Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Drawing Arrows
Medium4
Sorting, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Two Boxes
Medium4
Geometry, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drawing Arrows
Medium4
Sorting, Hash map+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
1, 2, 3 Sum 3
Medium4
Dynamic programming, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
One, Two, Three Plus Four
Medium4
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Harmonic number
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Choose your own path
Medium4
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Voronoi Villages
Medium4
Sorting, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Überwatch
Medium4
Dynamic programming, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
You Are Fired!
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Coolest Ski Route
Medium4
Graph, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
It's Time for a Montage
Medium4
Implementation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Combination
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
OBB (Oriented Bounding Box)
Medium4
Geometry, Math+1
No attempts yet
Time limit
0.3s
Memory limit
32 MB
Judgeable
Human-Computer Interaction
Medium4
Prefix sum, Array+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Gun Control
Medium4
Dynamic programming, Array
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Uphill and Gahui
Medium4
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Gahui and the 3-Step High Note
Medium4
Greedy, Array+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Collecting Energy
Medium4
Dynamic programming, Recursion+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hackathon
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Card Picking
Medium4
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Roll Cake
Medium4
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Zamjena
Medium4
Hash map, Implementation+1
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Spaceship
Medium4
Math, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Martian Volleyball
Medium4
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Very Important Persons
Medium4
Sorting, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Least Common Multiple
Medium4
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cardboard Container
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Janitor Troubles
Medium4
Math, Geometry+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Code Cleanups
Medium4
Simulation, Greedy
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
House Lawn
Medium4
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Zebras and Ocelots
Medium4
Bit manipulation, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drawing Lines
Medium4
Sorting, Intervals+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Planet Connection
Medium4
Minimum spanning tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Goat Rope
Medium4
Geometry, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Snakebird
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Friday the 13th
Medium4
Math, Simulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Kitty
Medium4
Sliding window, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Partition of a Circle
Medium4
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Circle Expert Jinwoo
Medium4
Math, Geometry+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Make the Largest Number
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String Discrimination
Medium4
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Finding Her
Medium4
Matrix, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Afraid of the Dark
Medium4
Prefix sum, Matrix
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Janggi
Medium4
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rational Ratio
Medium4
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Multiples of 3
Medium4
Math, Combinatorics+1
No attempts yet
Time limit
0.1s
Memory limit
128 MB
Judgeable
Hard Prime Factorization
Medium4
Number theory, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Heroes of the Storm Progamer
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary Kingdom
Medium4
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Enviska's Soul
Medium4
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Plate Parity
Medium4
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
A Study on Groups
Medium4
Array, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Inflation
Medium4
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Judging Divisionals
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Laps
Medium4
Array, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Das Blinkenlights
Medium4
Math, Number theory
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Accumulator Battery
Medium4
Math, Implementation
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Lazyland
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Devil Game
Medium4
String, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Contest Setting
Medium4
Math, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Greedy Scheduler
Medium4
Heap, Simulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Finding Love
Medium4
Simulation, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Generic Queries
Medium4
Prefix sum, Bit manipulation+2
No attempts yet
Time limit
2.5s
Memory limit
512 MB
Judgeable
Gyeol! Hap!
Medium4
Brute force, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Wonyoung Wants to Stay with ZOAC Forever
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Digits Are Not Just Characters
Medium4
String, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pismo
Medium4
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mooyo Mooyo
Medium4
DFS, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Bucket List
Medium4
Simulation, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Back and Forth
Medium4
Brute force, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Vector Field
Medium4
Graph, Simulation
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
GuruGuru
Medium4
String, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Are You Listening?
Medium4
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Score!
Medium4
Simulation, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Ups and Downs of Investing
Medium4
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bomberman
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Surface Area
Medium4
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Transform into a Magic Square
Medium4
Brute force, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Death Knight
Medium4
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Block Play
Medium4
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Omok: Can Kyusagwa Win?
Medium4
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tabs vs Spaces
Medium4
Array, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 21
Medium4
Array, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cracking Eggs with Eggs
Medium4
Backtracking, Recursion
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Akvizna
Medium4
Greedy, Math
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Jarvis
Medium4
Hash map, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sorting
Medium4
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Baby Shark 2
Medium4
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hide and Seek 6
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Three Friends
Medium4
Graph, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Goldbach Partition
Medium4
Number theory, Math+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Array Play
Medium4
Prefix sum, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Two Arrays
Medium4
Binary search, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Why the Williamson's Sapsucker Came Up to Information Island
Medium4
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Azulejos
Medium4
Sorting, Greedy
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
I'm Sick of Fibonacci~
Medium4
Dynamic programming, Recursion+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cipher Decoder
Medium4
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Lining Up
Medium4
Stack, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Milk Factory
Medium4
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Drawing ArrowsEach point shoots an arrow to the nearest same-colored point; find the total length of all N arrows. Points are given unsorted, so sort them by position first.	Medium4	SortingHash map+2	No attempts yet	2s	512 MB	Judgeable
Two BoxesGiven two axis-aligned rectangles, classify how they intersect: overlapping interiors (FACE), sharing a segment (LINE), touching at one point (POINT), or disjoint (NULL).	Medium4	GeometryImplementation+2	No attempts yet	2s	512 MB	Judgeable
Drawing ArrowsEach point shoots an arrow to the nearest same-colored point; compute the total length of all arrows.	Medium4	SortingHash map+2	No attempts yet	1s	256 MB	Judgeable
1, 2, 3 Sum 3Count the ordered ways to write n as a sum of 1, 2, and 3, with each test case answered modulo 1,000,000,009.	Medium4	Dynamic programmingMath+2	No attempts yet	1s	512 MB	Judgeable
One, Two, Three Plus FourCount the number of unordered sums of 1, 2, and 3 that add up to a given n, for each test case.	Medium4	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Harmonic numberCompute the numerator and denominator of the harmonic number H_N as an irreducible fraction for N up to 10000.	Medium4	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Choose your own pathGiven a directed graph of story pages starting at page 1, check whether every page is reachable, then report the shortest distance to any ending page.	Medium4	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Voronoi VillagesGiven N village positions on a line, find the smallest finite Voronoi neighbourhood size and print it with one decimal digit.	Medium4	SortingGeometry+2	No attempts yet	2s	512 MB	Judgeable
ÜberwatchGiven a sequence of opponent counts over n time slices and a cooldown m, choose firing times at least m slices apart to maximize total opponents defeated.	Medium4	Dynamic programmingArray+2	No attempts yet	2s	512 MB	Judgeable
You Are Fired!Pick at most k employees whose salaries sum to at least d, minimizing the number fired, or report that it cannot be done.	Medium4	GreedySorting+1	No attempts yet	2s	512 MB	Judgeable
Coolest Ski RouteGiven a DAG of slopes with condition values, find the maximum total condition along any downhill path.	Medium4	GraphDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
It's Time for a MontageEach day every hero gains 1 power; find the minimum number of days until the heroes win the ordered rival showdown.	Medium4	ImplementationGreedy+2	No attempts yet	2s	512 MB	Judgeable
CombinationCompute N choose R modulo 1,000,000,007 for 0 ≤ R ≤ N ≤ 1,000,000 using a prime modulus.	Medium4	MathNumber theory+2	No attempts yet	1s	256 MB	Judgeable
OBB (Oriented Bounding Box)Given two rotated 2D rectangles as vertex lists, test whether their areas overlap using the separating axis theorem on four edge normals.	Medium4	GeometryMath+1	No attempts yet	0.3s	32 MB	Judgeable
Human-Computer InteractionCount how often a given lowercase letter appears inside each query interval [l, r] of a fixed string S, answering up to 200,000 queries.	Medium4	Prefix sumArray+1	No attempts yet	1s	256 MB	Judgeable
Gun ControlGiven each lawmaker's defeat cost and compromise value, pick a subset whose costs sum to more than B with minimum total compromise.	Medium4	Dynamic programmingArray	No attempts yet	2s	512 MB	Judgeable
Uphill and GahuiGiven a polyline of checkpoints and two query positions, output the absolute average slope between them as a reduced fraction.	Medium4	GeometryMath+1	No attempts yet	1s	256 MB	Judgeable
Gahui and the 3-Step High NoteGiven a sequence of notes and an arithmetic progression with first term A and difference D, find the largest number of terms of the progression that appear as a subsequence in order.	Medium4	GreedyArray+2	No attempts yet	1.5s	256 MB	Judgeable
Collecting EnergyGiven a row of N weighted beads (N up to 10), remove interior beads one at a time, scoring the product of the neighbors left and right, and maximize the total score.	Medium4	Dynamic programmingRecursion+1	No attempts yet	1s	512 MB	Judgeable
HackathonPartition N students into the fewest teams so each student's team size does not exceed their limit Xi.	Medium4	GreedySorting+1	No attempts yet	2s	512 MB	Judgeable
Card PickingGiven N cards with M front O's, choose exactly K off sameSymbol cards get an O on the back and the rest an X to maximize front-back matches.	Medium4	MathGreedy+1	No attempts yet	1s	512 MB	Judgeable
Roll CakeGiven up to M cuts across cakes of length at most 1000, maximise how many length-10 pieces you can cut out of them.	Medium4	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
ZamjenaGiven two arrays of numbers and variables, decide if one assignment of integers to variables makes corresponding positions equal. Consistent positions give constraints; any conflict answers NE.	Medium4	Hash mapImplementation+1	No attempts yet	1s	64 MB	Judgeable
SpaceshipReorder n enemy powers so that the last one equals the sum of all the others.	Medium4	MathSorting+2	No attempts yet	2s	512 MB	Judgeable
Martian VolleyballGiven a volleyball score k x y, find the fewest remaining balls until one team wins by reaching k with a 2-point lead.	Medium4	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
Very Important PersonsAssign guest numbers 1 to nm to an n by m hall so seat (1,1) holds nm and numbers decrease with Manhattan distance from that seat.	Medium4	SortingMath+2	No attempts yet	2s	512 MB	Judgeable
Least Common MultipleGiven two irreducible fractions, find the smallest positive irreducible fraction divisible evenly by both, writing it in lowest terms.	Medium4	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Cardboard ContainerFold three unequal prime factors of V into factors a, b, c with abc = V to minimize 2(ab + bc + ca), the surface area of the shipping box.	Medium4	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Janitor TroublesGiven four side lengths that can form a quadrilateral, output its maximum possible area, given by Brahmagupta's formula with the semiperimeter.	Medium4	MathGeometry+1	No attempts yet	1s	512 MB	Judgeable
Code CleanupsGiven days of dirty pushes, clean up as late as possible at day end so dirtiness (sum of push ages) stays below 20; count cleanup phases.	Medium4	SimulationGreedy	No attempts yet	1s	512 MB	Judgeable
House LawnPick the cheapest lawnmower that cuts the whole lawn at least once a week on average, and print its name or report none.	Medium4	MathImplementation+1	No attempts yet	1s	512 MB	Judgeable
Zebras and OcelotsGiven a stack of zebras and ocelots, each bell ring flips the lowest ocelot and all zebras beneath it; count rings until no ocelots remain.	Medium4	Bit manipulationMath+2	No attempts yet	2s	512 MB	Judgeable
Drawing LinesGiven N segments on a number line, find the total length of their union, counting overlaps once and printing it as an integer.	Medium4	SortingIntervals+2	No attempts yet	1s	256 MB	Judgeable
Planet ConnectionGiven a complete symmetric cost matrix, find a minimum spanning tree connecting all planets and output its total maintenance cost.	Medium4	Minimum spanning treeGraph+2	No attempts yet	1s	256 MB	Judgeable
Goat RopeGiven a point outside an axis-aligned rectangle, print the minimum distance from the point to the rectangle's boundary.	Medium4	GeometryMath+1	No attempts yet	2s	512 MB	Judgeable
SnakebirdGiven N fruits at heights h_i and a snake of length L, grow by eating any fruit of height at most the current length and output the maximum length reached.	Medium4	GreedySorting+1	No attempts yet	1s	128 MB	Judgeable
Friday the 13thCount every Friday the 13th from 2019 through year N, given Jan 1, 2019 is a Tuesday and the leap-year rules.	Medium4	MathSimulation+1	No attempts yet	1s	512 MB	Judgeable
KittyFind the longest contiguous substring with at most N distinct lowercase letters.	Medium4	Sliding windowTwo pointers+1	No attempts yet	1s	512 MB	Judgeable
Partition of a CircleA circle is cut by two straight lines, giving four regions with three known boundary lengths; find the fourth length opposite the third.	Medium4	GeometryMath+1	No attempts yet	1s	512 MB	Judgeable
Circle Expert JinwooGiven the radii of the three excircles of a triangle, compute the incircle radius without constructing any triangle explicitly.	Medium4	MathGeometry+1	No attempts yet	1s	512 MB	Judgeable
Make the Largest NumberGiven up to 1000 non-negative integers, order the pieces so their concatenation is the largest possible number, and print it without leading zeros.	Medium4	GreedySorting+1	No attempts yet	2s	512 MB	Judgeable
String DiscriminationGiven a target string S and up to 100 words, decide whether S is a concatenation of words from the list, each reusable any number of times.	Medium4	Dynamic programmingString+1	No attempts yet	2s	512 MB	Judgeable
Finding HerGiven a weighted directed Markov chain on shops A, B, C, D and a number of 10-minute steps, compute the probability of her being in each shop after that time.	Medium4	MatrixMath+2	No attempts yet	2s	512 MB	Judgeable
Afraid of the DarkGiven an R x C grid of brightness values and Q rectangle corner queries, compute each rectangle's mean using integer division.	Medium4	Prefix sumMatrix	No attempts yet	1s	512 MB	Judgeable
JanggiOn a 10x9 janggi board, find the minimum number of elephant moves to reach the king, avoiding the board edges.	Medium4	BFSGraph+2	No attempts yet	1s	512 MB	Judgeable
Rational RatioConvert a decimal with a repeating rightmost digit block into a fully reduced fraction formed by integer subtraction.	Medium4	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Multiples of 3Count ordered triples of multiples of 3 that add to n, with n a multiple of 3 between 3 and 3000.	Medium4	MathCombinatorics+1	No attempts yet	0.1s	128 MB	Judgeable
Hard Prime FactorizationFactor each of up to one million numbers up to 5,000,000 and print its prime factors in increasing order.	Medium4	Number theoryArray+2	No attempts yet	2s	512 MB	Judgeable
Heroes of the Storm ProgamerGiven N character levels and a total increase K, raise levels to maximize the minimum of the chosen sequence.	Medium4	GreedySorting+1	No attempts yet	2s	512 MB	Judgeable
Binary KingdomMaintain a binary array under requests that set a cell to 1 and report how many runs of consecutive 1s exist.	Medium4	ArrayImplementation+1	No attempts yet	2s	512 MB	Judgeable
Enviska's SoulGiven N people ahead and jump sizes a and b, find the smallest time to reach the front using zero-time jumps or waiting.	Medium4	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
Plate ParityCount integers in [A, B] whose rightmost nonzero digit is odd versus even, where A and B go up to 10^16.	Medium4	MathImplementation+2	No attempts yet	1s	512 MB	Judgeable
A Study on GroupsSplit the N integers into M groups whose sizes differ by at most one, then compute the smallest and largest possible sums of the group minima.	Medium4	ArrayGreedy+2	No attempts yet	1s	512 MB	Judgeable
InflationPair canister amounts with balloon sizes 1 to n so the minimum fill fraction is as large as possible without exceeding any capacity.	Medium4	GreedySorting	No attempts yet	2s	512 MB	Judgeable
Judging DivisionalsGiven ranked teams with a division and university, apply two selection steps with university limits and output the 12 advancing teams by rank.	Medium4	SimulationImplementation+2	No attempts yet	1s	512 MB	Judgeable
LapsGiven per-minute track positions from a monotone run on an n-metre loop, find the smallest possible total forward distance modulo n in laps.	Medium4	ArrayMath+2	No attempts yet	1s	512 MB	Judgeable
Das BlinkenlightsGiven blink periods p and q and a horizon s, decide whether some integer time in 1 to s is a multiple of both.	Medium4	MathNumber theory	No attempts yet	2s	512 MB	Judgeable
Accumulator BatteryGiven travel time t and arrival battery p, find how many minutes the phone stays powered, using full drain rate until 20 percent and half rate below it.	Medium4	MathImplementation	No attempts yet	3s	512 MB	Judgeable
LazylandEach of n workers wants one of k jobs and costs b_i to reassign. Keep one worker per chosen job and reassign the cheapest extras to cover every missing job. Return the minimum total cost.	Medium4	GreedySorting+1	No attempts yet	2s	512 MB	Judgeable
Devil GameFind a dictionary word containing the original word as a subsequence and maximize mood-killing degree per inserted letter, breaking ties by input order.	Medium4	StringTwo pointers+1	No attempts yet	1s	256 MB	Judgeable
Contest SettingCount the ways to choose k problems whose difficulties are all distinct, given n problems and their difficulty values, modulo 998,244,353.	Medium4	MathCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Greedy SchedulerAssign each queued customer to the free cashier with the smallest number, track busy times, and output the cashier for every customer.	Medium4	HeapSimulation+1	No attempts yet	1s	512 MB	Judgeable
Finding LoveSimulate sliding contests of M people, each eliminating one person at rank V, then print the last M-1 skills sorted ascending.	Medium4	SimulationSorting+2	No attempts yet	1s	256 MB	Judgeable
Generic QueriesGiven an array and range queries, compute each interval XOR and output the XOR of all answers mixed with the given k values.	Medium4	Prefix sumBit manipulation+2	No attempts yet	2.5s	512 MB	Judgeable
Gyeol! Hap!Score a Set-like game by checking each called triple against the hap rule and each gyeol against remaining uncalled haps.	Medium4	Brute forceImplementation+1	No attempts yet	1s	256 MB	Judgeable
Wonyoung Wants to Stay with ZOAC ForeverFor each t from 1 to N, the number of participants is the largest power of two dividing 2t; find the sum over all t.	Medium4	MathNumber theory+2	No attempts yet	1s	256 MB	Judgeable
Digits Are Not Just CharactersCompare each name with s0 by splitting into letter and number items, then output "-" if it sorts before s0 or "+" otherwise.	Medium4	StringSorting+1	No attempts yet	2s	512 MB	Judgeable
PismoGiven an array of N integers, find two positions L < R minimizing the difference between the maximum and minimum of the subarray A[L..R].	Medium4	ArraySorting+1	No attempts yet	1s	512 MB	Judgeable
Mooyo MooyoRepeatedly find connected groups of at least K equal nonzero cells on a 10-wide grid, erase them all at once, apply gravity, and print the final board.	Medium4	DFSSimulation+2	No attempts yet	2s	512 MB	Judgeable
The Bucket ListGiven N milking intervals, each needing a fixed number of buckets, find the smallest labels FJ's greedy allocation ends up using across all cows.	Medium4	SimulationSorting+2	No attempts yet	2s	512 MB	Judgeable
Back and ForthGiven ten bucket sizes at each of two barns, count the distinct amounts of milk that can end up in the first barn's tank after four alternating pours.	Medium4	Brute forceSimulation+2	No attempts yet	2s	512 MB	Judgeable
Vector FieldGiven n points that each redirect a proton along an axis, find the most points a proton can pass through when its start position and direction are chosen freely.	Medium4	GraphSimulation	No attempts yet	5s	512 MB	Judgeable
GuruGuruCount disjoint substrings of an L/R command string that complete one full clockwise rotation from north with the required non-north directions visited.	Medium4	StringGreedy+1	No attempts yet	2s	512 MB	Judgeable
Are You Listening?Given your point and n listening circles, find the largest radius centered there overlapping at most two of them; output the floor of it, or 0 if three already cover you.	Medium4	GeometryMath+2	No attempts yet	2s	512 MB	Judgeable
Score!Given basketball scoring events in chronological order, compute each team's total leading time over the game and name the winner.	Medium4	SimulationImplementation	No attempts yet	2s	512 MB	Judgeable
The Ups and Downs of InvestingCount price peaks needing n rising and n falling days and valleys needing m falling and m rising days.	Medium4	ArrayImplementation+1	No attempts yet	2s	512 MB	Judgeable
BombermanSimulate Bomberman's bomb placement and explosion cycle on a grid and print the state after N seconds.	Medium4	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Surface AreaGiven a grid of cube stack heights, compute the total surface area of the resulting 3D figure, including the top, bottom, and exposed side faces.	Medium4	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Transform into a Magic SquareGiven a 3x3 grid of the numbers 1 through 9, find the minimum total cost of changing cells so the grid becomes a magic square, where changing a cell from a to b costs \|a - b\|.	Medium4	Brute forceImplementation+2	No attempts yet	2s	512 MB	Judgeable
Death KnightFind the minimum number of moves for a knight-like piece with six fixed moves to travel between two squares on an N by N board, or -1 if unreachable.	Medium4	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Block PlayEach tower can be changed to any height at least 1 in one minute. Find the fewest towers to change so that consecutive heights differ by K.	Medium4	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
Omok: Can Kyusagwa Win?On a 10x10 omok board, decide whether Kyusagwa, moving next with X stones, can place one stone to make five in a row.	Medium4	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable
Tabs vs SpacesFor each of up to 366 days, count tab and space guests from N intervals, then report occupancy days, peak headcount, fight-free days, peak headcount among those, and the longest stay length.	Medium4	ArraySimulation+2	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 21Support range-add updates and point queries on an array of up to 100,000 elements with up to 100,000 operations.	Medium4	ArrayPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
Cracking Eggs with EggsEach egg in a row is lifted from the left and hits one other unbroken egg once, and the task is to find the maximum number of eggs that can break.	Medium4	BacktrackingRecursion	No attempts yet	2s	512 MB	Judgeable
AkviznaGiven N opponents eliminated in exactly K rounds, find the maximum sum of each round's eliminated count divided by the remaining count.	Medium4	GreedyMath	No attempts yet	1.5s	512 MB	Judgeable
JarvisPick one integer X added to every factory frequency so that the count of indices with Ai + X = Bi is as large as possible.	Medium4	Hash mapArray+2	No attempts yet	1s	512 MB	Judgeable
SortingGiven an array, count how many single elements can be removed so that the remaining N-1 elements are in nondecreasing order.	Medium4	ArrayImplementation+2	No attempts yet	1s	512 MB	Judgeable
Baby Shark 2Given an N by M grid with some cells holding sharks, find the empty cell whose Chebyshev distance to the nearest shark is largest.	Medium4	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Hide and Seek 6Given Subin's position S and the positions of N siblings, find the largest step size D such that repeated moves of +D or -D from S can reach every sibling.	Medium4	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Three FriendsGiven a sparse undirected graph, find three mutually adjacent vertices minimizing the sum of their degrees excluding the other two chosen vertices.	Medium4	GraphBrute force+2	No attempts yet	2s	512 MB	Judgeable
Goldbach PartitionFor each even N up to one million, count the unordered pairs of primes that sum to N.	Medium4	Number theoryMath+2	No attempts yet	0.5s	512 MB	Judgeable
Array PlayGiven an N by N grid and M rectangle-add operations, output the final sum of each row and each column.	Medium4	Prefix sumArray+2	No attempts yet	2s	512 MB	Judgeable
Two ArraysFor each element of A, find the element of B closest in value (smallest on ties) and print the sum of these chosen values.	Medium4	Binary searchSorting+2	No attempts yet	2s	512 MB	Judgeable
Why the Williamson's Sapsucker Came Up to Information IslandOn a grid with walls, find which of three food cells is nearest to the start cell 2, and print TAK with that distance, or NIE if none is reachable.	Medium4	BFSGraph+2	No attempts yet	1s	256 MB	Judgeable
AzulejosArrange two rows of tiles in non-decreasing price order so each back tile is taller than the front tile in its column, or report impossible.	Medium4	SortingGreedy	No attempts yet	10s	512 MB	Judgeable
I'm Sick of Fibonacci~Given n, count the total number of calls made by the naive recursive Fibonacci function, modulo 1,000,000,007.	Medium4	Dynamic programmingRecursion+2	No attempts yet	1s	512 MB	Judgeable
Cipher DecoderCheck whether the multiset of integers in the ciphertext matches the multiset of character codes of the given plaintext.	Medium4	Hash mapSorting+2	No attempts yet	1s	512 MB	Judgeable
Lining UpGiven N lines of 5 people each, decide whether everyone can pass through a single LIFO waiting area in increasing ticket order.	Medium4	StackSimulation+2	No attempts yet	1s	512 MB	Judgeable
Milk FactoryGiven a directed tree on N nodes, find the smallest node reachable from every other node, or output -1 if none exists.	Medium4	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable