Problems

Pick a problem, code in the editor, and watch the judge run real test cases. The archive is open to browse

Under construction

Still being built. Things may change

Total results29,431 problems

Balancing Art
Medium7
Graph, Binary search
No attempts yet
Time limit
8s
Memory limit
2048 MB
Judgeable
Pascal Meets Boole
Medium7
Math, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Pony-less Express
Medium7
Dynamic programming, Tree
No attempts yet
Time limit
8s
Memory limit
2048 MB
Judgeable
Covers
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
WEB Machine
Medium7
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Colorful Quadrants
Medium7
Prefix sum, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Palindromic Length
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
0.5s
Memory limit
2048 MB
Judgeable
City Bike
Medium7
Greedy, Binary search+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Finding Keys
Medium7
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Island Memories
Medium7
Tree, Divide and conquer+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Virtual Reality Playspace
Medium7
Matrix, Stack+2
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Diversity
Medium7
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Blackboard
Medium7
Math, Greedy+1
No attempts yet
Time limit
6s
Memory limit
1024 MB
Judgeable
Connect Five
Medium7
Geometry, Brute force+1
No attempts yet
Time limit
2.5s
Memory limit
1024 MB
Judgeable
Electrician
Medium7
Combinatorics, Binary search+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Wooden Matrix
Medium7
Tree, Implementation+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Balls of Three Colors
Medium7
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Another Brick in the Wall
Medium7
Dynamic programming, Bit manipulation
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Defective Script
Medium7
Binary search, Greedy+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Eight-Shaped Figures
Medium7
Geometry, Hash map+1
No attempts yet
Time limit
5s
Memory limit
2048 MB
Judgeable
Hanoi Towers Reloaded
Medium7
Recursion, Math+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Longest Common Substring
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
5s
Memory limit
2048 MB
Judgeable
Stacking Blocks
Medium7
Greedy, Heap+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Making Okonomiyaki
Medium7
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Delivery
Medium7
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Parenthesis String Editor
Medium7
Segment tree, Linked list+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Rectangular Jigsaw Puzzle
Medium7
Sorting, Hash map+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Subway Ride
Medium7
Graph, BFS+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Dave's Worry
Medium7
Matrix, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
A Tree Problem Without Trees
Medium7
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mixing Solutions
Medium7
Greedy, Binary search+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Peculiar Protocol
Medium7
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Level Design
Medium7
Greedy, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Divisibility Test
Medium7
Number theory, Math+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Evaluate It and Back Again
Medium7
Math, Implementation
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Adrenaline Rush
Medium7
Array, Sorting+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Incompetent Delivery Guy
Medium7
Shortest path, Graph+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Judicious Watching
Medium7
Greedy, Binary search+2
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Knowns and Unknowns
Medium7
Array, String matching+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
All Pairs Similarity
Medium7
Bit manipulation, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
It's Mooin' Time
Medium7
Greedy, String+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Cowdependence
Medium7
Greedy, Hash map+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Cake Game
Medium7
Game theory, Prefix sum
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Harmonic Hideout
Medium7
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dormitory Lights Out
Medium7
Dynamic programming, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
SSHS Protocol
Medium7
Dynamic programming, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Independent Set (Sum)
Medium7
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Reverse Severer
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Interesting Couple
Medium7
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Numbers Combination
Medium7
Combinatorics, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
The Journey of the King
Medium7
String matching, Graph
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Alchembit Exam
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Microwavable Subsequence
Medium7
Array, Segment tree+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Xorderable Array
Medium7
Bit manipulation, Hash map+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Buggy DFS
Medium7
Graph, DFS+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Diverse T-Shirts
Medium7
Graph, DFS+1
No attempts yet
Time limit
0.5s
Memory limit
2048 MB
Judgeable
Inversion Insight
Medium7
Combinatorics, Math+1
No attempts yet
Time limit
0.5s
Memory limit
2048 MB
Judgeable
Merge Elements
Medium7
Bit manipulation, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Add Test Data
Medium7
Dynamic programming, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tree Tripping
Medium7
Tree, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Cafebazaar's Applications
Medium7
Segment tree, Sorting+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Parking Theory
Medium7
Matrix, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Trivial bases
Medium7
Math, Binary search+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
EA Enigma
Medium7
Probability, Math+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Krasan Code
Medium7
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Alice, Bob and Game
Medium7
Game theory, Combinatorics
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Difficult Password
Medium7
Dynamic programming, Matrix+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Surrounding Chess Pieces
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Game with triangles
Medium7
Sorting, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Counting Is Not Fun (Easy Version)
Medium7
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Safe Zone
Medium7
Segment tree, Union-find+1
No attempts yet
Time limit
9s
Memory limit
2048 MB
Judgeable
FS's Critical Concert
Medium7
Combinatorics, Graph+1
No attempts yet
Time limit
5s
Memory limit
2048 MB
Judgeable
Bitsets
Medium7
Bit manipulation, Prefix sum+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Drawing Lines
Medium7
Geometry, Binary search+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Flow Problem
Medium7
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Random Permutation
Medium7
Dynamic programming, Recursion+1
No attempts yet
Time limit
10s
Memory limit
2048 MB
Judgeable
Good Subsegments
Medium7
Hash map, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Many Many Cycles
Medium7
Graph, DFS+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Anti-Plagiarism
Medium7
Tree, Dynamic programming+1
No attempts yet
Time limit
5s
Memory limit
2048 MB
Judgeable
Interval Addition
Medium7
Bit manipulation, Dynamic programming+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
HearthStone
Medium7
Sorting, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Planar Graph
Medium7
Geometry, Graph+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Fast Algorithm
Medium7
Graph, Shortest path+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Submissions
Medium7
Simulation, Sorting+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Collinear Arrangements
Medium7
Geometry, Hash map+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Nasty Operations
Medium7
Combinatorics, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Shoes in the Wardrobe
Medium7
Greedy, Simulation+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Sequence, Queries, and Probability 1
Medium7
Math, Probability+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
What is the most tedious part of running a contest?
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Steganography
Medium7
String matching, Prefix sum+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Score of a Sequence
Medium7
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
KSA String 2
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
DFS Order
Medium7
Dynamic programming, DFS+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Diamond Mine
Hard8
Dynamic programming, Binary search+2
No attempts yet
Time limit
0.75s
Memory limit
128 MB
Judgeable
Shadow
Hard8
Geometry, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Fence
Hard8
Brute force, Geometry+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Unicorn
Hard8
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Palindrome Sentences
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Make a Number
Hard8
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Teaching Letters
Hard8
Brute force, Backtracking+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Balancing ArtGiven wires with disk counts between n spheres, find the largest equal balance per sphere and output the fewest disks left hanging between spheres.	Medium7	GraphBinary search	No attempts yet	8s	2048 MB	Judgeable
Pascal Meets BooleGiven a 4-bit Boolean function that builds a triangle from edge 1s, answer queries for one bit in row r or the count of 1s in the first r rows.	Medium7	MathBit manipulation+1	No attempts yet	1s	2048 MB	Judgeable
Pony-less ExpressAssign each farmstead in a rooted tree a delivery day so each parent's children get news on consecutive days after it, minimizing total squared error.	Medium7	Dynamic programmingTree	No attempts yet	8s	2048 MB	Judgeable
CoversFind the minimum cost to build string T from an empty string using appends of P (free), single characters (cost 1), or deleting a suffix and then appending P.	Medium7	Dynamic programmingString matching+1	No attempts yet	1s	2048 MB	Judgeable
WEB MachineWrite a WEB machine program that sorts the white and blue balls on a wheel into a W group, an E gap, and a B group, read clockwise from the head.	Medium7	SimulationImplementation	No attempts yet	1s	2048 MB	Judgeable
Colorful QuadrantsCount the uncolored interior points where each of the four quadrants can supply one point, with all four chosen colors different.	Medium7	Prefix sumBit manipulation+1	No attempts yet	1s	2048 MB	Judgeable
Palindromic LengthGiven a lowercase string of up to 100,000 letters, find the fewest palindromic substrings it can be split into with no overlaps.	Medium7	Dynamic programmingString+1	No attempts yet	0.5s	2048 MB	Judgeable
City BikeA truck with capacity c moves bikes among n stations, each holding at most d bikes. Find the smallest possible gap between the fullest and emptiest station.	Medium7	GreedyBinary search+1	No attempts yet	2s	2048 MB	Judgeable
Finding KeysFor each key on a circular keychain, find the smallest k whose k-pattern of up and down comparisons with the next k keys no other key shares.	Medium7	StringString matching+1	No attempts yet	2s	2048 MB	Judgeable
Island MemoriesGiven n islands and m remembered zones, decide whether some tree on the islands exists where each zone is exactly the component left after removing one edge.	Medium7	TreeDivide and conquer+1	No attempts yet	3s	2048 MB	Judgeable
Virtual Reality PlayspaceCount the maximal empty rectangles in an r by c grid with obstacles whose sides are at least s and t in length, where each side touches a wall or an obstacle.	Medium7	MatrixStack+2	No attempts yet	4s	2048 MB	Judgeable
DiversityGiven two periodic integer sequences with periods n and m, compute the sum of a_i XOR b_i over the first k indices, modulo 1e9+7.	Medium7	MathNumber theory+1	No attempts yet	2s	1024 MB	Judgeable
BlackboardSplit the given positive integers into real-valued parts, keeping the sum fixed, so the largest value is at most k percent above the smallest. Find the minimum number of splits.	Medium7	MathGreedy+1	No attempts yet	6s	1024 MB	Judgeable
Connect FiveGiven five grid points, find the fewest road segments that must be refurbished so every pair is joined by a shortest axis-aligned path.	Medium7	GeometryBrute force+1	No attempts yet	2.5s	1024 MB	Judgeable
ElectricianGiven n houses and a limit k on how many times the villain's light may go off, find the fewest hours needed to identify the villain and restore every light.	Medium7	CombinatoricsBinary search+1	No attempts yet	2s	2048 MB	Judgeable
Wooden MatrixGiven a symmetric n x n distance matrix with a zero diagonal, decide whether it is the path-distance matrix of some weighted tree with positive edge lengths.	Medium7	TreeImplementation+1	No attempts yet	2s	2048 MB	Judgeable
Balls of Three ColorsCount the arrangements of r red, g green, and b blue balls in a row where no two adjacent balls share a color, modulo 998244353.	Medium7	CombinatoricsMath+1	No attempts yet	2s	2048 MB	Judgeable
Another Brick in the WallFind the fewest 1 x 3 bricks needed to build an l by h wall from 1 x 2 and 1 x 3 bricks so that no two seams line up vertically.	Medium7	Dynamic programmingBit manipulation	No attempts yet	2s	2048 MB	Judgeable
Defective ScriptGiven a ring of n servers with loads a_i, find the largest equal load reachable by running a script that cuts server i by 2 and server i-1 by 1.	Medium7	Binary searchGreedy+1	No attempts yet	2s	2048 MB	Judgeable
Eight-Shaped FiguresCount the pairs of circles that touch externally, meaning each circle lies outside the other, for n circles with integer centers and radii.	Medium7	GeometryHash map+1	No attempts yet	5s	2048 MB	Judgeable
Hanoi Towers ReloadedGiven two disk configurations on three rods, find the minimum number of moves between adjacent rods to turn the first into the second, modulo 998244353.	Medium7	RecursionMath+1	No attempts yet	2s	2048 MB	Judgeable
Longest Common SubstringCount the pairs of binary strings s (length n) and t (length m) that have w as one of their longest common substrings, modulo 998244353.	Medium7	Dynamic programmingString matching+1	No attempts yet	5s	2048 MB	Judgeable
Stacking BlocksGiven target block counts a_i for N cells, find the fewest interval-stacking operations needed and the minimum total squared-length cost among solutions with that count.	Medium7	GreedyHeap+1	No attempts yet	1s	1024 MB	Judgeable
Making OkonomiyakiTwo doughs and one meat piece sit on a pan of N cells; find the fewest flips that move a dough with stuck meat to the target cell, or report -1.	Medium7	SimulationMath+1	No attempts yet	1s	1024 MB	Judgeable
DeliveryFind the earliest minute Gunwoo can reach E from S, moving or staying each minute while avoiding the intersection the supervisor watches.	Medium7	BFSGraph+1	No attempts yet	1s	1024 MB	Judgeable
Parenthesis String EditorSimulate cursor edits on a parenthesis string and XOR each step index into C whenever the text is balanced.	Medium7	Segment treeLinked list+1	No attempts yet	3s	2048 MB	Judgeable
Rectangular Jigsaw PuzzleOrder N pieces, each made of H stacked intervals and never rotated or flipped, so they tile a rectangle of height H with no gaps or overlaps.	Medium7	SortingHash map+1	No attempts yet	2s	2048 MB	Judgeable
Subway RideGiven N axis-parallel subway segments, find the sum of minimum transfer counts d(i,j) times i times j over all pairs, modulo 1000000007.	Medium7	GraphBFS+2	No attempts yet	8s	1024 MB	Judgeable
Dave's WorryAssign one of 5 species to each cell of an N by M grid so that no two side-adjacent cells match and each interior cell touches all four other species.	Medium7	MatrixImplementation+1	No attempts yet	2s	1024 MB	Judgeable
A Tree Problem Without TreesCut N^2 bulbs with cyclic colors into the fewest contiguous pieces that fill an N by N square where each cell's color is (i+j-1) mod N, then output the pieces.	Medium7	MathImplementation+1	No attempts yet	2s	1024 MB	Judgeable
Mixing SolutionsGiven containers with uncertain YY amounts, choose portions totaling s mg so the worst-case error from the target YY amount is minimized.	Medium7	GreedyBinary search+1	No attempts yet	2s	2048 MB	Judgeable
Peculiar ProtocolGiven banknotes and integers d and r, find the maximum total multiplier k when repeatedly removing a contiguous block whose sum is k*d+r.	Medium7	Dynamic programmingPrefix sum+1	No attempts yet	2s	2048 MB	Judgeable
Level DesignPermute the values 1 to N over rooms 1 to N to minimize the largest non-adjacent subset sum, then print the permutation and that minimum.	Medium7	GreedyDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Divisibility TestGiven a base b and modulus n, find the smallest group size k for which a last-k-digits, group-sum, or group-alternating-sum divisibility test exists.	Medium7	Number theoryMath+1	No attempts yet	3s	2048 MB	Judgeable
Evaluate It and Back AgainGiven p and q, print an arithmetic expression of at most 1000 characters that evaluates to p read left-to-right and to q read right-to-left.	Medium7	MathImplementation	No attempts yet	3s	2048 MB	Judgeable
Adrenaline RushGiven the final order of cars, find the longest sequence of overtakes in which each pair of cars overtakes each other at most twice, and print that sequence.	Medium7	ArraySorting+1	No attempts yet	3s	2048 MB	Judgeable
Incompetent Delivery GuyFind the largest d so an orc making up to d random moves is still guaranteed to reach tower n from tower 1, given the best pointer placement.	Medium7	Shortest pathGraph+1	No attempts yet	3s	2048 MB	Judgeable
Judicious WatchingFor each query time t, find how many episodes, watched in order, can finish before t while every homework task still meets its deadline.	Medium7	GreedyBinary search+2	No attempts yet	3s	2048 MB	Judgeable
Knowns and UnknownsGiven two professor orders and their partial visit lists, decide for each student whether they attended, skipped, or cannot be determined.	Medium7	ArrayString matching+1	No attempts yet	3s	2048 MB	Judgeable
All Pairs SimilarityGiven N bitstrings of length K, output for each cow the sum of its Jaccard similarities with all N bitstrings, including its own, modulo 10^9+7.	Medium7	Bit manipulationDynamic programming+1	No attempts yet	2s	2048 MB	Judgeable
It's Mooin' TimeGiven an M/O string with per-position flip costs, find the minimum cost to contain at least k moos of length L, for every k.	Medium7	GreedyString+1	No attempts yet	3s	2048 MB	Judgeable
CowdependenceFor each x from 1 to N, find the fewest groups of same-label cows where every two cows in a group are at most x positions apart.	Medium7	GreedyHash map+1	No attempts yet	2s	2048 MB	Judgeable
Cake GameGiven an even row of cakes, Bessie merges adjacent cakes and Elsie takes from either end; find how much each cow eats under optimal play.	Medium7	Game theoryPrefix sum	No attempts yet	2s	2048 MB	Judgeable
Harmonic HideoutPick exactly N of K appliance types at minimum total cost, with at least M picks from each person's preferred set, where the two sets may overlap.	Medium7	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
Dormitory Lights OutGiven rooms with on/off states, find the fewest rooms left on, where turning room i off requires the count of earlier off rooms to be in set A.	Medium7	Dynamic programmingBit manipulation	No attempts yet	1s	1024 MB	Judgeable
SSHS ProtocolSplit a binary string into consecutive even-length pieces so that the sum of each piece's two-half binary product is minimized.	Medium7	Dynamic programmingMath	No attempts yet	2s	1024 MB	Judgeable
Independent Set (Sum)Given a tree, sum over all non-empty independent node sets the set size times the edges needed to connect it, modulo 998244353.	Medium7	TreeDynamic programming+1	No attempts yet	1s	2048 MB	Judgeable
Reverse SevererGiven a string S and several queries T, decide whether each T can be formed by splitting S into pieces and concatenating them in reverse piece order.	Medium7	StringDynamic programming+1	No attempts yet	1s	2048 MB	Judgeable
Interesting CoupleGiven N points in the plane with Manhattan distance, find the smallest p(i, j) among pairs whose distance d(i, j) is no more than p(i, j).	Medium7	GeometrySorting+1	No attempts yet	2s	2048 MB	Judgeable
Numbers CombinationCount integer sequences with 1 <= A_i <= i and sum K, modulo 998244353, for N up to 100000 and K up to 200000.	Medium7	CombinatoricsDivide and conquer+1	No attempts yet	2s	2048 MB	Judgeable
The Journey of the KingGiven a dictionary, match Anda's cards with yours whenever a concatenation of the two words in either order is a dictionary word, maximizing the matches.	Medium7	String matchingGraph	No attempts yet	1s	2048 MB	Judgeable
Alchembit ExamGiven N potions with values A_i, repeatedly merge a contiguous range to score the bitwise AND of its values; find the maximum total score.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	1s	2048 MB	Judgeable
Microwavable SubsequenceGiven an array, find the longest subsequence using only x and y with no equal adjacent elements, and sum these lengths over all pairs x < y up to M.	Medium7	ArraySegment tree+1	No attempts yet	1s	2048 MB	Judgeable
Xorderable ArrayCount the pairs of values from X such that array A can be rearranged so that every ordered pair of positions satisfies two XOR inequalities.	Medium7	Bit manipulationHash map+1	No attempts yet	1s	2048 MB	Judgeable
Buggy DFSGiven K, build a simple undirected graph on which the buggy DFS counter returns K, or report -1 -1 if no such graph exists.	Medium7	GraphDFS+1	No attempts yet	1s	2048 MB	Judgeable
Diverse T-ShirtsGiven an N by N conflict matrix, find the most T-shirt models you can pick so that no two share a text color or a background color.	Medium7	GraphDFS+1	No attempts yet	0.5s	2048 MB	Judgeable
Inversion InsightGiven N and K, output the permutation of 1 to N that has rank K when all permutations are sorted by inversion count, then lexicographically.	Medium7	CombinatoricsMath+1	No attempts yet	0.5s	2048 MB	Judgeable
Merge ElementsGiven an array, merge adjacent elements with OR exactly K times, then find the maximum AND of the remaining N-K elements.	Medium7	Bit manipulationGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Add Test DataGiven M, print a maze of size at most 60 where the end is reachable but the number of paths from start to end is a multiple of M.	Medium7	Dynamic programmingMath+1	No attempts yet	1s	1024 MB	Judgeable
Tree TrippingGiven a tree and queries that each list k nodes, find the node whose total distance to the listed nodes is smallest and print that sum.	Medium7	TreeSorting+1	No attempts yet	2s	1024 MB	Judgeable
Cafebazaar's ApplicationsFor each application, find the minimum rank it can reach in a contiguous subsequence that contains it and at least k applications.	Medium7	Segment treeSorting+1	No attempts yet	1s	2048 MB	Judgeable
Parking TheoryCount the subgrids of a full n by m parking lot where every car can reach its space from its row or column entrance without turning or passing another car.	Medium7	MatrixTwo pointers+1	No attempts yet	1s	2048 MB	Judgeable
Trivial basesGiven A, B, and C as base-10 digit lists, find a base b below 10^19 where A times B equals C, or report impossible.	Medium7	MathBinary search+1	No attempts yet	3s	2048 MB	Judgeable
EA EnigmaFind the expected number of guesses to find a hidden length-N word over K letters when each guess reports which positions match, modulo 1e9+7.	Medium7	ProbabilityMath+1	No attempts yet	1s	2048 MB	Judgeable
Krasan CodeGiven 26 code words, one per letter, decide whether two different original words can translate to the same string (Ruzan) or never do (Krasan).	Medium7	StringString matching+1	No attempts yet	2s	2048 MB	Judgeable
Alice, Bob and GameGiven Alice's 26 cards in a simplified Seven card game, decide whether Alice wins, Bob wins, or the game is a draw under optimal play.	Medium7	Game theoryCombinatorics	No attempts yet	1s	2048 MB	Judgeable
Difficult PasswordCount passwords of length L to R that contain a digit and a letter, have no A equal characters in a row, and have no B-long ascending or descending run, modulo 1e9+7.	Medium7	Dynamic programmingMatrix+1	No attempts yet	3s	2048 MB	Judgeable
Surrounding Chess PiecesCount the ways to place white pieces on an 8x8 board so that no two black pieces are connected through empty squares.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	2s	2048 MB	Judgeable
Game with trianglesPoints lie on the lines y=0 and y=2. For each k, find the maximum total area of k disjoint triangles, plus the largest possible k.	Medium7	SortingPrefix sum+2	No attempts yet	2s	2048 MB	Judgeable
Counting Is Not Fun (Easy Version)After each clue fixing a good pair, count the balanced bracket sequences with n good pairs that contain all clues so far, modulo 998244353.	Medium7	Dynamic programmingCombinatorics+1	No attempts yet	3s	2048 MB	Judgeable
Safe ZoneGiven N axis-aligned rectangles, group them into alliances where rectangles connect through shared points, and report the groups.	Medium7	Segment treeUnion-find+1	No attempts yet	9s	2048 MB	Judgeable
FS's Critical ConcertSum the number of critical edges (bridges) over all labeled simple graphs on n vertices, modulo 998244353.	Medium7	CombinatoricsGraph+1	No attempts yet	5s	2048 MB	Judgeable
BitsetsCount the columns where the bits in rows l through r are all equal, with each query's l and r generated online from the previous answers.	Medium7	Bit manipulationPrefix sum+1	No attempts yet	3s	2048 MB	Judgeable
Drawing LinesReproduce a hidden segment with endpoints in [-10000, 10000] and length at least 100, using interactive guesses scored by endpoint distance within 25000 tries.	Medium7	GeometryBinary search+1	No attempts yet	1s	2048 MB	Judgeable
Flow ProblemGiven a 2 x n grid with a cyclic flow of unknown direction, find a sequence of moves that drops a token from the left and from the right within the move limit.	Medium7	SimulationImplementation+1	No attempts yet	2s	2048 MB	Judgeable
Random PermutationCount the distinct sequences of minimums obtainable from a random permutation by removing one end element each step, modulo 998244353.	Medium7	Dynamic programmingRecursion+1	No attempts yet	10s	2048 MB	Judgeable
Good SubsegmentsFor each k, count subsegments of length at least 2k whose first k elements are equal, whose last k elements are equal, and whose two end values match.	Medium7	Hash mapPrefix sum+1	No attempts yet	2s	2048 MB	Judgeable
Many Many CyclesGiven a weighted undirected graph, find the largest d that divides the length of every simple cycle, or 0 if no such d exists.	Medium7	GraphDFS+1	No attempts yet	2s	2048 MB	Judgeable
Anti-PlagiarismFor each pair of trees, decide whether the second tree is a subgraph of the first, meaning the first can be obtained by extending the second.	Medium7	TreeDynamic programming+1	No attempts yet	5s	2048 MB	Judgeable
Interval AdditionGiven an array of up to 23 values, find the fewest operations that add a real number to a contiguous interval to make every element zero.	Medium7	Bit manipulationDynamic programming+1	No attempts yet	4s	2048 MB	Judgeable
HearthStoneGiven n minion health values, find the fewest unit changes so that one Defile cast chains into killing every minion.	Medium7	SortingDynamic programming+1	No attempts yet	1s	2048 MB	Judgeable
Planar GraphFor each segment of a plane graph, decide whether some source point can reach its midpoint by a curve that crosses no other segment.	Medium7	GeometryGraph+1	No attempts yet	1s	2048 MB	Judgeable
Fast AlgorithmGiven a weakly connected directed graph with at most 1500 extra edges beyond a spanning tree, find the minimum total weight of a directed cycle, or report -1.	Medium7	GraphShortest path+1	No attempts yet	2s	2048 MB	Judgeable
SubmissionsGiven a log of ICPC submissions, find every team that can earn a gold medal after flipping the status of at most one submission.	Medium7	SimulationSorting+1	No attempts yet	2s	2048 MB	Judgeable
Collinear ArrangementsGiven a convex polygon, count vertex pairs collinear with a query point, or count vertices on the line through two query points.	Medium7	GeometryHash map+2	No attempts yet	2s	2048 MB	Judgeable
Nasty OperationsApply a sequence of prefix XOR, suffix XOR, and their inverse operations to an array, then print the final array.	Medium7	CombinatoricsBit manipulation+1	No attempts yet	1s	2048 MB	Judgeable
Shoes in the WardrobeGiven n shoe pairs in a wardrobe, a hallway of m slots, and q requests, find the minimum total retrieval time.	Medium7	GreedySimulation+1	No attempts yet	2s	2048 MB	Judgeable
Sequence, Queries, and Probability 1Given a sequence and M random operations that each either scale the prefix weights or multiply one element, find the expected ratio of final to initial sum (S) or product (P) modulo 1e9+7.	Medium7	MathProbability+1	No attempts yet	1s	1024 MB	Judgeable
What is the most tedious part of running a contest?Build S by typing single characters or pasting one copied prefix of S, minimizing typed characters first and total actions second.	Medium7	Dynamic programmingString matching+1	No attempts yet	1s	1024 MB	Judgeable
SteganographyGiven point-coloring updates and queries, check whether two equal-sized rectangles on the lattice have identical color patterns.	Medium7	String matchingPrefix sum+1	No attempts yet	4s	1024 MB	Judgeable
Score of a SequenceGiven bounds X and Y, choose x and y so that the sequence A_k = A_{k-2} - A_{k-1} keeps all terms positive for as long as possible.	Medium7	MathNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
KSA String 2Given a string of K, S, and A, find the minimum number of remove or move-to-front operations that turn it into the longest string repeating KSA.	Medium7	StringDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
DFS OrderGiven the cost to add or remove each edge, find the minimum total cost so that vertices 1 to N form a valid DFS order starting from vertex 1.	Medium7	Dynamic programmingDFS+2	No attempts yet	2s	2048 MB	Judgeable
Diamond MineGiven an R by C grid of 0s and 1s, find the largest size of a diamond shape (a 45-degree rotated square outline) formed entirely of 1s.	Hard8	Dynamic programmingBinary search+2	No attempts yet	0.75s	128 MB	Judgeable
ShadowGiven a grid room with one point light source and wall cells blocking light, compute the total area of empty cells lying in shadow.	Hard8	GeometrySimulation+2	No attempts yet	2s	128 MB	Judgeable
FenceCut down some trees (each gives a length of fencing) so that the remaining trees fit inside an axis-aligned rectangle whose perimeter the cut trees can pay for, minimizing the number cut.	Hard8	Brute forceGeometry+2	No attempts yet	2s	128 MB	Judgeable
UnicornCount the number of paths on an N by M letter grid where a chess unicorn piece spells out a given word, modulo 1e9+7.	Hard8	Dynamic programmingPrefix sum+2	No attempts yet	2s	128 MB	Judgeable
Palindrome SentencesGiven up to 13 distinct words, count ordered arrangements of a subset of them whose concatenation without spaces forms a palindrome.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	2s	128 MB	Judgeable
Make a NumberStarting from 1, find the minimum number of +1, -1, and power operations needed to reach a target N up to 10^18.	Hard8	Number theoryMath+2	No attempts yet	2s	128 MB	Judgeable
Teaching LettersGiven N Antarctic words that all begin with anta and end with tica, pick K letters to maximize how many words are fully readable.	Hard8	Brute forceBacktracking+1	No attempts yet	1s	128 MB	Judgeable