Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Jinwoo's Password
Medium4
String, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Making a Password
Medium4
String, Brute force+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Pineapple Advertising
Medium4
Graph, Hash map+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Overflowing Fandom
Medium4
Intervals, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
My Life Has Math in It
Medium4
Dynamic programming, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Enigma
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Pattern
Medium4
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Lawyers
Medium4
Graph, Implementation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Road Construction
Medium4
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Who Is on First Base
Medium4
Brute force, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
I Will Be Your Bridge!
Medium4
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sum of Divisors 2
Medium4
Math, Number theory+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Two Doors
Medium4
Brute force, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Jung's Restaurant
Medium4
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sequence and Shift Queries
Medium4
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Jerry and Tom 2
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
6789
Medium4
Implementation, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
And the Winner Is... Ourselves!
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Architecture
Medium4
Greedy, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Inquiry I
Medium4
Prefix sum, Array+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
City of Lights
Medium4
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bus Logic
Medium4
Bit manipulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
On-Screen Keyboard
Medium4
Implementation, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cap Size
Medium4
Implementation, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pocket Money
Medium4
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Breaking Branches
Medium4
Game theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dome Construction
Medium4
Binary search, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Feeding Seals
Medium4
Greedy, Two pointers+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
222-Pooling
Medium4
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Diamonds Are for Evers
Medium4
Implementation, Matrix+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flight Turbulence
Medium4
Array, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hardware Sales
Medium4
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Make America Grade Again
Medium4
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Integer Division
Medium4
Hash map, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tired Terry
Medium4
Sliding window, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Short Sell
Medium4
Array, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cooking Water
Medium4
Intervals, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Problem Classification
Medium4
Hash map, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Greedily Increasing Subsequence
Medium4
Array, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Homework Never Ends!
Medium4
Stack, Simulation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Eeny Meeny
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Parliamentary Procedure
Medium4
Stack, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Minecraft
Medium4
Implementation, Brute force+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gugu the Raccoon
Medium4
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Small World Network
Medium4
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
The New Year's Bell
Medium4
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
MooBuzz
Medium4
Math, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Where Am I?
Medium4
String, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Ants
Medium4
Array, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hiding Nuts
Medium4
Math, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Antenna
Medium4
Sorting, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Round Trip
Medium4
Array, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Photoshoot
Medium4
Brute force, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Valid Emails
Medium4
String, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Finding Cities at a Specific Distance
Medium4
Graph, BFS+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Arranging Soldiers
Medium4
Dynamic programming, Array+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
2048
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
TATCK
Medium4
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
LTBL
Medium4
Implementation, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
RUN
Medium4
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Digit Sum
Medium4
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Emacs
Medium4
Implementation, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Muscle Loss
Medium4
Brute force, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Hopscotch 50
Medium4
Dynamic programming, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mad Scientist
Medium4
Greedy, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Moving 3
Medium4
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Maximum Subarray 2147483647
Medium4
Dynamic programming, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sequence and Queries 38
Medium4
Hash map, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Ladder
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Toy Alliances
Medium4
Graph, BFS+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Don't Split The Atom!
Medium4
Game theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Triangle
Medium4
Sorting, Greedy+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
UFO Rectangles
Medium4
Matrix, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Zero Game
Medium4
Sliding window, String+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Repetition
Medium4
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Frog 2
Medium4
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cyber Opening Ceremony
Medium4
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Beadman
Medium4
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cow-abunga!
Medium4
Brute force, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Best Place
Medium4
Sorting, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
King's Inspection
Medium4
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Checking Answers to Test
Medium4
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fractification
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Escalator
Medium4
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
T-Shirt Delivery
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dunes
Medium4
Array, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Misha's Product
Medium4
Math, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sleep Pattern
Medium4
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Mountain Skiing
Medium4
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Difference of Squares
Medium4
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Chronicle
Medium4
Implementation, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Faulty Mars Rover
Medium4
Math, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hamburger Distribution
Medium4
Greedy, Two pointers+2
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Investment Genius Bae Juhyeong
Medium4
Dynamic programming, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Youngjae's Walk
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Robot
Medium4
Implementation, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Password Generator
Medium4
Greedy, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Apple Tree
Medium4
Prefix sum, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Baskin Robbins 31
Medium4
Game theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Ranked Matchmaking Queue
Medium4
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Jinwoo's PasswordGiven N and a lowercase password of length at most N, find its 1-based position among all strings of length 1 to N in lexicographic order.	Medium4	StringMath+2	No attempts yet	1s	256 MB	Judgeable
Making a PasswordGiven two uppercase strings, find the longest substring that appears in both strings; the answer is unique.	Medium4	StringBrute force+1	No attempts yet	1s	256 MB	Judgeable
Pineapple AdvertisingAfter each of Q pizza deliveries to a house, report how many houses (the house itself plus its direct neighbors) like pineapple pizza for the first time.	Medium4	GraphHash map+2	No attempts yet	1s	256 MB	Judgeable
Overflowing FandomGiven N intervals during which fans are at school, find the minimum length of a single visit window that meets every interval.	Medium4	IntervalsGreedy+2	No attempts yet	1s	256 MB	Judgeable
My Life Has Math in ItOn an N x N grid (N odd, 3 to 5) holding numbers and operators, find the max and min results of expressions along right/down paths from (1,1) to (N,N), evaluating left to right.	Medium4	Dynamic programmingImplementation+1	No attempts yet	1s	256 MB	Judgeable
EnigmaImplement a simplified Enigma machine whose two rotors advance together after each letter, and decrypt the given uppercase ciphertext using the rotor setting CHICKENS.	Medium4	SimulationImplementation+2	No attempts yet	1s	256 MB	Judgeable
PatternGiven a sequence of grid points, decide whether it is a valid Android unlock pattern under the no-repeat and no-skipped-point rules.	Medium4	ImplementationSimulation+2	No attempts yet	1s	512 MB	Judgeable
LawyersGiven N lawyers and M directed trust edges, decide whether every lawyer has at least one incoming edge and no two lawyers defend each other.	Medium4	GraphImplementation	No attempts yet	1s	512 MB	Judgeable
Road ConstructionGiven a tree with n countries and weighted edges, sum over all edges of weight times the absolute difference in size of the two components the edge splits the tree into.	Medium4	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
Who Is on First BaseGiven nine statements of the form 'player A is' or 'player A is not' the first baseman, and knowing exactly one statement is a lie and exactly one player holds the position, find the player forced to be the first baseman or print -1.	Medium4	Brute forceImplementation+1	No attempts yet	2s	512 MB	Judgeable
I Will Be Your Bridge!A tree lost one edge, splitting it into two components. Print any pair of islands, one from each component, that reconnects the tree.	Medium4	GraphDFS+2	No attempts yet	1s	512 MB	Judgeable
Sum of Divisors 2Given N, compute the sum over all y from 1 to N of the sum of divisors of y, by counting how often each integer divides some value up to N.	Medium4	MathNumber theory+2	No attempts yet	0.5s	512 MB	Judgeable
Two DoorsGiven n doors and m switches that flip doors, find a set of switches that makes the passage shift time by each i from -n to n years, or report that none exists.	Medium4	Brute forceBit manipulation	No attempts yet	1s	1024 MB	Judgeable
Jung's RestaurantDecide whether a customer's order satisfies the restaurant rules: special items need 20000+ in regular items, service items need 50000+ combined and at most one.	Medium4	Hash mapImplementation+2	No attempts yet	1s	256 MB	Judgeable
Sequence and Shift QueriesMaintain a sequence under point additions and cyclic rotations by s positions to the right or left, then print the final array.	Medium4	ArrayImplementation+2	No attempts yet	1s	256 MB	Judgeable
Jerry and Tom 2Given N and values a1..aN, compute 1 minus the continued fraction 1/(a1 + 1/(a2 + ... + 1/aN)) as a reduced fraction P/Q.	Medium4	MathNumber theory+2	No attempts yet	1s	256 MB	Judgeable
6789Each cell holds a card 6, 7, 8, or 9; turning a card rotates it (6 and 9 swap, 8 and 7 stay). Find the minimum number of turns so the grid stays the same after a 180-degree rotation, or -1 if impossible.	Medium4	ImplementationGreedy+1	No attempts yet	1s	1024 MB	Judgeable
And the Winner Is... Ourselves!Given 11 problems that are all solved, choose the solving order that minimizes total penalty, where each problem contributes its finish time plus 20 times its wrong submissions.	Medium4	GreedySorting+2	No attempts yet	4s	1024 MB	Judgeable
ArchitectureGiven the R row maxima and C column maxima of a grid, decide whether any grid of heights can realize both sets of maxima.	Medium4	GreedyImplementation+2	No attempts yet	1s	512 MB	Judgeable
Inquiry ISplit the array into a prefix and a suffix at some index k; maximize the sum of squares of the prefix times the sum of the suffix.	Medium4	Prefix sumArray+2	No attempts yet	3s	512 MB	Judgeable
City of LightsGiven N lights initially on and k toggles where toggle i flips every multiple of i, find the maximum number of lights that are off at any point during the sequence.	Medium4	ArrayImplementation+2	No attempts yet	1s	512 MB	Judgeable
Bus LogicGiven a starting stop and bus routes as bit strings of length s, find the maximum number of other stops reachable by choosing exactly one bus that serves the starting stop.	Medium4	Bit manipulationImplementation+2	No attempts yet	1s	512 MB	Judgeable
On-Screen KeyboardGiven a grid keyboard with a highlighted cell, find the total minimum button presses to type a string, where each character's cost is the Manhattan distance plus one for OK.	Medium4	ImplementationArray+2	No attempts yet	2s	512 MB	Judgeable
Cap SizeGiven cap sizes tried on with fit feedback, count how many untried sizes could still fit, or report inconsistent feedback.	Medium4	ImplementationSorting+2	No attempts yet	2s	512 MB	Judgeable
Pocket MoneyChoose banknotes from the wallet so the total is even and as large as possible, using any subset; print NIESTETY if only odd totals are reachable.	Medium4	GreedyMath+2	No attempts yet	2s	512 MB	Judgeable
Breaking BranchesTwo players alternately split pieces of a length n branch into integer parts; the last to move wins. Decide the winner and give Alice's winning first move.	Medium4	Game theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Dome ConstructionGiven n points in 3D with non-negative y, find the minimum radius of a dome (hemisphere on the xz-plane) that contains at least k of them.	Medium4	Binary searchGeometry+2	No attempts yet	2s	512 MB	Judgeable
Feeding SealsEach volunteer can carry one or two buckets as long as their combined weight stays within capacity c. Find the minimum number of volunteers needed to move all buckets.	Medium4	GreedyTwo pointers+2	No attempts yet	2s	512 MB	Judgeable
222-PoolingRepeatedly replace each 2x2 block of an NxN matrix with its second largest value until one number remains, and print it.	Medium4	ImplementationSimulation+2	No attempts yet	1s	256 MB	Judgeable
Diamonds Are for EversDecode a message written into a square grid along nested diamond diagonals, given the row-by-row concatenation of all cells.	Medium4	ImplementationMatrix+2	No attempts yet	1s	512 MB	Judgeable
Flight TurbulenceA permutation maps each seat to the passenger sitting there; count how many passengers shift when one passenger demands their assigned seat.	Medium4	ArraySimulation+2	No attempts yet	1s	512 MB	Judgeable
Hardware SalesGiven three lists of (item ID, units) purchases, count items whose total units reach 20 or more in all three stores, printing IDs in first-appearance order.	Medium4	Hash mapImplementation+2	No attempts yet	1s	512 MB	Judgeable
Make America Grade AgainGiven category weights and a list of graded assignments, sum points per category, weight each fraction, and print the truncated final grade.	Medium4	MathImplementation+2	No attempts yet	1s	512 MB	Judgeable
Integer DivisionCount pairs of indices whose values give the same quotient when both are divided by d using floor division.	Medium4	Hash mapMath+1	No attempts yet	2s	512 MB	Judgeable
Tired TerryGiven a circular sleep pattern of length n, count for how many seconds i the preceding p seconds contain fewer than d seconds of sleep.	Medium4	Sliding windowPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Short SellGiven N daily prices and a daily interest K per 100 borrowed coins, pick a borrow day and a repay day to maximize profit.	Medium4	ArrayPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
Cooking WaterGiven N intervals of time Edward did not watch a pot, decide whether some single boil time is possible, meaning it lies inside every unwatched interval.	Medium4	IntervalsImplementation+1	No attempts yet	1s	512 MB	Judgeable
Problem ClassificationCount exact whole-word occurrences of each category's keywords in a statement, then print the categories with the highest total count in lexicographic order.	Medium4	Hash mapString+2	No attempts yet	1s	512 MB	Judgeable
Greedily Increasing SubsequenceGiven a permutation, repeatedly take the leftmost unused element larger than the previous pick, and report the resulting subsequence.	Medium4	ArraySimulation+2	No attempts yet	1s	512 MB	Judgeable
Homework Never Ends!Each minute either adds homework (value A, work time T) or nothing; a new task preempts the current one, and finished tasks are submitted at the minute they finish. Sum the values of tasks completed within N minutes.	Medium4	StackSimulation+2	No attempts yet	2s	256 MB	Judgeable
Eeny MeenySimulate counting around a circle of kids with a rhyme length, removing one kid per round and assigning them to alternating teams.	Medium4	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Parliamentary ProcedureGiven a record of Add and Vote events for 26 parties, decide whether the events can be ordered consistently with a stack-like bill discussion rule.	Medium4	StackSimulation+1	No attempts yet	2s	512 MB	Judgeable
MinecraftGiven N by M ground heights and B starting blocks, pick a target height that minimizes flattening cost (remove 2s, place 1s, no outside blocks), breaking ties by the highest target.	Medium4	ImplementationBrute force+2	No attempts yet	1s	1024 MB	Judgeable
Gugu the RaccoonGiven a weighted tree rooted at node 1, find the maximum distance from node 1 to any other node.	Medium4	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
Small World NetworkGiven a graph of N people and K friendships, check whether every pair of people is connected within 6 steps, printing Small World! or Big World! accordingly.	Medium4	GraphBFS+2	No attempts yet	1s	512 MB	Judgeable
The New Year's BellGiven an N by M grid of who heard each bell ring, decide whether some distance thresholds R can produce exactly this pattern.	Medium4	SortingGreedy+2	No attempts yet	1s	512 MB	Judgeable
MooBuzzGiven N up to 1e9, find the Nth positive integer that is not a multiple of 3 or 5, since those turns are replaced by Moo.	Medium4	MathBinary search+2	No attempts yet	1s	512 MB	Judgeable
Where Am I?Given a string of N mailbox colors, find the smallest K such that all length-K substrings are distinct. The answer is always at most N.	Medium4	StringBrute force+2	No attempts yet	1s	512 MB	Judgeable
AntsGiven N integers, some negative or very large, find the smallest nonnegative integer that does not appear among the valid nonnegative values.	Medium4	ArrayHash map+2	No attempts yet	2s	512 MB	Judgeable
Hiding NutsGiven N grid points, pick the one minimizing the sum of Manhattan distances to all other points, breaking ties by smallest X then smallest Y.	Medium4	MathBrute force+2	No attempts yet	1s	512 MB	Judgeable
AntennaGiven positions of houses on a line, pick the house position that minimizes the total distance to all houses, choosing the smallest such position on ties.	Medium4	SortingMath+2	No attempts yet	1s	256 MB	Judgeable
Round TripA runner travels out and back along N courses given by their lengths; given total distance K, print which course the runner is on or about to enter.	Medium4	ArrayPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
PhotoshootGiven adjacent sums b_i = a_i + a_{i+1} of a hidden permutation of 1..N, reconstruct the lexicographically smallest permutation a.	Medium4	Brute forceImplementation+2	No attempts yet	2s	512 MB	Judgeable
Valid EmailsNormalize each email by its rules, count how many are valid and distinct.	Medium4	StringHash map+2	No attempts yet	2s	512 MB	Judgeable
Finding Cities at a Specific DistanceGiven a directed unweighted graph, print every city whose shortest distance from a start city equals K, in increasing order, or -1 if none exist.	Medium4	GraphBFS+1	No attempts yet	2s	256 MB	Judgeable
Arranging SoldiersGiven a sequence of N combat powers, find the minimum number of soldiers to remove so the remaining values are in strictly decreasing order.	Medium4	Dynamic programmingArray+2	No attempts yet	1s	256 MB	Judgeable
2048Simulate a sequence of 2048 moves, applying gravity, merging equal tiles once per move, and adding merge values to the score.	Medium4	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
TATCKFor each test case, find the area of the smallest axis-aligned square that contains all given points.	Medium4	GeometryMath+2	No attempts yet	2s	512 MB	Judgeable
LTBLRead match results between two teams, accumulate points, wins, draws, losses, and goals, then print the league table sorted by the six tiebreak rules.	Medium4	ImplementationSorting+2	No attempts yet	2s	512 MB	Judgeable
RUNGiven a directed weighted graph of N cells, one exit cell E, and a time limit T, count how many cells have a path to E within T time units.	Medium4	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Digit SumCount how many starting values between 1 and N can reach N by repeatedly adding the sum of their decimal digits.	Medium4	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
EmacsCount the non-overlapping, non-touching rectangles of '*' characters in an N by M grid.	Medium4	ImplementationArray+2	No attempts yet	1s	512 MB	Judgeable
Muscle LossCount orderings of N workout kits (N at most 8) such that a starting total of 500, which drops by K each day, never falls below 500.	Medium4	Brute forceBacktracking+2	No attempts yet	1s	256 MB	Judgeable
Hopscotch 50Given an n by n grid of labels 1 to k, find the minimum total Manhattan distance of a path that visits one tile of each label in order, or -1 if some label is missing.	Medium4	Dynamic programmingImplementation+2	No attempts yet	1s	512 MB	Judgeable
Mad ScientistGiven two strings A and B of H and G, find the minimum number of substring flips (toggling all characters) needed to turn B into A.	Medium4	GreedyString+2	No attempts yet	2s	512 MB	Judgeable
Moving 3A path from (0,0) to (N,M) using only down and right steps costs A[r] per down move and B[c] per right move; find the cheapest path.	Medium4	GreedyMath+1	No attempts yet	2s	512 MB	Judgeable
Maximum Subarray 2147483647Given a sequence of n integers, find the maximum possible sum of a contiguous subarray, choosing at least one element.	Medium4	Dynamic programmingArray+2	No attempts yet	2s	512 MB	Judgeable
Sequence and Queries 38Maintain a sequence under append, delete-one-copy, and report running sum and XOR of all elements.	Medium4	Hash mapImplementation+2	No attempts yet	2s	256 MB	Judgeable
LadderGiven n sticks that can only be shortened, decide whether two can become length x and k others length y.	Medium4	GreedySorting+2	No attempts yet	2s	64 MB	Judgeable
Toy AlliancesGiven N toys and M dislike pairs, decide whether the toys can be split into two alliances so no dislike pair shares a side, which is checking bipartiteness of the graph.	Medium4	GraphBFS+2	No attempts yet	1.5s	256 MB	Judgeable
Don't Split The Atom!Two players alternately split a pile of atoms, and whoever is forced to split a single atom loses; decide the winner for each n.	Medium4	Game theoryMath+2	No attempts yet	2s	512 MB	Judgeable
TriangleGiven N stick lengths, pick six to form two non-degenerate triangles and print the maximum total length, or 0 if that is impossible.	Medium4	SortingGreedy+1	No attempts yet	3s	512 MB	Judgeable
UFO RectanglesFind every flattened rectangle frame drawn with X cells in a grid and print the top-left and bottom-right coordinates of each.	Medium4	MatrixImplementation	No attempts yet	2s	512 MB	Judgeable
Zero GameGiven a binary string and Q values K, find for each K the longest run of zeros that can be formed with at most K moves of single characters.	Medium4	Sliding windowString+1	No attempts yet	1s	512 MB	Judgeable
RepetitionGiven a lowercase string S, find the smallest K such that S is a subsequence of the alphabet repeated K times.	Medium4	GreedyString+1	No attempts yet	1s	256 MB	Judgeable
Frog 2Each frog ends at (a,b) after c unit steps on the grid; find the initial lattice point, or NO, choosing the smallest x then y.	Medium4	MathImplementation+2	No attempts yet	1s	256 MB	Judgeable
Cyber Opening CeremonyGiven start, end, and stream-end times plus chat logs, count members who chatted at or before the start and again between the end and stream-end.	Medium4	Hash mapImplementation+2	No attempts yet	1s	1024 MB	Judgeable
BeadmanGiven counts of N bead types, repeatedly remove one bead of each of two different types; find the minimum number of beads that can remain.	Medium4	GreedyMath+2	No attempts yet	1s	1024 MB	Judgeable
Cow-abunga!Given at most 9 cow weights, choose M of them and print every prime number that appears as a subset sum, in increasing order.	Medium4	Brute forceCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Best PlaceGiven N points, find integer coordinates (X, Y) that minimize the sum of Manhattan distances from the point to every participant.	Medium4	SortingMath+2	No attempts yet	1s	512 MB	Judgeable
King's InspectionGiven three coin counts, each second you add one coin to two different chests; find the minimum number of seconds to make all three equal.	Medium4	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Checking Answers to TestGiven the correct answers and each student's answers, find every pair of students whose correct and incorrect answers each match on more than half of the questions.	Medium4	Brute forceImplementation+2	No attempts yet	1s	512 MB	Judgeable
FractificationGiven four positive integers, arrange them into two fractions a/b + c/d so the sum is as small as possible, and print the arrangement.	Medium4	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
EscalatorGiven n, sum the decimal digit counts of the numbers 1, n, and every multiple of 10 up to n.	Medium4	MathImplementation+1	No attempts yet	1s	512 MB	Judgeable
T-Shirt DeliveryGiven travel times and each recipient's earliest availability, simulate Bill's deliveries where he waits at most k minutes per stop and each handover takes t minutes, and report when he finishes.	Medium4	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
DunesEach gust adds +x to l and then alternates signs up to r; answer m queries for the final height at given positions.	Medium4	ArrayPrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Misha's ProductGiven n distinct integers, concatenate every ordered pair of them and report the sum of all these concatenations modulo 1e9+7.	Medium4	MathArray+2	No attempts yet	1s	512 MB	Judgeable
Sleep PatternGiven weekday sleep intervals on a Mon-Fri timeline, compute the minimum weekend hours needed so total weekly sleep reaches T, or report that even 48 hours is not enough.	Medium4	ImplementationMath+2	No attempts yet	1s	1024 MB	Judgeable
Mountain SkiingGiven winter length n, trip length k, and m days Tanya was at the resort, find the most winter days she could have spent in the city.	Medium4	GreedySorting	No attempts yet	2s	512 MB	Judgeable
Difference of SquaresGiven n up to 2^60, find positive integers x and y with x^2 - y^2 = n, or report that none exist.	Medium4	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
ChronicleGiven three two-digit numbers from a disk, list every valid 21st-century date dd/mm/yy that uses the three numbers in some order, or report none.	Medium4	ImplementationBrute force+2	No attempts yet	2s	512 MB	Judgeable
Faulty Mars RoverStarting from a, reach exactly b using steps of +1 and +2 while never landing on a multiple of c; find the fewest steps.	Medium4	MathGreedy+2	No attempts yet	2s	512 MB	Judgeable
Hamburger DistributionAlong a line of N positions holding people and hamburgers, each person can eat a hamburger within distance K; find the maximum number of people served.	Medium4	GreedyTwo pointers+2	No attempts yet	0.5s	256 MB	Judgeable
Investment Genius Bae JuhyeongStarting with H won over Y years, choose among three fixed-term investments (1, 3, or 5 years) to maximize final money, truncating fractions at each payout.	Medium4	Dynamic programmingBrute force+2	No attempts yet	1s	512 MB	Judgeable
Youngjae's WalkSimulate a walker who moves at speed v for one second, then turns right and updates v to (v*m)%10, and report the final coordinates after t seconds.	Medium4	SimulationImplementation+2	No attempts yet	1s	512 MB	Judgeable
RobotFind move lengths from 1 to 10^6 that match a given turn sequence and final point (x, y), or report that no route exists.	Medium4	ImplementationMath	No attempts yet	2s	512 MB	Judgeable
Password GeneratorBuild any length-n string of letters and digits meeting minimum counts of uppercase, lowercase, and digit characters, with no two equal adjacent characters.	Medium4	GreedyImplementation+2	No attempts yet	2s	512 MB	Judgeable
Apple TreeGiven an N by N grid of profits, find the K by K square subgrid with the largest sum.	Medium4	Prefix sumArray+2	No attempts yet	1s	512 MB	Judgeable
Baskin Robbins 31Given the cap A, list every move limit n up to A for which the second player wins the Baskin Robbins game ending at 31 where calling 31 loses.	Medium4	Game theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Ranked Matchmaking QueueSimulate matchmaking: place each player into the earliest created room whose level range fits, filling rooms of capacity m and reporting each room's final state.	Medium4	SimulationImplementation+2	No attempts yet	1s	256 MB	Judgeable