Problems

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Total results29,153 problems

Radio Watchtowers
Hard9
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Highways and Counties
Hard9
Minimum spanning tree, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Asynchronous Exceptions
Hard9
Simulation, Heap+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Dungeon Creation
Hard9
Dynamic programming, Graph+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Casino
Hard9
Probability, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Runner and Sniper
Hard9
Game theory, Geometry+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Wall Making Game
Hard9
Game theory, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Cactus edge move
Hard9
Graph, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Rotating Cutter Bits
Hard9
Geometry, Simulation+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Factories
Hard9
Divide and conquer, Tree+1
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Magical Subarrays
Hard9
Divide and conquer, Segment tree+1
No attempts yet
Time limit
4s
Memory limit
128 MB
Judgeable
Lights Out in the Barn
Hard9
Dynamic programming, Game theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Circus
Hard9
Shortest path, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Gauss
Hard9
Dynamic programming, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Willow
Hard9
Game theory, Tree+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Twirling Towards Freedom (Large)
Hard9
Geometry, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Lost Password (Large)
Hard9
Graph, Shortest path+1
No attempts yet
Time limit
100s
Memory limit
512 MB
Judgeable
Children Wearing Hats (Large)
Hard9
Dynamic programming, Game theory+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Ace in the Hole
Hard9
Game theory, Greedy+2
No attempts yet
Time limit
60s
Memory limit
512 MB
Judgeable
Expensive Dinner (Large)
Hard9
Number theory, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sheepwalking
Hard9
Probability, Game theory+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Ninjutsu (Large)
Hard9
Geometry, Dynamic programming+1
No attempts yet
Time limit
60s
Memory limit
512 MB
Judgeable
Paths of Yin and Yang (Small)
Hard9
Combinatorics, Backtracking+1
No attempts yet
Time limit
30s
Memory limit
512 MB
Judgeable
The Paths of Yin Yang (Large)
Hard9
Combinatorics, Graph
No attempts yet
Time limit
120s
Memory limit
512 MB
Judgeable
Watering Plants (Large)
Hard9
Geometry, Binary search+2
No attempts yet
Time limit
60s
Memory limit
512 MB
Judgeable
King Game
Hard9
Game theory, Graph+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Coloring Practice (Large)
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Clock Breaking
Hard9
Implementation, Brute force+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Polygonal Puzzle
Hard9
Geometry, Brute force+2
No attempts yet
Time limit
20s
Memory limit
512 MB
Judgeable
Road Times
Hard9
Shortest path, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Spin Doctor
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Connect Highways
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
0.4s
Memory limit
32 MB
Judgeable
Covering posters
Hard9
Segment tree, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Half-plane land grab 2
Hard9
Dynamic programming, Divide and conquer+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Archaeological Research
Hard9
Greedy, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Counting Strings
Hard9
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Number of walks
Hard9
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dinner
Hard9
Graph, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Clique on a Line
Hard9
Dynamic programming, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
New Track
Hard9
Implementation, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Growing a Binary Tree
Hard9
Tree, DFS+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Smallest Unpayable Amount
Hard9
Greedy, Sorting+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
YATP
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Reverse a Road II
Hard9
Graph, BFS+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Tree Transformation
Hard9
Tree, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Array
Hard9
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flowey's Love
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Solve this one too
Hard9
Matrix, Dynamic programming+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Posters
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Colored Brackets
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drawing lots
Hard9
Probability, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Laser Sensors
Hard9
Divide and conquer, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Distant Stars
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
One Pass Short
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dangerous Hashing
Hard9
Math, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minimum cost increasing sequence
Hard9
Dynamic programming, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Almost Euler graphs
Hard9
Combinatorics, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary cryptarithm decryption
Hard9
Backtracking, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Three Kingdoms of Bourdelot
Hard9
Graph, Union-find+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Oracle
Hard9
Dynamic programming, Divide and conquer+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Tree and queries 5
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Trees and Queries 10
Hard9
Segment tree, Tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fencing off the darkness
Hard9
Graph, Minimum spanning tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bracket Substrings
Hard9
String, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
XOR Queries
Hard9
Trie, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lowest common ancestor in a dynamic forest
Hard9
Tree, Linked list+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 0
Hard9
Segment tree, Prefix sum+2
No attempts yet
Time limit
2.5s
Memory limit
512 MB
Judgeable
Sequence and Queries 6
Hard9
Segment tree, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Counting points inside a circle
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Sequence and Queries 9
Hard9
Divide and conquer, Segment tree+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Polygon Shrinking Kit
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Where are the bubbles?
Hard9
Implementation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Allowed swaps
Hard9
Union-find, Implementation+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Appropriate Coordinate Map
Hard9
Geometry, Greedy+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Game Moves
Hard9
Dynamic programming, Backtracking+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Jumping Impala
Hard9
Binary search, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Mobile Network Bandwidth
Hard9
Graph, Greedy+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Blue Forest
Hard9
Geometry, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Magical Mystery Knight's Tour
Hard9
Backtracking, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and queries 12
Hard9
Segment tree, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
British Menu
Hard9
Graph, Dynamic programming+2
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Driving in Optimistan
Hard9
Tree, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dancing Disks
Hard9
Divide and conquer, Simulation+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Triple tree
Hard9
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Geohash Grid
Hard9
Divide and conquer, Tree+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Hangar Hurdles
Hard9
Union-find, BFS+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Risky Lottery
Hard9
Game theory, Probability+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Conference
Hard9
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hacker
Hard9
Segment tree, Hash map+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Acrobat
Hard9
Graph, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mole Tunnels
Hard9
Tree, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Large Ping Pong Tournament
Hard9
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Eggscavation
Hard9
Geometry, Prefix sum+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Legends
Hard9
Graph, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pirates
Hard9
Greedy, Dynamic programming+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Miner
Hard9
Geometry, Binary search+2
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Cactus gift
Hard9
Dynamic programming, Tree+2
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Robotic Cow Herd
Hard9
Heap, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Function and Queries
Hard9
Dynamic programming, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Unlucky 89
Hard9
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
ArrayStart with array a_i = i, apply up to 300000 queries that reverse or rotate subarrays and ask for range min, max, sum, value at index, or index of a value, then print the final array.	Hard9	ArrayImplementation+2	No attempts yet	1s	512 MB	Judgeable
Flowey's LoveA soul starting at the origin moves at speed at most 1 inside a rectangle; N moving points travel along fixed lines, and you must find the maximum number of points the soul can touch.	Hard9	GeometryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Solve this one tooGiven an N x L matrix, find windows of 3N columns split into matrices A, B, C with A*B=C; pick disjoint windows to maximize total colored cells.	Hard9	MatrixDynamic programming+2	No attempts yet	5s	512 MB	Judgeable
PostersCompute the visible area of each of N rectangles pasted in order on the plane, where later rectangles cover earlier ones.	Hard9	GeometryDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Colored BracketsCount valid bracket strings of 2N brackets over K colors that equal their own reversal, modulo 1e9+7.	Hard9	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Drawing lotsCompute the expected number of draws until a blue lot has been drawn K times, where red lots are removed and green and blue lots are returned.	Hard9	ProbabilityMath+1	No attempts yet	2s	512 MB	Judgeable
Laser SensorsGiven N blue points and 2N red points in general position, build the particular non-crossing perfect matching prescribed by the paper's recursive angular-sweep Solve/Attach procedure.	Hard9	Divide and conquerGeometry+2	No attempts yet	2s	512 MB	Judgeable
Distant StarsEach star moves at constant integer velocity; for each day 0 to T find the maximum pairwise squared distance, and report the earliest day attaining the minimum of that maximum.	Hard9	GeometryDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
One Pass ShortConstruct a directed graph with edge weights 1 or -1, no negative cycle, yet a Bellman-Ford variant that runs N-2 rounds then checks would falsely report a negative cycle; minimize the edge count and lexicographic order.	Hard9	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Dangerous HashingFind two distinct lowercase strings of equal length (at most 300000) that collide under ten polynomial hashes with bases 29, 31, 37, 41, 43, 47, 53, 59, 61, 67 modulo 1e9+7.	Hard9	MathNumber theory+2	No attempts yet	5s	512 MB	Judgeable
Minimum cost increasing sequenceTransform A into a strictly increasing integer sequence B minimizing the sum of \|B_i - A_i\|, and output the lexicographically smallest such B.	Hard9	Dynamic programmingGreedy+1	No attempts yet	2s	512 MB	Judgeable
Almost Euler graphsCount the simple graphs on N labeled vertices that become Eulerian after adding or removing one edge, modulo 1e9+7.	Hard9	CombinatoricsGraph+2	No attempts yet	2s	512 MB	Judgeable
Binary cryptarithm decryptionGiven a short cipher string where letters replace some characters of an unknown binary equation, count how many valid equations from the given grammar match it.	Hard9	BacktrackingDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Three Kingdoms of BourdelotDecide whether some assignment of positive or negative polarity to each document is consistent with the hypothesis that person p is an ancestor of person q.	Hard9	GraphUnion-find+2	No attempts yet	4s	512 MB	Judgeable
OracleGiven multipliers p_i and bet sizes j^2+aj+b for the j-th entered game, she picks a subsequence of exactly k games to maximize total profit, for every k.	Hard9	Dynamic programmingDivide and conquer+2	No attempts yet	3s	256 MB	Judgeable
Tree and queries 5On a tree where vertices flip black and white, answer for each query the distance from a given vertex to the nearest white vertex.	Hard9	TreeDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Trees and Queries 10Given a tree with vertex weights, answer path maximum-subarray-sum queries and path range-assign-weight updates.	Hard9	Segment treeTree+2	No attempts yet	2s	512 MB	Judgeable
Fencing off the darknessGiven a grid of bulb strengths and a ceiling height, compute each square's light level, mark the dark ones, then find the cheapest set of interior squares that contains all dark squares and minimizes the perimeter cost.	Hard9	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Bracket SubstringsCount how many distinct balanced bracket sequences appear as non-empty substrings of a given bracket string of length up to 500,000.	Hard9	StringHash map+2	No attempts yet	2s	512 MB	Judgeable
XOR QueriesMaintain an array under appends, rollbacks of the last k elements, and range queries for max XOR, count <= x, and k-th smallest.	Hard9	TrieSegment tree+2	No attempts yet	2s	512 MB	Judgeable
Lowest common ancestor in a dynamic forestMaintain a forest of rooted trees under link, cut, and lowest-common-ancestor queries, printing each LCA.	Hard9	TreeLinked list+2	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 0For each query range [i,j] of a ±1 sequence, report the length of the longest contiguous subarray inside it whose sum is 0, or 0 if none exists.	Hard9	Segment treePrefix sum+2	No attempts yet	2.5s	512 MB	Judgeable
Sequence and Queries 6For each query range [i, j], report the highest number of occurrences of any single value inside that range.	Hard9	Segment treeDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Counting points inside a circleFor each of M circle queries, count how many of N fixed points lie inside or on the circle, printing the count per query.	Hard9	GeometryDivide and conquer+2	No attempts yet	8s	512 MB	Judgeable
Sequence and Queries 9For each query range [i,j] and value k, count ordered pairs (p,q) from that range with A[p]*B[q] <= k.	Hard9	Divide and conquerSegment tree+2	No attempts yet	6s	512 MB	Judgeable
Polygon Shrinking KitEach polygon vertex is replaced by the midpoint toward A or toward B; among all choices keeping the vertices in convex order, find the minimum possible area.	Hard9	GeometryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Where are the bubbles?Given the per-turn swap counts of bubblesort, reconstruct the lexicographically largest permutation that produces exactly those swap counts.	Hard9	ImplementationGreedy+2	No attempts yet	2s	512 MB	Judgeable
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
Dancing DisksMove n numbered disks from the upper-left rod of a 6x6 rod grid to the lower-right rod, shifting stacks only down or right, and print a valid sequence of moves.	Hard9	Divide and conquerSimulation+1	No attempts yet	3s	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