Problems

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Total results29,125 problems

Lexicographically Smallest Sign Sequence
Hard9
Greedy, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Good Cable Management
Hard9
Tree, Graph+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Monitoring Ski Paths
Hard9
Graph, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Awesome Numbers
Hard9
Number theory, Math
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Decorator Cubelover
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
SquareFree
Hard9
Math, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Forgotten Land
Hard9
Dynamic programming, Tree+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Halves Not Equal
Hard9
Math, Greedy+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
LED-led Paths
Hard9
Graph, Topological sort+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Interval-Free Permutations
Hard9
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Minegraphed
Hard9
Implementation, Graph+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Bridge on the River Kawaii
Hard9
Dynamic programming, Union-find+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Congruence Equation
Hard9
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Youngkwail Club Room
Hard9
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cinema
Hard9
Dynamic programming, Stack+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Colored Tiles 2
Hard9
Dynamic programming, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Colored Tiles 4
Hard9
Graph, Matrix+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Removing Magical Tiles
Hard9
Greedy, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Black Company
Hard9
Graph, Topological sort+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Low Range-Sum Matrix
Hard9
Brute force, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Magic Triangles
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Snake
Hard9
Geometry, Binary search
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rook, Bishop, King, Knight, and Palace Game
Hard9
Game theory, Math+1
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Nim Game Without Repeats
Hard9
Game theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Quarry Game
Hard9
Game theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
mex
Hard9
Bit manipulation, Trie+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
mex and Queries
Hard9
Segment tree, Intervals+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Unique Cities
Hard9
Tree, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
XOR Sequences
Hard9
Bit manipulation, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Moorio Kart
Hard9
Tree, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Mowing Mischief
Hard9
Dynamic programming, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Message
Hard9
Dynamic programming, String matching+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sweet and Sour
Hard9
Probability, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Query and Query
Hard9
Segment tree, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sum of Equivalent Resistances Between Every Pair of Vertices Joined by an Edge, Given a Connected Graph with Unit Resistance Edges
Hard9
Graph, Matrix+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Africa 2
Hard9
Implementation, Brute force+2
No attempts yet
Time limit
1.357s
Memory limit
1357 MB
Judgeable
Directing Rainfall
Hard9
Geometry, Graph+2
No attempts yet
Time limit
15s
Memory limit
512 MB
Judgeable
Gahui's Sequence Mod Play (Large)
Hard9
Stack, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Dijkstra Is Playing At My House
Hard9
Shortest path, Segment tree+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Valleys
Hard9
Union-find, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Beautiful Manyeongro
Hard9
Trie, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Build a Workbook
Hard9
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
This is a bug!
Hard9
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Overflowing Uncertainty
Hard9
Number theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Calligrapher
Hard9
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
NOI Carnival
Hard9
Intervals, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Millennium Worm
Hard9
Dynamic programming, Greedy+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Maintaining a Sequence
Hard9
Dynamic programming, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Numbers in a Grid
Hard9
Matrix, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Working Cells
Hard9
Matrix, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
The Tallest and Widest Castle
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Looks like a sum of GCDs of Fibonacci numbers, but...
Hard9
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Parameterized Pattern Matching
Hard9
String, String matching+2
No attempts yet
Time limit
Not set
Memory limit
16 MB
Judgeable
Fruit Tree
Hard9
Tree, Binary search+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Gyojun's Errand Boy, Minje's Trouble ("Circle" Ver.)
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Dynamic Connectivity and Queries
Hard9
Graph, Union-find+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Sequence and Queries 26
Hard9
Segment tree, Dynamic programming+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Sequence and Queries 27
Hard9
Segment tree, Implementation
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Sequence and Queries 29
Hard9
Segment tree, Divide and conquer
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Mischievous Junseok
Hard9
Brute force, Recursion+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Calculator
Hard9
Binary search, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Bigger Sokoban 40k
Hard9
Implementation, Simulation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gosu 2
Hard9
Divide and conquer, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Wind of Change
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Addition on Convex Polygons
Hard9
Geometry, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Prospecting
Hard9
Tree, Binary search+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Traveling Merchant
Hard9
Segment tree, Divide and conquer+2
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Hotel
Hard9
Segment tree, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hanging Rack
Hard9
Math, Recursion+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
T - Covering
Hard9
Graph, Matrix
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dynamic Diameter
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Ruler
Hard9
Backtracking, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Seats
Hard9
Dynamic programming, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Virus Experiment
Hard9
Simulation, Matrix+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Meetings
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Two Dishes
Hard9
Dynamic programming, Graph+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Two Transportations
Hard9
Shortest path, Graph+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Asceticism
Hard9
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
0.6s
Memory limit
256 MB
Judgeable
Airline Route Map
Hard9
Graph, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Candies
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Arranging Tickets
Hard9
Prefix sum, Binary search+1
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Long Distance Coach
Hard9
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
City
Hard9
Tree, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Employment
Hard9
Segment tree, Divide and conquer+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sandwich
Hard9
Graph, Shortest path+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Toilets
Hard9
Binary search, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Road Development
Hard9
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Historical Research
Hard9
Divide and conquer, Array+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Construction Project
Hard9
Minimum spanning tree, Geometry+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Messenger
Hard9
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Spaceships
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Constellation
Hard9
Geometry, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sequence and Queries 32
Hard9
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Apollonian Network
Hard9
Graph, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Ski Lifts
Hard9
Graph, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Tree and Queries 13
Hard9
Tree, Segment tree+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Sequence and Queries 34
Hard9
String matching, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Graph and Cycles
Hard9
Graph, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Quadrilaterals
Hard9
Geometry, Sorting+1
No attempts yet
Time limit
1.7s
Memory limit
512 MB
Judgeable
Ghost
Hard9
Geometry, Sorting+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Lexicographically Smallest Sign SequenceFill a sign sequence of -1 and 1 with some fixed entries so that every range [Ai,Bi] has sum at least Ci, and output the lexicographically smallest valid sequence or Impossible.	Hard9	GreedyPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Good Cable ManagementCount the query pairs of switchboxes joined by a directed path in either direction after a sequence of length and parallel upgrades.	Hard9	TreeGraph+1	No attempts yet	5s	512 MB	Judgeable
Monitoring Ski PathsA DAG has at most one outgoing edge per junction and unique landing points; pick the fewest junctions met by all m registered s-to-t to-basement paths.	Hard9	GraphGreedy+2	No attempts yet	2s	512 MB	Judgeable
Awesome NumbersDecide whether n is reachable from 1 by repeatedly applying P (nth prime) or S (nth perfect square), and print the shortest such sequence.	Hard9	Number theoryMath	No attempts yet	0.5s	512 MB	Judgeable
Decorator CubeloverArrange n decorations on an n^3-cycle so each window of three labels is unique and the positional-value sum is minimal; report the nth digit of p-1.	Hard9	CombinatoricsMath+2	No attempts yet	1s	512 MB	Judgeable
SquareFreeGiven n up to 10^18, find the n-th squarefree positive integer using Mobius inversion and binary search.	Hard9	MathNumber theory+2	No attempts yet	5s	512 MB	Judgeable
Forgotten LandSum over all partitions of a tree's vertices into arbitrary sets of the total language difficulty, where a set's difficulty depends on the union of languages on its vertices and on paths between them.	Hard9	Dynamic programmingTree+2	No attempts yet	3s	512 MB	Judgeable
Halves Not EqualDivide s dinars among n wives so that every pair's shares match the given two-person fair split rule and the total equals s.	Hard9	MathGreedy+1	No attempts yet	3s	512 MB	Judgeable
LED-led PathsColor each directed edge of an acyclic graph red, green, or blue so that no single-color directed path has more than 42 edges.	Hard9	GraphTopological sort+1	No attempts yet	3s	512 MB	Judgeable
Interval-Free PermutationsCount permutations of length n with no contiguous block of length 2 to n-1 whose values form consecutive integers, modulo a prime p.	Hard9	CombinatoricsDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
MinegraphedGiven a directed graph on up to 9 vertices, build a 3D field of empty and obstacle cells so that labeled cells can reach each other exactly when the graph has a path.	Hard9	ImplementationGraph+1	No attempts yet	2s	512 MB	Judgeable
The Bridge on the River KawaiiMaintain a graph under bridge insertions and deletions, and for each query answer the minimum possible maximum edge weight on a path between two islands, where weights are single digits.	Hard9	Dynamic programmingUnion-find+2	No attempts yet	5s	512 MB	Judgeable
Congruence EquationCount ordered pairs (a, b) within 1 to p(p-1) whose residues satisfy a^b = b^a mod p, reducing to counting solutions of a discrete-log exponential congruence.	Hard9	Number theoryMath+1	No attempts yet	1s	256 MB	Judgeable
Youngkwail Club RoomCover all '.' cells of a grid with 1x1 and 1x2 tiles, avoiding 'X' pillars, using the fewest tiles possible.	Hard9	GraphDFS+2	No attempts yet	1s	256 MB	Judgeable
CinemaGiven rows of seat comfort values and a budget k for raising them, maximize the audiences seated, where each person takes the most comfortable reachable seat.	Hard9	Dynamic programmingStack+2	No attempts yet	2s	512 MB	Judgeable
Colored Tiles 2Place given 1x1 and 1x2 tiles on an H by W board without overlap to maximize the total score of edges between neighboring tiles, then output every tile's coordinates.	Hard9	Dynamic programmingImplementation+2	No attempts yet	1s	512 MB	Judgeable
Colored Tiles 4Place N tiles of given colors and sizes (1x1 or 1x2) on an HxW board without overlap to maximize the sum of edge scores between adjacent tiles.	Hard9	GraphMatrix+1	No attempts yet	1s	512 MB	Judgeable
Removing Magical TilesGiven trapezoid tiles above the x-axis, find the minimum number of groups where each group is a set of tiles that pairwise overlap.	Hard9	GreedyGeometry+2	No attempts yet	2s	512 MB	Judgeable
Black CompanyAssign positive salaries minimizing their sum so that every edge and every two edges sharing an endpoint order their endpoints consistently with contribution degrees.	Hard9	GraphTopological sort+2	No attempts yet	5s	512 MB	Judgeable
Low Range-Sum MatrixFlip signs of at most K cells in an N by M matrix (both at most 10) so that no horizontal or vertical contiguous segment sums to more than S.	Hard9	Brute forceDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Magic TrianglesGiven up to 100000 counter-clockwise triangles, compute the area of their common intersection.	Hard9	GeometryDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
SnakeGiven a polyline above the wall y = 0, decide whether rigid translations and rotations can move the whole snake entirely below the wall through the hole at the origin.	Hard9	GeometryBinary search	No attempts yet	1s	512 MB	Judgeable
Rook, Bishop, King, Knight, and Palace GameTwo players take turns moving chess pieces toward the lower left on a huge board, and the task is to find who wins with optimal play.	Hard9	Game theoryMath+1	No attempts yet	0.5s	512 MB	Judgeable
Nim Game Without RepeatsNim with piles of size up to 60, but each specific removal size can be used at most once per pile; decide the winner under optimal play.	Hard9	Game theoryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Quarry GameEach of N piles is a run of M consecutive pile sizes starting at X; a move takes at least one stone from one pile. Decide the winner under optimal play.	Hard9	Game theoryMath+2	No attempts yet	2s	512 MB	Judgeable
mexAfter XORing every element of a sequence with each query value x, report the mex (smallest missing non-negative integer) of the sequence.	Hard9	Bit manipulationTrie+2	No attempts yet	1s	512 MB	Judgeable
mex and QueriesMaintain a set of natural numbers under range add, range remove, and range toggle queries, then output the mex after each of up to 100000 queries with values up to 1e18.	Hard9	Segment treeIntervals+1	No attempts yet	2s	512 MB	Judgeable
Unique CitiesFor each city, count the distinct specialties among the unique cities, those whose distance from it differs from every other city's distance to it.	Hard9	TreeDivide and conquer+1	No attempts yet	2s	512 MB	Judgeable
XOR SequencesCount, modulo 1e9+7, the ordered sequences of n distinct m-bit integers consistent with a given nearest-XOR-label map over all 2^m query values.	Hard9	Bit manipulationDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Moorio KartCount and sum the lengths of simple cycles (at least Y) formed by joining every tree in a forest with one X-length edge between consecutive trees and a chosen path inside each tree.	Hard9	TreeDynamic programming+2	No attempts yet	3s	512 MB	Judgeable
Mowing MischiefGiven flowers on a grid, pick a longest chain of flowers both paths must visit, then find the minimum area the two monotone paths can sweep.	Hard9	Dynamic programmingSorting+2	No attempts yet	2s	512 MB	Judgeable
MessageCount length-n lowercase strings that contain a given pattern p as a substring, modulo m, where n can reach 10^12 and p has length at most 50.	Hard9	Dynamic programmingString matching+2	No attempts yet	5s	512 MB	Judgeable
Sweet and SourChoose which Candy Country players drink a potion that randomizes their sweetness and sourness, maximizing Candy's expected match points under all random player orders and event coin flips.	Hard9	ProbabilityCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Query and QueryEach query swaps two sequence values; after every swap, pair up the M left-pocket indices and M right-pocket indices to minimize the largest range maximum. Output that minimized maximum.	Hard9	Segment treeGreedy+2	No attempts yet	2s	512 MB	Judgeable
Sum of Equivalent Resistances Between Every Pair of Vertices Joined by an Edge, Given a Connected Graph with Unit Resistance EdgesGiven a connected unit-resistance graph, compute the sum of effective resistances over all m edges, using the fact that each equals the probability a random walk crosses that edge in the commute.	Hard9	GraphMatrix+2	No attempts yet	1s	512 MB	Judgeable
Africa 2Submit code that matches the judge on exactly half its hidden test cases while passing the sample, a problem about exploiting judge behavior rather than a computable answer.	Hard9	ImplementationBrute force+2	No attempts yet	1.357s	1357 MB	Judgeable
Directing RainfallGiven slanted tarps above a vineyard interval, find the fewest tarps to puncture so that rain falling from directly above the vineyard reaches the ground.	Hard9	GeometryGraph+2	No attempts yet	15s	512 MB	Judgeable
Gahui's Sequence Mod Play (Large)Maintain a stack under push and pop, and after each type 3 query report the shortest suffix whose remainders mod m cover every residue from 0 to m-1, printing -1 if impossible.	Hard9	StackTwo pointers+2	No attempts yet	1s	256 MB	Judgeable
Dijkstra Is Playing At My HouseFind the shortest Manhattan path from start to house around up to 250,000 non-overlapping axis-parallel rectangles, without entering any rectangle interior.	Hard9	Shortest pathSegment tree+2	No attempts yet	3s	1024 MB	Judgeable
ValleysGiven an N x N grid of distinct heights, sum the sizes of all non-holey edgewise-contiguous regions whose cells are strictly lower than every orthogonally adjacent border cell.	Hard9	Union-findGraph+2	No attempts yet	2s	512 MB	Judgeable
Beautiful ManyeongroCount directed paths in a rooted tree whose edge-label string equals a given pattern P.	Hard9	TrieDFS+2	No attempts yet	2s	512 MB	Judgeable
Build a WorkbookMaintain a dynamic precedence relation among N problems under edge inserts and deletes, and answer whether the subgraph induced by problems x through y is acyclic.	Hard9	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
This is a bug!Given a weighted tree with combat powers, for each fortress location x, find the maximum of Jisu's force power minus Sangmin's force power over all vanguard choices, where the power is taken modulo 2^32.	Hard9	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
Overflowing UncertaintyFor each interval [i,j] compute the probability that the gcd of j-i+1 independent uniform values in [1,Y] is coprime with Y, sum over all intervals, and report the numerator modulo 1e9+9 with denominator Y^N.	Hard9	Number theoryDynamic programming+2	No attempts yet	1s	256 MB	Judgeable
CalligrapherChoose disjoint placements of the letters N, O, and I on an n by m grid of signed values to maximize the total sum of covered cells.	Hard9	Dynamic programmingPrefix sum+1	No attempts yet	1s	512 MB	Judgeable
NOI CarnivalPlace each event at venue A, venue B, or skip it, with no overlapping events split across venues. Maximize the smaller venue's count, with each event forced in turn.	Hard9	IntervalsDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Millennium WormGiven n strips with left and right cell bounds for a corroded fossil, find the fewest cells corrosion could have removed from a valid worm body.	Hard9	Dynamic programmingGreedy+1	No attempts yet	1s	256 MB	Judgeable
Maintaining a SequenceMaintain a sequence under insert, delete, range assign, reverse, range sum, and global maximum subarray queries.	Hard9	Dynamic programmingImplementation+2	No attempts yet	2s	256 MB	Judgeable
Numbers in a GridDigits of 1, 2, 3, ... concatenated are written row by row into a grid M wide, and each query asks for the digit sum over a rectangle.	Hard9	MatrixPrefix sum+2	No attempts yet	3s	1024 MB	Judgeable
Working CellsGiven T periodic N-vertex weighted digraphs, count modulo 1e9+7 the number of D-step walks from every hub i to every hub j.	Hard9	MatrixDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
The Tallest and Widest CastleChoose which signposts serve as vertices of each floor so the castle has the most floors, then the largest total floor area, then the fewest signposts used, and report each signpost's floor number.	Hard9	GeometryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Looks like a sum of GCDs of Fibonacci numbers, but...Given n and k, compute the sum over all pairs (i, j) with 1 to n of gcd(i, j) to the power k times gcd(F_i, F_j), modulo 1,000,000,007.	Hard9	Number theoryMath	No attempts yet	2s	512 MB	Judgeable
Parameterized Pattern MatchingFind every substring of text T that p-matches pattern P, where parameter names must correspond under a bijection and tokens match exactly.	Hard9	StringString matching+2	No attempts yet	Not set	16 MB	Judgeable
Fruit TreeGiven a tree whose vertices hold fruit types, answer queries asking whether one type is a strict majority on the path between two vertices, and which type it is.	Hard9	TreeBinary search+2	No attempts yet	3s	1024 MB	Judgeable
Gyojun's Errand Boy, Minje's Trouble ("Circle" Ver.)Given disjoint circles and houses with XOR values, each query asks for the XOR of house values within crossing distance L of a point.	Hard9	TreeDivide and conquer+2	No attempts yet	4s	1024 MB	Judgeable
Dynamic Connectivity and QueriesEach query toggles an edge between two vertices or asks whether two vertices share a component, with inputs decoded online from the previous component count.	Hard9	GraphUnion-find+1	No attempts yet	3s	1024 MB	Judgeable
Sequence and Queries 26Maintain a sequence under range chmin updates, range maximum queries, and range sum queries, with up to a million elements and queries.	Hard9	Segment treeDynamic programming+2	No attempts yet	4s	512 MB	Judgeable
Sequence and Queries 27Apply range add, range chmax, and range chmin to array A, then answer the current range minimum of A and the range historical minimum and maximum of past values.	Hard9	Segment treeImplementation	No attempts yet	4s	512 MB	Judgeable
Sequence and Queries 29Given an array with range add, range chmax, and range chmin updates, count how many times each element changes, and answer range sum queries on those counts.	Hard9	Segment treeDivide and conquer	No attempts yet	4s	512 MB	Judgeable
Mischievous JunseokGiven a short English word and a multiset of letters, count the distinct strings obtainable from any contiguous substring with that letter multiset under the recursive half-split-and-reverse rule.	Hard9	Brute forceRecursion+2	No attempts yet	2s	256 MB	Judgeable
CalculatorStarting from X=0, reach a given N by pressing +2, -2, *2, /2 (floor) at most 99 times while X stays in [0, 2^63-1], or report that it is impossible.	Hard9	Binary searchMath+2	No attempts yet	1s	256 MB	Judgeable
Bigger Sokoban 40kBuild a Bigger Sokoban grid with one 2x2 box and one 2x2 storage area that takes at least 40,000 moves to solve.	Hard9	ImplementationSimulation	No attempts yet	1s	1024 MB	Judgeable
Gosu 2Given a tournament on N players, find a transitive subtournament (chain) of size exactly 1 + floor(log2 N).	Hard9	Divide and conquerCombinatorics+2	No attempts yet	2s	1024 MB	Judgeable
Wind of ChangeTwo weighted trees on the same vertex labels define a distance as the sum of both tree distances; for every vertex find the nearest other vertex under that combined metric.	Hard9	TreeDivide and conquer+2	No attempts yet	10s	1024 MB	Judgeable
Addition on Convex PolygonsGiven convex polygons R and S, find nonnegative a, b, c, d with ad-bc=1 and integer polygons P and Q with R=aP+bQ, S=cP+dQ, minimizing total area.	Hard9	GeometryNumber theory+1	No attempts yet	2s	512 MB	Judgeable
ProspectingGiven a tree of ore pockets with tunnel lengths and ore values, find the minimum starting money for a guaranteed path to the motherlode and for the best digging order.	Hard9	TreeBinary search+2	No attempts yet	2s	1024 MB	Judgeable
Traveling MerchantGiven weekly price cycles at n towns, answer q queries for the max profit from buying and later selling during a trip from town s to town t.	Hard9	Segment treeDivide and conquer+2	No attempts yet	10s	1024 MB	Judgeable
HotelMaintain an array under point height updates; after each update answer queries for the longest subsegment inside [l, r] that contains no strict interior valley.	Hard9	Segment treeArray+2	No attempts yet	2s	512 MB	Judgeable
Hanging RackGiven a binary hanging rack with 2^n hooks, find the hook number (mod 1e9+7) used on the k-th step when coats are hung to keep every rod balanced within 0 or 1.	Hard9	MathRecursion+2	No attempts yet	1s	512 MB	Judgeable
T - CoveringPlace one T-tetromino per special cell, centered on it, without overlap or leaving the grid, to maximize the total covered weight.	Hard9	GraphMatrix	No attempts yet	1s	512 MB	Judgeable
Dynamic DiameterMaintain a weighted tree under edge weight updates and report the diameter after each of q updates, decoding each query with the previous answer.	Hard9	TreeDivide and conquer+2	No attempts yet	5s	512 MB	Judgeable
RulerFind the shortest ruler with N marks (0 to L) where all pairwise distances between marks are distinct, and print the mark positions.	Hard9	BacktrackingBrute force+2	No attempts yet	2s	512 MB	Judgeable
SeatsChoose K of N passengers to sit in a row of L seats, maximizing the sum of A_i plus B_i per adjacent empty seat, for every K from 1 to N.	Hard9	Dynamic programmingDivide and conquer+1	No attempts yet	2s	512 MB	Judgeable
Virus ExperimentGiven wind directions for each time period and a resistance value per grid cell, find the minimum infected count after a huge horizon and how many starting cells reach it.	Hard9	SimulationMatrix+1	No attempts yet	2s	512 MB	Judgeable
MeetingsGiven only an oracle that returns the meeting point (tree median) of any three vertices, reconstruct the tree of N vertices with maximum degree 18.	Hard9	TreeDivide and conquer+2	No attempts yet	2s	256 MB	Judgeable
Two DishesInterleave two chains of timed steps so that each step finishing before its deadline adds its score, and find the maximum total score.	Hard9	Dynamic programmingGraph+1	No attempts yet	5s	1024 MB	Judgeable
Two TransportationsTwo programs, each holding one set of weighted edges, exchange at most 58000 bits to compute single-source shortest path distances from city 0 in the union graph.	Hard9	Shortest pathGraph+2	No attempts yet	10s	256 MB	Judgeable
AsceticismCount permutations of 1..N such that an optimal daily reading schedule (reading consecutive sentences within each day's time slots) finishes the sutra in exactly K days.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	0.6s	256 MB	Judgeable
Airline Route MapEncode an arbitrary simple graph with up to 1000 vertices as a graph with the fewest vertices, where vertex and edge labels are shuffled, so that the original map can be recovered.	Hard9	GraphImplementation+1	No attempts yet	2s	1024 MB	Judgeable
CandiesFor each j, find the maximum sum of j non-adjacent values chosen from N candies in a row.	Hard9	Dynamic programmingGreedy+2	No attempts yet	5s	512 MB	Judgeable
Arranging TicketsGiven N stations on a circular railway and M travel requests with passenger counts, find the minimum number of ticket packages needed to serve all requests.	Hard9	Prefix sumBinary search+1	No attempts yet	4s	256 MB	Judgeable
Long Distance CoachGiven refill stops, passenger deadlines modulo T, and a driver needing water every T, find the minimum total of water cost and refunds for the trip to city O.	Hard9	GreedySorting+1	No attempts yet	2s	256 MB	Judgeable
CityAssign small integer codes to nodes of a tree where depth from node 0 is at most 18, so that a decoder with only the two codes can tell which of two cities lies on the path from 0 to the other.	Hard9	TreeBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
EmploymentGiven candidate evaluation values with point updates, answer queries asking for the number of maximal contiguous blocks of hired candidates whose value is at least a threshold.	Hard9	Segment treeDivide and conquer+2	No attempts yet	5s	512 MB	Judgeable
SandwichGiven an R by C grid of N and Z cells, find for each cell the minimum number of sandwiches to take before both sandwiches in that cell can be taken, or -1 if impossible.	Hard9	GraphShortest path+1	No attempts yet	5s	512 MB	Judgeable
ToiletsGiven a line of 2N men and women (in run-length form), rearrange it so everyone finishes within N minutes and minimize the largest discontent, or report -1.	Hard9	Binary searchGreedy+1	No attempts yet	1s	512 MB	Judgeable
Road DevelopmentGiven N cities and Q plans, some carried out, find for each abandoned plan how many unpaved roads on shortest paths in the current graph it would have paved, or -1 if it builds a new road.	Hard9	GraphUnion-find+2	No attempts yet	2s	256 MB	Judgeable
Historical ResearchFor each query range, report the maximum over event types t of t times the count of t inside the range.	Hard9	Divide and conquerArray+2	No attempts yet	4s	512 MB	Judgeable
Construction ProjectPlace at most H airports among N towns and connect all towns with axis-parallel roads that avoid M rectangular obstacles, minimizing airport cost times count plus total road length.	Hard9	Minimum spanning treeGeometry+2	No attempts yet	5s	256 MB	Judgeable
MessengerDesign strategies for two players who alternately move a piece on a 4x4 grid, knowing neither the call order nor its timing, so B can deduce the secret value X within 10000 moves.	Hard9	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable
SpaceshipsShips add and remove one-way routes over time, and each query asks for the star that minimizes total hops from two given stars, or -1 if none exists.	Hard9	GraphShortest path+2	No attempts yet	10s	256 MB	Judgeable
ConstellationCount the ways to assign each unlabeled point to constellation A or B so that the two vertex sets can be drawn connected with mutually non-crossing segments.	Hard9	GeometryCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Sequence and Queries 32Maintain a sequence under point updates and answer whether it can be split into contiguous blocks whose xors all lie in a small given set.	Hard9	Dynamic programmingPrefix sum+2	No attempts yet	10s	512 MB	Judgeable
Apollonian NetworkGiven a weighted Apollonian network with n vertices, find the largest total edge weight of any simple path in the graph.	Hard9	GraphDynamic programming+1	No attempts yet	3s	512 MB	Judgeable
Ski LiftsGiven n pylons at integer points, find the most non-crossing segments you can place between pylons whose y-coordinates differ by exactly 1, under one-way and two-way degree limits.	Hard9	GraphDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
Tree and Queries 13On a tree whose root and parent links change, process 12 query types that assign or add to subtrees and paths, and report min, max, or sum over them.	Hard9	TreeSegment tree+1	No attempts yet	3s	512 MB	Judgeable
Sequence and Queries 34Maintain two integer sequences under updates and range queries: for a suffix of a compute the longest match against b and how many suffixes achieve it, compare suffixes of b, and test whether a concatenation of two b-substrings is itself a substring of b.	Hard9	String matchingSegment tree+2	No attempts yet	2s	512 MB	Judgeable
Graph and CyclesGiven a weighted complete graph on an odd number of vertices, partition all edges into edge-disjoint cycles and minimize the sum over each cycle of the max weight on consecutive edge pairs.	Hard9	GraphGreedy+2	No attempts yet	2s	256 MB	Judgeable
QuadrilateralsGiven n points with no three collinear, find the maximum total credit from all quadrilaterals, where convex and minimum-area shapes score more.	Hard9	GeometrySorting+1	No attempts yet	1.7s	512 MB	Judgeable
GhostGiven axis-aligned rectangles that move at constant speeds, answer each query by reporting the maximum area common to all rectangles during a time interval [l, r].	Hard9	GeometrySorting+1	No attempts yet	10s	512 MB	Judgeable