Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Manhattan Crepe Cart
Medium4
Matrix, Prefix sum+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Nesting Depth
Medium4
Greedy, String+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Parenting Partnering Returns
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Paradox With Averages
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Biased Standings
Medium4
Sorting, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Stamp Grid
Medium4
Brute force, Matrix+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Counting Pythagorean Triples
Medium4
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Caravan Trip Plans
Medium4
Dynamic programming, Array
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
aFan Event Planning
Medium4
Prefix sum, Binary search
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gold Mine
Medium4
Tree, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Shoulder Buddy
Medium4
Binary search, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Picking Hyper Branches
Medium4
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The score is just a helper
Medium4
Array, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Treasure Hunt 2
Medium4
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mentoring Matching
Medium4
Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Clear the Game
Medium4
Dynamic programming, Greedy
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Horse Race
Medium4
Topological sort, Graph+1
No attempts yet
Time limit
0.1s
Memory limit
1024 MB
Judgeable
I Love Geometry
Medium4
Brute force, Geometry+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Conveyor Belt Sushi
Medium4
Array, Simulation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Number Tower and Queries
Medium4
Binary search, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Interesting Modulo Operation
Medium4
Math, Number theory
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Another Goose Goose Duck Problem
Medium4
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Shelters
Medium4
Brute force, Implementation
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Grid Game
Medium4
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bullet Marks to Numbers
Medium4
Stack, Tree
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Study Cafe
Medium4
Sorting, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Redstone
Medium4
BFS, Matrix+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
More Common Tile Coloring
Medium4
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magnet
Medium4
Array, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
CCC Word Hunt
Medium4
Brute force, Matrix+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Symmetric Mountains
Medium4
Brute force, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
White Collar
Medium4
Shortest path, BFS+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Distributing Candy
Medium4
Binary search, Sorting
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Metro Construction
Medium4
Binary search, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Composite Functions for the Chairman
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Multiplication and Queries
Medium4
Hash map, Math
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Game
Medium4
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tricknology
Medium4
Number theory, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Avoiding Multiples
Medium4
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sketch
Medium4
Implementation, Brute force
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Artifacts (Basic)
Medium4
Tree, BFS
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Rick's Robe (Basic)
Medium4
Graph, BFS
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Faction Standoff
Medium4
Graph, BFS+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
We need fewer roads!
Medium4
Union-find, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Component Chemistry
Medium4
Hash map, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
An Important Scientific Number
Medium4
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Big Trampoline
Medium4
Brute force, Geometry
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Coins
Medium4
Simulation, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Defusing the Bomb
Medium4
Hash map, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
It
Medium4
Sliding window, Two pointers+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Maleficent Sum
Medium4
Prefix sum, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Jerry's Trap
Medium4
Sorting, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Commemorative Photos
Medium4
Sorting, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Headshot
Medium4
Greedy, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Archery Club
Medium4
Greedy, Simulation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
String Game
Medium4
Sliding window, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Going Home
Medium4
Greedy, Bit manipulation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sea Battle
Medium4
Math, Binary search
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Breaking into the Reliquary
Medium4
Array, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Non-decreasing array
Medium4
Greedy, Array
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gift for Luigi
Medium4
Sorting, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Thanos's Arrival
Medium4
Backtracking, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Armor Hall
Medium4
Prefix sum, Array+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Restaurant
Medium4
Array, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Max's Power Tower
Medium4
Math, Number theory
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Ventilation
Medium4
Tree, DFS+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Digital Riddle
Medium4
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Escalator
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tanya, the Balls, and XOR
Medium4
Math, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pursuit
Medium4
Brute force, Backtracking+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sparkling Pluses
Medium4
Matrix, Dynamic programming
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Castle for Adam
Medium4
Math, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Redistributing Stones
Medium4
Sorting, Sliding window+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Logan and Queries
Medium4
Prefix sum, Greedy+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
The Best Gift Is an Array!
Medium4
Sliding window, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Transistor Repair
Medium4
Number theory, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Way Home
Medium4
Stack, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Anagrams 2
Medium4
Array, Hash map+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Crossings of Crossings
Medium4
BFS, Shortest path+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Colors
Medium4
Math, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Well-Fed Game
Medium4
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Droids and the Hangar
Medium4
Prefix sum, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Candies
Medium4
Sliding window, Hash map
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sly Fox
Medium4
Array, Number theory
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Capital
Medium4
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sequence
Medium4
Implementation, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gureum's Job Prep Minimum Time
Medium4
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Walk in the Park
Medium4
Sorting, Prefix sum+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Mutant Ants
Medium4
Stack, Two pointers
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Bank Queue
Medium4
Array, Prefix sum
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Relatives
Medium4
Bit manipulation, Hash map
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Vampire Basketball
Medium4
Sorting, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magic Rods
Medium4
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Map
Medium4
String, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Miss Me?
Medium4
String, Two pointers
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Unlocking
Medium4
Dynamic programming, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
T-X vs T-850
Medium4
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Berries for the Lemurs
Medium4
Prefix sum, Array
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Let's fly!
Medium4
Sorting, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Appointments
Medium4
String, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Manhattan Crepe CartGiven people on a grid, each with a position and compass direction, find the intersection that the most people are heading toward, breaking ties by smallest x then smallest y.	Medium4	MatrixPrefix sum+1	No attempts yet	20s	1024 MB	Judgeable
Nesting DepthGiven a digit string, insert the fewest parentheses so each digit equals its nesting depth and every parenthesis is matched.	Medium4	GreedyString+1	No attempts yet	20s	1024 MB	Judgeable
Parenting Partnering ReturnsAssign each activity time interval to one of two people so that no person has overlapping intervals, or report IMPOSSIBLE if that cannot be done.	Medium4	GreedySorting+1	No attempts yet	20s	1024 MB	Judgeable
Paradox With AveragesCount the Computer Science students whose departure raises the CS average and whose arrival raises the Economics average.	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Biased StandingsGiven N teams with preferred places, assign each team a distinct place from 1 to N so the sum of absolute differences is minimal, and print that minimum.	Medium4	SortingGreedy	No attempts yet	1s	1024 MB	Judgeable
Stamp GridDecide whether a K x K stamp, rotated as needed, can be placed on an empty N x N canvas to match a target pattern without inking any blank cell.	Medium4	Brute forceMatrix+1	No attempts yet	2s	1024 MB	Judgeable
Counting Pythagorean TriplesGiven n, count the primitive and non-primitive Pythagorean triples where n is the hypotenuse and where n is a leg.	Medium4	Number theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
Caravan Trip PlansCount the distinct day-by-day camp sequences that start at camp 0, never move backward, and reach a given oasis on a given day.	Medium4	Dynamic programmingArray	No attempts yet	5s	1024 MB	Judgeable
aFan Event PlanningGiven daily token gains, process reset boundaries and, for each query, report the token sum from the last reset inside the range up to day e.	Medium4	Prefix sumBinary search	No attempts yet	2s	1024 MB	Judgeable
Gold MineGiven a rooted tree, find the fewest groups of rooms so that any two rooms in the same group are at odd distance from each other.	Medium4	TreeMath	No attempts yet	2s	1024 MB	Judgeable
Shoulder BuddyFind the smallest H so that at most k students have a height gap greater than H with at least one neighbor.	Medium4	Binary searchArray	No attempts yet	1s	1024 MB	Judgeable
Picking Hyper BranchesGiven 2047 of the 2048 corners of an 11-dimensional box, find the one corner that is missing.	Medium4	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
The score is just a helperGiven pitches in playing order, find the minimum N so that consecutive notes can be numbered from 1 to N while keeping each up, down, or equal relation.	Medium4	ArrayImplementation	No attempts yet	1s	1024 MB	Judgeable
Treasure Hunt 2Find the minimum fuel for a ship to reach the treasure on a grid, where moves to the three cells in the next column are free and all other moves cost 1.	Medium4	GraphShortest path+2	No attempts yet	1s	512 MB	Judgeable
Mentoring MatchingGiven each Hangwayeong student's ranking of KAIST students and a fixed KAIST preference by number distance, find a stable one-to-one matching.	Medium4	Greedy	No attempts yet	1s	1024 MB	Judgeable
Clear the GamePick one weapon per run so that consecutive runs never share a weapon, minimizing the total clear time over N runs.	Medium4	Dynamic programmingGreedy	No attempts yet	1s	512 MB	Judgeable
Horse RaceGiven the placement of each small race's winner, the task is to output one full-race finishing order that satisfies every winner constraint.	Medium4	Topological sortGraph+1	No attempts yet	0.1s	1024 MB	Judgeable
I Love GeometryCount the non-degenerate triangles with lattice-point vertices in an N by M yard, where triangles that match after rotation or reflection count once.	Medium4	Brute forceGeometry+1	No attempts yet	3s	1024 MB	Judgeable
Conveyor Belt SushiCount how many sushi pieces each customer eats, given each customer's wish list and the order the pieces pass down the belt.	Medium4	ArraySimulation	No attempts yet	1s	1024 MB	Judgeable
Number Tower and QueriesGiven a, d, and x, find the floor holding block number x and its position from the left on that floor, where floor i has a + (i-1)d blocks.	Medium4	Binary searchMath	No attempts yet	2s	1024 MB	Judgeable
Interesting Modulo OperationGiven N and R, find the sum of all positive integers m for which N mod m equals R.	Medium4	MathNumber theory	No attempts yet	1s	1024 MB	Judgeable
Another Goose Goose Duck ProblemChoose an integer cooldown a in [l, r] and find the minimum time to kill k geese that arrive every b seconds.	Medium4	MathGreedy	No attempts yet	1s	1024 MB	Judgeable
SheltersPick K of the N houses as shelters to minimize the largest Manhattan distance from any house to its nearest shelter.	Medium4	Brute forceImplementation	No attempts yet	3s	1024 MB	Judgeable
Grid GameFor each start cell on a grid with blocked cells, decide the winner of a game that moves a piece to the bottom-right corner with down, right, or diagonal moves of up to K cells.	Medium4	Dynamic programmingGame theory	No attempts yet	1s	1024 MB	Judgeable
Bullet Marks to NumbersGiven the DFS preorder levels of a tree's items, print each item's sibling index, or -1 if no tree matches the levels.	Medium4	StackTree	No attempts yet	2s	1024 MB	Judgeable
Study CafeGiven seat fees and customer stay intervals, find the minimum and maximum total revenue when each day every active customer takes a distinct seat.	Medium4	SortingPrefix sum+1	No attempts yet	2s	1024 MB	Judgeable
RedstoneGiven a grid of redstone dust, redstone blocks, and lamps, decide whether every lamp can be lit at the same moment as signals spread outward.	Medium4	BFSMatrix+1	No attempts yet	1s	1024 MB	Judgeable
More Common Tile ColoringGiven an N by M letter grid, find the fewest cells to repaint so every K by K block matches one shared K by K pattern, and print the result.	Medium4	ArrayImplementation+1	No attempts yet	2s	1024 MB	Judgeable
MagnetPick two different cells for the N and S poles to maximize a_i minus a_j minus K times the distance between them.	Medium4	ArrayDynamic programming	No attempts yet	2s	1024 MB	Judgeable
CCC Word HuntCount how many ways a word can be hidden in a letter grid, either along one straight line or along two segments that meet at a right angle.	Medium4	Brute forceMatrix+1	No attempts yet	1s	1024 MB	Judgeable
Symmetric MountainsFor each crop length, finds the minimum sum of height differences between mirrored mountain pairs over all consecutive crops of that length.	Medium4	Brute forceArray	No attempts yet	1s	1024 MB	Judgeable
White CollarGiven a map of one-way roads, list every city that lies on some shortest path from city 1 to city N.	Medium4	Shortest pathBFS+1	No attempts yet	1s	1024 MB	Judgeable
Distributing CandyFind the smallest non-negative X so that the sum of (A_i - X) over all scores above X does not exceed K.	Medium4	Binary searchSorting	No attempts yet	2s	1024 MB	Judgeable
Metro ConstructionFind the smallest integer voltage x so that the total power of n two-mode engines reaches at least p.	Medium4	Binary searchMath	No attempts yet	1s	1024 MB	Judgeable
Composite Functions for the ChairmanGiven an integer quadratic f and a linear g, count the x-values where f(g(x)) equals g(f(x)) and report the matching phrase.	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Multiplication and QueriesGiven a sequence where some elements are set to zero, answer whether two different elements multiply to x for each query.	Medium4	Hash mapMath	No attempts yet	1.5s	1024 MB	Judgeable
GameSum g(N) for every N from L to R, where g is 1 if repeatedly applying f reaches a fixed point, 0 if it never does, and -1 if a value exceeds 100000.	Medium4	SimulationImplementation	No attempts yet	1s	1024 MB	Judgeable
TricknologyFor each query L R, count pairs x < y within [L, R] where the sum of all integers from x to y is prime.	Medium4	Number theoryPrefix sum+1	No attempts yet	1s	1024 MB	Judgeable
Avoiding MultiplesCount subsets of size two or more where no two elements sum to a multiple of K, modulo 1,000,000,007.	Medium4	CombinatoricsMath+1	No attempts yet	1s	1024 MB	Judgeable
SketchDecide whether a grid of red and white pixels can be painted using only circle and cross brushes that may extend past the edge.	Medium4	ImplementationBrute force	No attempts yet	1s	1024 MB	Judgeable
Artifacts (Basic)Given a tree where each site holds artifact kind 0, 1, or 2, find the shortest walk that collects every required kind, or print -1 if one is missing.	Medium4	TreeBFS	No attempts yet	1.5s	1024 MB	Judgeable
Rick's Robe (Basic)Given an undirected graph with soaked vertices and hole vertices, find the maximum over soaked vertices of the distance to the nearest hole.	Medium4	GraphBFS	No attempts yet	1s	1024 MB	Judgeable
Faction StandoffGiven each city's faction and which cities can be flipped, find the fewest flips so that every road joins two cities of different factions, or -1 if impossible.	Medium4	GraphBFS+1	No attempts yet	1s	1024 MB	Judgeable
We need fewer roads!Given n houses and m roads, delete the fewest non-essential roads so no cycle remains, keeping every must-keep road, or report NO if impossible.	Medium4	Union-findGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Component ChemistryAfter each add or remove query, print how many pairs of current components have efficiencies whose sum is divisible by m.	Medium4	Hash mapMath	No attempts yet	1s	1024 MB	Judgeable
An Important Scientific NumberGiven gear sizes a and b, find the smallest non-negative x so that b divides a+x and a divides b+x.	Medium4	Number theoryMath	No attempts yet	2s	1024 MB	Judgeable
Big TrampolineGiven n points, find the vertex order that gives a simple polygon of maximum area, or report No when all points are collinear.	Medium4	Brute forceGeometry	No attempts yet	2s	1024 MB	Judgeable
CoinsCount the moves until no coins are heads up, where each move flips coin k and k is the current heads count, or print -1 if the game never ends.	Medium4	SimulationDynamic programming	No attempts yet	1s	1024 MB	Judgeable
Defusing the BombGiven n button values and a target k, find the fewest buttons to deactivate so that no two active values sum to k.	Medium4	Hash mapGreedy	No attempts yet	2s	1024 MB	Judgeable
ItCount the substrings of s whose letter counts do not exceed the letter counts of t, using each letter of t at most once.	Medium4	Sliding windowTwo pointers+1	No attempts yet	2s	1024 MB	Judgeable
Maleficent SumGiven n nonnegative integers, compute the sum of a_i * a_j * a_k over all index triples i < j < k, modulo 1000000007.	Medium4	Prefix sumMath+1	No attempts yet	2s	1024 MB	Judgeable
Jerry's TrapGiven platform heights, after each uniform shift x, print the sum of absolute values of all heights, with shifts accumulating.	Medium4	SortingPrefix sum+1	No attempts yet	2s	1024 MB	Judgeable
Commemorative PhotosSplit heights into the fewest groups of up to three, where a triple spans at most 10 cm and a pair at most 20 cm.	Medium4	SortingDynamic programming	No attempts yet	2s	1024 MB	Judgeable
HeadshotGiven n shots, magazine size m, full reload time a, and per-round load time b, find the minimum total time to fire exactly n shots.	Medium4	GreedyMath	No attempts yet	2s	1024 MB	Judgeable
Archery ClubGiven students on a line, each with a bow range and power, find the fewest students to order to shoot so that the chain of hits makes everyone shoot.	Medium4	GreedySimulation	No attempts yet	2s	1024 MB	Judgeable
String GameCheck whether some substring of s of length k has letter counts that t can supply using k of its characters in any order.	Medium4	Sliding windowString+1	No attempts yet	2s	1024 MB	Judgeable
Going HomeGiven buttons that OR-combine with the current universe number, find at most 100 presses that turn universe A into B, or report -1 if impossible.	Medium4	GreedyBit manipulation	No attempts yet	2s	1024 MB	Judgeable
Sea BattleFind the largest k such that one ship of size k, two of size k-1, up to k ships of size 1 fit non-touching on a 1 x n field.	Medium4	MathBinary search	No attempts yet	2s	1024 MB	Judgeable
Breaking into the ReliquaryGiven a sequence where each value may be off by at most 1, decide whether it could be a cyclic shift of 1 to n, and output a possible position of 1.	Medium4	ArrayImplementation	No attempts yet	2s	1024 MB	Judgeable
Non-decreasing arrayEach element may be negated; decide the signs so the array becomes non-decreasing, or report that it is impossible.	Medium4	GreedyArray	No attempts yet	2s	1024 MB	Judgeable
Gift for LuigiGiven four stick lengths, find the two side lengths of the largest-area rectangle that can be cut from the sticks.	Medium4	SortingGreedy	No attempts yet	2s	1024 MB	Judgeable
Thanos's ArrivalGiven a valid date as YYYY MM DD, list every valid date that can be formed by rearranging its eight digits, sorted from earliest to latest.	Medium4	BacktrackingImplementation	No attempts yet	2s	1024 MB	Judgeable
Armor HallGiven weighted points on a line, find the integer position that minimizes total weighted distance, taking the smallest coordinate on ties.	Medium4	Prefix sumArray+1	No attempts yet	2s	1024 MB	Judgeable
RestaurantGiven three priority rankings of n restaurants, find the one that at least two of the three diners prefer over every other restaurant, or report -1.	Medium4	ArrayImplementation	No attempts yet	1s	1024 MB	Judgeable
Max's Power TowerGiven a right-associative power tower of n natural numbers, find its value modulo 3.	Medium4	MathNumber theory	No attempts yet	2s	1024 MB	Judgeable
VentilationGiven a tree of n nodes, answer each query (s, t) with the neighbor of s on the unique path from s to t.	Medium4	TreeDFS+1	No attempts yet	3s	1024 MB	Judgeable
Digital RiddleGiven n numbers and at most k single-digit replacements, find the largest possible increase in their sum.	Medium4	GreedySorting	No attempts yet	2s	1024 MB	Judgeable
EscalatorCount the total digits written on the labeled steps: step 1, every multiple of ten up to n, and the last step n.	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Tanya, the Balls, and XORGiven n, compute the sum of i XOR j over all pairs 1 <= i < j <= n, modulo 10^9+7.	Medium4	MathBit manipulation	No attempts yet	1s	1024 MB	Judgeable
PursuitSplit the digits of x into k numbers without leading zeros so that each adjacent pair differs by between l and r, then count the splits.	Medium4	Brute forceBacktracking+1	No attempts yet	2s	1024 MB	Judgeable
Sparkling PlusesGiven an n by m matrix of 0s and 1s, find the largest plus shape made of 1s and print its size and the row and column of its center.	Medium4	MatrixDynamic programming	No attempts yet	4s	1024 MB	Judgeable
Castle for AdamGiven a log of length l, find the maximum number of pieces with pairwise distinct integer lengths that sum to l.	Medium4	MathGreedy	No attempts yet	2s	1024 MB	Judgeable
Redistributing StonesGiven n stone positions, find the fewest single-stone moves needed so the stones fill n consecutive chests, one per chest.	Medium4	SortingSliding window+1	No attempts yet	2s	1024 MB	Judgeable
Logan and QueriesRearrange an array so that the total of all q range-sum query answers is as large as possible, then report that maximum sum.	Medium4	Prefix sumGreedy+1	No attempts yet	2s	1024 MB	Judgeable
The Best Gift Is an Array!Find a contiguous subarray of a with the same length as p whose elements match p as a multiset, and print its start position or NO.	Medium4	Sliding windowHash map+1	No attempts yet	2s	1024 MB	Judgeable
Transistor RepairGiven n leg resistances, find three of them whose sum is A and product is B, or report -1 if none exist.	Medium4	Number theoryHash map+1	No attempts yet	2s	1024 MB	Judgeable
Way HomeGiven a stream of signs where positive x activates x, -x cancels x, and 0 cancels the active sign, print the active sign after each step.	Medium4	StackImplementation	No attempts yet	2s	1024 MB	Judgeable
Anagrams 2Find the longest contiguous subarray of the first array and one of the second array that are anagrams, and print its length and start indices.	Medium4	ArrayHash map+1	No attempts yet	3s	1024 MB	Judgeable
Crossings of CrossingsFind the fewest crossings needed to walk from house 0 on the left side to house f on the right side, given the crossings on each side and across the avenue.	Medium4	BFSShortest path+1	No attempts yet	2s	1024 MB	Judgeable
ColorsGiven n color numbers, count how many distinct colors can be produced by repeatedly taking the floor midpoint of two obtained colors.	Medium4	MathGreedy	No attempts yet	2s	1024 MB	Judgeable
Well-Fed GameGiven four moduli d_i and remainders r_i, find the smallest nonnegative x that satisfies x ≡ r_i (mod d_i) for all four congruences.	Medium4	Number theoryMath	No attempts yet	2s	1024 MB	Judgeable
Droids and the HangarGiven a row of rock cells and droids plus a string of L and R moves, find which droids never hit a rock and print their positions.	Medium4	Prefix sumImplementation+1	No attempts yet	2s	1024 MB	Judgeable
CandiesFind the length of the longest contiguous run of candies that contains exactly two distinct types.	Medium4	Sliding windowHash map	No attempts yet	2s	1024 MB	Judgeable
Sly FoxGiven n cards, find the one card whose removal leaves the largest GCD among the rest, and print its index and that GCD.	Medium4	ArrayNumber theory	No attempts yet	2s	1024 MB	Judgeable
CapitalGiven a digit sum a and a digit limit n, find the largest number whose digits sum to a and has at most n digits, or print -1.	Medium4	GreedyMath+1	No attempts yet	2s	1024 MB	Judgeable
SequenceGiven a sequence a, find any sequence b of length n+2 where each a_i equals the sum of three consecutive b values.	Medium4	ImplementationMath	No attempts yet	2s	1024 MB	Judgeable
Gureum's Job Prep Minimum TimePick p_j problems at each difficulty so that solving times plus rests are minimized, where each difficulty step costs a fixed 60 minutes of rest.	Medium4	SortingGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Walk in the ParkGiven vases with water a_i and drain rates b_i, print the total water left at each integer time from 0 to t.	Medium4	SortingPrefix sum+1	No attempts yet	4s	1024 MB	Judgeable
Mutant AntsAnts move right one unit per second and each falls into the first free trap it reaches; print the trap number for each ant or -1.	Medium4	StackTwo pointers	No attempts yet	2s	1024 MB	Judgeable
Bank QueueGiven a queue with joins, front departures, and queries, count the people in good mood (mood at least x) standing in front of a given person.	Medium4	ArrayPrefix sum	No attempts yet	2s	1024 MB	Judgeable
RelativesCount the pairs of animal numbers whose decimal representations share at least one digit.	Medium4	Bit manipulationHash map	No attempts yet	2s	1024 MB	Judgeable
Vampire BasketballSort Edward's teammates by a shot favorability score that drops with the defenders within distance l, and print their jersey numbers.	Medium4	SortingMath+1	No attempts yet	2s	1024 MB	Judgeable
Magic RodsChoose positive integer ignition times at both ends of each rod so that every rod's last point is lit at distance d_i and all rods finish at the same earliest moment.	Medium4	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
MapGiven a lowercase message with spaces removed, count the ways to pick three letters that form a palindrome in order.	Medium4	StringPrefix sum+1	No attempts yet	2s	1024 MB	Judgeable
Miss Me?Given a string, decide whether swapping exactly two characters (they may be equal) can turn it into a palindrome.	Medium4	StringTwo pointers	No attempts yet	2s	1024 MB	Judgeable
UnlockingGiven an n by m grid of integers, find the longest path of adjacent cells whose values increase by exactly 1 at each step.	Medium4	Dynamic programmingSorting+1	No attempts yet	2s	1024 MB	Judgeable
T-X vs T-850For each query, decide whether the segment between two points avoids the boundary of a circle, so the shooter can see the target.	Medium4	GeometryMath	No attempts yet	2s	1024 MB	Judgeable
Berries for the LemursGiven n lemurs with love levels a_i, find the sum over each i of a_i times the number of earlier lemurs j whose reach j+a_j extends past i.	Medium4	Prefix sumArray	No attempts yet	2s	1024 MB	Judgeable
Let's fly!Given altitudes h_i and weights a_i, find the single altitude minimizing the sum of \|h_i - x\| * a_i and print that altitude with the minimum cost.	Medium4	SortingPrefix sum+1	No attempts yet	2s	1024 MB	Judgeable
AppointmentsGiven a string, delete every occurrence of one character so that the remaining string is lexicographically smallest, and print it.	Medium4	StringGreedy	No attempts yet	2s	1024 MB	Judgeable