Problems

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Total results29,397 problems

Jogging in the Park
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hacker Cups and Balls
Hard8
Binary search, Segment tree+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Bored Dreamoon
Hard8
Sorting, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Crazy Dreamoon
Hard8
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Forest Game
Hard8
Tree, Divide and conquer+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Lines Game
Hard8
Dynamic programming, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lonely Dreamoon 2
Hard8
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Almost Bobo Number
Hard8
String, Greedy+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Rectangles Inside Rectangle
Hard8
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Order-Preserving Partition
Hard8
Array, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Prime Tree
Hard8
Tree, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Differencia
Hard8
Segment tree, Binary search+2
No attempts yet
Time limit
14s
Memory limit
256 MB
Judgeable
Helter Skelter
Hard8
Two pointers, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Join The Future
Hard8
Union-find, Greedy+1
No attempts yet
Time limit
5s
Memory limit
64 MB
Judgeable
La Vie En Rose
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
2.5s
Memory limit
64 MB
Judgeable
Alone in the Cactus
Hard8
DFS, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Dominoes
Hard8
Matrix, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Guess the Data Structure
Hard8
Bit manipulation, Trie+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Izhevsk Training Camp
Hard8
Bit manipulation, Brute force+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Expected LCP
Hard8
Probability, Combinatorics+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Finite Walking
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Hash Table
Hard8
Segment tree, Divide and conquer+1
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Immigration
Hard8
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Graph Coloring 2
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Reachable Sequences
Hard8
Combinatorics, Bit manipulation+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Physics
Hard8
Math, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Array and Operations
Hard8
Segment tree, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Value of the Array
Hard8
Combinatorics, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pruefsumme
Hard8
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Vier
Hard8
Hash map, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Weltall
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Championships
Hard8
Graph, Greedy+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Robots
Hard8
Graph, BFS+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Gym
Hard8
Greedy, Union-find+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Triangles
Hard8
Geometry, Hash map+2
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Subtract if Greater!
Hard8
Segment tree, Binary search+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
XOR Tree
Hard8
Tree, Game theory
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Friends and Berries - 2
Hard8
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Best Division
Hard8
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Easy Homework
Hard8
Number theory, Matrix+1
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Flight
Hard8
Tree, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Intersection is Not Allowed!
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
K-value
Hard8
Binary search, Tree+2
No attempts yet
Time limit
6s
Memory limit
256 MB
Judgeable
Circles
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Eel and Grid
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cups and Beans
Hard8
Game theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sublime Marathon
Hard8
Tree, DFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Proper String Problem
Hard8
String, Trie+1
No attempts yet
Time limit
9s
Memory limit
1024 MB
Judgeable
Length String
Hard8
String, Math+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Delivering Flyers
Hard8
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Function Reconstruction
Hard8
Graph, Combinatorics+2
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Why the Cow Crossed the Road 2020
Hard8
Dynamic programming, Tree+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tourism business
Hard8
Tree, Divide and conquer+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Mixture
Hard8
Geometry, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Viruses
Hard8
String matching, Dynamic programming+1
No attempts yet
Time limit
0.7s
Memory limit
256 MB
Judgeable
Triangulation
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2.5s
Memory limit
256 MB
Judgeable
Drought (Large)
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Taking Items
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Second Diameter of a Tree
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Urban Blight
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Voucher Preparation
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Searching for Strings
Hard8
Sliding window, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Swapping Seats
Hard8
Greedy, Sliding window+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Game with Grundy
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Exercise Deadlines
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mountains and Valleys
Hard8
Graph, Tree+1
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Interval Collection
Hard8
Sorting, Greedy+1
No attempts yet
Time limit
3.5s
Memory limit
512 MB
Judgeable
Sister Cities
Hard8
Graph, Minimum spanning tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pleasant Tour
Hard8
Tree, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Winter Driving
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Boring Lectures
Hard8
Segment tree, Sliding window+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Flop Sorting
Hard8
Implementation, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
How Many Burgers?
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sequence
Hard8
Dynamic programming, Prefix sum
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Progression
Hard8
Segment tree, Array+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Aesthetic
Hard8
Graph, Shortest path
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Feast
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Internet Problem
Hard8
Graph, DFS+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Fancy Fence
Hard8
Stack, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Spring cleaning
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Chess Rush
Hard8
Matrix, Math+1
No attempts yet
Time limit
2.3s
Memory limit
64 MB
Judgeable
Experiment
Hard8
Graph, Simulation+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Roadside Advertisements
Hard8
Tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rock Climbing
Hard8
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Panda Ski
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cash Gap
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Jet Trains
Hard8
Union-find, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Superpermutations
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Preparing Tests
Hard8
Dynamic programming, Union-find+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Race of robots
Hard8
Dynamic programming, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flexible Segments
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Counting in the Order
Hard8
Stack, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Drawing
Hard8
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Right-hand obstruction
Hard8
Simulation, Queue+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fraction Paradox
Hard8
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Operation <<Permutation>>
Hard8
Graph, Topological sort+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Shushpanchiks and the Cinema
Hard8
Math, Intervals+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cipher Breaking
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Strange Exhibit
Hard8
Implementation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String Processing
Hard8
Divide and conquer, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Jogging in the ParkExtend k walks that start at glade 1 so each ends at glade n with the same total length, or report -1 when that is impossible.	Hard8	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Hacker Cups and BallsGiven a permutation and range sort operations that go ascending or descending depending on whether l < r, find the value in the middle cup at the end.	Hard8	Binary searchSegment tree+2	No attempts yet	3s	512 MB	Judgeable
Bored DreamoonGiven soldier heights and a right-front relation matrix, find the minimum size of the front row in a valid row arrangement, or -1 if none exists.	Hard8	SortingImplementation+1	No attempts yet	1s	512 MB	Judgeable
Crazy DreamoonGiven up to 2000 line segments in a 2000 by 2000 grid, count the grid squares whose interior is crossed by at least one segment.	Hard8	GeometryMath+2	No attempts yet	1s	512 MB	Judgeable
Forest GameGiven a tree, nodes are removed in random order and each removal adds its component size to the score. Output the expected total times N! mod 1e9+7.	Hard8	TreeDivide and conquer+1	No attempts yet	4s	512 MB	Judgeable
Lines GameChoose segments with minimum total cost so that every segment is removed or crosses a chosen one.	Hard8	Dynamic programmingSegment tree+1	No attempts yet	2s	512 MB	Judgeable
Lonely Dreamoon 2Reorder the given integers so that the smallest absolute difference between adjacent elements is as large as possible, and print any optimal ordering.	Hard8	SortingGreedy+2	No attempts yet	1s	512 MB	Judgeable
Almost Bobo NumberGiven an integer n with up to 5,000,000 digits, find the largest almost bobo number strictly less than n, or report -1 if none exists.	Hard8	StringGreedy+1	No attempts yet	3s	512 MB	Judgeable
Rectangles Inside RectanglePick a non-overlapping subset of axis-parallel rectangles that each touch the left or right side of a big rectangle, maximizing total weight.	Hard8	Dynamic programmingSorting+2	No attempts yet	1s	512 MB	Judgeable
Order-Preserving PartitionCount the ways to split permutation P into four contiguous parts, each holding consecutive values, whose minima are ordered like Q.	Hard8	ArrayPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
Prime TreeGiven a rooted tree with n nodes, find the largest number of prime trees whose tree product equals it.	Hard8	TreeNumber theory+1	No attempts yet	2s	512 MB	Judgeable
DifferenciaGiven sequences a and b, process m generated operations that either assign x to a range of a or count positions in a range where a_i is at least b_i.	Hard8	Segment treeBinary search+2	No attempts yet	14s	256 MB	Judgeable
Helter SkelterGiven the run lengths of a binary string that starts with 0, answer for each query whether some substring has exactly a zeros and b ones.	Hard8	Two pointersPrefix sum+1	No attempts yet	2s	128 MB	Judgeable
Join The FutureGiven parity constraints on subarray sums and a lower and upper bound for each element, count the arrays that satisfy them and print the lexicographically smallest one.	Hard8	Union-findGreedy+1	No attempts yet	5s	64 MB	Judgeable
La Vie En RoseCount which length-m windows of s can be produced from pattern p by swapping disjoint adjacent pairs that are non-overlapping and strictly separated.	Hard8	String matchingDynamic programming+2	No attempts yet	2.5s	64 MB	Judgeable
Alone in the CactusGiven a colored cactus, find the probability that a random walk from s without revisits ends at a red vertex, restarting at s on blue.	Hard8	DFSDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
DominoesGiven a grid of white, green, and black cells, place dominoes on non-black cells to maximize the total dots on green cells.	Hard8	MatrixBit manipulation+2	No attempts yet	2s	256 MB	Judgeable
Guess the Data StructureMaintain an array that supports appending values, range sum queries, xoring every element with x, and sorting the array.	Hard8	Bit manipulationTrie+2	No attempts yet	5s	256 MB	Judgeable
Izhevsk Training CampGiven nine contests, each a ranking of n teams, pick three contests so that the number of team pairs ordered the same way in all three is minimized.	Hard8	Bit manipulationBrute force+2	No attempts yet	3s	256 MB	Judgeable
Expected LCPCompute the expected length of the longest common prefix among n independent uniform random infinite binary strings, output as a fraction mod 1e9+7.	Hard8	ProbabilityCombinatorics+2	No attempts yet	1.5s	256 MB	Judgeable
Finite WalkingGiven a graph whose edges have counters taken modulo a_i, count the distinct final counter arrays reachable by walks from any start, modulo 10^9+7.	Hard8	GraphDFS+2	No attempts yet	2s	256 MB	Judgeable
Hash TableProcess insertions and deletions into a sequence and report, after each query, the total linear-probing cost of the current hash values.	Hard8	Segment treeDivide and conquer+1	No attempts yet	5s	256 MB	Judgeable
ImmigrationPeter moves along the x-axis while tracking an object whose velocity changes n times; find the maximum absolute angular speed of his gaze from time t0 onward.	Hard8	GeometryMath+2	No attempts yet	2s	256 MB	Judgeable
Graph Coloring 2Compute the chromatic number of every non-empty vertex subset of a graph with n at most 18, then fold the values into one hash.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Reachable SequencesCount ordered pairs of permutations (i, j) where a^(i) can be reached from a^(j) by repeatedly swapping an out-of-order pair.	Hard8	CombinatoricsBit manipulation+1	No attempts yet	4s	512 MB	Judgeable
PhysicsBalls move on a line with acceleration tied to speed, collide elastically, and each query asks for the k-th smallest velocity at time t.	Hard8	MathSorting+2	No attempts yet	1s	512 MB	Judgeable
Array and OperationsMaintain an array under range add, range floor-square-root, and range sum queries, printing each sum.	Hard8	Segment treeBinary search+2	No attempts yet	1s	512 MB	Judgeable
Value of the ArrayFor each k from 1 to n, sum over all non-empty subsequences the sum of their min(size, k) largest elements, modulo 998244353.	Hard8	CombinatoricsSorting+2	No attempts yet	1s	512 MB	Judgeable
PruefsummeGiven n and m, build matrices p and q for a checksum that detects any single-digit change or adjacent swap, or report that none exists.	Hard8	MathNumber theory+1	No attempts yet	2s	256 MB	Judgeable
VierGiven a random permutation, find two distinct unordered pairs with equal sums of indices and equal sums of permutation values, both modulo n.	Hard8	Hash mapMath+2	No attempts yet	2s	256 MB	Judgeable
WeltallFind the d-th lexicographic permutation of 1..n that has exactly k fixed points.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	4s	256 MB	Judgeable
ChampionshipsFind the largest set S of vertices such that the induced subgraph on S is connected and every vertex in S has degree at least d within S.	Hard8	GraphGreedy+2	No attempts yet	1.5s	256 MB	Judgeable
RobotsFind a number k such that after k nondeterministic moves, every robot is surely in one of the first b strongholds, or report -1 if none exists.	Hard8	GraphBFS+2	No attempts yet	10s	256 MB	Judgeable
GymAssign each one-hour reservation a free hour within its interval on its machine, minimizing the number of hours any machine is in use, or print NIE.	Hard8	GreedyUnion-find+2	No attempts yet	10s	256 MB	Judgeable
TrianglesGiven up to 2000 distinct points, count right triangles formed by three of the points whose area falls in the inclusive range [A, B].	Hard8	GeometryHash map+2	No attempts yet	10s	256 MB	Judgeable
Subtract if Greater!Maintain a multiset under queries that ask for the k-th smallest element and queries that subtract x from every element greater than x, then report each k-th smallest.	Hard8	Segment treeBinary search+2	No attempts yet	5s	512 MB	Judgeable
XOR TreeGiven a tree whose edges have multiplicities, decide for each query pair S and T whether Alice can force a path between them in H.	Hard8	TreeGame theory	No attempts yet	2s	256 MB	Judgeable
Friends and Berries - 2Given n points in the plane, find all pairs u, v such that every other point w lies in the closed disk with diameter uv.	Hard8	GeometryMath	No attempts yet	2s	256 MB	Judgeable
Best DivisionGiven a pseudorandom array, find the largest K such that A can be split into K nonempty intervals of length at most L, each with XOR sum at most X.	Hard8	Dynamic programmingPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
Easy HomeworkCount the indices n in [L, R] where f(n) mod p equals x, for the sequence f(0)=0, f(1)=1, f(n)=A·f(n-1)+f(n-2).	Hard8	Number theoryMatrix+1	No attempts yet	1.5s	256 MB	Judgeable
FlightGiven a tree and queries (u, v, d), find the fewest steps from u to v when each step must join two vertices at distance at least d, or -1 if unreachable.	Hard8	TreeShortest path+1	No attempts yet	1s	256 MB	Judgeable
Intersection is Not Allowed!Count the ways to route K non-crossing monotone paths from fixed top squares to fixed bottom squares on an N by N board, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	256 MB	Judgeable
K-valueGiven a weighted tree, find the minimum k-value among simple paths with between L and R edges, where the k-value is the element at rank floor(r/k)+1 of the sorted edge weights.	Hard8	Binary searchTree+2	No attempts yet	6s	256 MB	Judgeable
CirclesGiven N circles that all pass through the origin, count the lattice points lying inside or on at least one of the circles.	Hard8	GeometrySorting+1	No attempts yet	1s	256 MB	Judgeable
Eel and GridAn eel on a toroidal H by W grid walks right or down, painting cells, until it returns to a painted cell; count Hamiltonian-style walks that cover every cell and end at (0,0).	Hard8	CombinatoricsMath+1	No attempts yet	1s	256 MB	Judgeable
Cups and BeansBeans sit in cups 1 through N-1, each with a move limit C_i; players alternate sliding one bean to a lower cup and whoever cannot move loses. Decide the winner.	Hard8	Game theoryDynamic programming+2	No attempts yet	1s	256 MB	Judgeable
Sublime MarathonGiven a tree with N intersections, count the ways to add exactly two roads so that some two intersections are joined by three internally disjoint paths.	Hard8	TreeDFS+1	No attempts yet	2s	512 MB	Judgeable
Proper String ProblemGiven n strings over A, C, G, T where none is a substring of another, sum over all ordered pairs the length of the longest string that is a proper suffix of s_i and a proper prefix of s_j.	Hard8	StringTrie+1	No attempts yet	9s	1024 MB	Judgeable
Length StringGiven a and b, output the length string of length a times 10 to the power b, printing only the first 17 characters when that length is at least 21.	Hard8	StringMath+1	No attempts yet	3s	1024 MB	Judgeable
Delivering FlyersOn a unit-weight tree, find the shortest closed walk from S that covers every node, given the rider can cover all nodes within distance D from any single stop.	Hard8	TreeGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Function ReconstructionGiven the full reachability matrix of a functional graph on N nodes, count the number of functions f consistent with it, modulo 1e9+7.	Hard8	GraphCombinatorics+2	No attempts yet	1.5s	1024 MB	Judgeable
Why the Cow Crossed the Road 2020Connect barns on two parallel lines with N+M-1 non-crossing segments, minimizing the sum over all barn pairs of shortest squared-length path costs.	Hard8	Dynamic programmingTree+1	No attempts yet	1s	1024 MB	Judgeable
Tourism businessGiven a weighted tree and two city sets A and B with populations, find the maximum of (C_X + C_Y) times the path distance over all X in A and Y in B.	Hard8	TreeDivide and conquer+1	No attempts yet	5s	1024 MB	Judgeable
MixtureAfter each add or remove of a bottle, find the fewest shelf bottles whose nonnegative combination gives the target salt:pepper:garlic ratio, or 0 if none exists.	Hard8	GeometrySegment tree+1	No attempts yet	2s	256 MB	Judgeable
VirusesFor each gene, check whether every virus it can produce contains an antibody fragment, and if not, give the length of the shortest undetected virus.	Hard8	String matchingDynamic programming+1	No attempts yet	0.7s	256 MB	Judgeable
TriangulationCount, over all triangulations of a regular N-gon with a proper red/blue coloring, the total number of red triangles, modulo 998244353.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2.5s	256 MB	Judgeable
Drought (Large)Maximize the sum of a_i minus the sum of b_j over nonnegative reals a and b subject to a_i - b_j <= c_ij, then round the answer to the nearest integer.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Taking ItemsEach item may require others first, cycles mean all-or-nothing; pick a feasible set of items maximizing total mood change.	Hard8	GraphDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Second Diameter of a TreeGiven a weighted tree with up to 100,000 vertices, find the distance of the second farthest pair of vertices, allowing a tie with the diameter.	Hard8	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
Urban BlightGiven points and weighted segments, find a horizontal line whose intersection with the segments maximizes the total weight of segments it touches.	Hard8	GeometrySorting+2	No attempts yet	2s	1024 MB	Judgeable
Voucher PreparationGiven members with distinct skills and names, answer many queries: remove the b highest-skilled members, then partition the best M*a remaining into a teams to maximize the summed product of skills, and output the XOR of the names of all chosen members.	Hard8	GreedySorting+2	No attempts yet	2s	1024 MB	Judgeable
Searching for StringsCount how many distinct permutations of the needle string N occur as a contiguous substring of the haystack string H.	Hard8	Sliding windowString matching+2	No attempts yet	2s	512 MB	Judgeable
Swapping SeatsGiven a circular string of A, B, C, find the minimum number of seat swaps needed so each letter forms one contiguous block.	Hard8	GreedySliding window+2	No attempts yet	2s	512 MB	Judgeable
A Game with GrundyFor each i from 0 to N, count integer x positions with L <= x <= R that lie strictly inside at most i of N triangular visibility wedges.	Hard8	GeometrySorting+2	No attempts yet	1s	512 MB	Judgeable
Exercise DeadlinesEach of N unit-time exercises has a deadline; find the minimum number of adjacent swaps of the identity permutation that orders the exercises so none misses its deadline, or -1.	Hard8	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Mountains and ValleysFind the minimum total difficulty of a walk that visits all N sites, where the flat trails of difficulty 1 form a spanning tree and all other trails are heavy.	Hard8	GraphTree+1	No attempts yet	7s	512 MB	Judgeable
Interval CollectionAfter each add or remove, find the shortest enclosing interval of a chosen set of intervals that has no common interval, and output its length.	Hard8	SortingGreedy+1	No attempts yet	3.5s	512 MB	Judgeable
Sister CitiesFor each city pair, find the smallest fuel capacity that lets two cars drive to each other's city on a connected road graph without ever meeting.	Hard8	GraphMinimum spanning tree+1	No attempts yet	2s	512 MB	Judgeable
Pleasant TourGiven a tree of N rides, find an order visiting every ride once where each walking distance is no greater than the one before, using distance and subtree-count queries.	Hard8	TreeDivide and conquer+1	No attempts yet	2s	512 MB	Judgeable
Winter DrivingOrient each tree road one way to maximize the number of ordered citizen pairs where one citizen's city can reach the other's city.	Hard8	TreeDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
Boring LecturesGiven an array with point updates, after each update find the maximum sum of two elements that lie inside one window of K consecutive positions.	Hard8	Segment treeSliding window+1	No attempts yet	8s	512 MB	Judgeable
Flop SortingGiven two permutations of 1..N, output a sequence of flop operations (swap the min and max inside [l,r]) that turns the first permutation into the second, with at most 300000 operations.	Hard8	ImplementationSorting+2	No attempts yet	2s	512 MB	Judgeable
How Many Burgers?Split N burgers with given utilities among three people so that the youngest gets the most he can while not exceeding either senior's total.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
SequencePick two strictly increasing index sequences of length K from a and b that share at least L indices, maximizing the total of the chosen values.	Hard8	Dynamic programmingPrefix sum	No attempts yet	1s	512 MB	Judgeable
ProgressionGiven N mission difficulties with range updates that add or assign arithmetic progressions, find the longest arithmetic run inside a query range.	Hard8	Segment treeArray+1	No attempts yet	1s	1024 MB	Judgeable
AestheticGiven a connected weighted graph whose roads are ordered by aesthetics, pick one pair i<j that adds W_j to W_i, maximizing the shortest 1-to-N distance afterward.	Hard8	GraphShortest path	No attempts yet	2s	1024 MB	Judgeable
FeastChoose at most K disjoint non-empty subarrays of A so that the total sum of their elements is as large as possible.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	512 MB	Judgeable
Internet ProblemGiven a directed graph, find all vertices lying on every walk from 1 to n, and only on walks from 1 to n, so a walk passes through each chosen vertex exactly once.	Hard8	GraphDFS+2	No attempts yet	5s	512 MB	Judgeable
Fancy FenceCount axis-aligned integer rectangles lying on a histogram of N sections with heights h_i and widths w_i, modulo 1e9+7.	Hard8	StackDivide and conquer+2	No attempts yet	1s	32 MB	Judgeable
Spring cleaningGiven a tree and Q variations that attach extra leaves, find the minimum total length of leaf-pair paths that cover every edge, or -1 if impossible.	Hard8	TreeDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
Chess RushFind the minimum number of moves and the count of shortest paths for a piece going from a column in row 1 to a target column in row R.	Hard8	MatrixMath+1	No attempts yet	2.3s	64 MB	Judgeable
ExperimentGiven users with group memberships and pairs of opposed users, decide whether a set of users can be chosen with at most one per group and at least one user from each opposed pair.	Hard8	GraphSimulation+2	No attempts yet	2s	1024 MB	Judgeable
Roadside AdvertisementsOn a weighted tree, for each of Q queries with five distinct nodes, find the total weight of every edge lying on some shortest path between a pair of the five.	Hard8	TreeGraph+2	No attempts yet	1s	512 MB	Judgeable
Rock ClimbingFind the smallest K such that every K-subset of N rocks contains two rocks A, B with A reachable from B by a strictly upward chain of moves, each move bounded by the max slippery rate.	Hard8	GraphGreedy+2	No attempts yet	1s	512 MB	Judgeable
Panda SkiGiven gates with scores and move limits, find the maximum total score of a downward path from peak to base, counting each gate once.	Hard8	GraphDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Cash GapGiven payments with allowed day ranges, decide whether some placement and ordering of the payments forces the balance below zero.	Hard8	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Jet TrainsMaintain a growing friendship graph and a growing train-route graph; each query asks how many friends of v lie in v's current connected component.	Hard8	Union-findGraph+2	No attempts yet	2s	512 MB	Judgeable
SuperpermutationsGiven a permutation of 1 to n, find the position where it starts in the superpermutation s_n built by Dima's insertion process, modulo 1e9+7.	Hard8	CombinatoricsMath+1	No attempts yet	1s	512 MB	Judgeable
Preparing TestsCount the subarrays that split into consecutive tests, where each test is a count m followed by m edges forming a forest with no loops or multi-edges.	Hard8	Dynamic programmingUnion-find+1	No attempts yet	2s	512 MB	Judgeable
Race of robotsCount the n by m grids that match Ivan's known barrier positions and in which every robot needs the same time to reach the finish, modulo 998244353.	Hard8	Dynamic programmingBit manipulation	No attempts yet	1s	512 MB	Judgeable
Flexible SegmentsFor each n up to 10000, decide whether some n consecutive positive integers admit a +1/-1 choice per element preserving the product, and output the start and signs.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Counting in the OrderEach soldier looks left or right and sees past people no taller than the target; count how many soldiers each one sees.	Hard8	StackArray+2	No attempts yet	1s	512 MB	Judgeable
DrawingPaint exactly a_ij cells in each 4x4 block of a wraparound grid so that the painted cells and the unpainted cells are each connected.	Hard8	ImplementationMath	No attempts yet	1s	512 MB	Judgeable
Right-hand obstructionCars arrive in four queues at a crossroad; a front car passes only if the queue on its right is empty, so simulate second by second and report each car's crossing time or -1.	Hard8	SimulationQueue+2	No attempts yet	1s	512 MB	Judgeable
Fraction ParadoxGiven k irreducible fractions, choose four distinct ones forming two pairs with a at most b and c at most d, maximizing (a+c)/(b+d) minus (e+g)/(f+h). Print their indices.	Hard8	SortingGreedy+1	No attempts yet	1s	512 MB	Judgeable
Operation <<Permutation>>Given inequalities between positions of an unknown permutation, find the earliest prefix of the conditions that pins down the permutation uniquely, or -1 if never.	Hard8	GraphTopological sort+2	No attempts yet	1s	512 MB	Judgeable
Shushpanchiks and the CinemaGiven an n by n grid with m blocked seats, choose k consecutive free seats in one row minimizing the sum of Manhattan distances to a target seat.	Hard8	MathIntervals+2	No attempts yet	2s	512 MB	Judgeable
Cipher BreakingOutput a press sequence of at most 2n! buttons so that every permutation of 1..n appears as a contiguous block, for n up to 9.	Hard8	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
A Strange ExhibitGiven the inversion counts of every window of length k in an unknown permutation of 1..n, reconstruct any valid permutation.	Hard8	ImplementationGreedy+2	No attempts yet	2s	512 MB	Judgeable
String ProcessingDecide whether a recursive split-and-swap program can turn string S into T, and if so output the 2^k - 1 bit program.	Hard8	Divide and conquerString+2	No attempts yet	2s	512 MB	Judgeable