	128 MB	Judgeable
CrystalSum the signed charges of all three-colored unit triangles in a hexagonal crystal filled row by row from a modular generator.	Hard9	MathGeometry+2	No attempts yet	1s	128 MB	Judgeable
Thirsty AntsAnts on a line walk at unit speed toward the nearest fallen dew drop, and the task asks for every ant's position when the last drop is drunk.	Hard9	SimulationSorting+2	No attempts yet	1s	128 MB	Judgeable
MultiplicationGiven prime p and each query pair a and b, find the smallest k with a to the k-th power congruent to b modulo p, or print -1 when b never appears.	Hard9	Number theoryMath+1	No attempts yet	5s	128 MB	Judgeable
DeliverySend as many trucks as possible from the top-left to the bottom-right corner of an n by n grid where each street has a daily usage limit.	Hard9	GraphShortest path	No attempts yet	10s	128 MB	Judgeable
WombatsFind the cheapest southbound path across a grid with free east-west moves and south-only vertical roads under weight updates and escape queries.	Hard9	Segment treeShortest path+1	No attempts yet	20s	256 MB	Judgeable
PuzzleBuild the longest string over the first n capital letters that avoids all forbidden substrings, or print No when no maximum exists.	Hard9	String matchingTrie+2	No attempts yet	1s	128 MB	Judgeable
RoofCompute the maximum height of the 45-degree straight-skeleton roof built over a rectilinear polygon.	Hard9	Geometry	No attempts yet	1s	128 MB	Judgeable
Aquarium DrainageGiven an orthogonal aquarium floor with holes on its segments, compute the total drain time and the water left behind.	Hard9	GeometrySorting+2	No attempts yet	1s	128 MB	Judgeable
Aquarium 3Place K holes on distinct horizontal floor segments to maximize the area of water that drains out.	Hard9	TreeGreedy+2	No attempts yet	1s	128 MB	Judgeable
Möbius StripGiven m and n, compute the average graph distance over all ordered square pairs on the m by 2n Mobius grid.	Hard9	MathCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Fence WatchPlace the fewest sensors on a convex polygon boundary so every boundary point forms an angle from alpha to 360 degrees minus alpha with some sensor pair.	Hard9	GeometryGreedy+1	No attempts yet	1s	128 MB	Judgeable
MineshaftRun a pipe of straight segments up a winding polygonal shaft so each segment touches the walls in at least two places and the number of bends is minimal.	Hard9	GeometryGraph+1	No attempts yet	1s	128 MB	Judgeable
Anchored BalloonFind the greatest height a balloon tied to ground anchors by fixed-length ropes can reach while all ropes hold and none cross.	Hard9	GeometryBinary search+1	No attempts yet	1s	128 MB	Judgeable
Dragon PatternCount how many times pattern S appears as a contiguous block in the length 2^n direction string of the order-n left dragon curve.	Hard9	String matchingRecursion+2	No attempts yet	5s	128 MB	Judgeable
AdriaticOn a 2500 by 2500 grid, islands ordered alike from northwest to southeast connect in one hop, and each island needs the sum of fewest hops from all others.	Hard9	GraphPrefix sum+1	No attempts yet	2s	256 MB	Judgeable
Lonely MountainGiven two orthogonal mountain silhouettes, decide whether any solid casts both and print the largest possible volume modulo 1000000007.	Hard9	GeometryMath+2	No attempts yet	2s	256 MB	Judgeable
Largest and Smallest TriangleGiven n points in the plane, compute the largest and smallest areas among all triangles formed by triples of the points.	Hard9	GeometrySorting+1	No attempts yet	6s	128 MB	Judgeable
It Takes a VillageProcess online trading-post additions that spread through biconnected blocks and capital dominators, and answer revenue queries for single villages.	Hard9	GraphDFS+2	No attempts yet	20s	128 MB	Judgeable
Chain & Co.Decide whether axis-aligned square links split into two nonempty groups with every cross pair linked.	Hard9	GeometryGraph+1	No attempts yet	10s	128 MB	Judgeable
Cactus AutomorphismsCount the automorphisms of a given cactus graph with up to 50000 vertices and print the count as a prime factorization.	Hard9	TreeDynamic programming+2	No attempts yet	5s	256 MB	Judgeable
Green EnergyPlace towers of given heights on a polygonal terrain to maximize the total length lit by parallel sun rays blocked by terrain and other towers.	Hard9	GeometryGreedy+1	No attempts yet	1s	128 MB	Judgeable
Teaching HazardGiven n and x, count pairs of bases b1 < b2 where n! ends in the same number of trailing zeros p with p at least x.	Hard9	Number theoryMath+1	No attempts yet	5s	128 MB	Judgeable
RecurrenceCount the decrement orders that reduce the given partition to all zeros while staying nonincreasing, modulo 1,000,000,009.	Hard9	CombinatoricsNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Strange GraphDecide whether a connected strange graph, where every high-degree vertex has a degree-2 neighbor and its other neighbors form a clique, has a Hamiltonian cycle.	Hard9	Graph	No attempts yet	1s	128 MB	Judgeable
Even cycle partition of a planar graphGiven a vertex-biconnected planar graph with at most two odd faces, decide whether its edges partition into even simple cycles.	Hard9	GraphMath	No attempts yet	1s	128 MB	Judgeable
GRADCities join the road network one by one with two roads each, and each query asks the shortest road distance between two cities.	Hard9	Shortest pathGraph+2	No attempts yet	2s	256 MB	Judgeable
Rail Station RecoveryRecover every station's block number and C or D type from the all-pairs shortest-route distances and station 0's block.	Hard9	GraphSorting+1	No attempts yet	3s	512 MB	Judgeable
Gondola replacement countCount the replacement orders that can produce the given circular gondola sequence, modulo 1000000009.	Hard9	CombinatoricsMath	No attempts yet	1s	256 MB	Judgeable
FriendChoose a set of people with maximum total confidence so that no two chosen people are friends in the network grown by the three joining rules.	Hard9	GraphDynamic programming+1	No attempts yet	1s	16 MB	Judgeable
OrbitPlace two opposite sensors on the radius-R circle so their brightest-star readings match, and print the pair with the smallest angle.	Hard9	GeometryMath+1	No attempts yet	2s	256 MB	Judgeable
Maximum Transport ProfitPick two villages in the tree so the total profit of the given routes with both endpoints on the path between them is as large as possible.	Hard9	TreeDynamic programming	No attempts yet	3s	256 MB	Judgeable
Bisecting the IslandSplit an axis-parallel simple polygon into two congruent pieces with one axis-parallel cut on integer coordinates, or report that none exists.	Hard9	GeometryBrute force	No attempts yet	1s	256 MB	Judgeable
The Forest of FangornFind which border camps connect to the start by a path where no tree ever hides behind another tree.	Hard9	GeometryGraph	No attempts yet	3s	64 MB	Judgeable
CakeStarting from piece a, Leopold always eats the less delicious piece next to the empty interval, and each query asks how many pieces are eaten before piece b.	Hard9	Segment treeDivide and conquer+2	No attempts yet	2s	1024 MB	Judgeable
Solar LampsCompute each lamp turn-on time from its place in the power-on order and the count of already lit lamps shining on it.	Hard9	GeometrySegment tree+1	No attempts yet	1s	256 MB	Judgeable
ParkingDecide whether axis-aligned cars in a strip of height w can be slid without overlap or rotation from the start layout to the target layout.	Hard9	GeometryGraph+2	No attempts yet	3s	256 MB	Judgeable
Sequence CenterGiven k integer sequences of length n, find an integer sequence that minimizes the maximum Manhattan distance to them.	Hard9	MathBinary search	No attempts yet	3s	256 MB	Judgeable
MuseumA burglar picks guards to bribe to maximize the value of exhibits no remaining guard sees minus bribe costs under downward cone views.	Hard9	GraphGeometry+1	No attempts yet	1s	256 MB	Judgeable
TollgateFind the road with the largest expected toll income when every resident visits every restaurant by a random shortest round trip.	Hard9	Shortest pathGraph+2	No attempts yet	2s	256 MB	Judgeable
Watering the Bean PlantsPlace at most one disk of radius R and cover the uncovered parts of N segments with unit-length sticks at minimum total cost.	Hard9	GeometryGreedy+1	No attempts yet	10s	256 MB	Judgeable
ExhibitionFind the cheapest linear-cost cuts to product 1's price, size and weight that put it in some k-set tying the best set without it.	Hard9	Dynamic programmingMath+1	No attempts yet	10s	256 MB	Judgeable
Combinator ExpressionCount the fewest BCKI rewrite steps that reduce the given expression to its normal form.	Hard9	Dynamic programmingTree+1	No attempts yet	1s	256 MB	Judgeable
Expression and SubstringFind the shortest string that matches the given regular expression and contains S as a substring, breaking ties by lexicographic order.	Hard9	Shortest pathGraph+1	No attempts yet	10s	256 MB	Judgeable
Growing Orthogonal SpiralDecide whether an orthogonal spiral whose segment lengths grow by at least 1 can end exactly at (x, y) and print the shortest such lengths.	Hard9	MathNumber theory+1	No attempts yet	1s	256 MB	Judgeable
Red and Black Stepping StonesFind the smallest lookahead queue size that lets the mover survive forever on a red-black directed graph against an adversarial color chooser.	Hard9	Game theoryGraph+1	No attempts yet	9s	256 MB	Judgeable
Pork barrelFor each query interval [l, h], build the cheapest forest using only roads with costs inside the interval that connects as many city pairs as possible.	Hard9	Minimum spanning treeDivide and conquer+2	No attempts yet	30s	256 MB	Judgeable
Hidden MazeCompute the expected median edge weight over all tree node pairs at odd distance, and print it as a reduced fraction.	Hard9	Divide and conquerTree+2	No attempts yet	2s	256 MB	Judgeable
Tokyo Olympics CenterAssign each lettered unit to one of K staff and order the visits to minimize the longest round trip from the start cell that checks every dead-end room.	Hard9	Dynamic programmingShortest path+1	No attempts yet	5s	128 MB	Judgeable
Revenge of Minimum Cost FlowSend f units of freight from city s to city t through directed carrier edges with two-piece linear costs and report the cheapest total.	Hard9	GraphShortest path+1	No attempts yet	3s	256 MB	Judgeable
Hashigo SamaCount black-white colorings of joined ladders where each monochrome block has size at most k, modulo 1,000,000,007.	Hard9	Dynamic programmingGraph	No attempts yet	8s	256 MB	Judgeable
Overwriting GameYou repeat random prefix-rectangle repaints until the board matches the target, and report the expected total of painted cells as a reduced fraction.	Hard9	ProbabilityMatrix+1	No attempts yet	8s	512 MB	Judgeable
Slave to Achievements 2Repeatedly craft as many N-scrap daggers as possible and reclaim 0 to K scraps per dagger, then find the distribution of the final leftover under N scraps.	Hard9	ProbabilityDynamic programming+1	No attempts yet	3s	256 MB	Judgeable
Believer in I 2Over every ordering of A push, B add, and C multiply cards on an infinite stack of I, report the total of each of the top K stack values modulo 1,000,000,007.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	3s	256 MB	Judgeable
Followers of I 3Sum, over every distinct order of the I, plus, and times cards run on an infinite I stack, the top K stack values modulo 1000000007.	Hard9	Dynamic programmingCombinatorics+1	No attempts yet	3s	256 MB	Judgeable
Same Suffix ArrayCount the strings that differ from the given length N string in exactly one position and keep the same suffix array.	Hard9	StringString matching+1	No attempts yet	2s	256 MB	Judgeable
Meeting in the Sierpinski LabyrinthTourists stand on cells of a grid that are free exactly when row and column share no binary 1 bit, and must meet in one cell with minimum total steps.	Hard9	TreeDivide and conquer+1	No attempts yet	3s	512 MB	Judgeable
Tile CuttingFor each query range, find the area with the largest count of inscribed parallelogram cuts and report that count, breaking ties by the smaller area.	Hard9	Number theoryMath+1	No attempts yet	15s	256 MB	Judgeable
Art GalleryFind the vertex sequence of the shortest interior path between two given vertices of a polygon lit from edge v0-v1.	Hard9	GeometryShortest path	No attempts yet	1s	256 MB	Judgeable
Dictionary SurveyFind how many leading pages of the integers from A to B in lexicographic order pin down both A and B.	Hard9	TrieMath+1	No attempts yet	3s	256 MB	Judgeable
Bulb PuzzleYou rotate every elbow and straight wire so all wires form one path that joins the two bulbs, and print the smallest such layout.	Hard9	GraphBacktracking+1	No attempts yet	1s	256 MB	Judgeable
PhibonacciGiven n and k, decide whether (P_n)^k equals A φ^k + B for integers A and B and print them modulo 1,000,000,007, or -1.	Hard9	Number theoryMath	No attempts yet	1s	256 MB	Judgeable