Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,164 problems

Judges' Time Calculation
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Teleporting Firefly Chase
Easy3
Simulation, Geometry+2
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
Hangover
Easy3
Math, 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
Self Numbers
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Do the Untwist
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Skew Binary
Easy3
Math, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Snail
Easy3
Implementation, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polynomial Showdown
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Semigroups
Easy3
Brute force, Implementation+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
Close Enough Computations
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Transposition
Easy3
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Take Your Vitamins
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Extrusion
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Beautiful Triangle
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Post Office
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Primorial Number System
Easy3
Math, Number theory+2
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
Seven-Segment Display Addition
Easy3
String, Implementation+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
Casting Out Nines
Easy3
Math, Number theory+2
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
Dirichlet's Theorem on Arithmetic Progressions
Easy3
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
MCXI Numeral System
Easy3
String, Implementation+1
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
Really Good Compression
Easy3
Math, Combinatorics+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
Street Numbers
Easy3
Simulation, Implementation+1
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
Countdown
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Weird Currency
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lobbying
Easy3
Implementation, Math+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
Sand Castles
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
School Colors
Easy3
Brute force, Geometry+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
Dividing the Pirate Hoard
Easy3
Simulation, Math+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
Secret Letter
Easy3
Implementation, Array+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
Commute Route
Easy3
Dynamic programming, Combinatorics+2
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
Reversed-Element Sort
Easy3
Sorting, Math+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
Elias Omega Coding
Easy3
Bit manipulation, Recursion+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
Bingo!
Easy3
Brute force, Math+2
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
Magic Trick
Easy3
Implementation, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Divide and Conquer
Easy3
Number theory, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
17 Times
Easy3
String, Math+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
Adding Commas
Easy3
String, Implementation+1
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
Lonesome Partners
Easy3
Brute force, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Theater Seating
Easy3
Sorting, Math+1
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
Perfect Squares
Easy3
Brute force, Math+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
Another Cow Number Game
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Serious Cow Tag
Easy3
Simulation, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prime Qualification
Easy3
Number theory, Math+2
No attempts yet
Time limit
2s
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
There's treasure everywhere!
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
Four Quarters
Easy3
Probability, Dynamic programming+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
Bode Plot
Easy3
Math, Simulation+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
Floppies
Easy3
Math, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Circle Through Three Points
Easy3
Geometry, Math+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
Factorial Frequencies
Easy3
Math, Implementation+1
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
Kilometers to Miles
Easy3
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Black and White Painting
Easy3
Math, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Edge
Easy3
Simulation, Implementation+1
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
Paths on a Grid
Easy3
Combinatorics, Math
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
Artificial Intelligence?
Easy3
String, Math+1
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
Globetrotter
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Circumference of a Circle
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mosquito Multiplication
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
Teleporting Firefly ChaseSimulate a chase where the chaser repeatedly teleports a fixed distance toward each firefly flash and is caught if distance drops to 1 or less.	Easy3	SimulationGeometry+2	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
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
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
Self NumbersPrint all self numbers up to 10000, that is, numbers with no generator under d(n) = n + digit sum of n.	Easy3	ImplementationMath+2	No attempts yet	1s	256 MB	Judgeable
Do the UntwistGiven a key and a twisted ciphertext, invert the twisting formula to recover the original plaintext message.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Skew BinaryRead each skew binary string and print its decimal value, stopping at the terminating 0 line.	Easy3	MathString+1	No attempts yet	1s	128 MB	Judgeable
The SnailSimulate a snail that climbs a bit less each day and slides a fixed distance each night, and report whether it escapes or falls back first.	Easy3	ImplementationSimulation+1	No attempts yet	1s	128 MB	Judgeable
Polynomial ShowdownGiven nine polynomial coefficients from degree 8 down to the constant, print each polynomial with signs, exponents, and coefficients formatted to drop all unnecessary characters.	Easy3	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
SemigroupsGiven a small multiplication table, decide whether it defines a semigroup, report the first counterexample if not, and check commutativity.	Easy3	Brute forceImplementation+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
Close Enough ComputationsDecide whether printed grams of fat, carbohydrate, and protein can come from true amounts whose calorie total rounds to the printed calories.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
TranspositionTranspose a list of note names by a given number of semitones, then print each note using the 12 canonical sharp names.	Easy3	StringHash map+2	No attempts yet	1s	128 MB	Judgeable
Take Your VitaminsFor each line of amount, unit, requirement, and name, print the rounded daily-value percentage; collect items under 1% into a trailing list.	Easy3	ImplementationMath+2	No attempts yet	1s	128 MB	Judgeable
ExtrusionGiven the vertices of a polygon in clockwise order and a volume of metal, compute the polygon's area and divide to get the bar length.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Beautiful TriangleGiven three vertices, classify the triangle by side lengths and by angles, or report that the points are collinear.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Post OfficeSort each item's three dimensions into length, height, and thickness, then apply the postal size rules to print one of four classes.	Easy3	ImplementationMath+2	No attempts yet	1s	128 MB	Judgeable
Primorial Number SystemRepresent each positive integer in the mixed-radix primorial system where the i-th place value is the product of the first i primes.	Easy3	MathNumber theory+2	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
Seven-Segment Display AdditionDecode two seven-segment code strings into integers, add them, then re-encode the sum using the given digit codes.	Easy3	StringImplementation+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
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
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
Dirichlet's Theorem on Arithmetic ProgressionsFor each dataset, print the n-th prime in the arithmetic progression a, a+d, a+2d, ... , where a and d are coprime.	Easy3	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
MCXI Numeral SystemRead two MCXI-strings, add their values, and print the canonical MCXI-string for the sum.	Easy3	StringImplementation+1	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
Really Good CompressionGiven N distinct 1000-bit files, decide whether each can be compressed to at most b bits.	Easy3	MathCombinatorics+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
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
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
CountdownGiven a Maya Long Count date and its Julian Day Number, convert today's Gregorian date to JDN and report the days until 13.0.0.0.0.	Easy3	ImplementationMath+2	No attempts yet	1s	128 MB	Judgeable
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
LobbyingSum each lawmaker's donations made within 1000 days before the vote, then weight each no vote by 1/(1+D/10000) and add up both sides.	Easy3	ImplementationMath+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
Sand CastlesGiven a rectangular patch, a perimeter moat, and cylindrical towers, compute how much the flat base level rises or falls so the sand volume stays fixed.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
School ColorsGiven up to 200 RGB colors, find every pair whose Euclidean distance is maximal and print the index pairs in sorted order.	Easy3	Brute forceGeometry+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
Dividing the Pirate HoardEach of N pirates in turn splits the pile into N equal parts, keeps one part plus the remainder, and returns the rest; report each pirate's hidden coins and the leftover pile.	Easy3	SimulationMath+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
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
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
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
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
Reversed-Element SortReverse the digits of each of n positive integers, drop leading zeros, then print the reversed values in ascending order.	Easy3	SortingMath+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
Elias Omega CodingFor each positive integer until a terminating 0, output its Elias omega code, built by recursively prepending the code of the bit length.	Easy3	Bit manipulationRecursion+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
Bingo!Given a set of balls, decide whether every value from 0 to N appears as the absolute difference of some ordered pair of balls in the set.	Easy3	Brute forceMath+2	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
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
Divide and ConquerAmong integers from M to N, pick the one with the most divisors, breaking ties by the largest value, and report it with its divisor count.	Easy3	Number theoryBrute force+2	No attempts yet	1s	128 MB	Judgeable
17 TimesGiven a binary number N of up to 1000 digits, print N times 17 in binary.	Easy3	StringMath+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
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
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
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
Theater SeatingAssign each seat a priority by Euclidean distance to the middle of row 1, breaking ties by row then by seat number, and print rows back to front.	Easy3	SortingMath+1	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
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
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
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
Serious Cow TagSimulate the elimination game where each active cow tags her nearest remaining cow, and report the last cow standing.	Easy3	SimulationGeometry+2	No attempts yet	1s	128 MB	Judgeable
Prime QualificationCount primes between A and B whose decimal representation contains the digit D.	Easy3	Number theoryMath+2	No attempts yet	2s	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
There's treasure everywhere!Parse a map of step counts and compass directions, compute the treasure's coordinates, and print the straight-line distance from the origin.	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
Four QuartersFor each round count from 1 to 20, compute the probability that A wins, B wins, or the game ties after that many rounds of this four-coin game.	Easy3	ProbabilityDynamic programming+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
Bode PlotGiven source voltage, resistance, capacitance, and several angular frequencies, compute the resistor voltage magnitude from the RC low-pass circuit equations.	Easy3	MathSimulation+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
FloppiesCompute the number of floppies by applying fixed roundings for compression, uuencoding, 30000-line splitting, and recompression.	Easy3	MathSimulation+1	No attempts yet	1s	128 MB	Judgeable
Circle Through Three PointsFor each line of three points, compute the circle through them and print its center-radius and general equations with signs adjusted.	Easy3	GeometryMath+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
Factorial FrequenciesRead n values until a terminating 0, and for each n count how many times each digit 0 through 9 appears in the decimal representation of n! (n up to 366), printing the counts in a fixed two-line format.	Easy3	MathImplementation+1	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
Kilometers to MilesConvert each kilometer value to miles by writing it in Zeckendorf Fibonacci form, dropping the lowest bit, and re-evaluating.	Easy3	MathGreedy+2	No attempts yet	1s	128 MB	Judgeable
Black and White PaintingCount the 8x8 blocks inside an n by m checkerboard whose bottom-right square is white, given the color of the painting's bottom-right corner.	Easy3	MathCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
EdgeGiven a string of A (clockwise) and V (counter-clockwise) turns, emit PostScript line commands tracing a unit-step path from a fixed start point.	Easy3	SimulationImplementation+1	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
Paths on a GridCount monotone lattice paths from the lower-left to the upper-right of an n by m grid.	Easy3	CombinatoricsMath	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
Artificial Intelligence?Given a word problem stating two of power, voltage, and current with optional metric prefixes, compute the missing quantity using P = U * I.	Easy3	StringMath+1	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
GlobetrotterRead a list of cities with latitudes and longitudes, then for each query print the great-circle distance between two cities rounded to the nearest km.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Circumference of a CircleFor each line of three non-collinear points, compute the perimeter of the circle passing through them, rounded to two decimals.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Mosquito MultiplicationSimulate weekly mosquito stages (eggs become larvae, larvae become pupae, pupae become adults) with floor divisions and report the adult count after N Sundays.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable