Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Weird Currency
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grocery Shopping
Easy3
Hash map, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Subway Fares
Easy3
Array, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gadget Purchases
Easy3
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Toxic Assets
Easy3
Dynamic programming, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fingerprints
Easy3
Array, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Campus Buildings
Easy3
String, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Global Warming
Easy3
Array, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Base K
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Longest Decreasing Suffix
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mining Maps
Easy3
Hash map, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Samba
Easy3
Hash map, Array
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Parity Bit
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
PLU Count
Easy3
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Duplicate SSN
Easy3
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Coin Row
Easy3
Dynamic programming, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Music
Easy3
Sliding window, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Decoder
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Escape Route
Easy3
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Asteroid Field
Easy3
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Secret Letter
Easy3
Implementation, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
POI
Easy3
Implementation, Array+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Rings
Easy3
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tiles
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Traveler
Easy3
Prefix sum, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Placing Cards
Easy3
Brute force, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Card Captor Sanggeun
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Maximum Sum
Easy3
Array, Sliding window+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Card Rearrangement
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Commute Route
Easy3
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
School Trip Destination Ranking
Easy3
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Look-and-Say String
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Character Conversion
Easy3
Hash map, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rolling a Die
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Calculator Program
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Common Divisors
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Rotary Dial
Easy3
Implementation, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Longest Word
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Line of Best Fit
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hotel Room Numbers
Easy3
Brute force, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
In Braille
Easy3
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tautogram
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Electricity
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
He is offside!
Easy3
Implementation, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Magic Trick
Easy3
Implementation, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grandpa is Famous!
Easy3
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Fake Tickets
Easy3
Array, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Breed Assignment
Easy3
Graph, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Find the Cow
Easy3
String, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hay Bales
Easy3
Array, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Daisy Chains in the Field
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Race Results
Easy3
Sorting, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Adding Commas
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Profits
Easy3
Array, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Crop Circles
Easy3
Geometry, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cow Cotillion
Easy3
Stack, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A Spiral Walk
Easy3
Simulation, Matrix+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
3D Space Exploration
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Robot Plow
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Invasion of the Milkweed
Easy3
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lonesome Partners
Easy3
Brute force, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Feeding Time
Easy3
DFS, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Rock Game
Easy3
Bit manipulation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Wheel Rotation
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bad Grass
Easy3
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Plumbing the Pond
Easy3
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Perfect Cow
Easy3
Sorting, Array+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Good Grass
Easy3
Array, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Perfect Squares
Easy3
Brute force, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bookshelf
Easy3
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Superlatives
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Game of Lines
Easy3
Hash map, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
World Cup Noise
Easy3
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Best Grass
Easy3
Array, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Going to the Movies
Easy3
Brute force, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Another Cow Number Game
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mileage Bank
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Balloon Game
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Encrypted SMS
Easy3
String, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Blowing Fuses
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Box of Bricks
Easy3
Array, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Missing Side of a Right Triangle
Easy3
Math, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Carbon Dating
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
URLs
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Definite Values
Easy3
Simulation, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Drunken Jailer
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Set Me
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Digital Root
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prime Cuts
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Uniform Generator
Easy3
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Palindromes
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Shipping Routes
Easy3
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Donghyeok Pizza
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ambiguous Permutations
Easy3
Array, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Help the problem setter
Easy3
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Subsequence
Easy3
Two pointers, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polygon Programming with Ease
Easy3
Math, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Average is not Fast Enough!
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
HTML
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Error Correction
Easy3
Implementation, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Weird CurrencyGiven a chain of denomination conversion rates, convert each vendor's price to the smallest unit and report the difference between the highest and lowest price.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Grocery ShoppingFor each grocery item, find its matching store item by case-insensitive name and add the club-card saving on the units actually bought.	Easy3	Hash mapString+1	No attempts yet	1s	128 MB	Judgeable
Subway FaresGiven a per-stop fare table and an ordered list of station names, find the number of stops between two stations and print the corresponding fare.	Easy3	ArrayString+2	No attempts yet	1s	128 MB	Judgeable
Gadget PurchasesCount how many visits demand each machine, cap each count at its usage limit, and report the machines whose revenue beats purchase plus usage cost.	Easy3	ArrayImplementation+2	No attempts yet	1s	128 MB	Judgeable
Toxic AssetsGiven current values of basic investments and acyclic derivative definitions, compute the current worth of a portfolio made of these investments.	Easy3	Dynamic programmingMath+1	No attempts yet	1s	128 MB	Judgeable
FingerprintsFor each of K query 5x5 bitmaps, find the database bitmap with the smallest Hamming distance and print all tied indices in increasing order.	Easy3	ArrayBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
Campus BuildingsGiven building names and an abbreviation, list the names whose letters contain the abbreviation as a case-insensitive subsequence, in input order.	Easy3	StringTwo pointers+1	No attempts yet	1s	128 MB	Judgeable
Global WarmingGiven a small land/sea grid, mark every land cell with three or more sea neighbours as sea simultaneously, then print the tight bounding box of the remaining land.	Easy3	ArraySimulation+2	No attempts yet	1s	128 MB	Judgeable
Base KConvert each n to base k and report whether every digit from 0 to k-1 appears, formatting the output line exactly as specified.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Longest Decreasing SuffixFor each string, print its longest suffix whose characters strictly decrease from left to right.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Mining MapsParse each graph block, count distinct node names, and count distinct undirected tunnels including self-loops.	Easy3	Hash mapGraph+2	No attempts yet	1s	128 MB	Judgeable
SambaGiven the school IDs of n dancers, find the single school whose total dancer count is not a multiple of k.	Easy3	Hash mapArray	No attempts yet	1s	64 MB	Judgeable
Parity BitSplit each line into 8-bit blocks, check whether the parity bit matches the parity of the first 7 bits, and count the mismatches.	Easy3	ImplementationString+2	No attempts yet	1s	128 MB	Judgeable
PLU CountFor each text string, find the largest k such that PLU repeated k times is a subsequence, ignoring case.	Easy3	GreedyString+1	No attempts yet	1s	128 MB	Judgeable
Duplicate SSNRead a list of Social Security numbers until the sentinel 000-00-0000, then print every number that appears more than once in ascending order.	Easy3	Hash mapSorting+2	No attempts yet	1s	128 MB	Judgeable
Coin RowGiven rows of coin values, pick non-adjacent coins to maximize the total collected in each row.	Easy3	Dynamic programmingArray	No attempts yet	1s	128 MB	Judgeable
MusicCount length-m windows whose max minus min is at most c, across several small arrays.	Easy3	Sliding windowArray	No attempts yet	1s	128 MB	Judgeable
DecoderEach word contributes one letter: the first letter of the first word, then the k-th letter of each word where k is the previous word's length; spaces appear when the previous word is too long.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Escape RouteFor each grid, find the ship and the planet nearest to it, breaking ties by row-major order, and print both coordinates with the distance to two decimals.	Easy3	ArrayImplementation+2	No attempts yet	1s	128 MB	Judgeable
Asteroid FieldFind the minimum number of moves from the top-left cell to the bottom-right cell in a grid, avoiding asteroid cells.	Easy3	BFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Secret LetterGiven a ciphertext, undo a 90-degree clockwise rotation of a square grid to recover the original letter.	Easy3	ImplementationArray+2	No attempts yet	1s	128 MB	Judgeable
POIEach problem's value is the count of contestants who missed it; report Philip's total score and his rank using the four tiebreak terms.	Easy3	ImplementationArray+2	No attempts yet	1s	256 MB	Judgeable
RingsCount how many of N rings, each a 10-letter circular string, contain a given search string when read around the circle.	Easy3	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
TilesFor each of K tiles in an N x N ring-colored square, find which concentric ring holds it and output the ring's color.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
The TravelerGiven gaps between n towns and a walk of m east/west jumps, find the total distance covered, reported mod 100000.	Easy3	Prefix sumArray+2	No attempts yet	1s	128 MB	Judgeable
Placing CardsGiven up to 10 cards with 1 or 2 digit numbers, count the distinct integers formed by ordering exactly k chosen cards.	Easy3	Brute forceBacktracking+2	No attempts yet	1s	256 MB	Judgeable
Card Captor SanggeunSimulate a two-player card game where each player always plays the smallest legal card, and report the final scores.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Maximum SumGiven n integers and a window size k, find the largest sum of any k consecutive terms.	Easy3	ArraySliding window+1	No attempts yet	1s	128 MB	Judgeable
Card RearrangementStarting from the stack 1, 2, ..., 2n, apply a sequence of cuts and riffle shuffles and print the final order of the cards.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Commute RouteCount monotone east/north lattice paths from (1,1) to (a,b) that avoid n blocked intersections, with a and b at most 16.	Easy3	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
School Trip Destination RankingCount how many of n students want each of m destinations, then print destination numbers by descending count with ties broken by ascending number.	Easy3	ArraySorting+1	No attempts yet	1s	128 MB	Judgeable
Look-and-Say StringApply the look-and-say run-length encoding to a digit string n times and print the resulting string.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Character ConversionMap each character according to a conversion table where every replacement happens exactly once, and print the resulting string.	Easy3	Hash mapImplementation+1	No attempts yet	1s	128 MB	Judgeable
Rolling a DieSimulate rolling a die through a list of moves and sum the top face value after each move.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Calculator ProgramRead alternating numbers and operators, evaluate left to right ignoring precedence, and print the value when = appears.	Easy3	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
Common DivisorsGiven 2 or 3 numbers up to 1e8, print every positive integer that divides all of them, in increasing order.	Easy3	MathNumber theory+2	No attempts yet	1s	256 MB	Judgeable
Rotary DialGiven an uppercase word, map each letter to its phone digit and sum the dial times, where digit d costs d+1 seconds and 0 costs 11.	Easy3	ImplementationString+1	No attempts yet	1s	128 MB	Judgeable
Longest WordScan text until the token E-N-D, split it into words made of letters and hyphens, and print the longest such word in lowercase, breaking ties by first occurrence.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Line of Best FitGiven n points in the plane, compute the slope and intercept of the least squares regression line and print each rounded to three decimals.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Hotel Room NumbersFor each pair N and M, count the integers in [N, M] whose decimal digits are all distinct, reading cases until end of file.	Easy3	Brute forceMath+1	No attempts yet	1s	128 MB	Judgeable
In BrailleTranslate a string of digits to Braille cells, or three lines of Braille cells back to digits, using the fixed digit-to-cell table.	Easy3	StringHash map+2	No attempts yet	1s	128 MB	Judgeable
TautogramFor each sentence, decide whether every word begins with the same letter, ignoring case, until a line containing only *.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
ElectricityGiven dated meter readings sorted by date, count pairs on consecutive calendar days and report how many such days exist plus the total consumption between them.	Easy3	ImplementationMath+2	No attempts yet	1s	128 MB	Judgeable
He is offside!Given distances of attackers and defenders to the goal line, decide whether any attacker is offside, meaning nearer to the goal than the second-last defender.	Easy3	ImplementationSorting+2	No attempts yet	1s	128 MB	Judgeable
Magic TrickGiven four cards in the order shown, decode the hidden fifth card using the suit of the first card and the permutation of the last three.	Easy3	ImplementationSorting+2	No attempts yet	1s	128 MB	Judgeable
Grandpa is Famous!Given weekly ranking lists, count how many times each player appears, then print the players with the second-highest count in ascending order.	Easy3	Hash mapSorting+2	No attempts yet	1s	256 MB	Judgeable
Fake TicketsGiven N genuine ticket numbers and a list of M collected ticket numbers, count how many distinct values appear more than once in the list.	Easy3	ArrayHash map+1	No attempts yet	1s	128 MB	Judgeable
Breed AssignmentCount the breed assignments for N cows under same/different constraints, or report 0 if they conflict.	Easy3	GraphBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Find the CowCount ordered pairs of indices (x, y) with x < y where an "((" starts at x and a "))" starts at y in a parenthesis string.	Easy3	StringPrefix sum+2	No attempts yet	1s	128 MB	Judgeable
Hay BalesGiven N piles of hay with possibly unequal heights, find the minimum number of bales to move so all piles have equal height.	Easy3	ArrayMath+1	No attempts yet	1s	128 MB	Judgeable
Daisy Chains in the FieldGiven an undirected graph of cows joined by ropes, list in ascending order every cow that cannot reach cow 1, or print 0 if all cows are connected to it.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Race ResultsSort N finish times given as hours, minutes, and seconds in ascending order and print each on its own line.	Easy3	SortingImplementation	No attempts yet	1s	128 MB	Judgeable
Adding CommasInsert a comma every three digits from the right in a given integer and print the formatted number.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
ProfitsGiven a sequence of N daily profits, find the maximum sum over any contiguous stretch of days.	Easy3	ArrayDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Crop CirclesGiven N circles, count for each circle how many of the other circles it overlaps, using the strict distance-versus-sum-of-radii test.	Easy3	GeometryBrute force+2	No attempts yet	1s	128 MB	Judgeable
Cow CotillionGiven strings of '<' and '>', decide for each whether every character can be paired as a properly nested '><' bow, i.e. whether the brackets are balanced.	Easy3	StackString+2	No attempts yet	1s	128 MB	Judgeable
A Spiral WalkFill an N by N grid with the visit order of a clockwise spiral that starts at the top-left and ends near the center.	Easy3	SimulationMatrix+1	No attempts yet	1s	128 MB	Judgeable
3D Space ExplorationCount connected groups of '*' blocks in an N x N x N grid, where blocks connect only across shared faces.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
The Robot PlowGiven up to 200 axis-aligned rectangles on a grid at most 240 by 240, count the number of unit squares covered by at least one rectangle.	Easy3	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
Invasion of the MilkweedSpread milkweed from a start cell to all eight neighbors each week and report the week it covers the last non-boulder cell.	Easy3	BFSGraph+2	No attempts yet	1s	128 MB	Judgeable
Lonesome PartnersGiven N points, find the 1-based indices of the two points with the largest Euclidean distance, guaranteed unique.	Easy3	Brute forceGeometry+2	No attempts yet	1s	128 MB	Judgeable
Feeding TimeGiven a W by H grid of grass and rock, find the size of the largest connected grass region using 8-directional adjacency.	Easy3	DFSBFS+2	No attempts yet	1s	128 MB	Judgeable
The Rock GamePrint the reflected binary Gray code cycle for N bits as 2^N + 1 lines, each line showing X for covered holes and O for uncovered ones.	Easy3	Bit manipulationMath+2	No attempts yet	1s	128 MB	Judgeable
Wheel RotationGiven N-1 belts that chain N pulleys from pulley 1, with each belt either straight (same direction) or crossed (reversed), find the rotation direction of pulley N.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Bad GrassCount connected components of nonzero cells in a grid, where two cells connect if they touch horizontally, vertically, or diagonally.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Plumbing the PondGiven a grid of depth readings, find the largest positive value that appears in at least two cells adjacent horizontally, vertically, or diagonally.	Easy3	ArrayImplementation+2	No attempts yet	1s	128 MB	Judgeable
The Perfect CowGiven an odd N by N grid, take the median of each row, then return the median of those N row medians.	Easy3	SortingArray+1	No attempts yet	1s	128 MB	Judgeable
Good GrassFind the 3x3 subgrid with the largest sum in a grid of milk values and report that sum with the upper-left corner, breaking ties by smallest row then column.	Easy3	ArrayPrefix sum+2	No attempts yet	1s	128 MB	Judgeable
Perfect SquaresGiven N, count ordered pairs (A, B) with 1 <= B <= A <= 500 and A^2 - B^2 = N.	Easy3	Brute forceMath+2	No attempts yet	1s	128 MB	Judgeable
BookshelfGiven cow heights and a shelf height B, find the smallest number of cows whose heights sum to at least B.	Easy3	GreedySorting+2	No attempts yet	1s	128 MB	Judgeable
SuperlativesGiven expected rain E and actual rain A, print how many times the word mega precedes drought based on the ratio E/A, or no drought if E <= A.	Easy3	ImplementationMath+1	No attempts yet	1s	128 MB	Judgeable
Game of LinesGiven N distinct lattice points, count how many distinct slopes the lines through pairs of points can have.	Easy3	Hash mapMath+2	No attempts yet	1s	128 MB	Judgeable
World Cup NoiseFor each n below 45, count the n-bit strings that contain no two adjacent 1s, and print the result per scenario with a blank line between cases.	Easy3	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Best GrassCount clumps of # cells in a grid, where each clump is one cell or two orthogonally adjacent cells and different clumps never touch.	Easy3	ArraySimulation+2	No attempts yet	1s	128 MB	Judgeable
Going to the MoviesGiven a truck capacity C and up to 16 cow weights, pick a subset whose total weight is as large as possible without exceeding C.	Easy3	Brute forceBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Another Cow Number GameStarting from N, repeatedly apply the Collatz rule (3N+1 if odd, N/2 if even) and count the steps until N reaches 1.	Easy3	SimulationMath+1	No attempts yet	1s	128 MB	Judgeable
Mileage BankEach line gives a flight's distance and cabin class; sum the ACMPerk miles earned per flight, with bonuses for B and F and a 500 mile floor for Y.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Balloon GameGiven N slots and Q arithmetic progressions, mark the slots each pass would fill (skipping already filled ones), then count the empty slots.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Encrypted SMSEach encrypted letter was shifted forward within its phone keypad key by its 1-based position; given the ciphertext, recover the original password.	Easy3	StringSimulation+1	No attempts yet	1s	128 MB	Judgeable
Blowing FusesSimulate toggling devices on and off, tracking the running total power and whether it ever exceeds the fuse capacity.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Box of BricksGiven stack heights whose total is divisible by n, find how many bricks must move so every stack reaches the equal target height.	Easy3	ArrayGreedy+2	No attempts yet	1s	128 MB	Judgeable
The Missing Side of a Right TriangleGiven two sides of a right triangle with one side marked -1, find the missing side or report that no right triangle exists.	Easy3	MathGeometry+2	No attempts yet	1s	128 MB	Judgeable
Carbon DatingGiven sample carbon mass and hourly decays, estimate age from the half-life decay formula, then round to 100 or 1000 years depending on size.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
URLsParse each URL into protocol, host, optional port, and optional path, printing <default> for missing components.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Definite ValuesProcess a sequence of single-letter assignments, starting with only 'a' defined, and after each program part print the defined variables in alphabetical order.	Easy3	SimulationHash map+1	No attempts yet	1s	128 MB	Judgeable
The Drunken JailerA jailer toggles the doors of cells that are multiples of k in round k; count how many doors end up open after n rounds.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Set MeGiven tableaus of Set cards, print each tableau and then every triple of cards that forms a valid set, in index order.	Easy3	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Digital RootGiven positive integers up to 1000 digits, each line until a terminating 0, print the digital root of each number.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Prime CutsFor each N and C, build the primes from 1 to N and print the middle C2 or C2-1 of them, or the whole list if that many do not exist.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Uniform GeneratorFor each pair STEP and MOD, decide whether seed(x+1) = (seed(x) + STEP) mod MOD cycles through all MOD values, which holds exactly when gcd(STEP, MOD) = 1.	Easy3	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
PalindromesFor each string, decide whether it reads the same backward and whether replacing each character by its mirror and reversing gives the same string.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Shipping RoutesGiven warehouses and bidirectional shipping legs, answer each request with the cheapest cost, which is shipment size times the minimum number of legs times 100, or report no route.	Easy3	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Donghyeok PizzaGiven a circular table of radius r and a rectangular pizza w by l, decide whether the rectangle fits inside the circle.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Ambiguous PermutationsFor each permutation, decide whether it equals its own inverse, meaning position of value i equals the value at position i.	Easy3	ArrayImplementation	No attempts yet	1s	128 MB	Judgeable
Help the problem setterFor each test case, read a binary search tree on labels 1..n and print each node's frequency, computed bottom-up as 1 plus the sum of the frequencies of all its proper descendants.	Easy3	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
SubsequenceFor each line of input, decide whether the first string is a subsequence of the second, printing Yes or No.	Easy3	Two pointersString+2	No attempts yet	1s	128 MB	Judgeable
Polygon Programming with EaseGiven the midpoints of the edges of a polygon with an odd number of vertices, recover the original vertex coordinates using an alternating sum and forward substitution.	Easy3	MathGeometry+2	No attempts yet	1s	128 MB	Judgeable
Average is not Fast Enough!Parse each team's section times in h:mm:ss form, sum them, and print the average seconds per kilometer rounded to the nearest second, or a dash if any runner was disqualified.	Easy3	ImplementationString+2	No attempts yet	1s	128 MB	Judgeable
HTMLRender an HTML fragment of plain text with <br> and <hr> tags, wrapping lines at 80 characters.	Easy3	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Error CorrectionFor each square 0/1 matrix, report OK if every row and column sum is even, the single bit that fixes the parity if exactly one row and one column are odd, or Corrupt otherwise.	Easy3	ImplementationArray+2	No attempts yet	1s	128 MB	Judgeable