Problems

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Total results29,414 problems

City Attractions
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Monsters
Hard8
Array, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Permutation Swaps
Hard8
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Goodness of a sequence
Hard8
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
ACG
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rectangle Coloring
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Even substrings
Hard8
Bit manipulation, Hash map+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Number of good permutations
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 19
Hard8
Segment tree, Linked list+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tree path decomposition
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Turning off every lamp
Hard8
Bit manipulation, Brute force+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Who made the Christmas sound
Hard8
Dynamic programming, Tree+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Alien microbes
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Broadcast Stations
Hard8
Dynamic programming, Tree+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Rectilinear Regions
Hard8
Geometry, Two pointers+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Period of a Slot Machine
Hard8
String matching, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Vacation Plans
Hard8
Shortest path, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sheets and Paintballs
Hard8
Sorting, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Making Lunch Boxes
Hard8
Math, Bit manipulation+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Shooting Gallery
Hard8
Dynamic programming, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ice cream samples
Hard8
Sliding window, Two pointers+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Booming Business
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Crowd Control
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Flatland Fidget Spinner
Hard8
Geometry, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ghostbusters
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Knight's Marathon
Hard8
Math, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Easter Eggs
Hard8
Binary search, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hoarse Horses
Hard8
Geometry, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Jumping Choreography
Hard8
Math, Number theory+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Airport Coffee
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Compass Card Sales
Hard8
Simulation, Sorting+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Hubtown
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Hiker Safety
Hard8
Greedy, Simulation+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Intergalactic Chords
Hard8
Segment tree, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Brincadeira
Hard8
Prefix sum, Hash map+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Periodical cicadas
Hard8
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Royal Tax
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Daunting device
Hard8
Segment tree, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Imperial roads
Hard8
Minimum spanning tree, Union-find+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Jumping Frog
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Keep it covered
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Linearville
Hard8
Shortest path, Graph+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Abstract Art
Hard8
Geometry, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Uncertainty of Politics
Hard8
Dynamic programming, Probability+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rainbow Roads
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Distinct Distances
Hard8
Geometry, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Avoiding Airports
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Long Long Strings
Hard8
String, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Spinning Up Palindromes
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flipping Out
Hard8
String, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dividing Marbles
Hard8
Math, Number theory+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Hidden Supervisors
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Joker's Card Trick
Hard8
Segment tree, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Extra Judicial Operation
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hot Sand and Umbrellas
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Haggling With a Witcher
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Balloon Warehouse
Hard8
Tree, DFS+2
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Dendroctonus
Hard8
Geometry, Brute force+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Election Frenzy
Hard8
Graph, BFS+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Graphics Design
Hard8
Simulation, Heap+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Hilbert's Hash Browns
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Infinite Trees
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Competition Day
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Calendar Fragment
Hard8
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Painting polygon outlines
Hard8
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pyramid
Hard8
Binary search, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Power plants
Hard8
Geometry, Divide and conquer+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Bracket Path
Hard8
Graph, BFS+2
No attempts yet
Time limit
0.2s
Memory limit
512 MB
Judgeable
Counterspells
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The Battle for Wesnoth
Hard8
Probability, Math+2
No attempts yet
Time limit
0.1s
Memory limit
1024 MB
Judgeable
Corporate life after a hostile takeover
Hard8
Tree, DFS+2
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
Posters on the wall
Hard8
Segment tree, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Ironman
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Racetrack
Hard8
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Saturn Bees
Hard8
Math, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
EvenOdd
Hard8
Math, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Islands of Weenesia
Hard8
Graph, Geometry+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Wolf
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lights Out
Hard8
Graph, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Boom!
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mousetrap
Hard8
Tree, DFS+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Building Bridges
Hard8
Dynamic programming, Greedy+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Chase
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Buffalo Barricades
Hard8
Sorting, Prefix sum+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Cumulative Code
Hard8
Math, Tree+2
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Donut Drone
Hard8
Simulation, Binary search+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Embedding Enumeration
Hard8
Tree, DFS+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Faulty Factorial
Hard8
Number theory, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Gambling Guide
Hard8
Graph, Probability+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Kitchen Knobs
Hard8
Greedy, Implementation+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Open-Pit Mining
Hard8
Graph, Minimum spanning tree+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Archery Tournament
Hard8
Geometry, Binary search+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Box
Hard8
Geometry, Brute force+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Connections
Hard8
Graph, BFS+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
The Final Level
Hard8
Math, Greedy+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
The Great Wall
Hard8
Binary search, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Knapsack Cryptosystem
Hard8
Number theory, Brute force+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Sumdoku
Hard8
Backtracking, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fence Invasion
Hard8
Geometry, Combinatorics+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Mindol Tour
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
City AttractionsOn a weighted tree, Gigel repeatedly jumps from his current city to the city maximizing a_y - dist(x, y), breaking ties by smallest index, and we must report his position after K days.	Hard8	TreeDFS+2	No attempts yet	2s	64 MB	Judgeable
MonstersGiven a binary N x M grid, choose one intact cell to destroy so that the number of all-1 submatrices remaining is minimized, and report that minimum count.	Hard8	ArrayDynamic programming+2	No attempts yet	1s	32 MB	Judgeable
Permutation SwapsFor each k from 1 to n-1, count permutations reachable from A in exactly k swaps, modulo 1e9+7.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
Goodness of a sequenceFor every contiguous block, subtract the maximum increasing-subsequence sum from the block sum, then report the best value and how many shortest blocks achieve it.	Hard8	Dynamic programmingPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
ACGCount assignments of N ordered problems to three solvers so A's count is a multiple of k, C never solves two in a row, and G solves at least one, modulo 10000007.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Rectangle ColoringCount the black-or-white colorings of an N by M grid where every X by Y subrectangle contains both colors.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Even substringsFor each query listing up to 5 letters, count substrings of S in which every listed letter occurs an even number of times.	Hard8	Bit manipulationHash map+1	No attempts yet	2s	512 MB	Judgeable
Number of good permutationsCount permutations of 1..N that respect given fixed positions and contain at least one pair i<j with P[i]>j and P[j]>i, modulo 2000000011.	Hard8	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 19Maintain an array under range add, range floor-division by d, and report the minimum and sum over a range. The division step needs a segment tree with min and sum.	Hard8	Segment treeLinked list+1	No attempts yet	2s	512 MB	Judgeable
Tree path decompositionCount the ways to partition all nodes of an unrooted tree into vertex-disjoint paths, where each path's node sum is nonnegative, modulo 1e9+7.	Hard8	TreeDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
Turning off every lampGiven an N x N grid of lamps, pressing a cell toggles it and its orthogonal neighbors; find the minimum number of presses that turns all lamps off, or -1 if impossible.	Hard8	Bit manipulationBrute force+2	No attempts yet	4s	512 MB	Judgeable
Who made the Christmas soundRoot the tree at socket 1 and count colorings with R, G, B bulbs, respecting the green and blue adjacency rules, whose total cost is divisible by K.	Hard8	Dynamic programmingTree+2	No attempts yet	1s	512 MB	Judgeable
Alien microbesCount the breeding patterns over H days starting from one microbe, where each day the microbes alive produce children with a total of at most W.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	256 MB	Judgeable
Broadcast StationsGiven a tree, assign non-negative integer powers to vertices so every zero-power vertex lies within reach of some positive-power vertex, minimizing the total power. Report that minimum sum.	Hard8	Dynamic programmingTree+2	No attempts yet	0.5s	512 MB	Judgeable
Rectilinear RegionsGiven two unbounded staircase polylines L and U, count the closed regions they enclose with L below and U above, and sum their areas.	Hard8	GeometryTwo pointers+2	No attempts yet	0.5s	512 MB	Judgeable
Period of a Slot MachineGiven a sequence of n outcomes, find k and p minimizing k+p (ties by smaller p) such that T[i+p]=T[i] for all i>k with i+p<=n.	Hard8	String matchingImplementation+1	No attempts yet	2s	512 MB	Judgeable
Vacation PlansFind the minimum total cost for up to three people to each travel from city 1 to their airports across separate countries in the same number of days.	Hard8	Shortest pathDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Sheets and PaintballsGiven axis-aligned rectangles and colored points, count the distinct color labels that reach each rectangle along the vertical stacking order.	Hard8	SortingSegment tree+2	No attempts yet	2s	512 MB	Judgeable
Making Lunch BoxesGiven binary recipe vectors, choose the largest subset with every ingredient appearing in an even number of chosen recipes, meaning their XOR is zero.	Hard8	MathBit manipulation+1	No attempts yet	8s	512 MB	Judgeable
Shooting GalleryA row of ducks, each with a species; a good round hits two ducks of the same species and keeps only the ducks strictly between them, and rounds continue while same-species pairs remain. Find the longest possible run of good rounds.	Hard8	Dynamic programmingArray+2	No attempts yet	2s	512 MB	Judgeable
Ice cream samplesGiven a circular sequence of sample boxes, find the shortest consecutive run whose multiset union covers all brands 1 to K, and report its total sample count.	Hard8	Sliding windowTwo pointers+2	No attempts yet	3s	512 MB	Judgeable
Booming BusinessCount ordered rooted trees with exactly w nodes and height exactly h, modulo 1e9+7, where children of each node are an ordered sequence.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Crowd ControlFind the unique maximum-capacity simple path from node 0 to node n-1 and list every other edge incident to a vertex on that path that must be closed.	Hard8	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Flatland Fidget SpinnerGiven the pixel colors a camera recorded of a three-armed spinner, recover the camera's position and rotation angle.	Hard8	GeometryBinary search+2	No attempts yet	2s	512 MB	Judgeable
GhostbustersGiven independent button press probabilities, find the most likely set of pressed buttons that produces the observed row-to-column connectivity signals.	Hard8	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Knight's MarathonOn a huge rectangular board, find the minimum number of knight moves from one square to another while staying inside the board.	Hard8	MathBFS+2	No attempts yet	2s	512 MB	Judgeable
Easter EggsChoose a red egg set and a blue egg set from given plants, total N eggs, maximizing the minimum red-blue distance.	Hard8	Binary searchGraph+2	No attempts yet	2s	512 MB	Judgeable
Hoarse HorsesGiven line segments in the plane, count the maximum number of faces enclosed by them, i.e. bounded regions of their arrangement.	Hard8	GeometryGraph+2	No attempts yet	2s	512 MB	Judgeable
Jumping ChoreographyMaintain the minimum total number of jumps for frogs to gather at a tower that also moves, under insertions and deletions.	Hard8	MathNumber theory+1	No attempts yet	3s	512 MB	Judgeable
Airport CoffeeGiven spaced coffee carts along a corridor, choose where to buy cups so the total walking time with alternating slow and fast phases is minimized, output as a fraction.	Hard8	Dynamic programmingGreedy+2	No attempts yet	6s	512 MB	Judgeable
Compass Card SalesRepeatedly remove the remaining card with the smallest uniqueness score, breaking ties by larger ID, and print the removal order.	Hard8	SimulationSorting+2	No attempts yet	6s	512 MB	Judgeable
HubtownAssign citizens to one of their two angularly nearest train rays, respecting each ray's capacity, and maximize the number assigned.	Hard8	GreedySorting+2	No attempts yet	10s	512 MB	Judgeable
Hiker SafetyHikers on markers along a route must take turns stepping forward so that neighbours stay within distance B and everyone keeps their personal space; output the lexicographically smallest order in which all reach the end, or impossible.	Hard8	GreedySimulation+1	No attempts yet	4s	512 MB	Judgeable
Intergalactic ChordsMaintain an array of N notes (0 to 8); for each chord [a,b] find the most frequent note in the range, break ties by largest, then add it modulo 9 to every note in the range.	Hard8	Segment treeImplementation+2	No attempts yet	1s	1024 MB	Judgeable
BrincadeiraGiven an LFSR over N up to 30 bits, find a contiguous run of at least Y generated values whose sum is divisible by X, minimizing the end index then the start index.	Hard8	Prefix sumHash map+1	No attempts yet	1s	1024 MB	Judgeable
Periodical cicadasGiven cycle lengths that already coincide within L, choose the smallest extra cycle maximizing the next common multiple not exceeding L.	Hard8	Number theoryMath+1	No attempts yet	1s	1024 MB	Judgeable
Royal TaxGiven a tree of cities, each with tax gold and a carriage of capacity C, find the minimum total distance to collect all gold into the capital vault.	Hard8	TreeDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Daunting deviceApply N range-recolor operations whose endpoints depend on the current count of a query color, then report the highest cell frequency.	Hard8	Segment treeImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Imperial roadsFor each road, report the cost of a minimum spanning tree forced to include that road. Queries are offline and non-repeating.	Hard8	Minimum spanning treeUnion-find+1	No attempts yet	1s	1024 MB	Judgeable
Jumping FrogGiven a circular string of rocks and ponds, count the step sizes K (1 to N-1) for which some rock's K-step cycle stays entirely on rocks.	Hard8	Number theoryMath+2	No attempts yet	1s	1024 MB	Judgeable
Keep it coveredDecide whether a grid of dots and empty cells can be tiled by four line-piece types so that lines match across shared sides and never touch the border.	Hard8	GraphDFS+2	No attempts yet	1s	1024 MB	Judgeable
LinearvilleFor each query, find the length of a shortest path between two grid crossings when the path must alternate directions at every crossing.	Hard8	Shortest pathGraph+2	No attempts yet	1s	1024 MB	Judgeable
Abstract ArtGiven up to 100 simple polygons with 3 to 20 vertices each, compute the sum of their areas and the area of their union, each rounded to six decimals.	Hard8	GeometryImplementation+1	No attempts yet	2s	512 MB	Judgeable
The Uncertainty of PoliticsEach hearing has a start time and a uniform integer length in [a,b]; pick hearings to attend fully so the expected count is maximized.	Hard8	Dynamic programmingProbability+2	No attempts yet	2s	512 MB	Judgeable
Rainbow RoadsGiven a tree whose edges are colored, find every node v such that all simple paths starting at v have no two consecutive edges of the same color.	Hard8	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
Distinct DistancesChoose any point q in the plane and minimize the number of distinct Euclidean distances from q to n given integer points.	Hard8	GeometryMath+2	No attempts yet	3s	512 MB	Judgeable
Avoiding AirportsFind a flight itinerary from country 1 to country n minimizing the sum of squared waiting times at airports.	Hard8	GraphShortest path+2	No attempts yet	3s	512 MB	Judgeable
Long Long StringsDecide whether two sequences of insertions and deletions, applied to any sufficiently long string, produce identical results.	Hard8	StringMath+2	No attempts yet	1s	512 MB	Judgeable
Spinning Up PalindromesGiven a digit string of up to 40 wheels, find the minimum number of single-digit advances (with cascading carries) to reach a palindrome.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	512 MB	Judgeable
Flipping OutCount the strings that, added to the given patterns, make the flip rule reproduce the given flip sequence, or -1 if infinitely many work.	Hard8	StringDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Dividing MarblesFour players each contribute a power of two marbles; splitting piles while merging equal sizes, find the fewest turns to leave exactly one marble.	Hard8	MathNumber theory+2	No attempts yet	3s	512 MB	Judgeable
Hidden SupervisorsGiven a partial parent array, fill in the missing supervisors to complete a rooted tree and maximize the number of disjoint parent-child pairs.	Hard8	TreeDynamic programming+2	No attempts yet	3s	512 MB	Judgeable
Joker's Card TrickAfter each point update to a row of nonzero integers, find the smallest prefix index maximizing the running sum of values scaled by the total positive and total negative sums.	Hard8	Segment treePrefix sum+2	No attempts yet	3s	512 MB	Judgeable
Extra Judicial OperationGiven a connected undirected graph, find the minimum number of vertices beyond one that must hold servers so every vertex still reaches a server after any single edge is removed.	Hard8	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
Hot Sand and UmbrellasFind the minimum total time Kevin sprints on hot sand to go from the car to the ball and back, cooling at circular umbrellas, where each sun run is at most k seconds and the ball visit does not reset the limit.	Hard8	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Haggling With a WitcherGiven an unknown target fee uniform on [L,R], maximize expected gold by naming fees over time, where each attempt or save-reload costs 100 ms and time is capped by T.	Hard8	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
Balloon WarehouseSimulate repeated insertions into an infinite balloon line, then report the colors at positions l to r-1 after all instructions.	Hard8	TreeDFS+2	No attempts yet	7s	512 MB	Judgeable
DendroctonusDecide whether the infected and non-infected points can be separated by a single circle centered anywhere, where boundary non-infected points are allowed but interior ones are not.	Hard8	GeometryBrute force+2	No attempts yet	8s	512 MB	Judgeable
Election FrenzyGiven each table's visible set either explicitly or as a complement, build the visibility graph and 2-color each connected component by BFS distance parity.	Hard8	GraphBFS+1	No attempts yet	10s	512 MB	Judgeable
Graphics DesignSimulate discrete events where students claim cameras, camcorders, and computers for subprojects in priority order and report each student's finish time.	Hard8	SimulationHeap+2	No attempts yet	4s	512 MB	Judgeable
Hilbert's Hash BrownsCount how many residues mod n are reachable as x^p + q mod n over all nonnegative integers x.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Infinite TreesGiven two possibly infinite trees defined by node-to-children mappings, decide whether their roots have the same ordered structure, where recursive nodes make the unfolding infinite and require comparing regular trees.	Hard8	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
Competition DayFind the shortest simple path from F to C, then the shortest simple path different from it, and report their time difference.	Hard8	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Calendar FragmentGiven a small rectangular fragment cut from a fixed-format yearly calendar, list all years from 1900 to 2100 whose calendar could contain that fragment.	Hard8	ImplementationSimulation+2	No attempts yet	1s	512 MB	Judgeable
Painting polygon outlinesFor each polygon side, split it at intersections with later polygons, then sum over the pieces where the depth t counts how many later polygons contain the piece.	Hard8	GeometryImplementation+1	No attempts yet	1s	512 MB	Judgeable
PyramidFor each query Q, find the Q-th smallest positive integer divisible by at least one of up to 15 given numbers, with every answer at most 10^18.	Hard8	Binary searchCombinatorics+2	No attempts yet	2s	1024 MB	Judgeable
Power plantsColor n points with two colors so the closest same-color pair is as far apart as possible, and output that squared distance plus the lexicographically smallest optimal coloring.	Hard8	GeometryDivide and conquer+2	No attempts yet	3s	1024 MB	Judgeable
Bracket PathGiven a directed graph whose edges carry bracket symbols, find the length of a shortest path from s to t whose edge labels form a correct bracket expression, or -1 if none exists.	Hard8	GraphBFS+2	No attempts yet	0.2s	512 MB	Judgeable
CounterspellsAfter each of n leaf insertions into a rooted tree, find the minimum number of vertex recolorings needed to restore the unique well coloring.	Hard8	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
The Battle for WesnothChoose positive d and b with d*b <= m to maximize the chance that the total damage of b independent blows, each landing with probability p/100 and dealing d, kills a unit with h hitpoints; report the smallest-d, smallest-b optimum or 1 1 if impossible.	Hard8	ProbabilityMath+2	No attempts yet	0.1s	1024 MB	Judgeable
Corporate life after a hostile takeoverGiven two rooted trees on the same n employees, count for each employee how many others are descendants in both trees.	Hard8	TreeDFS+2	No attempts yet	0.5s	1024 MB	Judgeable
Posters on the wallGiven up to 50000 non-overlapping axis-aligned rectangles, answer online queries that ask for the total rectangle area inside a query rectangle, with coordinates decoded from the previous answer.	Hard8	Segment treeSorting+2	No attempts yet	2s	1024 MB	Judgeable
IronmanFind the fastest path across n horizontal layers with different speeds, entering and exiting each layer boundary at an optimal x position, and print the minimum travel time.	Hard8	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
RacetrackGiven ordered lap times and lap counts and the rule that passes happen only at the finish line, compute when each runner finishes the race.	Hard8	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Saturn BeesOn a torus-like hexagonal grid, decide whether nm/4 vertices can each dominate a closed neighborhood of 4 vertices, covering every vertex.	Hard8	MathCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
EvenOddSum f(X) for every X in [L, R], where f counts the steps of a process that halves even numbers and adds 1 to odd numbers until reaching 1. The bounds reach 10^18.	Hard8	MathBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Islands of WeenesiaFind the shortest tunnel between two circular islands whose entrance points sit at least 100 cm inside the rims, so that the reachability graph over islands becomes strongly connected.	Hard8	GraphGeometry+2	No attempts yet	5s	512 MB	Judgeable
WolfGiven your n-card pile and the opponent's remaining 51... wait 52-n cards, decide whether reordering both piles can make you win the next turn.	Hard8	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Lights OutFind the shortest walk from room 1 to room 0 whose switches span exactly the set of reachable lamp states, counting repeated visits.	Hard8	GraphBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Boom!Count the ways to fold a strip of N segments so that no two chemically coated faces touch.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
MousetrapOn a tree, Dumbo blocks or cleans edges while an edge-averse mouse moves; find the minimum moves to force it into the trap.	Hard8	TreeDFS+2	No attempts yet	5s	512 MB	Judgeable
Building BridgesPick a subset containing the first and last pillars, pay (h_i-h_j)^2 for each bridge section and w_i for each skipped pillar, and minimize the total.	Hard8	Dynamic programmingGreedy+1	No attempts yet	3s	128 MB	Judgeable
ChaseJerry walks a simple path in a tree, dropping up to v breadcrumbs that zero out neighbor pigeon counts; maximize the pigeons Tom later meets minus the pigeons Jerry met.	Hard8	TreeDynamic programming+1	No attempts yet	4s	512 MB	Judgeable
Buffalo BarricadesFor each settler arriving in order, count the buffalos inside the region bounded by rivers and fences whose upper right corner is the settler's post.	Hard8	SortingPrefix sum+2	No attempts yet	5s	512 MB	Judgeable
Cumulative CodeFor the complete binary tree of depth k, answer q queries each summing m elements of its Prüfer code at positions a, a+d, ..., a+(m-1)d.	Hard8	MathTree+2	No attempts yet	7s	512 MB	Judgeable
Donut DroneSimulate a drone on a toroidal grid where each step moves to the highest of three rightward neighbors, handling up to 1e9 steps per move query and elevation updates.	Hard8	SimulationBinary search+2	No attempts yet	8s	512 MB	Judgeable
Embedding EnumerationCount the ways to place a labeled tree's nodes into a 2 by n grid so node 1 sits at the top-left, edges touch, and no cell repeats, modulo 1e9+7.	Hard8	TreeDFS+2	No attempts yet	4s	512 MB	Judgeable
Faulty FactorialGiven n, prime p, and target r mod p, find the faulty factorial (one factor reduced below its index) with remainder r, printing the smallest such (index, value).	Hard8	Number theoryMath+2	No attempts yet	3s	512 MB	Judgeable
Gambling GuideOn an undirected graph, find the minimum expected number of random tickets (with rejection allowed) needed to travel from city 1 to city n.	Hard8	GraphProbability+2	No attempts yet	3s	512 MB	Judgeable
Kitchen KnobsGiven n seven-digit knobs, find the fewest range rotations (each turning a contiguous block by the same amount) so every knob reads its maximum-power digit.	Hard8	GreedyImplementation+2	No attempts yet	3s	512 MB	Judgeable
Open-Pit MiningGiven blocks with values and digging costs plus precedence constraints, find the maximum profit subset closed under the dig-before relation.	Hard8	GraphMinimum spanning tree+2	No attempts yet	1s	512 MB	Judgeable
Archery TournamentMaintain a dynamic set of non-overlapping circles tangent to the ground, support insertions and point queries that remove the hit circle, and report which circle each arrow hits.	Hard8	GeometryBinary search+2	No attempts yet	3s	512 MB	Judgeable
BoxGiven a box with edges a, b, c and a w by h cardboard, decide whether some edge-aligned net of the box fits on the cardboard.	Hard8	GeometryBrute force+2	No attempts yet	3s	512 MB	Judgeable
ConnectionsGiven a strongly connected directed graph, run two specified BFS traversals to build a set of 2n kept roads and print the rest in input order.	Hard8	GraphBFS+2	No attempts yet	3s	512 MB	Judgeable
The Final LevelFind the minimum number of L-shaped n-blocks needed to cover a connected path of squares from (0,0) to (a,b) on an infinite grid.	Hard8	MathGreedy+2	No attempts yet	3s	512 MB	Judgeable
The Great WallEach design picks two length-r intervals whose overlap height adds extra cost; find the k-th smallest total wall height over all interval pairs.	Hard8	Binary searchPrefix sum+2	No attempts yet	3s	512 MB	Judgeable
Knapsack CryptosystemRecover the plaintext bits from a Merkle-Hellman knapsack instance where q = 2^64, exploiting the known modulus to invert the hidden superincreasing sequence.	Hard8	Number theoryBrute force+2	No attempts yet	3s	512 MB	Judgeable
SumdokuFill a 9x9 Sudoku grid so that constrained adjacent cells inside each 3x3 block satisfy <, =, or > versus 10, and print the lexicographically smallest solution.	Hard8	BacktrackingImplementation+1	No attempts yet	2s	512 MB	Judgeable
Fence InvasionCount how many distinct convex polygons can be formed as the convex hull of some subset of at least 3 of the given points, modulo 1e9+7.	Hard8	GeometryCombinatorics+2	No attempts yet	5s	512 MB	Judgeable
Mindol TourCount Hamiltonian cycles starting and ending at trampoline 0 in a graph where node 0 connects to all and node i reaches nodes within distance A_i, with A_i at least i.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable