Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,164 problems

Icebergs
Easy3
Geometry, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
PRIM
Easy3
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
DISPER
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Military Service
Easy3
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Coffee
Easy3
Hash map, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Triangles (Bronze)
Easy3
Brute force, Geometry+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Feedback
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
New Year and Naming
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Time Zone
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Drought (Small)
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Polynomial
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Epidemiology
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Labels
Easy3
Array, Implementation+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Palindromic FizzBuzz
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Patterns
Easy3
Implementation, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Big Round Table
Easy3
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sapsan
Easy3
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Attractive Flowers
Easy3
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dates
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Restoring the Sequence
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Gold Bars
Easy3
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Maximum Product
Easy3
Prefix sum, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Calculating Powers of Two
Easy3
Math, Binary search+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Moon in the Photo
Easy3
Brute force, Geometry
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Race
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Computer Assembly
Easy3
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bombs In My Deck
Easy3
Probability, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Who Is the Winner of This Area?!
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Jam-packed
Easy3
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Keystroke
Easy3
Brute force, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tournament turn-around
Easy3
Brute force, Probability
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Divvying Up
Easy3
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Gleaming the Cubes
Easy3
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Operation Protect the Lottery Prize! (Normal)
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Greatest Common Divisor
Easy3
Number theory, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hotel
Easy3
Math, Brute force+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The World Is a Single Handkerchief
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Do You Know Your ABCs?
Easy3
Sorting, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sanic
Easy3
Math, Geometry+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Islands
Easy3
Math, Simulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Adolescent Architecture
Easy3
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Palindrome Cheokhwabi
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hyojeong and the New Monitor
Easy3
Sorting, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Even More Odd Photos
Easy3
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Almost Free Falling
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Over the Hill, Part 1
Easy3
Matrix, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Reconstruct Sum
Easy3
Array, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Stopwatch
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Vaccine Efficacy
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Train Boarding
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
le français
Easy3
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Personnummer
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Casting
Easy3
Math, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Herons
Easy3
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Checkers
Easy3
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pascal's Triangle
Easy3
Math, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Eraser
Easy3
Simulation, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Gahee, Are You Sleeping There?
Easy3
Implementation, Geometry+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Getting Started with Calculus
Easy3
Math, Implementation+1
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
Innohorse
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Coprime Average
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Buying a Bicycle
Easy3
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Digital Roots
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Magic Cards
Easy3
Sorting, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Opinion Poll
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Triangles
Easy3
Brute force, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Origami
Easy3
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Game
Easy3
Game theory, Math+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Universal Socket
Easy3
Geometry, Hash map+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Dessert Preparation
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Map
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cataloguing numbers
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Non-Integer Donuts
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
squarePrime
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hey Kakao
Easy3
Probability, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
nm Grid Multiplication
Easy3
Implementation, Brute force+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Era Name Change
Easy3
Implementation, Math
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Koto Municipal Subway
Easy3
Math, Brute force+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Moonlight Farm
Easy3
Sorting, Implementation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Luck Manipulator
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Galaxy Wide Web Service
Easy3
Array, Simulation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Princess' Gamble
Easy3
Math, Implementation+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Prime Digital Roots
Easy3
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Exploring Caves
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fermat's Last Theorem
Easy3
Brute force, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Die Game
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary Strawberry
Easy3
Math, Implementation+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Twinkle Twinkle 2
Easy3
Probability, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
K-Goodness String
Easy3
String, Greedy+2
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Arithmetic Square
Easy3
Implementation, Brute force+2
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Packing Items
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Heliocentric
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
In or Out
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Unique Shapes
Easy3
Brute force, Backtracking+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sport Climbing Combined
Easy3
Sorting, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Periodical Cicadas
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Movie Rating
Easy3
Sorting, Array+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Aliquot Sum
Easy3
Math, Number theory+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Histogram
Easy3
Array, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Quadratic equation
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
IcebergsGiven N simple polygons, compute the total area and print its floor as an integer.	Easy3	GeometryMath+2	No attempts yet	3s	512 MB	Judgeable
PRIMFor each of T test cases, given an array of n integers, replace every element with the smallest prime that is at least that element, then print the sum.	Easy3	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
DISPERFor each professor, treat all student marks as one set, compute the variance of those marks, and report the professor with the highest dispersion to two decimals.	Easy3	MathImplementation+1	No attempts yet	2s	512 MB	Judgeable
Military ServiceEach soldier works at most K consecutive months then rests one month; find the largest number of soldiers that can be guaranteed on duty in every month.	Easy3	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
CoffeeFor each person, add the price of their ordered coffee size to a shared delivery fee of floor(100/P), then snap the total to a multiple of 5 only when it is 1 off.	Easy3	Hash mapImplementation+2	No attempts yet	1s	512 MB	Judgeable
Triangles (Bronze)Given up to 100 points, find the largest triangle with one horizontal and one vertical side, and print twice its area.	Easy3	Brute forceGeometry+1	No attempts yet	2s	512 MB	Judgeable
FeedbackBuild a strictly increasing length-N sequence with values at most 1000, second element 2, and last element prime.	Easy3	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
New Year and NamingGiven two cyclic string sequences, return the concatenation of the pair selected by each queried year index.	Easy3	ImplementationMath+2	No attempts yet	1s	1024 MB	Judgeable
Time ZoneGiven a time in Beijing (UTC+8) and a target time zone string, print the corresponding 24-hour clock time.	Easy3	ImplementationMath+2	No attempts yet	1s	256 MB	Judgeable
Drought (Small)Given three target rainfall totals, find positive amounts a, b, c applied to each pair of plots so every plot hits its total exactly, or report that it is impossible.	Easy3	MathImplementation+1	No attempts yet	1s	1024 MB	Judgeable
PolynomialGiven the coefficients and degrees of a polynomial in descending order, evaluate it at x using Horner's method and print the result modulo 1e9+7.	Easy3	MathImplementation+2	No attempts yet	1s	1024 MB	Judgeable
EpidemiologySimulate a disease where each infected person infects R new people the next day, and find the first day the cumulative case count exceeds P.	Easy3	SimulationMath+1	No attempts yet	2s	512 MB	Judgeable
LabelsGiven the difference sequence D of an unknown sequence A with values in [1, N], output A if it is uniquely determined, otherwise -1.	Easy3	ArrayImplementation+2	No attempts yet	2s	1024 MB	Judgeable
Palindromic FizzBuzzPrint every integer from S to E, replacing any palindromic number with the string Palindrome!.	Easy3	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
PatternsFill an n by n grid with 1 to n^2 in row-major order, then mark each cell with an asterisk if its number has at most k divisors, otherwise a dot.	Easy3	ImplementationNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Big Round TableMasha sits at a round table of n seats and makes exactly k swaps with a left or right neighbor; count the seats she could occupy at the end.	Easy3	MathGreedy+1	No attempts yet	1s	512 MB	Judgeable
SapsanGiven a row of n seats split into n/2 adjacent pairs, find the largest number of occupied seats so that exactly half the seated people sit next to an occupied neighbor.	Easy3	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
Attractive FlowersGiven the stock of each flower type, pick an odd count from each type so the total is odd and as large as possible.	Easy3	GreedyMath+1	No attempts yet	1s	512 MB	Judgeable
DatesEach input line is a date in day.month.year or month/day/year format; print both formats, validating that the date actually exists.	Easy3	ImplementationString+2	No attempts yet	1s	512 MB	Judgeable
Restoring the SequenceGiven n, m, and m board values, decide whether they are 1..n with exactly one number erased, and print that number.	Easy3	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Gold BarsGiven three bar weights with an even total, decide whether the bars already split evenly, or which single bar to cut in two so the pieces divide equally.	Easy3	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
Maximum ProductSplit the array after one index so the product of the two part sums is maximized, and print that index.	Easy3	Prefix sumArray+2	No attempts yet	2s	512 MB	Judgeable
Calculating Powers of TwoGiven the final value Taeyoung got after subtracting 1 once during his powers-of-two computation, find which step K he made that mistake at.	Easy3	MathBinary search+2	No attempts yet	1s	512 MB	Judgeable
Moon in the PhotoFind the largest circle that contains no black pixels in a grid of white and black points, and print its radius and center as column then row.	Easy3	Brute forceGeometry	No attempts yet	2s	512 MB	Judgeable
RaceEach car alternates between driving for t hours at v km/h and charging for t hours; compare which one covers x km first.	Easy3	MathImplementation+1	No attempts yet	2s	512 MB	Judgeable
Computer AssemblyGiven counts of VGA-only, DVI-only, and dual-interface units and monitors, find the maximum number of pairable unit-monitor sets.	Easy3	GreedyMath+1	No attempts yet	2s	512 MB	Judgeable
Bombs In My DeckGiven a deck of A cards with B bombs, find the probability that drawing cards until a non-bomb appears never drops HP (C, 5 per bomb) to 0 or below.	Easy3	ProbabilityCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Who Is the Winner of This Area?!Map each letter of a string to its stroke count, repeatedly sum adjacent pairs modulo 10, and report whether the final single value is odd.	Easy3	SimulationImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Jam-packedGiven n jars and boxes holding up to k, distribute all jars so the emptiest box holds as many jars as possible, and report that count.	Easy3	MathGreedy	No attempts yet	1s	512 MB	Judgeable
KeystrokeCount how many subsets of the four keys can produce the given set of received row numbers and set of received column numbers.	Easy3	Brute forceCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Tournament turn-aroundGiven head-to-head win counts for eight teams, find the bracket order that maximizes team 1's chance of winning the tournament.	Easy3	Brute forceProbability	No attempts yet	5s	512 MB	Judgeable
Divvying UpGiven prize amounts from n contests, decide whether each total can be split among three team members so all three end with equal sums.	Easy3	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
Gleaming the CubesGiven several sets of axis-aligned cubes, compute for each set the volume of the region shared by all cubes in that set.	Easy3	GeometryImplementation+1	No attempts yet	1s	512 MB	Judgeable
Operation Protect the Lottery Prize! (Normal)Given a prime m and three values Seed, X1, X2 with X1 = (aSeed+c) mod m and X2 = (aX1+c) mod m, find any valid a and c.	Easy3	MathNumber theory+1	No attempts yet	1s	512 MB	Judgeable
Greatest Common DivisorGiven n numbers, choose a subset whose greatest common divisor is exactly d, or report -1 if no such subset exists.	Easy3	Number theoryImplementation	No attempts yet	2s	512 MB	Judgeable
HotelGiven a delegation of n people, find the minimum number of double and triple rooms that hold exactly n people with no free beds.	Easy3	MathBrute force+1	No attempts yet	2s	512 MB	Judgeable
The World Is a Single HandkerchiefA walker starts at the origin heading along +x and turns 90 degrees left or right at given times; find the position after T seconds.	Easy3	ImplementationSimulation+2	No attempts yet	1s	1024 MB	Judgeable
Do You Know Your ABCs?Given seven numbers that are A, B, C and their pairwise and total sums in some order, recover the three sorted positive integers.	Easy3	SortingMath+1	No attempts yet	1s	512 MB	Judgeable
SanicGiven the loop radius r (Sanic's radius is 1), compute how many revolutions Sanic makes while rolling once around the inside of the loop.	Easy3	MathGeometry+2	No attempts yet	1s	1024 MB	Judgeable
IslandsContestants disappear on islands following a Fibonacci-like rule, and we must find the island where the Nth contestant vanishes.	Easy3	MathSimulation+1	No attempts yet	1s	1024 MB	Judgeable
Adolescent ArchitectureGiven cubes and cylinders, order them top to bottom so each block fits inside the one below it, or report that no order works.	Easy3	SortingGreedy+2	No attempts yet	1s	512 MB	Judgeable
Palindrome CheokhwabiGiven N, print any length-N lowercase string that is both a palindrome and has identical front and back halves.	Easy3	ImplementationString+2	No attempts yet	1s	1024 MB	Judgeable
Hyojeong and the New MonitorGiven N monitors with the same 77-inch diagonal, print their indices sorted by decreasing PPI, breaking ties by smaller index.	Easy3	SortingMath+1	No attempts yet	1s	1024 MB	Judgeable
Even More Odd PhotosPartition all cows into the maximum number of groups whose breed-ID sums alternate even, odd, even, and so on, starting with even.	Easy3	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Almost Free FallingGiven mass, two air-resistance constants, parachute time, and height, compute Bob's fallen distance at query times and the total fall time.	Easy3	MathImplementation+2	No attempts yet	1s	512 MB	Judgeable
Over the Hill, Part 1Given an n by n matrix and a plaintext, encode the text using Hill cipher over a 37 character alphabet with modular arithmetic.	Easy3	MatrixMath+2	No attempts yet	1s	1024 MB	Judgeable
Reconstruct SumGiven a list of integers, find one element that equals the sum of all the other elements, or report that none exists.	Easy3	ArrayMath+2	No attempts yet	1s	512 MB	Judgeable
StopwatchGiven the increasing times when a stopwatch button toggles the timer, report the total running seconds, or that the timer is still running.	Easy3	SimulationImplementation+1	No attempts yet	1s	1024 MB	Judgeable
Vaccine EfficacyGiven N participants marked as vaccinated or control and infected by strains A, B, C, compute each strain's vaccine efficacy as a percentage reduction in infection rate, or print Not Effective.	Easy3	ImplementationMath+1	No attempts yet	1s	1024 MB	Judgeable
Train BoardingEach passenger walks to the door at the center of the nearest car, breaking ties toward the higher-numbered car; report the longest walk and the busiest car's passenger count.	Easy3	ImplementationMath+2	No attempts yet	1s	1024 MB	Judgeable
le françaisCount the alphabetic letters in a French sentence, then print the multiple of seven closest to that count, spelled out in French words with lowercase letters and spaces.	Easy3	StringImplementation+2	No attempts yet	1s	512 MB	Judgeable
PersonnummerConvert a ten-digit Swedish personal identity number with a separator into twelve-digit YYYYMMDDXXXX form, using the separator to decide the birth century.	Easy3	ImplementationMath+2	No attempts yet	1s	1024 MB	Judgeable
CastingGiven counts of tall, blue-eyed, and blond actors, find the minimum or maximum possible number who are all three.	Easy3	MathCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
HeronsEach heron shows one or two legs, and counts a and b come from two moments. Find the minimum and maximum possible total number of herons.	Easy3	MathGreedy+1	No attempts yet	2s	1024 MB	Judgeable
CheckersGiven a white pieces and b black pieces, arrange them in a tower to maximize the number of black stripes, where a stripe is a maximal run of adjacent black pieces.	Easy3	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Pascal's TriangleCount how many entries in row n of Pascal's triangle are odd, where n can be as large as 2 billion.	Easy3	MathBit manipulation+2	No attempts yet	2s	1024 MB	Judgeable
EraserStarting with 1..N in cells, repeatedly delete numbers in odd positions and shift left until one number remains; report that survivor.	Easy3	SimulationArray+2	No attempts yet	1s	512 MB	Judgeable
Gahee, Are You Sleeping There?Given a grid with one Gahee rectangle and one pillow rectangle, decide whether the two rectangles overlap, counting hidden pillow parts as overlap.	Easy3	ImplementationGeometry+2	No attempts yet	1s	512 MB	Judgeable
Getting Started with CalculusGiven epsilon as a fraction and a linear polynomial f, compute the limit L at x0 and the largest delta with \|f(x)-L\|<epsilon, printing delta as a fraction or 0 0.	Easy3	MathImplementation+1	No attempts yet	0.5s	1024 MB	Judgeable
InnohorseGiven the start and end cells of a knight-like jump on an 8x8 board, recover the ordered pair (x, y) with x <= y that describes the move.	Easy3	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Coprime AverageGiven a sequence and a number X, find the average of all elements that are coprime with X, within an error of 1e-6.	Easy3	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Buying a BicycleGiven a one-ruble coins, b two-ruble coins, and a price c, decide whether some subset of the coins sums to exactly c.	Easy3	MathGreedy+1	No attempts yet	2s	256 MB	Judgeable
Digital RootsFor each range [a, b], count how often each digital root (1 to 9) appears and report the ones that appear most often.	Easy3	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Magic CardsGiven two n-card hands and a pick size l, decide whether Grisha's best l-card sum always beats Dima's worst l-card sum.	Easy3	SortingGreedy+2	No attempts yet	2s	256 MB	Judgeable
Opinion PollGiven n people, a who can solve the problem and b who refuse, find the minimum and maximum number who both can solve it and do not refuse.	Easy3	MathImplementation+1	No attempts yet	2s	256 MB	Judgeable
TrianglesFor each of T test cases with four segment lengths, count how many triples form a right, acute, or obtuse non-degenerate triangle.	Easy3	Brute forceMath+2	No attempts yet	1s	512 MB	Judgeable
OrigamiGiven an a by b grid, decide whether repeated full-length cuts that discard one piece can leave a rectangle of exactly S cells.	Easy3	MathImplementation+2	No attempts yet	2s	256 MB	Judgeable
GameIf the start is within Manhattan distance m of the finish, First wins on move 1; otherwise both players can avoid losing forever, so the result is Infinity.	Easy3	Game theoryMath+1	No attempts yet	2s	256 MB	Judgeable
Universal SocketGiven n labeled points (phase or neutral), decide whether two points of opposite labels sit exactly distance d apart.	Easy3	GeometryHash map+2	No attempts yet	2s	256 MB	Judgeable
Dessert PreparationCount triples (dough, filling, ice cream) where none of the three ingredient pairs appears in the given lists of incompatible pairs.	Easy3	Brute forceImplementation+2	No attempts yet	2s	256 MB	Judgeable
MapParse a string of letters n, s, e, w each followed by 1-2 digit step counts, ignoring other characters, and report the distance from the red square to the final square.	Easy3	ImplementationString+2	No attempts yet	1s	512 MB	Judgeable
Cataloguing numbersFor each of three 9-digit cataloguing numbers, check that the encoded date is valid, the author digit is 1, 6, or 9, and the last digit equals the sum of squares of the first eight digits modulo 7.	Easy3	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Non-Integer DonutsGiven an initial balance and N daily deposits, count the days on which the running balance is not a whole dollar amount.	Easy3	ImplementationMath+1	No attempts yet	1s	1024 MB	Judgeable
squarePrimeGiven a list of integers, return the sum of the values whose indices are prime numbers.	Easy3	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Hey KakaoGiven win probability d% rising by k% after each loss, find the expected time in minutes until Iha wins a round of word chain.	Easy3	ProbabilityMath+2	No attempts yet	1s	1024 MB	Judgeable
nm Grid MultiplicationGiven sequences a and b, count how many times each digit 0-9 appears when writing every product a[i]*b[j] in decimal over the grid.	Easy3	ImplementationBrute force+1	No attempts yet	8s	512 MB	Judgeable
Era Name ChangeGiven a stored date as Heisei year, month, and day, decide whether it falls in Heisei or the new era starting May 1, 2019, and print the correct era name with the date.	Easy3	ImplementationMath	No attempts yet	8s	512 MB	Judgeable
Koto Municipal SubwayGiven D and E, find the integer point (x, y) with x + y = D that minimizes \|sqrt(x^2 + y^2) - E\| and print that minimum difference.	Easy3	MathBrute force+1	No attempts yet	8s	512 MB	Judgeable
Moonlight FarmFor each crop dataset, compute income per unit time from seed cost, growth stages, fruit yield, and harvest count, then list names by descending efficiency with ties broken alphabetically.	Easy3	SortingImplementation+2	No attempts yet	8s	512 MB	Judgeable
Luck ManipulatorSimulate an LCG frame by frame, advancing a reel whenever the random number matches its target, and report the frame when all N reels stop or -1 after 10000 frames.	Easy3	SimulationImplementation+1	No attempts yet	8s	512 MB	Judgeable
Galaxy Wide Web ServiceGiven each planet's daily access cycle and current hour, compute the maximum total access across all planets in any single absolute hour.	Easy3	ArraySimulation+2	No attempts yet	8s	512 MB	Judgeable
Princess' GambleGiven ticket counts per competitor, a winning competitor, and a deduction percentage, compute the payout per winning ticket, or 0 if no winning tickets exist.	Easy3	MathImplementation+1	No attempts yet	8s	512 MB	Judgeable
Prime Digital RootsFor each number until 0, repeatedly sum its digits and stop early if a prime appears, then print the original and the prime digital root or none.	Easy3	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Exploring CavesEach cave's path is given as successive displacement vectors; reconstruct the room coordinates and report the point farthest from the origin, breaking ties by largest x.	Easy3	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Fermat's Last TheoremFor each z, find the largest sum of two positive cubes not exceeding z^3, then print z^3 minus that sum.	Easy3	Brute forceMath+2	No attempts yet	2s	512 MB	Judgeable
Die GameSimulate rolling a die on a table from a fixed starting orientation and report the number on the top face after each command sequence.	Easy3	SimulationImplementation+1	No attempts yet	2s	512 MB	Judgeable
Binary StrawberryGiven a turn number N, output the 4-beat binary strawberry chant, where each beat is V or strawberry according to the bouncing count from 1 to 15.	Easy3	MathImplementation+2	No attempts yet	0.5s	512 MB	Judgeable
Twinkle Twinkle 2Each light has an on-probability; an added light between neighbors turns on exactly when one neighbor is on. Find the expected total number of lit lights.	Easy3	ProbabilityMath+2	No attempts yet	1s	1024 MB	Judgeable
K-Goodness StringGiven a string, find the minimum number of character changes needed so exactly K mirrored position pairs differ.	Easy3	StringGreedy+2	No attempts yet	Not set	1024 MB	Judgeable
Arithmetic SquareGiven a 3x3 grid with the center missing, choose any integer for the center to maximize how many of the 8 lines (3 rows, 3 columns, 2 diagonals) form arithmetic progressions.	Easy3	ImplementationBrute force+2	No attempts yet	Not set	1024 MB	Judgeable
Packing ItemsGiven R identical trucks each carrying the same n items in order, count how many length-B boxes are needed to pack all items greedily in sequence.	Easy3	SimulationMath+1	No attempts yet	1s	512 MB	Judgeable
HeliocentricGiven the current day of Earth's 365-day orbit and Mars's 687-day orbit, find the smallest number of days until both planets are at day 0.	Easy3	MathNumber theory+2	No attempts yet	1s	1024 MB	Judgeable
In or OutFor each complex number c, iterate z = z^2 + c up to r times and report IN if \|z\| never exceeds 2, otherwise OUT.	Easy3	SimulationMath+1	No attempts yet	2s	1024 MB	Judgeable
Unique ShapesCount the number of distinct polyominoes (free polyominoes) that can be formed from exactly 8 unit squares, where shapes matching under rotation, translation, or reflection count as one.	Easy3	Brute forceBacktracking+2	No attempts yet	2s	1024 MB	Judgeable
Sport Climbing CombinedGiven each athlete's ranks in three climbing events, sort them by the product of ranks, then by rank sum, then by bib number, and print the top three bib numbers.	Easy3	SortingImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Periodical CicadasFor each pair of cicadas with cycles c1 and c2 last seen together in year y, find the earliest year any pair reappears together, which is y plus lcm(c1, c2).	Easy3	MathNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Movie RatingGiven N ratings, remove the L lowest and H highest scores and print the average of the rest.	Easy3	SortingArray+1	No attempts yet	1s	1024 MB	Judgeable
Aliquot SumFor each of up to a million numbers, sum its proper divisors and report whether it is abundant, deficient, or perfect.	Easy3	MathNumber theory+2	No attempts yet	8s	1024 MB	Judgeable
HistogramGiven bin size, bin count, and data points, count how many points fall in each bin and print a histogram with # bars on a - base.	Easy3	ArrayImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Quadratic equationGiven a nonzero integer Y, output nonzero integer coefficients A, B, C with absolute value at most 10^6 such that AY^2 + BY + C = 0.	Easy3	MathImplementation+1	No attempts yet	2s	256 MB	Judgeable