Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Flag Recognition
Easy3
Brute force, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
IPv6
Easy3
String, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Radio
Easy3
Graph, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Date Validation
Easy3
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Worm Turns
Easy3
Math, Simulation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pizza
Easy3
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Phone Bill
Easy3
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Multiply
Easy3
Brute force, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Luka
Easy3
Simulation, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Unreachable Functions
Easy3
Graph, BFS+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rhyme Pattern
Easy3
String, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Comport
Easy3
Simulation, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sum of Two Numbers
Easy3
Hash map, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
ICONS
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Most Visited Domains
Easy3
String, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hotel Room Assignment
Easy3
Simulation, Queue+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
DECODE
Easy3
String, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hal's Calculator
Easy3
Stack, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Towers of Coins
Easy3
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polygon
Easy3
Greedy, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Darts
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Game
Easy3
Matrix, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bug King
Easy3
Stack, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Easy Task
Easy3
Hash map, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hotline
Easy3
Hash map, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Adding Reversed Numbers
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Binary Encoding
Easy3
Bit manipulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Whitespace King: Aligning Columns
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Building for the UN
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Water Main Break
Easy3
Array, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Beer Refrigerator
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
iChess
Easy3
Binary search, Math+1
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Java vs C++
Easy3
String, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Roots Intervals
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Control Points
Easy3
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Build Your Home
Easy3
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Networking
Easy3
Minimum spanning tree, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Working at the Restaurant
Easy3
Stack, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
And Then There Was One
Easy3
Simulation, Queue+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prime Gap Sequence
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
How I Wonder What You Are!
Easy3
Geometry, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Unreliable Messengers
Easy3
String, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
My Brother's Diary
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Windows
Easy3
Array, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Alien Base Conversion
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fibonacci Number
Easy3
Dynamic programming, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Exact Change
Easy3
Dynamic programming, Array+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Smeech
Easy3
Recursion, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Conformity Prize
Easy3
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
To and Fro
Easy3
String, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ferry Loading IV
Easy3
Simulation, Queue
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Ratios
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Traditional BINGO
Easy3
Simulation, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Blocks
Easy3
Brute force, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Forests
Easy3
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Jolly Jumpers
Easy3
Array, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Carry Count
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Election
Easy3
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
ROT13
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Robot Roll Call
Easy3
Hash map, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Geek Challenge [SKRZAT] (Base Minus Two)
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Defining Moment
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Choose Your Own Adventure
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Is the Name of This Problem
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Judges' Time Calculation
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mad Scientist
Easy3
Array, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Copier Reduction
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Symmetric Order
Easy3
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Flow Layout
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tanning Salon
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
W's Cipher
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hangover
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pronounceable Passwords
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Loansome Car Buyer
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Amalgamation
Easy3
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Basically Speaking
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Losers Are Winners
Easy3
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Spelling Be
Easy3
Hash map, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Counting Pages
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Look and Say
Easy3
String, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Faulty Odometer
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gold Coins
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gym
Easy3
Math, Matrix+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Relax! It's Just a Game
Easy3
Math, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tetromino Maximum Sum
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Casting Out Nines
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A Balanced World
Easy3
Stack, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Equal Total Scores
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Car Trouble
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Skyline
Easy3
Geometry, Intervals+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Carbonated Drinks
Easy3
Math, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The God of Parking
Easy3
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
When Do We Finish?
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Car Park
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Shirts
Easy3
Sorting, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Street Numbers
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Air Old Zeeland
Easy3
Implementation, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sequences
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Postman Joe
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Coded Communication
Easy3
String, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Flag RecognitionGiven a 6x9 letter grid, compute the minimum edits needed to make it a valid three-stripe flag, either horizontal (2-row bands) or vertical (3-column bands) with the middle band's color differing from both outer bands.	Easy3	Brute forceImplementation+1	No attempts yet	1s	128 MB	Judgeable
IPv6Given a shortened IPv6 address with omitted leading zeros and possibly one '::' run, expand it into eight full 4-digit hex groups.	Easy3	StringImplementation	No attempts yet	1s	128 MB	Judgeable
RadioGiven a start and target frequency plus up to 5 preset shortcut buttons, find the minimum presses using +1, -1, or jump to a preset to reach the target.	Easy3	GraphShortest path+1	No attempts yet	1s	128 MB	Judgeable
Date ValidationRead day, month, year triples until a terminator and print whether each represents a real calendar date, accounting for leap years.	Easy3	ImplementationMath	No attempts yet	1s	128 MB	Judgeable
Worm TurnsGiven an M by N grid eaten in a clockwise spiral, compute how many times the direction changes before the whole grid is consumed.	Easy3	MathSimulation	No attempts yet	1s	128 MB	Judgeable
PizzaGiven each friend's pizza appetite of 1/4, 1/2, or 3/4, compute the minimum number of whole pizzas needed to serve exact slices to all.	Easy3	GreedyMath+1	No attempts yet	1s	128 MB	Judgeable
Phone BillGiven N calls with a start time and duration under 60 minutes, sum the cost by charging 10 won per minute in 07:00-19:00 and 5 won otherwise, splitting calls that cross the boundary.	Easy3	SimulationImplementation	No attempts yet	1s	128 MB	Judgeable
MultiplyFor each test case, find the smallest base from 2 to 16 in which the digit strings p, q, r satisfy p times q equals r, or output 0 if none works.	Easy3	Brute forceMath+1	No attempts yet	1s	128 MB	Judgeable
LukaSimulate a walker's path on a grid and output every time step when the walker is within Chebyshev distance 1 of a fixed point.	Easy3	SimulationArray	No attempts yet	1s	128 MB	Judgeable
Unreachable FunctionsGiven a control flow graph built from three instruction types with fall-through or jump edges, count how many functions are unreachable from the first one.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
Rhyme PatternGiven verses of four lines, extract each line's last syllable from its final word and classify the rhyme pattern as perfect, even, cross, shell, or free.	Easy3	StringImplementation	No attempts yet	1s	128 MB	Judgeable
ComportFind the smallest step size K (1 to N) so repeatedly moving K fields clockwise from field 1 reaches field Z without landing on any obstacle field along the way.	Easy3	SimulationBrute force+1	No attempts yet	1s	128 MB	Judgeable
Sum of Two NumbersCount pairs of distinct integers in an array that sum exactly to a given value x.	Easy3	Hash mapTwo pointers+1	No attempts yet	1s	128 MB	Judgeable
ICONSGiven N, find rows R and columns C with R<=C, R*C>=N, minimizing R+C, and output the most balanced such pair.	Easy3	MathBrute force+1	No attempts yet	1s	128 MB	Judgeable
Most Visited DomainsParse a list of URLs to extract each domain suffix and print the maximum visit count along with all domains that reach it, sorted alphabetically.	Easy3	StringHash map+1	No attempts yet	1s	128 MB	Judgeable
Hotel Room AssignmentSimulate assigning arriving groups to hotel rooms with two beds each, filling empty rooms first then pairing singles, and output the final occupancy per room.	Easy3	SimulationQueue+1	No attempts yet	1s	128 MB	Judgeable
DECODEBuild a substitution cipher table from a key word placed at a given offset, then decode a given ciphertext using it.	Easy3	StringSimulation+1	No attempts yet	1s	128 MB	Judgeable
Hal's CalculatorSimulate a stack-like list of expressions under six commands (HASH, DOLLAR, SWAP, DROP, DUP, ROT), enforcing size and availability constraints, and output the final list or ERROR.	Easy3	StackSimulation+1	No attempts yet	1s	128 MB	Judgeable
Towers of CoinsGiven move options 1, K, or L coins in a Nim-like turn game, determine for each pile size whether the first player wins under optimal play.	Easy3	Dynamic programmingGame theory	No attempts yet	1s	128 MB	Judgeable
PolygonDecide whether N given segment lengths can form the sides of some convex polygon, which reduces to checking that the largest length is smaller than the sum of the rest.	Easy3	GreedyMath	No attempts yet	1s	128 MB	Judgeable
DartsFor each dart throw coordinate, determine the score based on concentric circle radius bands and sum the scores per test case.	Easy3	MathImplementation+1	No attempts yet	1s	256 MB	Judgeable
GameGiven many filled 5x5 tic-tac-toe boards, determine for each whether A, B, or neither has three consecutive same marbles in a row, column, or diagonal.	Easy3	MatrixSimulation+1	No attempts yet	1s	128 MB	Judgeable
Bug KingRepeatedly remove all occurrences of the substring "BUG" from each input line, using a stack-like scan since removals can form new matches, until none remain.	Easy3	StackString	No attempts yet	1s	128 MB	Judgeable
Easy TaskProcess a list of contest submissions to compute, for each of nine problems, the number of teams that solved it and the average submissions and solve time.	Easy3	Hash mapSimulation+1	No attempts yet	1s	128 MB	Judgeable
HotlineAnswer yes, no, or maybe questions about one-word subjects and verb-object activities using the statements heard earlier in each dialogue.	Easy3	Hash mapSimulation+1	No attempts yet	1s	128 MB	Judgeable
Adding Reversed NumbersReverse two given numbers, add them, then output the sum reversed with leading zeros dropped.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Binary EncodingGiven m, output the truncated binary code for each integer from 0 to m-1 following the standard truncated binary encoding rules.	Easy3	Bit manipulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Whitespace King: Aligning ColumnsReformat text lines so that words in each column line up to a width equal to the longest word in that column, with single spaces separating columns.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Building for the UNPrint a fixed two-floor n by n grid where the lower floor's rows and upper floor's columns each represent a labeled country, satisfying a connectivity and adjacency construction.	Easy3	ImplementationSimulation+1	No attempts yet	3s	128 MB	Judgeable
Water Main BreakGiven several water main breaks with start, end, and flow rate, sum the gallons leaked during each second of a given query interval.	Easy3	ArraySimulation+1	No attempts yet	1s	128 MB	Judgeable
Beer RefrigeratorGiven n, find integer dimensions a,b,c with abc=n that minimize the box surface area 2(ab+bc+ca).	Easy3	Brute forceMath	No attempts yet	1s	128 MB	Judgeable
iChessGiven counts of black and white tiles, find the largest square side length whose checkerboard pattern fits within those tile counts, or report impossibility.	Easy3	Binary searchMath+1	No attempts yet	2s	64 MB	Judgeable
Java vs C++Detect whether a name follows Java camelCase or C++ snake_case rules and convert it to the other style, or print an error if invalid.	Easy3	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Roots IntervalsGiven interval [a,b] split into nb equal subintervals, count subintervals where f(x)=1-x^2 has a sign change or zero at endpoints.	Easy3	ImplementationSimulation+1	No attempts yet	1s	128 MB	Judgeable
Control PointsGiven sorted coordinates of control points, find the minimum number of length-1 half-open intervals needed to cover all points using a greedy sweep.	Easy3	GreedySorting+1	No attempts yet	1s	128 MB	Judgeable
Build Your HomeCompute and round the area of each given simple polygon, including degenerate cases with fewer than three vertices, until a terminating zero.	Easy3	GeometryImplementation+1	No attempts yet	1s	128 MB	Judgeable
NetworkingGiven points and weighted candidate cable routes, compute the minimum total cable length needed to connect all points (minimum spanning tree).	Easy3	Minimum spanning treeGraph+1	No attempts yet	1s	128 MB	Judgeable
Working at the RestaurantSimulate a two-pile plate stacking strategy that always drops on pile 2 and serves from pile 1, moving plates when pile 1 runs out, and output the exact operation transcript.	Easy3	StackSimulation+1	No attempts yet	1s	128 MB	Judgeable
And Then There Was OneSimulate a Josephus-style circle elimination game with a custom starting removal point and report the last remaining stone for each test case.	Easy3	SimulationQueue+1	No attempts yet	1s	128 MB	Judgeable
Prime Gap SequenceGiven a number k, find the gap length between the two consecutive primes surrounding it if k is composite, otherwise output 0.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
How I Wonder What You Are!For each dataset, count how many of the given stars fall within the angular radius of at least one of several telescopes all located at the origin.	Easy3	GeometryBrute force+1	No attempts yet	1s	128 MB	Judgeable
Unreliable MessengersGiven a sequence of reversible string transformations and the final message, undo each transformation in reverse order to recover the original message.	Easy3	StringSimulation+1	No attempts yet	1s	128 MB	Judgeable
My Brother's DiaryFind the Caesar shift whose most frequent ciphertext letter maps to E, print the smallest valid shift and the decrypted text, or NOT POSSIBLE if several shifts work.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
WindowsGiven windows in opening order, answer clicks by returning the most recently opened window covering each click point, or background if none does.	Easy3	ArrayBrute force+2	No attempts yet	1s	128 MB	Judgeable
Alien Base ConversionConvert a number written in base x into the same value written in base y, where both bases are between 2 and 36 and the value fits in four billion.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Fibonacci NumberGiven n, print the n-th Fibonacci number, where the sequence starts 1, 1 and each later term is the sum of the previous two.	Easy3	Dynamic programmingMath+2	No attempts yet	1s	128 MB	Judgeable
Exact ChangeGiven a price and a multiset of up to 100 coin values, pick a subset summing to at least the price; minimize the sum first, then the number of coins.	Easy3	Dynamic programmingArray+1	No attempts yet	1s	128 MB	Judgeable
SmeechParse a prefix Smeech expression with probabilistic plus or minus operators and compute its expected value to two decimals.	Easy3	RecursionMath+2	No attempts yet	1s	128 MB	Judgeable
Conformity PrizeCanonicalize each frosh's five courses, count how many frosh share each set, then output the total over all sets with the maximum count.	Easy3	Hash mapSorting+2	No attempts yet	1s	128 MB	Judgeable
To and FroDecode a message written row by row in alternating left-to-right and right-to-left order back into column-major plaintext.	Easy3	StringSimulation+2	No attempts yet	1s	128 MB	Judgeable
Ferry Loading IVSimulate a ferry of given length that repeatedly crosses between two banks, loading waiting cars in arrival order.	Easy3	SimulationQueue	No attempts yet	1s	128 MB	Judgeable
Word RatiosFor each line of three equal-length lowercase words, apply the per-letter alphabet shift from the first word to the second onto the third, and output all four words.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Traditional BINGOFor each card, find how many announced numbers are needed before some row, column, or diagonal of five spaces is fully marked, with the center free.	Easy3	SimulationArray+2	No attempts yet	1s	128 MB	Judgeable
BlocksGiven N unit cubes, find positive integers a, b, c with abc = N that minimize the surface area 2(ab+bc+ca).	Easy3	Brute forceMath+2	No attempts yet	1s	128 MB	Judgeable
ForestsCount how many distinct nonempty sets of trees appear among the (person, tree) pairs; people who heard nothing are excluded.	Easy3	Hash mapSorting+2	No attempts yet	1s	128 MB	Judgeable
Jolly JumpersFor each sequence, check whether the absolute differences of adjacent elements are exactly the set 1 to n-1.	Easy3	ArrayHash map+2	No attempts yet	1s	128 MB	Judgeable
Carry CountFor each pair of non-negative integers, count how many carries occur while adding them column by column from the right. Stop at the 0 0 line.	Easy3	ImplementationMath+1	No attempts yet	1s	128 MB	Judgeable
ElectionCount the votes each candidate receives in one riding, ignore unknown names, and report the winner's party or independent, or tie if there is no strict winner.	Easy3	Hash mapImplementation+2	No attempts yet	1s	128 MB	Judgeable
ROT13Decode lines of text by reversing the ROT13 cipher: each vowel shifts three places back in a fixed vowel order, each consonant ten back in a consonant order.	Easy3	ImplementationString+2	No attempts yet	1s	128 MB	Judgeable
Robot Roll CallGiven a roster of names and a multi-line data stream split on spaces and tabs, report for each roster name whether it appears as an exact token.	Easy3	Hash mapString+2	No attempts yet	1s	128 MB	Judgeable
Geek Challenge [SKRZAT] (Base Minus Two)Convert numbers between decimal and base -2 (Weird Binary), echoing each query with its formatted result.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Defining MomentFor each word, strip at most one valid prefix and one valid suffix, then substitute the matching English meaning, expanding the suffix after the prefix.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Choose Your Own AdventureEach page is a node with two outgoing choices or a terminal ending; print the unique path from page 1 to the single HAPPY ending.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Is the Name of This ProblemRead sentences until END and for each decide whether it has the form quote, phrase A, quote, space, A, printing Quine(A) or not a quine.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Judges' Time CalculationGiven a 12-hour start time and a contest duration, print a lookup table giving the elapsed minutes formula for each hour block.	Easy3	ImplementationSimulation+1	No attempts yet	1s	128 MB	Judgeable
Mad ScientistRecover a non-decreasing sequence of measurements from its cumulative counts P(j), the number of measurements at most j, for each j from 1 to k.	Easy3	ArrayPrefix sum+1	No attempts yet	1s	128 MB	Judgeable
Copier ReductionGiven an image and paper size in millimeters, find the largest integer percentage scale (with optional 90-degree rotation) that still fits on the paper.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Symmetric OrderGiven a list of names sorted by length, rearrange them so shorter names sit at the top and bottom and longer ones in the middle, pairing names from the start.	Easy3	ArrayImplementation+2	No attempts yet	1s	128 MB	Judgeable
Flow LayoutPlace rectangles left to right into rows under a max width, wrap when one does not fit, and report the final window width and total height.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Tanning SalonSimulate a tanning salon with a fixed number of beds, tracking arrivals and departures, and count how many customers leave without a bed.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
W's CipherDecrypt messages by extracting each of three character groups and rotating its subsequence right by the matching key.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
HangoverFor each target overhang c, find the smallest n such that the harmonic sum 1/2 + 1/3 + ... + 1/(n+1) reaches c, and report n.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Pronounceable PasswordsFor each lowercase password, check three rules: at least one vowel, no three vowels or consonants in a row, and no double letter except ee and oo.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Loansome Car BuyerSimulate monthly depreciation and payments on a car loan, and report the first month when the amount owed drops below the car's value.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Word AmalgamationFor each scrambled word, print all dictionary words that are anagrams of it in alphabetical order, or NOT A VALID WORD.	Easy3	Hash mapSorting+2	No attempts yet	1s	128 MB	Judgeable
Basically SpeakingConvert a number from one base to another (bases 2 to 16) and print the result right-justified in a 7-character field, or ERROR if it exceeds 7 digits.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Losers Are WinnersGroup contestants into teams of two, compute each team's percentage of combined weight lost, and print the winner with one decimal place.	Easy3	Hash mapImplementation+2	No attempts yet	1s	128 MB	Judgeable
Spelling BeRead a dictionary and several emails, then report for each email whether all its words are known and list the unknown words in order.	Easy3	Hash mapString+2	No attempts yet	1s	128 MB	Judgeable
Counting PagesGiven a document's page count and a comma-separated list of page ranges, count the distinct pages that are actually printed, ignoring empty ranges and pages past the end.	Easy3	ImplementationString+2	No attempts yet	1s	256 MB	Judgeable
Look and SayFor each input string of digits, produce the next look-and-say element by counting runs of equal digits and writing each count followed by the digit.	Easy3	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Faulty OdometerRead odometer values that skip the digit 4 and print the true mileage by treating each reading as a base-9 number.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Gold CoinsFor each number of days, add up the gold coins when the knight is paid N coins on each of N consecutive days.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
GymGiven an N by N matrix of card counts, compute the probability distribution over N baskets for the first 10 steps of a Markov process starting at basket 1.	Easy3	MathMatrix+2	No attempts yet	1s	128 MB	Judgeable
Relax! It's Just a GameFor each score (A, B), check whether the binomial coefficient C(A+B, A) equals the sum A+B, and print the comparison.	Easy3	MathCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Tetromino Maximum SumGiven an N x N grid of integers, place one of the five tetrominoes (with rotations, not flips) so the four covered cells have the largest sum.	Easy3	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Casting Out NinesFor each line like a+b=c. or a*b=c., compute digit sums modulo 9 and print PASS if the operation is congruent, otherwise NOT!.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
A Balanced WorldFor each line ending in a period, decide whether its round and square brackets are properly matched and nested, printing yes or no.	Easy3	StackString+1	No attempts yet	1s	128 MB	Judgeable
Equal Total ScoresFind one card from each person to swap so their total scores match, choosing the pair with the smallest sum, or print -1.	Easy3	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Car TroubleGiven a directed graph of street ids with ring road 0, report streets that cannot reach 0 and streets that 0 cannot reach, preserving input order.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
SkylineWe have N trapezoidal buildings listed from nearest to farthest. For each building, we must compute the fraction of its area that remains visible, i.e., the part of the trapezoid not hidden by any closer building. The presence of overlapping sloped roofs makes the computation nontrivial: for a given building we need to determine, for each horizontal coordinate, the maximum roof height among all closer buildings. Then the visible area is the integral, over the building’s own range [x1, x2], of the positive part of the difference between the building's top edge (roof) and that maximum height.For	Easy3	GeometryIntervals+2	No attempts yet	1s	128 MB	Judgeable
Carbonated DrinksGiven starting empties, empties found, and the empties needed per exchange, count how many drinks Junmin can obtain and drink in total.	Easy3	MathSimulation+2	No attempts yet	1s	128 MB	Judgeable
The God of ParkingGiven shop coordinates on a line, pick an integer parking spot and visit all shops, returning to the car, to minimize total walking distance.	Easy3	MathGreedy+2	No attempts yet	1s	128 MB	Judgeable
When Do We Finish?Add each event's duration to its start time and print the resulting clock time, appending the number of days past midnight when the end crosses into later days.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Car ParkSimulate a sequence of car entry and exit signals for a car park of capacity S starting with C cars, stopping early if an exit occurs while empty.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
ShirtsMerge two already sorted lists of shirts and print one merged list ordered by size, then by colour letter. Multiple scenarios end with a 0.	Easy3	SortingTwo pointers+2	No attempts yet	1s	128 MB	Judgeable
Street NumbersCount how many times each digit 0 to 9 appears on house numbers from L to H, skipping the given gap ranges.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Air Old ZeelandFor each customer, sum the prices of requested products whose shipping delay fits the wait limit, flag customers who miss any product, and count them.	Easy3	ImplementationArray+2	No attempts yet	1s	128 MB	Judgeable
SequencesFor each query with a first term, non-zero common difference, and value, print the term index if the value is in the arithmetic sequence, otherwise X.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Postman JoeSimulate Joe's walk on 20 houses, flag any out-of-range or repeated house as illegal, else list the houses with no delivery.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Coded CommunicationGiven n binary strings of length b and a received string r, find the minimum Hamming distance from r to any of the n strings.	Easy3	StringBrute force+2	No attempts yet	1s	128 MB	Judgeable