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 results29,077 problems

Planar Drawing
Medium7
Graph, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Selecting the capital
Medium7
Graph, Minimum spanning tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Block Game
Medium7
Game theory, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Millionaire Madness
Medium7
Graph, Binary search+2
No attempts yet
Time limit
20s
Memory limit
512 MB
Judgeable
Translators' Dinner
Medium7
Graph, Greedy+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Card Hand Sorting
Medium7
Sorting, Brute force+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Jumping Worm
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Glass Bridge
Medium7
Array, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Organization
Medium7
Binary search, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dungeon
Medium7
BFS, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Meeting at the Agreed Minute
Medium7
Matrix, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Jump
Medium7
Dynamic programming, Graph+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pry Sequence Transformation
Medium7
Dynamic programming, String
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Square Cutting
Medium7
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Slowest Speed Past the Traps
Medium7
Binary search, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Inverse RMQ
Medium7
Greedy, Intervals+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Algorithm study membership
Medium7
Dynamic programming, Tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Travel
Medium7
Graph, Matrix+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Partition into segments 2
Medium7
Binary search, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Distribution Center
Medium7
Graph, Union-find+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Animal Companion in Maze
Medium7
Graph, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Skinny Polygon
Medium7
Math, Number theory+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Pyramid Sequences
Medium7
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Stair Climbing Workout
Medium7
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Factorials and a recurrence
Medium7
Number theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Metal Is Life
Medium7
Combinatorics, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Contiguous Subsequence XOR
Medium7
Bit manipulation, Trie+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Stephen Cook
Medium7
Game theory, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Jack Edmonds
Medium7
Minimum spanning tree, Graph+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Marble Escape
Medium7
BFS, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Airport Logistics
Medium7
Shortest path, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bridge Automation
Medium7
Dynamic programming, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Charles in Charge
Medium7
Shortest path, Binary search+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Endless Turning
Medium7
Geometry, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
CodeCoder vs TopForces
Medium7
Graph, Sorting+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Easy Reading
Medium7
String matching, Hash map+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Gangsters in Central City
Medium7
Tree, Greedy+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Integral Polygons
Medium7
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Path Magic
Medium7
Math, DFS+1
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
The Witch's Puzzle
Medium7
Trie, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Sand Tiger Shark
Medium7
Simulation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Octopus
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Midsummer Night's Dream
Medium7
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Largest XOR sum subarray
Medium7
Bit manipulation, Trie+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Chameleon Substring
Medium7
String matching, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tree and Queries 2
Medium7
Tree, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
First black vertex on a path
Medium7
Tree, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Maximum weight in a monochromatic component
Medium7
Tree, Segment tree+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Build a Boat
Medium7
Geometry, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Gondolas
Medium7
Dynamic programming, Sorting+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Buying Flowers
Medium7
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Birthday Party
Medium7
Dynamic programming, Number theory+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Bracket substring queries
Medium7
Prefix sum, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
K-th Substring
Medium7
String, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 4
Medium7
Array, Prefix sum+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Distinct values in a range
Medium7
Array, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Increasing subsequences of length K
Medium7
Dynamic programming, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Distinct Increasing Subsequences of Length K
Medium7
Dynamic programming, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
House Rental
Medium7
Binary search, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Meteorites
Medium7
Geometry, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Power Supply
Medium7
Tree, DFS+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Prefix and Suffix
Medium7
String matching, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Containers
Medium7
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hex statistics
Medium7
Math, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Merging trees
Medium7
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Curious Guardians
Medium7
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Palindromic Subsequence
Medium7
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Convex polygon quadrangulation
Medium7
Dynamic programming, Geometry
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Folding Machine
Medium7
Divide and conquer, Recursion+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Trucks
Medium7
Graph, Minimum spanning tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Countries at War
Medium7
Shortest path, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Perfect Choir
Medium7
Math, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Space Elevator
Medium7
Binary search, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Same word
Medium7
String, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
MegaDamas
Medium7
DFS, Backtracking+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
SMS Championship
Medium7
Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Man, Elephant, and Rat
Medium7
Segment tree, Linked list+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
One-Dimensional Tic-Tac-Toe
Medium7
Game theory, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Babel
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Club Hall
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Critical Route
Medium7
Graph, DFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tecle & Some
Medium7
DFS, Backtracking+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Square Root
Medium7
Math, Binary search+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Strings and Queries
Medium7
String, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
3D Queries
Medium7
Math, Brute force+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Random Sort 2
Medium7
Probability, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Buggy Robot
Medium7
Dynamic programming, BFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Illumination
Medium7
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Water Supply Upgrades
Medium7
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Perfect Sets
Medium7
Bit manipulation, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
RNG 2
Medium7
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Distinct AND values of subsequences
Medium7
Bit manipulation, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dropped Water Bottle
Medium7
Shortest path, Graph
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String Hashing
Medium7
Dynamic programming, Combinatorics
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Resistance
Medium7
Probability, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Butterfly
Medium7
Intervals, Dynamic programming+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Full Text Search
Medium7
String, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Mysterious Maze
Medium7
BFS, Simulation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Dungeon Quest II
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Road Construction
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Planar DrawingCheck a proposed certificate: verify an embedding's Euler formula or validate a subgraph as a subdivision of K5 or K3,3.	Medium7	GraphImplementation+2	No attempts yet	1s	512 MB	Judgeable
Selecting the capitalGiven a connected multigraph where city i links to city R[i], merge adjacent cities the fewest times so that some city lies on every simple path between any two cities.	Medium7	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Block GameTwo stacks of blocks; each move removes a positive multiple of the smaller stack from the larger, and whoever empties a stack wins. Decide the winner with optimal play.	Medium7	Game theoryMath	No attempts yet	5s	512 MB	Judgeable
Millionaire MadnessGiven a grid of stack heights, find the smallest ladder length L such that a path from the top-left cell to the bottom-right cell only steps up at most L at a time.	Medium7	GraphBinary search+2	No attempts yet	20s	512 MB	Judgeable
Translators' DinnerPair all translators so that each pair shares a language, printing the lexicographically smallest pairing or 'impossible'.	Medium7	GraphGreedy+1	No attempts yet	5s	512 MB	Judgeable
Card Hand SortingGiven a hand of up to 52 distinct cards, find the minimum number of remove-and-reinsert moves needed so each suit forms a block with ranks sorted ascending or descending.	Medium7	SortingBrute force+1	No attempts yet	1s	512 MB	Judgeable
Jumping WormFind the shortest time for a worm to travel from the base of tree 1 to the top of tree N, where each climb, jump, and gravity rest costs one second, with a free move when standing on a tree top.	Medium7	GraphShortest path+2	No attempts yet	1s	512 MB	Judgeable
Glass BridgeGiven N and values a_i, count pairs i < j with a_i > a_j.	Medium7	ArrayDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
OrganizationPartition N points into k nonempty teams so that the minimum Manhattan distance between points in different teams is as large as possible.	Medium7	Binary searchSorting+1	No attempts yet	2s	512 MB	Judgeable
DungeonA hero moves on a small grid while rectangular traps slide and freeze at the walls; find the earliest time to reach the exit without ever standing on a trapped cell.	Medium7	BFSSimulation+2	No attempts yet	2s	512 MB	Judgeable
Meeting at the Agreed MinuteCount pairs of walks of length T from nodes 1 and N that meet only at minute T, modulo 9973.	Medium7	MatrixDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
JumpTiles on a grid give energy when visited; jump only right or up at cost B, and maximize the energy left on reaching tile N.	Medium7	Dynamic programmingGraph+1	No attempts yet	2s	512 MB	Judgeable
Pry Sequence TransformationFind the minimum edit distance between strings A and B under weighted insert, delete, and replace costs, or print TOSS if it exceeds budget K.	Medium7	Dynamic programmingString	No attempts yet	2s	512 MB	Judgeable
Square CuttingGiven only the counts of squares cut per turn, recover the smallest possible long side L of the original rectangle.	Medium7	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
The Slowest Speed Past the TrapsFind the minimum constant running speed that lets Fred cross every trap during an inactive window, or report IMPOSSIBLE.	Medium7	Binary searchMath+1	No attempts yet	2s	512 MB	Judgeable
Inverse RMQGiven query intervals and their maximum answers over a hidden permutation of 1..N, decide whether some permutation of 1..N satisfies all queries.	Medium7	GreedyIntervals+1	No attempts yet	2s	512 MB	Judgeable
Algorithm study membershipChoose two algorithm types for each of N members in a mentor tree so every team (a node plus its children) can assign distinct types to its members, minimizing total teaching cost.	Medium7	Dynamic programmingTree+2	No attempts yet	2s	512 MB	Judgeable
TravelDecide whether one can travel from city 1 to city N using exactly T minutes of total road-crossing time, revisiting cities and roads freely.	Medium7	GraphMatrix+1	No attempts yet	2s	512 MB	Judgeable
Partition into segments 2Split the array into at most M contiguous segments, minimizing the maximum difference between the largest and smallest value within any one segment.	Medium7	Binary searchDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Distribution CenterGiven conveyor lanes and connector arms between adjacent lanes, count for each lane how many starting lanes can reach it.	Medium7	GraphUnion-find+1	No attempts yet	3s	512 MB	Judgeable
Animal Companion in MazeGiven a directed room graph, find the longest walk where George never immediately reverses the door he just used, or report Infinite if he can walk forever.	Medium7	GraphSimulation+1	No attempts yet	2s	512 MB	Judgeable
Skinny PolygonFor each pair (xbb, ybb), output four vertices of the prescribed skinny polygon: Q1 built from the modular inverse of ybb/g mod xbb/g when 2g <= p+q, otherwise Q2.	Medium7	MathNumber theory+2	No attempts yet	3s	512 MB	Judgeable
Pyramid SequencesGiven heights N and M of two repeating pyramid sequences, count the distinct ordered pairs (A[i], B[i]) that appear.	Medium7	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Stair Climbing WorkoutCount length-N balanced U/D walk strings (never going below 0, ending at 0) that contain a given piece as a contiguous substring.	Medium7	Dynamic programmingCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Factorials and a recurrenceGiven N and K, compute the number of divisors of S(N,K), where S follows the given recurrence, modulo 1,000,000,009.	Medium7	Number theoryDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Metal Is LifeCount permutations of N distinct strings that satisfy up to 8 prefix constraints between fixed positions, modulo 1e9+7.	Medium7	CombinatoricsBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Contiguous Subsequence XORCount contiguous subsequences of the given sequence whose bitwise XOR is less than K.	Medium7	Bit manipulationTrie+1	No attempts yet	1s	512 MB	Judgeable
Stephen CookTwo players alternately assign truth values to variables of a boolean formula; Cook moves first and wins if the formula ends true. Decide the winner under optimal play.	Medium7	Game theoryDynamic programming+2	No attempts yet	3s	256 MB	Judgeable
Jack EdmondsChoose at most n-1 Manhattan-distance roads so the round trip from the origin visiting all points (reusing edges freely) is shortest.	Medium7	Minimum spanning treeGraph+1	No attempts yet	2s	256 MB	Judgeable
Marble EscapeA board holds a red marble, a blue marble and one hole; tilting slides both marbles at once, and you must decide whether the red marble can drop into the hole within 10 tilts without the blue marble falling in.	Medium7	BFSSimulation+1	No attempts yet	2s	512 MB	Judgeable
Airport LogisticsFind the minimum travel time from A to B when moving at speed 1 m/s on the floor and 2 m/s along straight conveyor segments that can be entered or left at any point.	Medium7	Shortest pathGeometry+2	No attempts yet	2s	512 MB	Judgeable
Bridge AutomationGiven sorted boat arrival times, schedule bridge raises and lowers so no boat waits over 1800 seconds while minimizing total road closure time.	Medium7	Dynamic programmingGreedy+1	No attempts yet	2s	512 MB	Judgeable
Charles in ChargeAmong all routes from city 1 to city N whose length is within X percent of the shortest route, minimize the longest single highway segment on the route.	Medium7	Shortest pathBinary search+1	No attempts yet	2s	512 MB	Judgeable
Endless TurningSimulate a scooter rider who turns right at every intersection, and report her road after N turns or when she exits the city.	Medium7	GeometrySimulation+1	No attempts yet	2s	512 MB	Judgeable
CodeCoder vs TopForcesEach citizen reaches another through a chain of pairwise wins on at least one of two rating sites; count reachable citizens from each node.	Medium7	GraphSorting+2	No attempts yet	2s	256 MB	Judgeable
Easy ReadingGiven a book text and a picture of painted cells, find the shortest prefix-contiguous text segment whose pen strokes draw exactly that picture up to translation.	Medium7	String matchingHash map+1	No attempts yet	2s	256 MB	Judgeable
Gangsters in Central CityOn a rooted tree, after each update marking a leaf as gangster-held, report the minimum pipes to clog and the fewest innocent houses left dry.	Medium7	TreeGreedy+1	No attempts yet	2s	256 MB	Judgeable
Integral PolygonsCount the diagonals of a convex polygon that split it into two pieces of integer area, given integer vertex coordinates.	Medium7	GeometryMath+2	No attempts yet	2s	256 MB	Judgeable
Path MagicFind the simple path in a tree minimizing (product of node values)/(path length), and output the reduced fraction.	Medium7	MathDFS+1	No attempts yet	4s	256 MB	Judgeable
The Witch's PuzzleGiven N words, permute the letters of each word independently and find the minimum number of nodes in the prefix tree (trie) of the resulting set.	Medium7	TrieDynamic programming+2	No attempts yet	2s	64 MB	Judgeable
Sand Tiger SharkSimulate a daily cannibalism process where each embryo eats the largest living embryo below it, and find the latest day embryo m can survive by choosing its meals.	Medium7	SimulationGreedy+2	No attempts yet	2s	512 MB	Judgeable
OctopusAn octopus walks a graph starting with no protection, collects tools to raise its shield, and each visit to a predator location risks being eaten with probability max(0, p - h); find the route from s to t with the highest survival probability.	Medium7	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
A Midsummer Night's DreamSimulate sightings and potion timings to determine who each dosed person first sees, then count mutual pairs.	Medium7	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Largest XOR sum subarrayGiven a sequence, find the maximum XOR value over all contiguous subarrays of length at least one.	Medium7	Bit manipulationTrie+2	No attempts yet	10s	512 MB	Judgeable
Chameleon SubstringGiven a string S, find the longest substring that is both a prefix and a suffix of S and also appears somewhere strictly inside S.	Medium7	String matchingString+1	No attempts yet	2s	512 MB	Judgeable
Tree and Queries 2Answer path-cost and k-th-vertex queries on a weighted tree with up to 100,000 nodes and queries.	Medium7	TreeBinary search+2	No attempts yet	2s	512 MB	Judgeable
First black vertex on a pathFlip vertex colors and, along the root-to-v path, report the first black vertex encountered from the root.	Medium7	TreeSegment tree+1	No attempts yet	2s	512 MB	Judgeable
Maximum weight in a monochromatic componentOn a colored tree, handle color flips, weight updates, and queries for the maximum weight in the monochromatic component containing a vertex.	Medium7	TreeSegment tree+1	No attempts yet	2s	512 MB	Judgeable
Build a BoatSplit a simple polygon into the largest number of equal-area vertical sections, each of area at least C, and print the bulkhead x-coordinates.	Medium7	GeometryPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
GondolasPlace G gondolas at integer offsets on a loop of period 2T to minimize the total wait of N skiers, where each skier boards the first departure at or after their arrival.	Medium7	Dynamic programmingSorting+2	No attempts yet	5s	512 MB	Judgeable
Buying FlowersCount integer sequences x_i with 0 <= x_i <= f_i summing to S, where N <= 20 and S up to 1e14.	Medium7	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Birthday PartyCount ordered tuples of f positive integers summing to n whose greatest common divisor is 1, modulo 1e9+7, for up to 100000 queries.	Medium7	Dynamic programmingNumber theory+2	No attempts yet	5s	512 MB	Judgeable
Bracket substring queriesFor each query substring, find the length of the longest balanced bracket subsequence within it.	Medium7	Prefix sumString+2	No attempts yet	2s	512 MB	Judgeable
K-th SubstringSort every substring of S lexicographically and print the K-th one, or -1 if there are fewer than K substrings.	Medium7	StringSorting+1	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 4For each query range [l,r], find the maximum distance between two positions in the range that hold the same value.	Medium7	ArrayPrefix sum+2	No attempts yet	4s	512 MB	Judgeable
Distinct values in a rangeGiven a static array and many range queries, report how many distinct values occur in each subarray.	Medium7	ArraySorting+2	No attempts yet	2s	512 MB	Judgeable
Increasing subsequences of length KCount length-K index subsequences whose values are strictly increasing, modulo 5,000,000.	Medium7	Dynamic programmingSegment tree+2	No attempts yet	2s	512 MB	Judgeable
Distinct Increasing Subsequences of Length KCount the distinct value sequences of length K that appear as increasing subsequences of the given array, modulo 5000000.	Medium7	Dynamic programmingSorting+1	No attempts yet	2s	512 MB	Judgeable
House RentalGiven facilities of k types on a line, find the integer location minimizing the largest distance to the nearest facility of each type, smallest such location on ties.	Medium7	Binary searchSorting+1	No attempts yet	2s	512 MB	Judgeable
MeteoritesGiven non-overlapping skyline rectangles and falling point meteorites with integer direction vectors, report the building each ray hits first or 0 if none.	Medium7	GeometryBinary search+2	No attempts yet	1s	512 MB	Judgeable
Power SupplyGiven a tree whose vertices are supplies or demands and whose edges have capacities, decide if deleting some edges yields subtrees each holding exactly one supply that meets its demands.	Medium7	TreeDFS+1	No attempts yet	1s	512 MB	Judgeable
Prefix and SuffixFor each prefix of S that is also a suffix, output its length and how many times it occurs as a substring.	Medium7	String matchingPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
ContainersPlace eight weights into a 2x4 grid; swapping two adjacent cells costs the sum of the two weights, and you must reach the target arrangement at minimum total cost.	Medium7	GraphBFS+2	No attempts yet	1s	512 MB	Judgeable
Hex statisticsFor every digit of a hexadecimal string S, find the smallest, largest, and sum over all 16! deletion orders of the total of the 16 prefix sums.	Medium7	MathCombinatorics+1	No attempts yet	1s	512 MB	Judgeable
Merging treesGiven a left-handed and a right-handed ternary tree, find the minimum number of vertices in a ternary tree that is a superposition of both.	Medium7	TreeDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
Curious GuardiansCount labeled trees on N cities where every vertex has degree at most K.	Medium7	CombinatoricsDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
Palindromic SubsequenceGiven a string and marked positions, find a palindromic subsequence covering the most marked positions, and report the length of the longest such one.	Medium7	Dynamic programmingString	No attempts yet	1s	512 MB	Judgeable
Convex polygon quadrangulationSplit a convex 2N-gon into N-1 quadrilaterals with diagonal cuts and find the minimum total cut length.	Medium7	Dynamic programmingGeometry	No attempts yet	2s	512 MB	Judgeable
Folding MachineGiven two integer tapes, decide whether folding one tape can ever produce the other.	Medium7	Divide and conquerRecursion+2	No attempts yet	2s	512 MB	Judgeable
TrucksGiven an undirected weighted graph, answer S queries asking for the maximum bottleneck (minimum edge on the best path) between two vertices.	Medium7	GraphMinimum spanning tree+2	No attempts yet	2s	512 MB	Judgeable
Countries at WarGiven directed weighted edges between cities, treat mutually reachable cities as zero-cost (same country), then answer shortest path queries.	Medium7	Shortest pathGraph+2	No attempts yet	2s	512 MB	Judgeable
Perfect ChoirGiven sorted starting notes for N singers, each measure moves one singer up and another down by one; find the minimum measures until all notes are equal, or -1 if impossible.	Medium7	MathGreedy+2	No attempts yet	2s	512 MB	Judgeable
Space ElevatorFind the number on the N-th floor when floor numbers skip any containing the digit 4 or the substring 13, for N up to 10^18.	Medium7	Binary searchMath+2	No attempts yet	2s	512 MB	Judgeable
Same wordGiven two sets of binary words, decide whether some nonempty concatenation of words from the first set equals some nonempty concatenation from the second.	Medium7	StringBFS+2	No attempts yet	2s	512 MB	Judgeable
MegaDamasGiven a checkers-like board with your and opponent pieces, find the maximum number of opponent pieces one capture move can take.	Medium7	DFSBacktracking+2	No attempts yet	2s	512 MB	Judgeable
SMS ChampionshipGiven a keypad where letters need repeated presses and # separates same-key letters, find the minimum typing time with two alternating thumbs.	Medium7	Dynamic programming	No attempts yet	2s	512 MB	Judgeable
Man, Elephant, and RatMaintain a line of players cycling through three signs; range updates advance each player to the next sign, and range queries report counts of each sign.	Medium7	Segment treeLinked list+1	No attempts yet	2s	512 MB	Judgeable
One-Dimensional Tic-Tac-ToeGiven a 1D tic-tac-toe board where both players place the same mark, decide if the player to move can force three consecutive crosses.	Medium7	Game theoryGreedy+1	No attempts yet	2s	512 MB	Judgeable
BabelGiven M words, each shared by two languages, find the shortest word sequence from an origin to a destination language where adjacent words differ in first letter.	Medium7	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
The Club HallGiven plank lengths and a rectangular hall, decide whether each row can be spanned by one or two planks and find the fewest planks that cover the floor.	Medium7	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Critical RouteGiven a directed multigraph where every city reaches the capital, list every road segment whose removal disconnects some city from the capital.	Medium7	GraphDFS+1	No attempts yet	2s	512 MB	Judgeable
Tecle & SomeList every way to split S into terms of at most D digits whose concatenated digits form a path on a phone keypad using each digit at most once.	Medium7	DFSBacktracking+1	No attempts yet	2s	512 MB	Judgeable
Square RootGiven an integer N with up to 800 digits whose square root is a whole number, print that square root.	Medium7	MathBinary search+1	No attempts yet	2s	512 MB	Judgeable
Strings and QueriesFor a string S, F(i) is the length of the longest common suffix of S and the prefix of S ending at position i; answer M queries for F(i).	Medium7	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
3D QueriesGiven up to 777777 3D points with coordinates in [1,77], answer each query that sums a linear expression over all ordered point pairs divided by a fourth-power distance norm, rounded to six decimals.	Medium7	MathBrute force+2	No attempts yet	10s	512 MB	Judgeable
Random Sort 2Compute the expected number of random swaps the process needs to turn a given permutation of size up to 10 into increasing order.	Medium7	ProbabilityDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Buggy RobotGiven a grid and an existing command string, insert or delete single commands at minimum cost so the robot reaches the exit.	Medium7	Dynamic programmingBFS+1	No attempts yet	2s	512 MB	Judgeable
IlluminationGiven lamps on an n by n grid, decide whether each lamp can point along its row or column so that no cell gets same-direction light from two lamps.	Medium7	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
Water Supply UpgradesAfter each of k permanent capacity increases on edges of a small graph, report the maximum flow between station 1 and station 2.	Medium7	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Perfect SetsCount the subsets of {0,...,k} closed under bitwise XOR, where k can be as large as 10^9, modulo 10^9+7.	Medium7	Bit manipulationCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
RNG 2Count length-N arrays with entries from 0 to K whose bitwise XOR is nonzero, modulo 30011.	Medium7	CombinatoricsMath+1	No attempts yet	2s	512 MB	Judgeable
Distinct AND values of subsequencesCount how many distinct values can appear as the bitwise AND of some subsequence of a given array, including the empty subsequence whose AND is 0.	Medium7	Bit manipulationDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Dropped Water BottleJoe runs along two river banks with obstacles that force crossings; find the earliest time he intercepts a drifting bottle, or report impossibility.	Medium7	Shortest pathGraph	No attempts yet	2s	512 MB	Judgeable
String HashingCount valid strings of any length over ASCII 32 to 126 whose base-31 polynomial hash equals a given string's hash, modulo 1e9+7.	Medium7	Dynamic programmingCombinatorics	No attempts yet	2s	512 MB	Judgeable
The ResistanceGiven past mission teams and sabotage counts, choose Q players most likely to contain no spy and print that probability.	Medium7	ProbabilityCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
ButterflyChoose non-overlapping dates; each person pays only if all their dates are kept, so maximize total satisfaction.	Medium7	IntervalsDynamic programming+2	No attempts yet	8s	512 MB	Judgeable
Full Text SearchFor each query, find the shortest letter string whose set of length-1 and length-2 substrings contains the query's set but which does not contain the query itself.	Medium7	StringGraph+2	No attempts yet	8s	512 MB	Judgeable
Mysterious MazeA robot in a grid moves forward or turns according to a fixed sequence of turns; decide whether it can reach the exit once the turns run out.	Medium7	BFSSimulation+2	No attempts yet	8s	512 MB	Judgeable
Dungeon Quest IIGiven a fixed walking route through a grid of traps and up to 12 one-use potions, decide whether the agent can survive to the end.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	8s	512 MB	Judgeable
Road ConstructionGiven a weighted bidirectional graph, find the minimum total building cost of a spanning subgraph that keeps every pairwise connection and preserves the shortest distance from the capital to every city.	Medium7	GraphShortest path+2	No attempts yet	8s	512 MB	Judgeable