Problems

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Total results21,187 problems

Teaching HazardHard9
Number theory, Math +1No attempts yetTime limit5sMemory limit128 MB
Judgeable
RecurrenceHard9
Combinatorics, Number theory +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Strange GraphHard9
GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Even cycle partition of a planar graphHard9
Graph, MathNo attempts yetTime limit1sMemory limit128 MB
Judgeable
GRADHard9
Shortest path, Graph +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Rail Station RecoveryHard9
Graph, Sorting +1No attempts yetTime limit3sMemory limit512 MB
Judgeable
Gondola replacement countHard9
Combinatorics, MathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
FriendHard9
Graph, Dynamic programming +1No attempts yetTime limit1sMemory limit16 MB
Judgeable
OrbitHard9
Geometry, Math +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Maximum Transport ProfitHard9
Tree, Dynamic programmingNo attempts yetTime limit3sMemory limit256 MB
Judgeable
Bisecting the IslandHard9
Geometry, Brute forceNo attempts yetTime limit1sMemory limit256 MB
Judgeable
The Forest of FangornHard9
Geometry, GraphNo attempts yetTime limit3sMemory limit64 MB
Judgeable
CakeHard9
Segment tree, Divide and conquer +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Solar LampsHard9
Geometry, Segment tree +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
ParkingHard9
Geometry, Graph +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
Sequence CenterHard9
Math, Binary searchNo attempts yetTime limit3sMemory limit256 MB
Judgeable
MuseumHard9
Graph, Geometry +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
TollgateHard9
Shortest path, Graph +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Watering the Bean PlantsHard9
Geometry, Greedy +1No attempts yetTime limit10sMemory limit256 MB
Judgeable
ExhibitionHard9
Dynamic programming, Math +1No attempts yetTime limit10sMemory limit256 MB
Judgeable
Combinator ExpressionHard9
Dynamic programming, Tree +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Expression and SubstringHard9
Shortest path, Graph +1No attempts yetTime limit10sMemory limit256 MB
Judgeable
Growing Orthogonal SpiralHard9
Math, Number theory +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Red and Black Stepping StonesHard9
Game theory, Graph +1No attempts yetTime limit9sMemory limit256 MB
Judgeable
Pork barrelHard9
Minimum spanning tree, Divide and conquer +2No attempts yetTime limit30sMemory limit256 MB
Judgeable
Hidden MazeHard9
Divide and conquer, Tree +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Tokyo Olympics CenterHard9
Dynamic programming, Shortest path +1No attempts yetTime limit5sMemory limit128 MB
Judgeable
Revenge of Minimum Cost FlowHard9
Graph, Shortest path +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
Hashigo SamaHard9
Dynamic programming, GraphNo attempts yetTime limit8sMemory limit256 MB
Judgeable
Overwriting GameHard9
Probability, Matrix +1No attempts yetTime limit8sMemory limit512 MB
Judgeable
Slave to Achievements 2Hard9
Probability, Dynamic programming +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
Believer in I 2Hard9
Combinatorics, Dynamic programming +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
Followers of I 3Hard9
Dynamic programming, Combinatorics +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
Same Suffix ArrayHard9
String, String matching +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Meeting in the Sierpinski LabyrinthHard9
Tree, Divide and conquer +1No attempts yetTime limit3sMemory limit512 MB
Judgeable
Tile CuttingHard9
Number theory, Math +1No attempts yetTime limit15sMemory limit256 MB
Judgeable
Art GalleryHard9
Geometry, Shortest pathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Dictionary SurveyHard9
Trie, Math +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
Bulb PuzzleHard9
Graph, Backtracking +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
PhibonacciHard9
Number theory, MathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Random signalsHard9
Geometry, Probability +1No attempts yetTime limit12sMemory limit256 MB
Judgeable
Sorting under interferenceHard9
Math, GreedyNo attempts yetTime limit1sMemory limit512 MB
Judgeable
Calvinball Championship, Again 2Hard9
Graph, Backtracking +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Card Rarity EncodingHard9
Greedy, Heap +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
Development of Small Flying RobotsHard9
Shortest path, Graph +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
FroggerHard9
Math, BFS +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Join My TeamHard9
Graph, Game theoryNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Hogwarts staircasesHard9
BFS, Shortest path +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Canyon MappingHard9
Geometry, Binary search +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Nim with a Robot RefereeHard9
Game theory, Number theoryNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Counting Distinct Suffix ArraysHard9
Combinatorics, String +1No attempts yetTime limit1sMemory limit512 MB
Judgeable
Quaternary ComputerHard9
Bit manipulation, Math +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Balancing LineHard9
Geometry, Brute force +1No attempts yetTime limit10sMemory limit256 MB
Judgeable
KernelHard9
GeometryNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Tree Edit DistanceHard9
Dynamic programming, TreeNo attempts yetTime limit2sMemory limit256 MB
Judgeable
Radio WatchtowersHard9
Greedy, Sorting +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Highways and CountiesHard9
Minimum spanning tree, Dynamic programming +2No attempts yetTime limit2sMemory limit64 MB
Judgeable
Asynchronous ExceptionsHard9
Simulation, Heap +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Dungeon CreationHard9
Dynamic programming, Graph +1No attempts yetTime limit3sMemory limit512 MB
Judgeable
CasinoHard9
Probability, Dynamic programming +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Runner and SniperHard9
Game theory, Geometry +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Wall Making GameHard9
Game theory, Divide and conquer +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Cactus edge moveHard9
Graph, CombinatoricsNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Rotating Cutter BitsHard9
Geometry, Simulation +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
FactoriesHard9
Divide and conquer, Tree +1No attempts yetTime limit6sMemory limit512 MB
Judgeable
Magical SubarraysHard9
Divide and conquer, Segment tree +1No attempts yetTime limit4sMemory limit128 MB
Judgeable
Lights Out in the BarnHard9
Dynamic programming, Game theory +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
CircusHard9
Shortest path, Segment tree +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
GaussHard9
Dynamic programming, Shortest path +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
WillowHard9
Game theory, Tree +1No attempts yetTime limit5sMemory limit512 MB
Judgeable
Twirling Towards Freedom (Large)Hard9
Geometry, Number theory +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Lost Password (Large)Hard9
Graph, Shortest path +1No attempts yetTime limit100sMemory limit512 MB
Judgeable
Children Wearing Hats (Large)Hard9
Dynamic programming, Game theory +1No attempts yetTime limit5sMemory limit512 MB
Judgeable
Ace in the HoleHard9
Game theory, Greedy +2No attempts yetTime limit60sMemory limit512 MB
Judgeable
Expensive Dinner (Large)Hard9
Number theory, MathNo attempts yetTime limit5sMemory limit512 MB
Judgeable
SheepwalkingHard9
Probability, Game theory +1No attempts yetTime limit20sMemory limit1024 MB
Judgeable
Ninjutsu (Large)Hard9
Geometry, Dynamic programming +1No attempts yetTime limit60sMemory limit512 MB
Judgeable
Paths of Yin and Yang (Small)Hard9
Combinatorics, Backtracking +1No attempts yetTime limit30sMemory limit512 MB
Judgeable
The Paths of Yin Yang (Large)Hard9
Combinatorics, GraphNo attempts yetTime limit120sMemory limit512 MB
Judgeable
Watering Plants (Large)Hard9
Geometry, Binary search +2No attempts yetTime limit60sMemory limit512 MB
Judgeable
King GameHard9
Game theory, Graph +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Coloring Practice (Large)Hard9
Combinatorics, Math +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Clock BreakingHard9
Implementation, Brute force +1No attempts yetTime limit5sMemory limit512 MB
Judgeable
Polygonal PuzzleHard9
Geometry, Brute force +2No attempts yetTime limit20sMemory limit512 MB
Judgeable
Road TimesHard9
Shortest path, Math +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Spin DoctorHard9
Geometry, Sorting +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Connect HighwaysHard9
Geometry, Sorting +2No attempts yetTime limit0.4sMemory limit32 MB
Judgeable
Covering postersHard9
Segment tree, Prefix sum +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Half-plane land grab 2Hard9
Dynamic programming, Divide and conquer +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
Archaeological ResearchHard9
Greedy, Graph +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Counting StringsHard9
Dynamic programming, String matching +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Number of walksHard9
Graph, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
DinnerHard9
Graph, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Clique on a LineHard9
Dynamic programming, Sorting +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
New TrackHard9
Implementation, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Growing a Binary TreeHard9
Tree, DFS +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
Smallest Unpayable AmountHard9
Greedy, Sorting +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
YATPHard9
Tree, Divide and conquer +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Reverse a Road IIHard9
Graph, BFS +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Tree TransformationHard9
Tree, Dynamic programming +2No attempts yetTime limit1sMemory limit512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
Random signalsCompute the expected plane integral of the strongest covering signal when each of up to 20 stations draws an independent uniform power that activates its disks.	Hard9	GeometryProbability+1	No attempts yet	12s	256 MB	Judgeable
Sorting under interferenceFind the fewest rounds of one swap per round that sort a permutation despite known interfering swaps, with the smallest move list on ties.	Hard9	MathGreedy	No attempts yet	1s	512 MB	Judgeable
Calvinball Championship, Again 2Split n players into the fewest teams so no pair who dislike each other shares a team.	Hard9	GraphBacktracking+1	No attempts yet	1s	256 MB	Judgeable
Card Rarity EncodingGiven N draws over four rarities with known probabilities, find the smallest possible expected length of a prefix-free binary code for the N-draw sequences.	Hard9	GreedyHeap+2	No attempts yet	3s	128 MB	Judgeable
Development of Small Flying RobotsEach robot moves sideways for 1 energy and rises through a hole for 100, and all must meet on one hole-free cell of the top floor for the least total energy.	Hard9	Shortest pathGraph+1	No attempts yet	1s	256 MB	Judgeable
FroggerFind the fewest frogs to place left of the y-axis so peg jumps can bring one frog to (X, 0), or print frogger when it is impossible.	Hard9	MathBFS+1	No attempts yet	1s	256 MB	Judgeable
Join My TeamPair N participants by ranked preference lists into the lexicographically smallest stable pairing with no blocking pair, or report NO SOLUTION.	Hard9	GraphGame theory	No attempts yet	1s	256 MB	Judgeable
Hogwarts staircasesFind the shortest sequence of red and green button presses that turns the current staircase layout into the desired one, breaking ties by lexicographic order.	Hard9	BFSShortest path+2	No attempts yet	1s	256 MB	Judgeable
Canyon MappingCover a simple polygon with k equal axis-aligned squares and print the smallest side length that covers it, rounded to two decimals.	Hard9	GeometryBinary search+1	No attempts yet	1s	256 MB	Judgeable
Nim with a Robot RefereeDecide each bag's winning first takes in a Nim variant where piles with forbidden divisor patterns vanish before every turn.	Hard9	Game theoryNumber theory	No attempts yet	2s	512 MB	Judgeable
Counting Distinct Suffix ArraysCount how many distinct suffix arrays length-N strings with at most M distinct letters produce, modulo 1e9+7.	Hard9	CombinatoricsString+1	No attempts yet	1s	512 MB	Judgeable
Quaternary ComputerGiven N base-4 variables, M add and xor commands, and one forbidden start value per variable, print each output total over all inputs modulo 4.	Hard9	Bit manipulationMath+2	No attempts yet	1s	512 MB	Judgeable
Balancing LineFind the shortest closed curve avoiding square lamp footprints that encloses a nonempty lamp group holding half the total energy.	Hard9	GeometryBrute force+1	No attempts yet	10s	256 MB	Judgeable
KernelDecide whether a rectilinear polygon contains a beacon point that attracts every other point under greedy distance-decreasing motion.	Hard9	Geometry	No attempts yet	1s	256 MB	Judgeable
Tree Edit DistanceCompute the minimum leaf insertions, leaf deletions, and relabels that turn one ordered labeled tree into another.	Hard9	Dynamic programmingTree	No attempts yet	2s	256 MB	Judgeable
Radio WatchtowersKeep K of N towers on a line and raise their radio powers so each pair of kept towers can talk, minimizing raise cost minus sale income.	Hard9	GreedySorting+2	No attempts yet	1s	256 MB	Judgeable
Highways and CountiesFind the smallest road length limit so cities joined by shorter roads form a group whose populations hold a subset summing to a multiple of K.	Hard9	Minimum spanning treeDynamic programming+2	No attempts yet	2s	64 MB	Judgeable
Asynchronous ExceptionsSimulate a multithreaded scheduler with yields, kills, fork modes, loops, and semaphores, then report each thread's finishing time and the final state.	Hard9	SimulationHeap+2	No attempts yet	5s	512 MB	Judgeable
Dungeon CreationCount the spanning trees of the obstacle-free grid graph for each test case, modulo 1,000,000,007.	Hard9	Dynamic programmingGraph+1	No attempts yet	3s	512 MB	Judgeable
CasinoWith m dollars, a goal of n dollars and win chance p percent per play, pick each stake to maximize the chance of reaching the goal.	Hard9	ProbabilityDynamic programming+1	No attempts yet	2s	256 MB	Judgeable
Runner and SniperYou give your start position and the gun's start angle and turn rate, then compute the fastest run speed at which the rotating gun still catches you.	Hard9	Game theoryGeometry+1	No attempts yet	2s	256 MB	Judgeable
Wall Making GameTwo players alternately pick an empty cell and turn its row and column lines into walls until blocked, and the player unable to move loses.	Hard9	Game theoryDivide and conquer+1	No attempts yet	2s	256 MB	Judgeable
Cactus edge moveCount the pairs of deleting one edge and inserting a different edge that keep the given graph a cactus.	Hard9	GraphCombinatorics	No attempts yet	1s	256 MB	Judgeable
Rotating Cutter BitsThe program counts interior lattice points of a polygonal workpiece that survive one full rotation against a second rotating polygonal cutter.	Hard9	GeometrySimulation+1	No attempts yet	3s	256 MB	Judgeable
FactoriesEach query gives two factory sets on a weighted tree and asks for the minimum distance between any factory in one set and any in the other.	Hard9	Divide and conquerTree+1	No attempts yet	6s	512 MB	Judgeable
Magical SubarraysEach query asks for the longest subarray inside [L,R] with every element between its first and last values.	Hard9	Divide and conquerSegment tree+1	No attempts yet	4s	128 MB	Judgeable
Lights Out in the BarnStarting at an unknown vertex of a rectilinear barn, walk the walls to identify the position and reach the exit with the smallest worst-case extra distance.	Hard9	Dynamic programmingGame theory+1	No attempts yet	2s	512 MB	Judgeable
CircusFind the smallest starting hold depth on a temporary rope at D that reaches distance M by hopping between ropes within swing range.	Hard9	Shortest pathSegment tree+1	No attempts yet	2s	512 MB	Judgeable
GaussStarting from A, pay divisor-based costs to shrink the number or stay on lucky numbers, and find the cheapest exact-move cost to end at B.	Hard9	Dynamic programmingShortest path+2	No attempts yet	2s	256 MB	Judgeable
WillowTwo players choose starting cities on a tree with coins and alternately collect cities, each road usable once, and Hanaa maximizes the final score difference.	Hard9	Game theoryTree+1	No attempts yet	5s	512 MB	Judgeable
Twirling Towards Freedom (Large)Each minute you stay put or rotate 90 degrees clockwise around a star, and must report the largest squared distance from the origin reachable in M minutes.	Hard9	GeometryNumber theory+2	No attempts yet	5s	512 MB	Judgeable
Lost Password (Large)Given string S and integer k, compute the length of the shortest string containing every l33tspeak variant of each substring of S with length 1 to k.	Hard9	GraphShortest path+1	No attempts yet	100s	512 MB	Judgeable
Children Wearing Hats (Large)Given B black and W white hats for k children, count color sequences where the i-th child from the back first deduces their hat color, modulo 32749.	Hard9	Dynamic programmingGame theory+1	No attempts yet	5s	512 MB	Judgeable
Ace in the HoleGiven Ben's examination order, restore the lexicographically greatest deck with no decreasing triple that makes his optimal search follow it.	Hard9	Game theoryGreedy+2	No attempts yet	60s	512 MB	Judgeable
Expensive Dinner (Large)Friends 1 to N arrive in any order and raise the shared bill to multiples of their numbers, and you report the gap between the most and fewest waiter calls.	Hard9	Number theoryMath	No attempts yet	5s	512 MB	Judgeable
SheepwalkingTwo sheepdogs block two neighboring cells each turn to steer a randomly moving sheep home and minimize its expected number of moves there.	Hard9	ProbabilityGame theory+1	No attempts yet	20s	1024 MB	Judgeable
Ninjutsu (Large)Pick a starting rope length so the counterclockwise swing catches as many targets as possible before settling into orbit.	Hard9	GeometryDynamic programming+1	No attempts yet	60s	512 MB	Judgeable
Paths of Yin and Yang (Small)Count the black-and-white colorings of an N by M grid in which each color class forms a single path with two ends.	Hard9	CombinatoricsBacktracking+1	No attempts yet	30s	512 MB	Judgeable
The Paths of Yin Yang (Large)Count the black-and-white colorings of an N by M grid in which each color forms one edge-adjacent path.	Hard9	CombinatoricsGraph	No attempts yet	120s	512 MB	Judgeable
Watering Plants (Large)Given non-overlapping plant disks, find the smallest radius R so that two disks of radius R together cover every plant disk completely.	Hard9	GeometryBinary search+2	No attempts yet	60s	512 MB	Judgeable
King GameOn a small board with burned squares, two players alternately move a king to an unvisited neighboring square; report who wins under optimal play.	Hard9	Game theoryGraph+2	No attempts yet	5s	512 MB	Judgeable
Coloring Practice (Large)Count colorings of a regular n-gon up to rotation, reflection, and arbitrary permutation of the k colors, modulo 1e9+7.	Hard9	CombinatoricsMath+2	No attempts yet	3s	512 MB	Judgeable
Clock BreakingGiven several consecutive LCD clock displays, find segments that are always burnt out, burnt in, working, or unknown across all consistent start times and fault assignments.	Hard9	ImplementationBrute force+1	No attempts yet	5s	512 MB	Judgeable
Polygonal PuzzleGiven two simple polygons, translate and rotate them without reflection so their interiors stay disjoint and their shared boundary is as long as possible; print that maximum length.	Hard9	GeometryBrute force+2	No attempts yet	20s	512 MB	Judgeable
Road TimesGiven a unique shortest route for each ordered city pair, recorded delivery times constrain 30 to 60 km/h road speeds; for each query find the minimum and maximum travel time consistent with all records.	Hard9	Shortest pathMath+2	No attempts yet	5s	512 MB	Judgeable
Spin DoctorGiven n points (a_i, b_i) labeled 1 or 0, choose a direction (S, T); with ties broken adversarially, minimize the span covering all label-1 points.	Hard9	GeometrySorting+2	No attempts yet	5s	512 MB	Judgeable
Connect HighwaysGiven two planar connected networks, find the Red-Blue junction pair allowed to be joined by a segment, following a fixed angular tie-breaking rule.	Hard9	GeometrySorting+2	No attempts yet	0.4s	32 MB	Judgeable
Covering postersFor each new axis-aligned rectangle, compute the total area of the given union of rectangles that it covers.	Hard9	Segment treePrefix sum+2	No attempts yet	2s	1024 MB	Judgeable
Half-plane land grab 2Maintain a dynamic set of lines under insertions and deletions and answer maximum-at-x queries online.	Hard9	Dynamic programmingDivide and conquer+2	No attempts yet	4s	512 MB	Judgeable
Archaeological ResearchGiven the surviving shuffled entries of a table of next occurrences for an unknown alphabet size, recover the lexicographically smallest original sequence or report that none exists.	Hard9	GreedyGraph+2	No attempts yet	2s	512 MB	Judgeable
Counting StringsCount strings over the lowercase alphabet whose length lies between LK and LK+N and in which at most K non-overlapping copies of a given pattern S can be found.	Hard9	Dynamic programmingString matching+2	No attempts yet	2s	512 MB	Judgeable
Number of walksGiven a directed graph as an adjacency matrix, find the smallest K such that the number of walks of length L grows as O(L^K), or -1 if none exists.	Hard9	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
DinnerGiven ages, decide whether all people can be split into round tables of size at least 3 so that every pair of adjacent ages sums to a prime.	Hard9	GraphMath+2	No attempts yet	2s	512 MB	Judgeable
Clique on a LineGiven n points on a line with weights, two points are adjacent when their weights sum to at most their distance; find the largest clique.	Hard9	Dynamic programmingSorting+2	No attempts yet	2s	512 MB	Judgeable
New TrackConstruct a fixed alternating axis-parallel polyline through a formula that encodes exactly k crossings, using a zigzag permutation of y coordinates to place them.	Hard9	ImplementationCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Growing a Binary TreeFor each tree, pick a root and count the fewest vertices to add so that the result becomes a complete binary tree (every internal vertex has exactly two children, all leaves equidistant from the root), minimizing that count and then the vertex index; output the count mod 1e9+7.	Hard9	TreeDFS+2	No attempts yet	4s	512 MB	Judgeable
Smallest Unpayable AmountFor each query interval, find the smallest positive amount that cannot be formed as a subset sum of the coins in that interval.	Hard9	GreedySorting+2	No attempts yet	4s	512 MB	Judgeable
YATPGiven a node-weighted, edge-weighted tree, for each node find the minimum of dist(u,v) + p_u*p_v over all v, and sum these minima over all nodes.	Hard9	TreeDivide and conquer+2	No attempts yet	5s	512 MB	Judgeable
Reverse a Road IIEach directed road carries at most one truck; find whether reversing one road increases the max number of edge-disjoint S-to-T paths, the new maximum, and how many roads achieve it.	Hard9	GraphBFS+2	No attempts yet	8s	512 MB	Judgeable
Tree TransformationCount the minimum-size sets of edges whose removal splits the tree into components of power-of-two sizes, modulo 1e9+7.	Hard9	TreeDynamic programming+2	No attempts yet	1s	512 MB	Judgeable