Problems

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Total results21,088 problems

mex and QueriesHard9
Segment tree, Intervals +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
XOR SequencesHard9
Bit manipulation, Divide and conquer +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Moorio KartHard9
Tree, Dynamic programming +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Mowing MischiefHard9
Dynamic programming, Sorting +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
MessageHard9
Dynamic programming, String matching +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Sweet and SourHard9
Probability, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Query and QueryHard9
Segment tree, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Sum of Equivalent Resistances Between Every Pair of Vertices Joined by an Edge, Given a Connected Graph with Unit Resistance EdgesHard9
Graph, Matrix +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Africa 2Hard9
Implementation, Brute force +2No attempts yetTime limit1.357sMemory limit1357 MB
Judgeable
Gahui's Sequence Mod Play (Large)Hard9
Stack, Two pointers +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
ValleysHard9
Union-find, Graph +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Beautiful ManyeongroHard9
Trie, DFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Build a WorkbookHard9
Graph, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Overflowing UncertaintyHard9
Number theory, Dynamic programming +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Maintaining a SequenceHard9
Dynamic programming, Implementation +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Working CellsHard9
Matrix, Divide and conquer +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
The Tallest and Widest CastleHard9
Geometry, Dynamic programming +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Parameterized Pattern MatchingHard9
String, String matching +2No attempts yetTime limitNot setMemory limit16 MB
Judgeable
Fruit TreeHard9
Tree, Binary search +2No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Sequence and Queries 26Hard9
Segment tree, Dynamic programming +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
Mischievous JunseokHard9
Brute force, Recursion +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
CalculatorHard9
Binary search, Math +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Gosu 2Hard9
Divide and conquer, Combinatorics +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Wind of ChangeHard9
Tree, Divide and conquer +2No attempts yetTime limit10sMemory limit1024 MB
Judgeable
Traveling MerchantHard9
Segment tree, Divide and conquer +2No attempts yetTime limit10sMemory limit1024 MB
Judgeable
HotelHard9
Segment tree, Array +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Hanging RackHard9
Math, Recursion +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Dynamic DiameterHard9
Tree, Divide and conquer +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
RulerHard9
Backtracking, Brute force +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
MeetingsHard9
Tree, Divide and conquer +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Two TransportationsHard9
Shortest path, Graph +2No attempts yetTime limit10sMemory limit256 MB
Judgeable
AsceticismHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit0.6sMemory limit256 MB
Judgeable
CandiesHard9
Dynamic programming, Greedy +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
CityHard9
Tree, Bit manipulation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
EmploymentHard9
Segment tree, Divide and conquer +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Road DevelopmentHard9
Graph, Union-find +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Historical ResearchHard9
Divide and conquer, Array +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
Construction ProjectHard9
Minimum spanning tree, Geometry +2No attempts yetTime limit5sMemory limit256 MB
Judgeable
MessengerHard9
Implementation, Simulation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
ConstellationHard9
Geometry, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Sequence and Queries 32Hard9
Dynamic programming, Prefix sum +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
Sequence and Queries 34Hard9
String matching, Segment tree +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Graph and CyclesHard9
Graph, Greedy +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Nearest PointsHard9
Geometry, Divide and conquer +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Mining aHard9
Math, Bit manipulation +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
DivModuloHard9
Math, Number theory +2No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Be Geeks!Hard9
Math, Number theory +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Dance CircleHard9
Math, Prefix sum +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Colored Paper and QueriesHard9
Segment tree, Divide and conquer +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Regarding How a Simple DFS Problem I Thought Was Problem A Became Problem E in This Contest (Easy)Hard9
Divide and conquer, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Tree DepthHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Chessboard MovementHard9
Dynamic programming, Matrix +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
GnalcatsHard9
String, Stack +2No attempts yetTime limit0.3sMemory limit512 MB
Judgeable
Speed Reading CourseHard9
Number theory, String matching +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Good Word, Bad WordHard9
Shortest path, Graph +2No attempts yetTime limit2.5sMemory limit1024 MB
Judgeable
Patrol RouteHard9
Graph, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
TenkeyHard9
Graph, BFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Graph CountingHard9
Combinatorics, Graph +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
KnowledgeHard9
String, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Bitwise XorHard9
Bit manipulation, Trie +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Easy WinHard9
Game theory, Union-find +2No attempts yetTime limit1.5sMemory limit512 MB
Judgeable
Six WordsHard9
Graph, Minimum spanning tree +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Seven NeversHard9
Dynamic programming, Segment tree +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Um_nik's AlgorithmHard9
Graph, Greedy +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
String AlgorithmHard9
String, Hash map +2No attempts yetTime limit20sMemory limit512 MB
Judgeable
FFT AlgorithmHard9
Number theory, Math +2No attempts yetTime limit1.5sMemory limit512 MB
Judgeable
Bracket Euler TourHard9
Graph, DFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
One RootHard9
Math, Number theory +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Another Coin Weighing PuzzleHard9
Combinatorics, Math +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Counting Edit DistancesHard9
Dynamic programming, String +2No attempts yetTime limit10sMemory limit512 MB
Judgeable
Rooted SubtreesHard9
Tree, DFS +2No attempts yetTime limit11sMemory limit512 MB
Judgeable
Basis ChangeHard9
Math, Implementation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Modulo-magic squaresHard9
Math, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Call It What You WantHard9
Number theory, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
KaleidoscopeHard9
Combinatorics, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Expected CostHard9
Combinatorics, Tree +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Long GameHard9
Game theory, Greedy +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
FarawayHard9
Math, Number theory +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
TDLHard9
Number theory, Bit manipulation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Monster HunterHard9
Greedy, DFS +2No attempts yetTime limit4sMemory limit512 MB
Judgeable
Make Rounddog HappyHard9
Divide and conquer, Two pointers +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Decimal ExpansionHard9
Math, Number theory +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Lati@sHard9
Game theory, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Linear Congruential GeneratorHard9
Math, Number theory +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Count the GraphsHard9
Combinatorics, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Greatest Chicken DishHard9
Dynamic programming, Number theory +2No attempts yetTime limit15sMemory limit512 MB
Judgeable
The HalfwittersHard9
Dynamic programming, Graph +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
IneqHard9
Geometry, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Delightful (Hard)Hard9
Number theory, Implementation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Xorshift32Hard9
Math, Bit manipulation +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Help Yourself (Platinum)Hard9
Combinatorics, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
814 - 2Hard9
Graph, DFS +2No attempts yetTime limit0.814sMemory limit814 MB
Judgeable
OR and QueriesHard9
Segment tree, Bit manipulation +2No attempts yetTime limit1.5sMemory limit256 MB
Judgeable
Karaoke MeetupHard9
Tree, DFS +2No attempts yetTime limit8sMemory limit512 MB
Judgeable
Nonogram QRHard9
Backtracking, Simulation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Chameleon's LoveHard9
Graph, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Something in the ChestHard9
Union-find, Divide and conquer +2No attempts yetTime limit3sMemory limit1024 MB
Judgeable
Sprinklers 2: Return of the AlfalfaHard9
Dynamic programming, Prefix sum +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
ExerciseHard9
Combinatorics, Number theory +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Cow ExerciseHard9
Math, Number theory +2No attempts yetTime limit1sMemory limit512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
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
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
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
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
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
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
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
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
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
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
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
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
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 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
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
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
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
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
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
Nearest PointsCount the integer lattice points in an axis-aligned rectangle whose Euclidean distance to p1 is the minimum among K marked points.	Hard9	GeometryDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Mining aFor each n, find the largest a such that 1/n = 1/(a xor b) + 1/b for some positive integer b.	Hard9	MathBit manipulation+2	No attempts yet	2s	1024 MB	Judgeable
DivModuloCompute C(M,N) after removing every factor of D, and report the remainder modulo D, for M up to 4e18 and D up to 1.6e7.	Hard9	MathNumber theory+2	No attempts yet	3s	1024 MB	Judgeable
Be Geeks!Sum gcd(a_i..a_j) * max(a_i..a_j) over all subarrays, modulo 1e9+7, with N up to 2e5.	Hard9	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Dance CircleCount, modulo 1e9+7, the binary assignments to n children around a circle matching n parity constraints, each covering a contiguous arc centered at some child.	Hard9	MathPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Colored Paper and QueriesGiven N axis-aligned rectangles and M axis-aligned query rectangles, report for each query the maximum number of input rectangles covering any single point inside it.	Hard9	Segment treeDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
Regarding How a Simple DFS Problem I Thought Was Problem A Became Problem E in This Contest (Easy)Given a perfect binary tree with N = 2^k - 1 weighted nodes numbered in heap order and an implied axis-aligned layout, find the maximum sum of weights inside any axis-parallel rectangle whose sides don't cross a node.	Hard9	Divide and conquerDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Tree DepthFor each node i, sum its depth over all permutations of 1..N with exactly K inversions, using the Cartesian-tree BST built by recursively taking the minimum. Output each sum mod a large prime.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Chessboard MovementCount paths from row 1 to row N on an N x M chessboard where odd rows restrict moves to same-colored adjacent cells and even rows allow any adjacent move, modulo 1e9+7.	Hard9	Dynamic programmingMatrix+2	No attempts yet	2s	512 MB	Judgeable
GnalcatsDecide whether two genes, each a sequence of seven possible base transformations on proteins, produce identical results or both fail on every sufficiently long input protein.	Hard9	StringStack+2	No attempts yet	0.3s	512 MB	Judgeable
Speed Reading CourseCount how many positions i where c contains the given m-bit word w, with c defined by an arithmetic progression modulo n against threshold p.	Hard9	Number theoryString matching+2	No attempts yet	2s	512 MB	Judgeable
Good Word, Bad WordBacteria on an N by N grid can step to an orthogonal neighbor for cost a, or jump up to Chebyshev distance D from a good cell for cost b; for each meeting cell find the total minimum cost for all bacteria to reach it.	Hard9	Shortest pathGraph+2	No attempts yet	2.5s	1024 MB	Judgeable
Patrol RouteFind the minimum closed walk covering every edge of a connected weighted undirected multigraph at least once, with at most 15 vertices.	Hard9	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
TenkeyFind the minimum number of keypad operations (cursor moves plus key presses) to type a positive integer congruent to R modulo M, starting from the 0 key.	Hard9	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Graph CountingCount, modulo 998244353, the non-isomorphic undirected graphs on 2n vertices that have no perfect matching but lose that property when any missing edge is added.	Hard9	CombinatoricsGraph+2	No attempts yet	5s	512 MB	Judgeable
KnowledgeCount strings of length x reachable from s by inserting or deleting the blocks aa, bbb, and ababab, modulo 998244353.	Hard9	StringCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Bitwise XorCount non-empty subsequences in which the pairwise xor of every two chosen elements is at least x, modulo 998244353.	Hard9	Bit manipulationTrie+2	No attempts yet	2s	512 MB	Judgeable
Easy WinAfter each edge insertion, find the maximum total weight of a subset of edges such that no non-empty edge-disjoint union of cycles in it has Nim value (xor of stone counts) equal to zero.	Hard9	Game theoryUnion-find+2	No attempts yet	1.5s	512 MB	Judgeable
Six WordsGiven a connected graph whose vertex i has potential i and edge i has weight i, find the total weight of a minimum spanning tree of the line graph of the line graph.	Hard9	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Seven NeversFor every window of k consecutive elements in a permutation, compute the LIS length after deleting that window.	Hard9	Dynamic programmingSegment tree+2	No attempts yet	2s	512 MB	Judgeable
Um_nik's AlgorithmGiven an undirected bipartite graph with up to 2e6 vertices and edges per side, output a matching whose size is at least 0.95 times the maximum matching size, with heavy constant-factor optimization required.	Hard9	GraphGreedy+2	No attempts yet	4s	512 MB	Judgeable
String AlgorithmFor every k, cut s into blocks of length k, discard the tail, and count block pairs whose Hamming distance is at most one.	Hard9	StringHash map+2	No attempts yet	20s	512 MB	Judgeable
FFT AlgorithmGiven m and k, find a primitive 2^k-th root of unity modulo m, or report that none exists.	Hard9	Number theoryMath+2	No attempts yet	1.5s	512 MB	Judgeable
Bracket Euler TourFind an Euler tour of an undirected graph whose vertex bracket labels, read in traversal order, form a correct bracket sequence, or report that none exists.	Hard9	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
One RootCount pairs (p, q) with \|p\|, \|q\| <= m for which x^n + px + q has exactly one real root.	Hard9	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Another Coin Weighing PuzzleGiven m weighings and k coins per bag, find the maximum number of bags whose unique heavy bag can be identified, modulo 998244353.	Hard9	CombinatoricsMath+2	No attempts yet	1s	512 MB	Judgeable
Counting Edit DistancesCount the number of distinct strings over 'A' to 'Z' whose Levenshtein distance from a given string s is exactly d, modulo 998244353.	Hard9	Dynamic programmingString+2	No attempts yet	10s	512 MB	Judgeable
Rooted SubtreesFor each query with two roots r and p, count the distinct non-empty sets that are the intersection of a subtree of the tree rooted at r and a subtree of the tree rooted at p.	Hard9	TreeDFS+2	No attempts yet	11s	512 MB	Judgeable
Basis ChangeGiven one linear recurrence with coefficients a_i, find the unique recurrence with prescribed lags b_i that every sequence satisfying the first also satisfies.	Hard9	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
Modulo-magic squaresCount n x n matrices over Z_m whose row, column, and two diagonal sums are all congruent to one constant, for n and m up to 1e9.	Hard9	MathCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Call It What You WantFor each n, factor x^n - 1 over the integers into cyclotomic polynomials, print the factors in a specified coefficient order and a specific sign and exponent format.	Hard9	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
KaleidoscopeCount colorings of the 60 faces of a rhombic hexecontahedron with n colors, each color i used at least c_i times, where colorings are identified under the rotational symmetry group, modulo p.	Hard9	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Expected CostPick a labeled tree on n vertices uniformly at random and find the expected value of the minimum sum of distances from any vertex to all others, modulo a prime.	Hard9	CombinatoricsTree+2	No attempts yet	3s	512 MB	Judgeable
Long GamePlayers alternately cut a strip of a permutation while every cut must leave at least one strip containing an inversion; decide the winner with optimal play.	Hard9	Game theoryGreedy+2	No attempts yet	1s	512 MB	Judgeable
FarawayCount lattice points (xe, ye) in [0, m]^2 such that for each of up to 10 constraints, (\|xi - xe\| + \|yi - ye\|) mod ki equals ti, with ki at most 5 and m up to 1e9.	Hard9	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
TDLGiven m and k, find the smallest n such that the m-th integer above n coprime to n differs from n by a value whose XOR with n equals k.	Hard9	Number theoryBit manipulation+2	No attempts yet	1s	512 MB	Judgeable
Monster HunterGiven a tree rooted at node 1, each node has a cost and a reward; find the minimum starting HP so some walk clearing every monster never drops below zero.	Hard9	GreedyDFS+2	No attempts yet	4s	512 MB	Judgeable
Make Rounddog HappyCount subarrays whose elements are all distinct and whose maximum minus length is at most k, for arrays up to 300,000 with values bounded by n.	Hard9	Divide and conquerTwo pointers+2	No attempts yet	2s	512 MB	Judgeable
Decimal ExpansionFor each query n up to 10^18, find the n-th digit after the decimal point of the infinite product (9/10)(99/100)(999/1000)...	Hard9	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Lati@sDetermine the winner of a finite impartial game whose starting multiset is built from all permutation diagonals of an n by n matrix.	Hard9	Game theoryCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Linear Congruential GeneratorGiven a linear congruential generator and two index ranges, sum X_i mod (X_j+1) over all pairs i in the first range and j in the second.	Hard9	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Count the GraphsCount labeled connected undirected graphs on N nodes with exactly K bridges, modulo a possibly composite M, for up to 100 test cases.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Greatest Chicken DishCount, for each query range [L, R] and value D, the number of contiguous subarrays inside [L, R] whose GCD equals D.	Hard9	Dynamic programmingNumber theory+2	No attempts yet	15s	512 MB	Judgeable
The HalfwittersFor each start permutation, compute the minimum expected time to reach the identity order using adjacent swaps (cost a), a full reversal (cost b), or a random reshuffle (cost c).	Hard9	Dynamic programmingGraph+2	No attempts yet	5s	512 MB	Judgeable
IneqGiven a finite set S of integer lattice points, decide whether S can be cut out as exactly the integer points lying strictly below every line of some finite family of half-planes.	Hard9	GeometryMath+2	No attempts yet	2s	512 MB	Judgeable
Delightful (Hard)Write a program of at most 5000 commands for a ternary computer with 26 forty-trit registers that sets Y to 1 if the input X (0 to 109) is prime and 0 otherwise.	Hard9	Number theoryImplementation+2	No attempts yet	1s	512 MB	Judgeable
Xorshift32Given a starting value x and a target t, find the index at which t first appears in the Xorshift32 pseudorandom sequence.	Hard9	MathBit manipulation+2	No attempts yet	1s	256 MB	Judgeable
Help Yourself (Platinum)Sum the K-th power of the number of connected components of the union over all 2^N subsets of N intervals, modulo 1e9+7.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
814 - 2Print an 8 by 14 grid of digits so that every number from 1 up to some X can be traced as an adjacent-cell path, maximizing X.	Hard9	GraphDFS+2	No attempts yet	0.814s	814 MB	Judgeable
OR and QueriesProcess range bitwise-OR updates on an array and count how many positions in a range currently equal a fixed K.	Hard9	Segment treeBit manipulation+2	No attempts yet	1.5s	256 MB	Judgeable
Karaoke MeetupIn a weighted tree, some vertices are marked as houses. For each vertex compute the ratio of the nearest marked vertex distance to the farthest, and output the maximum ratio as a reduced fraction.	Hard9	TreeDFS+2	No attempts yet	8s	512 MB	Judgeable
Nonogram QRSolve a chain of 2000 nonograms to reconstruct QR codes, decode them, follow indicator links, and recover a flag.	Hard9	BacktrackingSimulation+2	No attempts yet	1s	512 MB	Judgeable
Chameleon's LoveUsing at most 20000 queries that return the number of distinct skin colors in a chosen subset, recover every pair of chameleons sharing an original color.	Hard9	GraphCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Something in the ChestMaintain a dynamic graph under edge insertions and global threshold changes, and answer the largest threshold at which two cells stay connected.	Hard9	Union-findDivide and conquer+2	No attempts yet	3s	1024 MB	Judgeable
Sprinklers 2: Return of the AlfalfaCount the ways to place sweet corn and alfalfa sprinklers on an N by N grid, with some blocked squares, so that every square is covered by exactly one sprinkler type.	Hard9	Dynamic programmingPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
ExerciseGiven N and prime M, compute modulo M the product over all N! permutations of the order (number of iterations until identity) of each permutation.	Hard9	CombinatoricsNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Cow ExerciseGiven N and prime M, sum every positive integer K for which some permutation of length N has order K, then output the sum modulo M.	Hard9	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable