Problems

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Total results29,413 problems

Fabulous Photos
Hard8
Union-find, Bit manipulation+1
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Solving a Problem (Park Seungwon)
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Longest Increasing Subsequence K
Hard8
Dynamic programming, Binary search+1
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Hamburg Steak
Hard8
Backtracking, Geometry+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Sweeping
Hard8
Simulation, Segment tree+1
No attempts yet
Time limit
11s
Memory limit
2048 MB
Judgeable
Harvest
Hard8
Simulation, Binary search+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Stray Cat
Hard8
Graph, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Treatment Project
Hard8
Shortest path, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lingering Regret
Hard8
Tree, DFS+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Everything Is New
Hard8
Math, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
O Life of My Youth
Hard8
Sorting, Greedy+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Circus
Hard8
Tree, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Haircut
Hard8
Sorting, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Social Distancing
Hard8
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
The Moo Particle
Hard8
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
New Year and Conference
Hard8
Intervals, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
New Year and Castle Construction
Hard8
Geometry, Combinatorics+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Longest Increasing Subsequence ks
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Nam Hyeon-uk
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Cartoons
Hard8
Two pointers, Divide and conquer+2
No attempts yet
Time limit
2.5s
Memory limit
256 MB
Judgeable
Daycare Children
Hard8
Combinatorics, Greedy+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Encryption Function
Hard8
Math, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Printer's Head
Hard8
Greedy, Dynamic programming+1
No attempts yet
Time limit
1.5s
Memory limit
64 MB
Judgeable
Passwords
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1.5s
Memory limit
64 MB
Judgeable
Chip Cards
Hard8
Dynamic programming, Array+1
No attempts yet
Time limit
2s
Memory limit
16 MB
Judgeable
Minimal Variance Tree
Hard8
Minimum spanning tree, Sorting+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Alice and Bob
Hard8
Game theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Funny Salesman
Hard8
Tree, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hidden Graph
Hard8
Graph, Divide and conquer+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Insects
Hard8
Graph, Sorting+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Joining Points
Hard8
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Banned Words
Hard8
String matching, Trie+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cost Of Subtree
Hard8
Tree, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Disk Troubles
Hard8
Math, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fox Labeling
Hard8
Probability, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Lands of Infinistan
Hard8
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Tree and Queries 16
Hard8
Tree, Graph
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Planar Graph and Game
Hard8
Graph, Union-find+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Region Decoration Game
Hard8
Segment tree, Implementation
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Non-Decreasing Subarray Game
Hard8
Game theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Tree Hull
Hard8
Tree, DFS+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Knapsack
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Algebra on Segment
Hard8
Segment tree, Number theory+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Partition into Teams
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Determinant of a Graph
Hard8
Graph, Tree+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Classic Quotation
Hard8
String matching, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Counting Divisors
Hard8
Number theory, Math+2
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Lazy Running
Hard8
Shortest path, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Logical Chain
Hard8
Graph, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Matching In Multiplication
Hard8
Graph, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Questionnaire
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bag of Bags
Hard8
Intervals, Union-find+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Balanced Sequence
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Maximum Weighted Matching
Hard8
Dynamic programming, Graph+1
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Turn Off The Light
Hard8
Dynamic programming, Greedy+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Stable Permutation
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Rikka with Linker
Hard8
Bit manipulation, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rikka with XOR
Hard8
Bit manipulation, Number theory+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Remove the Tree
Hard8
Tree, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Road Connectivity
Hard8
Probability, Matrix+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Automorphism
Hard8
Tree, Combinatorics+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Border
Hard8
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Decomposition
Hard8
String matching, Dynamic programming
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Tree Transformation Cost
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Flow
Hard8
Graph, Shortest path
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Knight
Hard8
Game theory, Graph
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Exact Arithmetic
Hard8
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Form the Maximal Set
Hard8
Combinatorics, Greedy+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Hokusai Artworks
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Labeled Points
Hard8
Graph, Greedy
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Wavel Sequence
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Movies
Hard8
Greedy, Simulation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Origami
Hard8
String matching, Hash map+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Tris
Hard8
Implementation, Matrix+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Xormites
Hard8
Game theory, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Nutella's Life
Hard8
Dynamic programming, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Oleg and Data Science
Hard8
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Christmas Garland
Hard8
Array, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Anna and Lucky Tickets
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Mikhail's Problem
Hard8
String, String matching+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Rat-O-Matic
Hard8
Tree, String matching+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Binary Strings
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sequence
Hard8
Segment tree, Array+1
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Criminals
Hard8
Divide and conquer, Segment tree+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Build the Graph
Hard8
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Match
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Subsequence Sums
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
K-matching
Hard8
Dynamic programming, Binary search+1
No attempts yet
Time limit
9s
Memory limit
512 MB
Judgeable
Lying From You
Hard8
Math, Geometry+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
From The Inside
Hard8
Game theory, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
One Step Closer
Hard8
Math, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Invisible
Hard8
Segment tree, Bit manipulation+1
No attempts yet
Time limit
12s
Memory limit
512 MB
Judgeable
Leave Out All The Rest
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Faint
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Biggest Number
Hard8
Segment tree, Sorting+2
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Hotter-colder
Hard8
Binary search, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Painting
Hard8
Dynamic programming, Intervals
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Ones
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Seats
Hard8
Probability, Math+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Primes
Hard8
Number theory, Prefix sum+2
No attempts yet
Time limit
8s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Fabulous PhotosGiven the set of balls in each photo, find for each ball the smallest-numbered ball that must share its colour in every consistent colouring.	Hard8	Union-findBit manipulation+1	No attempts yet	6s	512 MB	Judgeable
Solving a Problem (Park Seungwon)Count the ways to tile an n×m grid (n, m up to 10) with 1×1, 2×2, and 4×4 tiles, where each size comes in several kinds, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	1s	512 MB	Judgeable
Longest Increasing Subsequence KGiven a sequence of N integers and K, find the K-th longest increasing subsequence in lexicographic order of index sequences, or print -1 if fewer than K exist.	Hard8	Dynamic programmingBinary search+1	No attempts yet	0.25s	512 MB	Judgeable
Hamburg SteakPlace K points on the grid so that every given rectangle contains at least one point, then output the K coordinates.	Hard8	BacktrackingGeometry+1	No attempts yet	3s	1024 MB	Judgeable
SweepingDust in an isosceles right triangle room shifts after each broom sweep, and new dust is added, so the task is to report a given dust's current coordinates at each query.	Hard8	SimulationSegment tree+1	No attempts yet	11s	2048 MB	Judgeable
HarvestCount the apples each employee harvests by time T around a circular lake, where a tree regrows its apple C seconds after each harvest.	Hard8	SimulationBinary search+1	No attempts yet	3s	512 MB	Judgeable
Stray CatMark the edges of a connected graph so that a cat walking from any town can reach town 0 in at most d+B steps, knowing only the mark types of edges at its current town and the last edge used.	Hard8	GraphGreedy+2	No attempts yet	5s	512 MB	Judgeable
Treatment ProjectChoose treatment projects with the smallest total cost so that no citizen stays infected. Each project treats a range of consecutive houses on one day.	Hard8	Shortest pathGraph+2	No attempts yet	2s	512 MB	Judgeable
Lingering RegretFor each valley, the task counts how many valleys Uk-je can reach by jumping down the source-rooted tree under the bounce rule, starting from that valley.	Hard8	TreeDFS+1	No attempts yet	3s	1024 MB	Judgeable
Everything Is NewGiven a shuffled Ukdimensional sliding puzzle on an a x b x c x d x e x f grid, decide whether the pieces can be returned to the solved order.	Hard8	MathGraph+1	No attempts yet	1s	1024 MB	Judgeable
O Life of My YouthGiven N pairs of happiness and fatigue with some values missing (0), find the largest K < N such that all young-day pairs can exceed all old-day pairs in happiness and stay below them in fatigue.	Hard8	SortingGreedy+2	No attempts yet	2s	1024 MB	Judgeable
CircusFor each K, count the equivalence classes of starting states of K labeled cows on a tree, where cows move to adjacent empty vertices.	Hard8	TreeDivide and conquer+1	No attempts yet	1s	512 MB	Judgeable
HaircutFor each threshold j from 0 to N-1, clip every value above j down to j and count the resulting inversions.	Hard8	SortingPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Social DistancingPlace N cows on distinct integer grass points across M disjoint intervals on a line so that the minimum pairwise distance D is as large as possible, and output the largest achievable D.	Hard8	Binary searchGreedy+2	No attempts yet	1s	512 MB	Judgeable
The Moo ParticleGiven N points with distinct coordinates, one of two points may vanish when one dominates the other; find the minimum number of points that can remain.	Hard8	SortingGreedy+2	No attempts yet	1s	512 MB	Judgeable
New Year and ConferenceGiven n lectures, each with one time interval at venue a and another at venue b, decide whether every subset that is conflict-free at one venue is also conflict-free at the other.	Hard8	IntervalsSorting+2	No attempts yet	2s	1024 MB	Judgeable
New Year and Castle ConstructionGiven n points with no three collinear, count over all points p the number of 4-point subsets whose convex quadrilateral strictly contains p, and sum these counts.	Hard8	GeometryCombinatorics+2	No attempts yet	3s	512 MB	Judgeable
Longest Increasing Subsequence ksGiven a permutation-like sequence, find the K-th longest increasing subsequence when all LISs are sorted lexicographically by index, or -1 if fewer than K exist.	Hard8	Dynamic programmingGreedy+2	No attempts yet	0.25s	512 MB	Judgeable
Nam Hyeon-ukGiven n and m (0 to 3), sum the inversion counts of all length-n permutations with exactly m increasing subsequences of length 3, mod 998244353.	Hard8	CombinatoricsMath+1	No attempts yet	2s	1024 MB	Judgeable
CartoonsCount subarrays in which every sub-subarray contains at least one value that appears exactly once, over a sequence of up to 500,000 values.	Hard8	Two pointersDivide and conquer+2	No attempts yet	2.5s	256 MB	Judgeable
Daycare ChildrenAssign each of n children at least k toy kinds from floor(3k^2/2) available kinds so that every pair shares exactly one kind and no two sets are equal.	Hard8	CombinatoricsGreedy+2	No attempts yet	2s	64 MB	Judgeable
Encryption FunctionGiven the output of a digit-subset-sum encryption, find any positive integer that encrypts to it or report that none exists.	Hard8	MathDynamic programming+2	No attempts yet	1s	64 MB	Judgeable
Printer's HeadGiven a permutation of heights 1..n to print in order, find the minimum number of left-to-right or right-to-left sweeps, where each sweep prints positions in order with heights dropping by 1.	Hard8	GreedyDynamic programming+1	No attempts yet	1.5s	64 MB	Judgeable
PasswordsGiven n rows of m letters, permute the columns so the rows become lexicographically nondecreasing, choosing the smallest such permutation or reporting NIE.	Hard8	GreedySorting+2	No attempts yet	1.5s	64 MB	Judgeable
Chip CardsGiven the bottom port order and socket sizes on both boundaries, find the maximum number of layers needed when each socket can be reversed.	Hard8	Dynamic programmingArray+1	No attempts yet	2s	16 MB	Judgeable
Minimal Variance TreeGiven a connected multigraph, find the spanning tree whose edge weights have the smallest variance, and print that minimal variance.	Hard8	Minimum spanning treeSorting+1	No attempts yet	1s	256 MB	Judgeable
Alice and BobCount placements of at most one token per vertex on a colored DAG where Alice (white moves) beats Bob (black moves) under optimal play.	Hard8	Game theoryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Funny SalesmanGiven a weighted tree, find the largest sum of 2^d over consecutive pairs of a vertex permutation, where d is the maximum edge weight on their path.	Hard8	TreeUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Hidden GraphFind a hidden undirected graph on n vertices, where every induced subgraph has a vertex of degree at most k, using at most 2nk+n independence queries that return an edge when the set is not independent.	Hard8	GraphDivide and conquer+2	No attempts yet	5s	512 MB	Judgeable
InsectsGiven black and white ants on a grid, find after each new white ant the fewest ants to feed so that no white ant dominates a hungry black ant.	Hard8	GraphSorting+1	No attempts yet	5s	512 MB	Judgeable
Joining PointsCount the sets of n non-crossing arcs on a circle, each joining two same-colored points with no point of that color inside the arc.	Hard8	Dynamic programmingCombinatorics	No attempts yet	1s	512 MB	Judgeable
Banned WordsCount length-L strings over 26 letters avoiding a given set of banned substrings, modulo 998244353, with L up to 1e9.	Hard8	String matchingTrie+2	No attempts yet	2s	512 MB	Judgeable
Cost Of SubtreeGiven a tree with weighted edges, find a non-empty connected edge set maximizing its edge count times the minimum edge weight in it.	Hard8	TreeUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Disk TroublesGiven a polynomial remainder Q(x) modulo a fixed degree-32 binary polynomial, find the smallest k with x^k mod P(x) equal to Q(x), inverting a discrete-log-like map.	Hard8	MathBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Fox LabelingGiven n foxes with their initial colors and a label size k, find the expected minutes until every pair of foxes becomes distinguishable by repeatedly labeling random k-subsets.	Hard8	ProbabilityCombinatorics+1	No attempts yet	3s	512 MB	Judgeable
Lands of InfinistanCount the lands that n straight walls and one quadratic river curve divide the plane into, given all their equations.	Hard8	GeometryMath+1	No attempts yet	1s	512 MB	Judgeable
Tree and Queries 16Edges are added to a forest online, and each type 2 query takes a vertex u and an integer k, but the statement never defines the query answer.	Hard8	TreeGraph	No attempts yet	8s	512 MB	Judgeable
Planar Graph and GameDelete edges from a planar graph and answer connectivity queries whose vertex indices are shifted by the number of earlier Cow A wins.	Hard8	GraphUnion-find+1	No attempts yet	1s	256 MB	Judgeable
Region Decoration GameAn N by N grid is split by horizontal and vertical lines, and each query either adds X to a whole region or asks for the maximum beauty inside a rectangle.	Hard8	Segment treeImplementation	No attempts yet	8s	1024 MB	Judgeable
Non-Decreasing Subarray GameFor each query range, Yuto picks an integer to minimize and Platina then picks one to maximize the count of non-decreasing subarrays inside the interval they bound; output the resulting score.	Hard8	Game theoryDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
Tree HullMaintain a set of tree vertices under insertions and deletions, and after each query report the total edge weight of the minimal subtree spanning the current set.	Hard8	TreeDFS+2	No attempts yet	3s	256 MB	Judgeable
KnapsackCount subsets of weights where each of n types has 2 copies and masses grow at least by a factor of 2, so the total equals W.	Hard8	Dynamic programmingGreedy+2	No attempts yet	3s	512 MB	Judgeable
Algebra on SegmentGiven an array modulo a prime p, support range multiplication and report the order of the subgroup generated by the elements of a segment.	Hard8	Segment treeNumber theory+1	No attempts yet	10s	512 MB	Judgeable
Partition into TeamsFor n people each choosing red, blue, or spectator uniformly, compute 3^n times the probability that red wins, modulo a prime p.	Hard8	CombinatoricsMath+2	No attempts yet	1s	256 MB	Judgeable
Determinant of a GraphGiven a connected graph with at most 50 more edges than vertices, compute the determinant of its adjacency matrix modulo 998244353.	Hard8	GraphTree+1	No attempts yet	1s	256 MB	Judgeable
Classic QuotationGiven strings S and T and queries (L, R), compute the expected number of occurrences of T after deleting a random substring spanning positions L to R, scaled by the number of choices.	Hard8	String matchingPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Counting DivisorsFor each query with l, r, k, compute the sum of d(i^k) for i from l to r, modulo 998244353, where d counts divisors.	Hard8	Number theoryMath+2	No attempts yet	7s	512 MB	Judgeable
Lazy RunningStarting and ending at checkpoint p2 on a 4-cycle, find the shortest closed walk whose swipe-recorded total distance is at least K, given the four edge lengths.	Hard8	Shortest pathDynamic programming+2	No attempts yet	1s	256 MB	Judgeable
Logical ChainAfter each day's flips of up to 10 edges in a directed graph of n up to 250 nodes, count the unordered pairs of nodes that reach each other.	Hard8	GraphBit manipulation+1	No attempts yet	1s	512 MB	Judgeable
Matching In MultiplicationGiven a bipartite graph where each of the n vertices on one side has degree 2, sum the products of edge weights over all perfect matchings, modulo 998244353.	Hard8	GraphMath+2	No attempts yet	1s	512 MB	Judgeable
QuestionnaireGiven n distinct positive integers, find a modulus m and residue k so that at least half the numbers are congruent to k mod m.	Hard8	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Bag of BagsProcess bags one by one; keep a bag unless its equality class merges two classes that were already equal, and report the decision for each.	Hard8	IntervalsUnion-find+2	No attempts yet	2s	256 MB	Judgeable
Balanced SequenceReorder n bracket strings to maximize the length of the longest balanced subsequence of their concatenation.	Hard8	GreedySorting+2	No attempts yet	1s	256 MB	Judgeable
Maximum Weighted MatchingGiven a weighted graph built by repeatedly copying edges and inserting path vertices, find the maximum weight matching and how many maximum matchings exist modulo 10^9+7.	Hard8	Dynamic programmingGraph+1	No attempts yet	4s	256 MB	Judgeable
Turn Off The LightFor each start position p, find the fewest steps needed to turn off all lights, then print the sum of p times that minimum, modulo 1e9+7.	Hard8	Dynamic programmingGreedy+1	No attempts yet	2s	256 MB	Judgeable
Stable PermutationFind the k-th lexicographically smallest permutation of length n whose inversion count is exactly half of all pairs, or report NO if none exists.	Hard8	CombinatoricsMath+1	No attempts yet	3s	256 MB	Judgeable
Rikka with LinkerGiven a directed dependency graph on n libraries, find the shortest sequence of library names in which every edge (a,b) has some occurrence of a before some occurrence of b.	Hard8	Bit manipulationDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Rikka with XORGiven n and m, compute the product of n xor i for i from 0 to m, modulo 1500000001.	Hard8	Bit manipulationNumber theory+1	No attempts yet	1s	512 MB	Judgeable
Remove the TreeGiven a tree, repeatedly delete the vertices of any chosen path (and incident edges); find the minimum number of path-deletions needed to remove every edge.	Hard8	TreeGreedy+2	No attempts yet	2s	256 MB	Judgeable
Road ConnectivityEach day one of the 10 roads is picked at random and its open or closed state is flipped. For each query [l, r], find the probability the country is connected on some day in that range.	Hard8	ProbabilityMatrix+2	No attempts yet	2s	256 MB	Judgeable
AutomorphismVertices are attached one at a time under a given parent, and each query asks for the number of automorphisms of the subtree rooted at a vertex, modulo 998244353.	Hard8	TreeCombinatorics+1	No attempts yet	8s	512 MB	Judgeable
BorderGiven a string generated from a seed, compute the sum over all pairs i<j of the longest k where the prefix starting at i of length k equals the suffix ending at j of length k.	Hard8	StringString matching+1	No attempts yet	2s	512 MB	Judgeable
DecompositionFor each string, sum the products of smallest periods over all ways to split it into substrings, modulo 1e9+7.	Hard8	String matchingDynamic programming	No attempts yet	3s	512 MB	Judgeable
Tree Transformation CostFind the minimum cost to turn one weighted ordered rooted tree into another using grow, expand, contract, and relabel operations.	Hard8	TreeDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
FlowGiven a bipartite network copied into k stacked layers, find the limit of the maximum flow as k grows, or -1 if it does not converge.	Hard8	GraphShortest path	No attempts yet	2s	256 MB	Judgeable
KnightGiven a board with broken squares and two knights that share one (r, c) move rule, decide whether Alice or Bob wins when no earlier knight configuration may repeat.	Hard8	Game theoryGraph	No attempts yet	2s	512 MB	Judgeable
Exact ArithmeticSimulate a stack calculator whose values are sums of rationals and rational multiples of square roots, and print each result in a canonical exact form.	Hard8	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Form the Maximal SetGiven n points on a circle joined by n/2 chords, replace up to k chords with arbitrary ones to get the largest set of pairwise intersecting chords.	Hard8	CombinatoricsGreedy+1	No attempts yet	5s	512 MB	Judgeable
Hokusai ArtworksOn a directed graph, each city has a museum open only on even days; find the maximum total weight of distinct museums visitable starting at city 0 on an even day.	Hard8	GraphDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Labeled PointsPick K of N labeled points so that every pair is at distance at least 2, choosing the sequence of labels that is lexicographically smallest.	Hard8	GraphGreedy	No attempts yet	1s	512 MB	Judgeable
Wavel SequenceCount pairs of increasing index sequences from two arrays whose selected values are equal and form a strictly alternating up-down wave, modulo 998244353.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
MoviesAlternately watch the best and worst movie in the main list, refilling it from the secondary list, and find the minimum steps until the main list is sorted.	Hard8	GreedySimulation+1	No attempts yet	1s	256 MB	Judgeable
OrigamiCount the distinct submatrices of a letter grid that folding can produce, where each fold needs every mirrored pair of cells on the folded part to match in color.	Hard8	String matchingHash map+1	No attempts yet	1s	256 MB	Judgeable
TrisGiven how many pieces of each of four tromino-like types there are, build a grid of at most 800 by 800 where all pieces form one simple cycle enclosing a single connected interior.	Hard8	ImplementationMatrix+1	No attempts yet	1s	256 MB	Judgeable
XormitesTwo players take turns removing values from either end of a sequence and XOR them into their own sums. Decide whether the first player wins, the second player wins, or the game is a draw.	Hard8	Game theoryBit manipulation+1	No attempts yet	1s	256 MB	Judgeable
Nutella's LifeChoose a subsequence of contests with nondecreasing values, where skipping x contests in a row costs x+1 each, to maximize total fun.	Hard8	Dynamic programmingSegment tree+1	No attempts yet	2s	512 MB	Judgeable
Oleg and Data ScienceCount positive integers X such that ((S mod Q) mod X) equals (S mod X) for every S in [L, R], or report infinity.	Hard8	Number theoryMath+2	No attempts yet	2s	256 MB	Judgeable
Christmas GarlandGiven a garland of n bulbs with colors, each query flips the state of every bulb of one color, and after each flip you report the number of maximal lit segments.	Hard8	ArrayImplementation+2	No attempts yet	2s	256 MB	Judgeable
Anna and Lucky TicketsCount n-digit palindromes that are lucky under neither the alternating-position sum test nor the first-half-versus-second-half sum test, modulo 1e9+7.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
Mikhail's ProblemGiven a string and several index ranges [l, r], count the distinct palindromic substrings inside each range s[l..r].	Hard8	StringString matching+1	No attempts yet	3s	512 MB	Judgeable
Rat-O-MaticFrames nest into a tree, and each query asks how many database melodies contain the sound string of the path from outside to an active frame.	Hard8	TreeString matching+1	No attempts yet	3s	256 MB	Judgeable
Binary StringsCount the antisymmetric binary strings of length 2L that contain each of n given binary strings (n up to 6, length up to 20) as a substring, modulo 998244353.	Hard8	Dynamic programmingString matching+1	No attempts yet	1s	512 MB	Judgeable
SequenceGiven an array with range operations that copy shifted values, reset ranges to a saved copy, and query range sums, compute the sum for each type 1 query.	Hard8	Segment treeArray+1	No attempts yet	7s	512 MB	Judgeable
CriminalsGiven a grid with K unsafe cells, count for each tourist's start cell how many cells can be reached when every cell in the rectangle between start and target is safe.	Hard8	Divide and conquerSegment tree+1	No attempts yet	4s	512 MB	Judgeable
Build the GraphGiven n nodes and at most m edges, build an undirected graph minimizing the sum of all-pairs shortest distances, where unreachable pairs count as n.	Hard8	GraphGreedy+2	No attempts yet	1s	512 MB	Judgeable
MatchGiven a tree with n nodes, count the edge subsets whose remaining forest has a maximum matching size divisible by m, modulo 998244353.	Hard8	TreeDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Subsequence SumsGiven the multiset of all subsequence sums of a hidden positive-integer sequence, reconstruct the sequence, choosing the lexicographically smallest one.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	512 MB	Judgeable
K-matchingGiven an n by m grid graph with edge weights, find the minimum total weight of K edges that share no endpoints (a K-matching).	Hard8	Dynamic programmingBinary search+1	No attempts yet	9s	512 MB	Judgeable
Lying From YouGiven n lines y = a_i x + b_i, change coefficients at L1 cost so all lines pass through one point; find the infimum total cost.	Hard8	MathGeometry+2	No attempts yet	10s	512 MB	Judgeable
From The InsideGiven board sizes n and m and square size k with k <= n, m <= 3k, count the first moves that let Alice win under optimal play.	Hard8	Game theoryMath+1	No attempts yet	1s	512 MB	Judgeable
One Step CloserGiven a grid built from q rectangle XOR flips, decide whether repeatedly flipping the row and column of every plus cell ends with all minus, and count the operations.	Hard8	MathBit manipulation+1	No attempts yet	2s	512 MB	Judgeable
InvisibleProcess point updates and range queries on an array, printing any value that appears an odd number of times in the range, or -1 if none exists.	Hard8	Segment treeBit manipulation+1	No attempts yet	12s	512 MB	Judgeable
Leave Out All The RestGiven two arrays with distinct values, interleave them into one sequence so that its longest increasing subsequence is as long as possible, and output that maximum length.	Hard8	Dynamic programmingGreedy+2	No attempts yet	2s	512 MB	Judgeable
FaintSum the absolute differences between consecutive rows of a fixed column in the lexicographically ordered list of k-subsets of {1,...,n}, modulo 1e9+7.	Hard8	CombinatoricsMath+2	No attempts yet	1s	512 MB	Judgeable
Biggest NumberAfter each of Q point updates to the digits on N cards, report the largest base-D number obtainable by rearranging the cards, modulo 1e9+7.	Hard8	Segment treeSorting+2	No attempts yet	0.5s	256 MB	Judgeable
Hotter-colderAn interactive problem: locate a hidden point in a d-dimensional integer grid using at most 100d queries that only report whether the latest Chebyshev distance got smaller or larger.	Hard8	Binary searchImplementation+2	No attempts yet	1s	256 MB	Judgeable
PaintingPaint a fence of n sections to final colors c_i using exactly m phases, each phase one color on a contiguous range; find the maximum total painting hours.	Hard8	Dynamic programmingIntervals	No attempts yet	2s	256 MB	Judgeable
OnesFor each k up to 1e9, output a 1-expression using only ones, +, *, and parentheses that evaluates to k with at most 100 ones, or NO.	Hard8	Dynamic programmingMath+2	No attempts yet	1s	512 MB	Judgeable
SeatsGiven n prize values, choose one probability distribution over seats so that a player's expected prize, accounting for random contests at each seat, is maximized.	Hard8	ProbabilityMath+2	No attempts yet	1.5s	256 MB	Judgeable
PrimesAnswer online queries that ask for the sum of shared distinct prime counts over all pairs in a range [a, b] up to 10^6.	Hard8	Number theoryPrefix sum+2	No attempts yet	8s	256 MB	Judgeable