Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Picture Comparison
Easy3
Brute force, Matrix+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Card 1
Easy3
Queue, Simulation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Card 2
Easy3
Queue, Simulation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Polygon Area
Easy3
Geometry, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
2D Array Range Sum
Easy3
Prefix sum, Matrix+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Drawing Lines
Easy3
Intervals, Sorting+1
No attempts yet
Time limit
1s
Memory limit
192 MB
Judgeable
Maze Search
Easy3
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
192 MB
Judgeable
Magic Square Classification
Easy3
Matrix, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pinary Numbers
Easy3
Dynamic programming, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Ropes
Easy3
Sorting, Greedy
No attempts yet
Time limit
2s
Memory limit
192 MB
Judgeable
Sum Decomposition
Easy3
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Decomposition Sum
Easy3
Brute force, Math+1
No attempts yet
Time limit
2s
Memory limit
192 MB
Judgeable
Auction
Easy3
Hash map, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
LCD Display Test
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Minimum Coin Count
Easy3
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Number Game
Easy3
Brute force, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Seven Dwarfs
Easy3
Brute force, Array+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Repeated Sequence
Easy3
Simulation, Hash map+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Axis-Parallel Lines
Easy3
Hash map, Array
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Distinguishing Files
Easy3
String, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sascha
Easy3
String, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Making Equal-Length Sticks
Easy3
Math, Greedy+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Combination
Easy3
Math, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Integer Square Root
Easy3
Binary search, Math
No attempts yet
Time limit
0.4s
Memory limit
128 MB
Judgeable
Choosing Ice Cream in Italy
Easy3
Brute force, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Greatest Common Divisor and Least Common Multiple
Easy3
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
I Am the Class President
Easy3
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Melon Field
Easy3
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Four Dice
Easy3
Implementation, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sequence
Easy3
Array, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rice Cakes for the Tiger
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Number Baseball
Easy3
Brute force, Simulation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Candy Doctor Changyoung
Easy3
Matrix, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Running
Easy3
Array, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Pancake Love
Easy3
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Remainder Sequence Cycle
Easy3
Simulation, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rectangle Overlap Type
Easy3
Geometry, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Asian Informatics Olympiad
Easy3
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Student Who Raises Both Averages
Easy3
Array, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Representative Natural Number
Easy3
Sorting, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Two Representative Natural Numbers
Easy3
Math, Sorting+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Temperature Sequence
Easy3
Sliding window, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Colored Paper
Easy3
Array, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bingo
Easy3
Simulation, Array+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prime Numbers
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Secret Letter
Easy3
String, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Student Lineup
Easy3
Simulation, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Similar Words
Easy3
Hash map, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Roman Numerals
Easy3
String, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Card Game Score
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Making Triangles with Matchsticks
Easy3
Math, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Paper Cutting
Easy3
Sorting, Array+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Making Colored Paper
Easy3
Recursion, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Line Up
Easy3
Dynamic programming, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Kinship Distance
Easy3
Graph, BFS+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Chairperson Candidates
Easy3
Graph, BFS+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Housing Complex Numbering
Easy3
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Nim Sum
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Receiving a Fax
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Equal-Sum Segments
Easy3
Prefix sum, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Binary Clock
Easy3
Bit manipulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Darts
Easy3
Geometry, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Spreadsheet Cell Names
Easy3
Math, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bicycle Speed
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Apartment Residents
Easy3
Dynamic programming, Math+1
No attempts yet
Time limit
0.5s
Memory limit
128 MB
Judgeable
Blackjack
Easy3
Brute force, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Make a Crossword
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Math Homework
Easy3
String, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Contest or Internship
Easy3
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Frog Leaps
Easy3
Simulation, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Chocolate Lunch
Easy3
Bit manipulation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sangbeom's Game
Easy3
Math, Array+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Kayak
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Non-Alcoholic Cocktail
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ancient Lock
Easy3
Array, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Candy Purchase
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ruler and Protractor
Easy3
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Machine Code
Easy3
Greedy, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rock-Paper-Scissors Score
Easy3
Simulation, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Croatian Alphabet
Easy3
String, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sieve of Eratosthenes
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Truck Parking Fees
Easy3
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Road and Traffic Lights
Easy3
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Three Numbers
Easy3
Brute force, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Aggressive Dogs
Easy3
Math, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Three Parts
Easy3
Brute force, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Fourth Number
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Secret Email
Easy3
Matrix, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lexicographically Smallest Crossword Word
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lunch Warnings
Easy3
Hash map, Simulation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Magician Lee Minhyuk
Easy3
Array, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Marathon Tic-Tac-Toe
Easy3
Matrix, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Completing a League Table
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rings
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polygon Diagonal Intersections
Easy3
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Visible Poster Area
Easy3
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Counting Coin Combinations
Easy3
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Heart Number System
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cutting Chocolate
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Walking Route
Easy3
Array, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Picture ComparisonGiven N small 5x7 grids, find the pair of pictures with the fewest differing cells and output their indices.	Easy3	Brute forceMatrix+1	No attempts yet	2s	128 MB	Judgeable
Card 1Simulate a queue where you discard the front card then rotate the next card to the back, printing the discard order and final survivor.	Easy3	QueueSimulation	No attempts yet	2s	128 MB	Judgeable
Card 2Simulate the Josephus-style card elimination process to find which card number remains last for a given N.	Easy3	QueueSimulation+1	No attempts yet	2s	128 MB	Judgeable
Polygon AreaGiven the ordered vertices of a simple polygon, compute its area using the shoelace formula, rounded to one decimal place.	Easy3	GeometryMath+1	No attempts yet	2s	128 MB	Judgeable
2D Array Range SumBuild a 2D prefix sum over an N by M grid and answer up to 10,000 rectangle sum queries in O(1) each.	Easy3	Prefix sumMatrix+1	No attempts yet	2s	128 MB	Judgeable
Drawing LinesGiven N line segments on a number line, compute the total length covered by at least one segment, merging overlaps.	Easy3	IntervalsSorting+1	No attempts yet	1s	192 MB	Judgeable
Maze SearchFind the minimum number of cells traversed on a grid path from top-left to bottom-right using BFS shortest path.	Easy3	BFSGraph+1	No attempts yet	1s	192 MB	Judgeable
Magic Square ClassificationRead multiple square matrices and classify each into one of five magic square categories based on row, column, diagonal sums, distinctness, and consecutiveness.	Easy3	MatrixImplementation+1	No attempts yet	1s	128 MB	Judgeable
Pinary NumbersCount binary strings of length N that start with 1 and have no two consecutive 1s, using Fibonacci-style counting with big integers up to N=90.	Easy3	Dynamic programmingMath+1	No attempts yet	2s	128 MB	Judgeable
RopesChoose a subset of ropes so that each rope's capacity times the count of chosen ropes is maximized, to find the greatest liftable weight.	Easy3	SortingGreedy	No attempts yet	2s	192 MB	Judgeable
Sum DecompositionCount ordered sequences of K integers from 0 to N whose sum equals N, modulo 1,000,000,000.	Easy3	Dynamic programmingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Decomposition SumGiven N up to 1,000,000, find the smallest number M such that M plus its digit sum equals N, or print 0 if none exists.	Easy3	Brute forceMath+1	No attempts yet	2s	192 MB	Judgeable
AuctionGiven a sequence of bids, find the least-frequent price (lowest if tied) and output the name of the first bidder who offered that price.	Easy3	Hash mapImplementation+1	No attempts yet	2s	128 MB	Judgeable
LCD Display TestPrint a given number in seven-segment LCD style using dashes and bars, scaled to a given digit size.	Easy3	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
Minimum Coin CountGiven n coin denominations, compute the minimum number of coins (unlimited supply) that sum to exactly k, or -1 if impossible.	Easy3	Dynamic programming	No attempts yet	1s	128 MB	Judgeable
Number GameFor each of N players, pick 3 of 5 cards maximizing the units digit of their sum, then find the player with the highest such score, breaking ties by largest player number.	Easy3	Brute forceImplementation	No attempts yet	2s	128 MB	Judgeable
Seven DwarfsGiven nine distinct heights, find seven that sum to exactly 100 and print them in ascending order.	Easy3	Brute forceArray+1	No attempts yet	2s	128 MB	Judgeable
Repeated SequenceSimulate a digit-power sequence until it cycles, then output how many distinct values appear before the repetition starts.	Easy3	SimulationHash map+1	No attempts yet	2s	256 MB	Judgeable
Axis-Parallel LinesGiven n points, count how many horizontal or vertical lines pass through at least two of them.	Easy3	Hash mapArray	No attempts yet	2s	128 MB	Judgeable
Distinguishing FilesGiven N files as sequences padded with zeros, find the minimum prefix length K that makes all files pairwise distinct.	Easy3	StringBrute force+1	No attempts yet	2s	128 MB	Judgeable
SaschaGiven a pronounced word and a dictionary of same-length words, find the dictionary word with the minimum Hamming distance, breaking ties by input order.	Easy3	StringBrute force+1	No attempts yet	2s	128 MB	Judgeable
Making Equal-Length SticksGiven piece lengths, find the smallest stick length such that all pieces can be regrouped into sticks of that equal length (the sum divided by a suitable divisor, bounded by the maximum piece).	Easy3	MathGreedy+1	No attempts yet	3s	128 MB	Judgeable
CombinationGiven n and m within 100, compute the exact value of the binomial coefficient C(n, m).	Easy3	MathCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Integer Square RootGiven an integer n up to 2^63-1, compute the smallest nonnegative integer q whose square is at least n.	Easy3	Binary searchMath	No attempts yet	0.4s	128 MB	Judgeable
Choosing Ice Cream in ItalyGiven N items and forbidden pairs, count the triples of items where no two form a forbidden pair.	Easy3	Brute forceArray	No attempts yet	1s	128 MB	Judgeable
Greatest Common Divisor and Least Common MultipleGiven the gcd and lcm of two unknown natural numbers, find the pair with the smallest sum satisfying both conditions.	Easy3	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
I Am the Class PresidentCompute total votes for three candidates and pick the winner using tie-break rules on 3-point then 2-point counts, or output 0 if still tied.	Easy3	SimulationImplementation	No attempts yet	1s	128 MB	Judgeable
Melon FieldGiven an L-shaped rectilinear hexagon described by six directional side lengths, compute its area and multiply by a melon density constant.	Easy3	GeometryMath+1	No attempts yet	1s	128 MB	Judgeable
Four DiceGiven N sets of four dice rolls, compute each participant's prize by rules based on matching-face patterns and output the maximum prize.	Easy3	ImplementationHash map+1	No attempts yet	1s	128 MB	Judgeable
SequenceFind the maximum length of a contiguous subarray of digits that is either nondecreasing or nonincreasing.	Easy3	ArrayDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
Rice Cakes for the TigerGiven the day index D and Fibonacci-like combination coefficients, find starting values A and B (A ≤ B) so the D-th term equals K.	Easy3	MathBrute force+1	No attempts yet	1s	128 MB	Judgeable
Number BaseballGiven N guesses with strike and ball counts in a number-baseball game, count how many three-distinct-digit numbers are consistent with all clues.	Easy3	Brute forceSimulation	No attempts yet	1s	128 MB	Judgeable
Candy Doctor ChangyoungScan a character grid to count fixed 3-cell horizontal ('>o<') or vertical ('v/o/^') candy patterns.	Easy3	MatrixImplementation+1	No attempts yet	1s	128 MB	Judgeable
RunningFor each runner, count how many runners ahead have higher ability and output that count plus one, using a running maximum.	Easy3	ArrayImplementation	No attempts yet	1s	256 MB	Judgeable
Pancake LoveGiven raw ingredient counts, compute the maximum batter portions (limited by a scaling factor) and topping-based pancake counts, then output the minimum of total toppings possible and batter portions.	Easy3	MathGreedy+1	No attempts yet	1s	128 MB	Judgeable
Remainder Sequence CycleGiven N and P, simulate the sequence a_{i+1} = a_i*N mod P and output the length of the eventual repeating cycle.	Easy3	SimulationHash map+1	No attempts yet	1s	128 MB	Judgeable
Rectangle Overlap TypeFor four pairs of axis-aligned rectangles, determine whether their intersection is a rectangle, a line segment, a point, or empty, printing a code letter per case.	Easy3	GeometryImplementation	No attempts yet	1s	128 MB	Judgeable
Asian Informatics OlympiadSort students by descending score and pick the top three medalists while capping each country to at most two medals.	Easy3	SortingGreedy+1	No attempts yet	1s	128 MB	Judgeable
Student Who Raises Both AveragesGiven two groups' IQ lists, count students in the first group whose IQ is below that group's average but above the second group's average.	Easy3	ArrayMath+1	No attempts yet	1s	128 MB	Judgeable
Representative Natural NumberFind the smallest integer minimizing the sum of absolute differences to a list of numbers, which is the lower median.	Easy3	SortingMath+1	No attempts yet	1s	128 MB	Judgeable
Two Representative Natural NumbersGiven up to 5,000,000 integers from 1 to 10,000, output the median (smallest if tie) and the rounded mean as representatives.	Easy3	MathSorting+1	No attempts yet	2s	256 MB	Judgeable
Temperature SequenceFind the maximum sum of any K consecutive elements in an array of N temperatures.	Easy3	Sliding windowPrefix sum+1	No attempts yet	1s	128 MB	Judgeable
Colored PaperGiven up to 100 axis-aligned 10x10 black squares placed on a 100x100 sheet, compute the total area they cover without double-counting overlaps.	Easy3	ArraySimulation+1	No attempts yet	1s	128 MB	Judgeable
BingoSimulate marking a 5x5 bingo board as numbers are called and find the call count when 3 lines (rows, columns, or diagonals) are first completed.	Easy3	SimulationArray+1	No attempts yet	1s	128 MB	Judgeable
Prime NumbersGiven a range M to N up to 10,000, find all primes in it and print their sum plus the smallest one, or -1 if none exist.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Secret LetterDecode a binary string into 6-bit chunks matching a fixed 8-letter code table by Hamming distance at most 1, printing the first unidentifiable chunk's position if any.	Easy3	StringBrute force+1	No attempts yet	1s	128 MB	Judgeable
Student LineupSimulate inserting students one by one into a line, each moving forward from the end by a given number of positions, then output the final order.	Easy3	SimulationArray	No attempts yet	1s	128 MB	Judgeable
Similar WordsCount how many words differ from the first word's letter multiset by at most one insertion, deletion, or substitution.	Easy3	Hash mapString+1	No attempts yet	1s	128 MB	Judgeable
Roman NumeralsConvert two Roman numerals to integers, sum them, and output the sum as both an Arabic and a Roman numeral.	Easy3	StringMath+1	No attempts yet	1s	128 MB	Judgeable
Card Game ScoreGiven five playing cards with color and number, compute a poker-like score by checking a fixed priority list of hand patterns.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Making Triangles with MatchsticksGiven n identical matchsticks, count the number of non-congruent integer-sided triangles whose perimeter equals n.	Easy3	MathCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Paper CuttingGiven a rectangular sheet and a series of horizontal or vertical cuts along grid lines, compute the area of the largest resulting piece.	Easy3	SortingArray+1	No attempts yet	1s	128 MB	Judgeable
Making Colored PaperRecursively quadtree-split an N×N grid of 0/1 cells into uniform-color squares and count the resulting white and blue pieces.	Easy3	RecursionDivide and conquer+1	No attempts yet	1s	128 MB	Judgeable
Line UpFind the minimum number of children to move so the line ends in sorted order, equivalent to N minus the longest increasing subsequence length.	Easy3	Dynamic programmingArray	No attempts yet	1s	128 MB	Judgeable
Kinship DistanceGiven a family forest of parent-child edges, find the shortest kinship distance between two given people or output -1 if unconnected.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
Chairperson CandidatesGiven a friendship graph, compute each member's eccentricity via shortest paths and report the minimum eccentricity value with all members achieving it.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
Housing Complex NumberingGiven a binary grid, count connected groups of adjacent 1-cells and print the number of groups plus each group's size in ascending order.	Easy3	BFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Nim SumCompute a generalized digit-wise sum of two numbers in base B, adding digits modulo B, for multiple test cases.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Receiving a FaxDecode a run-length-encoded byte stream using control bytes that mark literal or repeated runs, then print the result as hex.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Equal-Sum SegmentsSplit an array into contiguous segments with equal sums and output the smallest possible such common sum.	Easy3	Prefix sumGreedy+1	No attempts yet	1s	128 MB	Judgeable
Binary ClockConvert a given HH:MM:SS time into two 18-bit binary clock representations, read column-major-mixed 3-column and row-major 3-row layouts.	Easy3	Bit manipulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
DartsFor each test case, sum dartboard scores from coordinates for two players and print the winner or a tie.	Easy3	GeometrySimulation+1	No attempts yet	1s	128 MB	Judgeable
Spreadsheet Cell NamesConvert given row and column numbers into spreadsheet-style cell names like A1 or BC23, stopping at R0C0.	Easy3	MathString+1	No attempts yet	1s	128 MB	Judgeable
Bicycle SpeedGiven wheel diameter, rotation count, and elapsed time per line, compute total distance in miles and average speed in mph until a zero-rotation terminator.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Apartment ResidentsCompute the resident count in room n on floor k, defined by repeated prefix sums starting from room i having i residents on floor 0.	Easy3	Dynamic programmingMath+1	No attempts yet	0.5s	128 MB	Judgeable
BlackjackGiven N card values and a target M, find the maximum sum of three distinct cards not exceeding M.	Easy3	Brute forceTwo pointers+1	No attempts yet	1s	128 MB	Judgeable
Make a CrosswordBuild a grid where word A is placed horizontally and word B vertically, crossing at the first shared letter following a defined scan rule, filling the rest with dots.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Math HomeworkExtract every maximal run of digits from up to 100 strings, strip leading zeros, and print all extracted numbers sorted nondecreasing.	Easy3	StringSorting+1	No attempts yet	1s	128 MB	Judgeable
Contest or InternshipGiven female and male student counts and a number who must leave for internship, decide who to remove to maximize teams of 2 females and 1 male each.	Easy3	GreedyMath+1	No attempts yet	1s	128 MB	Judgeable
Frog LeapsSimulate a circular arrangement where a proclaimed frog repeatedly swaps forward with its neighbor B times, then output the final order starting from frog 1.	Easy3	SimulationArray	No attempts yet	1s	128 MB	Judgeable
Chocolate LunchGiven K, find the smallest power-of-two chocolate bar size and the minimum number of halving splits needed to obtain exactly K unit pieces.	Easy3	Bit manipulationMath+1	No attempts yet	1s	128 MB	Judgeable
Sangbeom's GameGiven a grid with two players' king pieces, compute for each player the sum over all pairs of their kings of the Chebyshev distance between them.	Easy3	MathArray+1	No attempts yet	1s	128 MB	Judgeable
KayakParse a grid to find each of nine teams' kayak position, rank teams by distance from the rightmost kayak cell to the finish line with tie handling.	Easy3	ImplementationSimulation+1	No attempts yet	1s	128 MB	Judgeable
Non-Alcoholic CocktailGiven amounts of three juices and a mixing ratio, compute the leftover of each juice after making the maximum possible cocktail.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Ancient LockGroup locks by whether one lock's row sequence is a constant horizontal shift of another, and count the number of distinct groups (keys) needed.	Easy3	ArrayHash map+1	No attempts yet	1s	128 MB	Judgeable
Candy PurchaseGiven a price and a bill denomination that is a power of ten, round the price to the nearest multiple of that denomination, rounding up on ties.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Ruler and ProtractorGiven N base angles closable under addition/subtraction mod 360, determine for K query angles whether each is reachable, which reduces to checking divisibility by gcd of the base angles and 360.	Easy3	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
Machine CodeGiven a sequence of instructions with parameters, compute the minimum NOPs needed so each instruction starts at an address divisible by 4.	Easy3	GreedySimulation+1	No attempts yet	1s	128 MB	Judgeable
Rock-Paper-Scissors ScoreGiven a player's rock-paper-scissors choices against several friends over multiple rounds, compute the actual score and the best possible score with foreknowledge each round.	Easy3	SimulationGreedy+1	No attempts yet	1s	128 MB	Judgeable
Croatian AlphabetParse a string left to right, greedily matching multi-character Croatian letter codes (like c=, dz=, lj), and count total letters.	Easy3	StringGreedy+1	No attempts yet	1s	128 MB	Judgeable
Sieve of EratosthenesSimulate the Sieve of Eratosthenes and output which number gets crossed out on the K-th removal step.	Easy3	SimulationMath	No attempts yet	1s	128 MB	Judgeable
Truck Parking FeesGiven per-truck rates depending on how many of three trucks overlap in time, compute the total parking fee over discrete minute intervals.	Easy3	SimulationImplementation	No attempts yet	1s	128 MB	Judgeable
Road and Traffic LightsSimulate a truck moving at 1 m/s along a road with traffic lights that cycle red then green, waiting at reds, and output total travel time to the end.	Easy3	SimulationImplementation	No attempts yet	1s	128 MB	Judgeable
Three NumbersGiven three numbers in order, insert one arithmetic operator and one equals sign to form a valid equation like a op b = c or a = b op c.	Easy3	Brute forceMath+1	No attempts yet	1s	128 MB	Judgeable
Aggressive DogsGiven two dogs' attack/rest cycle lengths, determine for three given minute timestamps how many dogs are attacking at that minute.	Easy3	MathSimulation+1	No attempts yet	1s	128 MB	Judgeable
Three PartsSplit a short lowercase string into three contiguous non-empty parts, reverse each part, and find the split that yields the lexicographically smallest concatenation.	Easy3	Brute forceString+1	No attempts yet	1s	128 MB	Judgeable
The Fourth NumberGiven three integers from a 4-term arithmetic progression (order unspecified), find the missing fourth integer.	Easy3	MathBrute force+1	No attempts yet	1s	128 MB	Judgeable
Secret EmailGiven an encrypted string, find matrix dimensions R<=C with R*C=N and largest R, then reverse a row-major-write column-major-read transposition to recover the original message.	Easy3	MatrixString+1	No attempts yet	1s	128 MB	Judgeable
Lexicographically Smallest Crossword WordExtract all horizontal and vertical maximal letter sequences of length at least 2 from a grid and output the lexicographically smallest one.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Lunch WarningsGiven a sequence of children taking food, count how many times a child's total pieces so far exceed all other children's combined total before their next pick.	Easy3	Hash mapSimulation	No attempts yet	1s	128 MB	Judgeable
Magician Lee MinhyukMirror a given top-left quarter grid horizontally and vertically to build a full card, then flip a single specified cell.	Easy3	ArrayImplementation+1	No attempts yet	1s	128 MB	Judgeable
Marathon Tic-Tac-ToeScan an N by N board to find if any letter forms three consecutive equal marks in a row, column, or diagonal, and print that letter or 'ongoing'.	Easy3	MatrixSimulation+1	No attempts yet	1s	128 MB	Judgeable
Completing a League TableFill in missing values (marked ?) in each football league row using matches=wins+draws+losses and points=3*wins+draws, with a unique solution guaranteed.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
RingsGiven radii of N touching rings, compute how many rotations each ring after the first makes as a reduced fraction when the first ring completes one rotation.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Polygon Diagonal IntersectionsGiven N, a convex N-gon with no three diagonals concurrent, compute the number of interior diagonal intersection points using the combinatorial formula C(N,4).	Easy3	CombinatoricsMath	No attempts yet	1s	128 MB	Judgeable
Visible Poster AreaGiven two axis-aligned rectangles, compute the visible area of the first rectangle after subtracting its overlap with the second.	Easy3	GeometryImplementation+1	No attempts yet	1s	128 MB	Judgeable
Counting Coin CombinationsCount the number of ways to sum a set of coin denominations (unlimited use, order ignored) to reach a target amount, for multiple test cases.	Easy3	Dynamic programming	No attempts yet	1s	128 MB	Judgeable
Heart Number SystemConvert a decimal integer to balanced ternary notation using digits 1, 0, and - for -1, without leading zeros.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Cutting ChocolateGiven an N by M chocolate bar, find the minimum number of square pieces obtained by repeatedly cutting it fully along rows or columns.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Walking RouteGiven N vectors forming a walking route, output the total displacement and the minimum distance from the start after removing exactly one segment.	Easy3	ArrayMath+1	No attempts yet	1s	128 MB	Judgeable