Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,164 problems

Counting non-decreasing digit sequences
Easy3
Combinatorics, Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fashion King Haebin
Easy3
Combinatorics, Hash map
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Calculate the Fence Needed
Easy3
Hash map, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Largest Pairwise GCD
Easy3
Number theory, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Effective Infection Time
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Pisano Period
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bus 3000
Easy3
Math, Recursion
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Equal Sum Sets
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
GCD Sum
Easy3
Number theory, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
BABBA
Easy3
Dynamic programming, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grachten
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stone Game
Easy3
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stone Game 2
Easy3
Game theory, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stone Game 3
Easy3
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stone Game 4
Easy3
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stone Game 6
Easy3
Game theory, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Original Number of Medallions
Easy3
Math, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Picking a device for the movie
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sifar
Easy3
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Charles Babbage's Difference Engine
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Perfect Cube
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Negative Binary
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Dihedral Group Product
Easy3
Math, Implementation
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Sharkovski's Ordering
Easy3
Sorting, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Permutation
Easy3
Combinatorics, Math
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Product of two distinct primes
Easy3
Number theory, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Village closeness
Easy3
Brute force, Geometry
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Six Equations
Easy3
Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Largest Pairwise GCD
Easy3
Brute force, Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Unlock My Safe
Easy3
Combinatorics, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Common Fraction
Easy3
Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The nth prime number
Easy3
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ski Course Design
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Recycling Bin Allocation
Easy3
Brute force, Combinatorics
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
World's Worst Bus Schedule
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
One Number Hint
Easy3
Combinatorics, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Ant
Easy3
Math
No attempts yet
Time limit
0.15s
Memory limit
256 MB
Judgeable
Grid Path Count
Easy3
Combinatorics, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Federation Favorites
Easy3
Number theory, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Counting Communication Groups
Easy3
Union-find, Geometry
No attempts yet
Time limit
8s
Memory limit
256 MB
Judgeable
Real Estate Auction
Easy3
Sliding window, Two pointers+1
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Henry
Easy3
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Algebraic Teamwork
Easy3
Combinatorics, Math
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Gold Rush
Easy3
Bit manipulation, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Ribbon
Easy3
Number theory
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Tigger's bounces
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cookie Farm
Easy3
Greedy, Math
No attempts yet
Time limit
10s
Memory limit
64 MB
Judgeable
Spiral Area Division
Easy3
Geometry, Simulation+1
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Word Cloud
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Grave
Easy3
Geometry, Implementation
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Two Tower Mod 3
Easy3
Math, Number theory
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Valid Parenthesis Count
Easy3
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Happy Prime
Easy3
Simulation, Hash map+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Eureka Theorem
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Time Travel
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
XOR Range
Easy3
Bit manipulation, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Goldbach's Conjecture
Easy3
Number theory, Brute force
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Skyscraper Silhouette
Easy3
Simulation, Array+1
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Knockout Racing
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Multiple of 30
Easy3
Sorting, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Marathon 1
Easy3
Greedy, Array+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Cable Cleanup
Easy3
Graph, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Prof. Ossama's budget
Easy3
Math, String
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Bessie Gets Even
Easy3
Brute force, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Largest Stock Price Decline
Easy3
Array, Greedy+1
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Binomial Coefficient 2
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Ascending Numbers
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Palindrome in Some Base
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Folding Code
Easy3
Geometry, Implementation
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Bobby's Bet
Easy3
Probability, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Geometry Darts
Easy3
Geometry, Brute force
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Neurotic Network
Easy3
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Birds on a Wire
Easy3
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Lifting Walls
Easy3
Brute force, Geometry
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
FreeCell
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Numbers on a Tree
Easy3
Math, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Falling Mugs
Easy3
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
PIN Code Possibilities
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Ethel's Encryption
Easy3
Number theory, String+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Covering an equilateral triangle
Easy3
Math, Geometry
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Roots! Really?
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Largest inscribed rectangle
Easy3
Math, Geometry
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
A Serious Reading Problem
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Safe Zone
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Counting Primes in a Range
Easy3
Number theory, Prefix sum
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Maximum Number of Divisors
Easy3
Number theory, Prefix sum
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
The Owl and the Fox
Easy3
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Milestone Counter
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sum of Three Primes
Easy3
Number theory, Brute force
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Positive Con Sequences
Easy3
Math, Brute force
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Compositions Missing a Sequence
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Stepping Stones
Easy3
Math, Binary search
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Blur
Easy3
Simulation, Matrix+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Space Junk
Easy3
Math, Geometry
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Prime factorization
Easy3
Number theory
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Minho and Kangho
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Segment and Point
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Settlement Office
Easy3
Hash map, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Shuffling Along
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Even? Odd?
Easy3
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Counting non-decreasing digit sequencesCount length-N non-decreasing sequences of digits 0 to 9, modulo 1000000007, for each test case.	Easy3	CombinatoricsNumber theory	No attempts yet	1s	128 MB	Judgeable
Fashion King HaebinCount all nonempty outfits by picking at most one item from each clothing kind.	Easy3	CombinatoricsHash map	No attempts yet	1s	128 MB	Judgeable
Calculate the Fence NeededGiven the coordinates of N unit squares, compute the perimeter of the combined farm shape.	Easy3	Hash mapMath	No attempts yet	1s	128 MB	Judgeable
Largest Pairwise GCDFor each test case, print the largest GCD found among all pairs of the given integers.	Easy3	Number theoryBrute force	No attempts yet	1s	128 MB	Judgeable
Effective Infection TimeGiven each zone infection month and strike month, compute its Effective Infection Time under the half-weight first-year rule, rounded to four decimals.	Easy3	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Pisano PeriodThe program finds the period length of Fibonacci remainders modulo M for each test case.	Easy3	SimulationMath	No attempts yet	1s	128 MB	Judgeable
Bus 3000Given k stops where half the riders plus half a rider get off each time until the bus is empty, find the starting passenger count.	Easy3	MathRecursion	No attempts yet	1s	128 MB	Judgeable
Equal Sum SetsCount subsets of {1..n} with exactly k elements that sum to s for each dataset.	Easy3	Dynamic programmingCombinatorics	No attempts yet	3s	128 MB	Judgeable
GCD SumGiven several integers per test case, add the greatest common divisor of every unordered pair and print each sum.	Easy3	Number theoryBrute force	No attempts yet	1s	128 MB	Judgeable
BABBAStarting from A and rewriting each B as BA and each A as B, count the As and Bs after K presses.	Easy3	Dynamic programmingMath	No attempts yet	1s	128 MB	Judgeable
GrachtenThree paced distances along two sight lines fix similar triangles that yield the canal width as a reduced fraction.	Easy3	GeometryMath	No attempts yet	1s	128 MB	Judgeable
Stone GameTwo players alternately take 1 or 3 stones from a pile of N, and the program names the winner under perfect play.	Easy3	Dynamic programmingGame theory	No attempts yet	1s	128 MB	Judgeable
Stone Game 2Two players alternately take 1 or 3 stones from a pile of N and the player taking the last stone loses, so print whether the first player wins.	Easy3	Game theoryDynamic programming	No attempts yet	1s	128 MB	Judgeable
Stone Game 3Two players alternately take 1, 3, or 4 stones from a pile of N, and the program reports whether the first player wins with perfect play.	Easy3	Dynamic programmingGame theory	No attempts yet	1s	128 MB	Judgeable
Stone Game 4Two players alternately take 1, 3, or 4 stones and the player taking the last stone loses; report whether the first player wins with optimal play.	Easy3	Dynamic programmingGame theory	No attempts yet	1s	128 MB	Judgeable
Stone Game 6Two players alternately take 1, 3, or 4 stones from a pile of N, and the program prints which player wins with perfect play.	Easy3	Game theoryDynamic programming	No attempts yet	1s	128 MB	Judgeable
The Original Number of MedallionsGiven the daughter count and the medallions left after the youngest keeps one smallest split share, find the smallest and largest possible original counts.	Easy3	MathBrute force	No attempts yet	1s	128 MB	Judgeable
Picking a device for the movieGiven a movie resolution, pick the cheapest of eight listed devices that maximizes the full-screen usage ratio in either orientation.	Easy3	SimulationMath+1	No attempts yet	1s	128 MB	Judgeable
SifarFor each N up to 1,000,000 given one per line until 0, print the count of trailing zeros of N! as Case #x: M.	Easy3	Number theoryMath	No attempts yet	1s	128 MB	Judgeable
Charles Babbage's Difference EngineGiven the first values of a low-degree polynomial, extend its finite-difference table forward and report the value at x = 50.	Easy3	SimulationMath+1	No attempts yet	1s	128 MB	Judgeable
Perfect CubeCount the integers between A and B, inclusive, that are perfect cubes for each of up to 100000 test cases.	Easy3	Math	No attempts yet	1s	128 MB	Judgeable
Negative BinaryConvert each given decimal integer to its base negative two representation without leading zeros.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Dihedral Group ProductMultiply two given elements of D_{m,n} with the relation ba = a^{m-1}b and print each product with exponents reduced modulo m and n.	Easy3	MathImplementation	No attempts yet	5s	128 MB	Judgeable
Sharkovski's OrderingSort each test case of up to 255 integers into Sharkovski ordering and print them space-separated on one line.	Easy3	SortingMath	No attempts yet	2s	128 MB	Judgeable
PermutationGiven up to 10 distinct sorted characters and a 1-based position, print the permutation at that position or No permutation when it exceeds n!.	Easy3	CombinatoricsMath	No attempts yet	5s	128 MB	Judgeable
Product of two distinct primesFor each K, print the smallest number at or above K that equals the product of two different primes.	Easy3	Number theoryBrute force	No attempts yet	1s	128 MB	Judgeable
Village closenessGiven N points in 3D, find the smallest sum of Manhattan distances from one point to two other distinct points.	Easy3	Brute forceGeometry	No attempts yet	1s	128 MB	Judgeable
Six EquationsRecover six bounded primes from six pairwise products by taking gcds of the pairs that share a prime.	Easy3	Number theory	No attempts yet	1s	128 MB	Judgeable
Largest Pairwise GCDGiven up to 100 positive integers below one million, find the largest GCD over all pairs from distinct positions.	Easy3	Brute forceNumber theory	No attempts yet	1s	128 MB	Judgeable
Unlock My SafeThe program prints the sorted permutation of digits 1 to N at index floor(N factorial / 3) for each N.	Easy3	CombinatoricsSorting+1	No attempts yet	1s	128 MB	Judgeable
Common FractionReduce each of n fractions to lowest terms by dividing out the greatest common divisor.	Easy3	Number theory	No attempts yet	1s	128 MB	Judgeable
The nth prime numberGiven n up to 10000, print the nth prime number.	Easy3	Number theoryMath	No attempts yet	2s	512 MB	Judgeable
Ski Course DesignJohn moves each hill by an integer amount at squared cost so all heights fit in an interval of length 17 for the minimum total.	Easy3	Brute forceMath	No attempts yet	1s	128 MB	Judgeable
Recycling Bin AllocationFind the waste-to-bin assignment that needs the fewest bin changes across all surveyed cities.	Easy3	Brute forceCombinatorics	No attempts yet	1s	128 MB	Judgeable
World's Worst Bus ScheduleGiven each bus's repeating route durations and your arrival time, compute how long you wait for the next bus to reach the station.	Easy3	SimulationMath	No attempts yet	1s	128 MB	Judgeable
One Number HintImplement two fixed rules over 6-element subsets of 1 to 12: output the smallest element in S(x) missing from S(y), and answer yes when h lies in S(q).	Easy3	CombinatoricsImplementation	No attempts yet	1s	256 MB	Judgeable
AntCompute the position of an ant moving diagonally and reflecting off the walls of a w by h box after t hours.	Easy3	Math	No attempts yet	0.15s	256 MB	Judgeable
Grid Path CountCount right-and-down paths from the top-left to the bottom-right corner that pass through a given cell, if one is specified.	Easy3	CombinatoricsDynamic programming	No attempts yet	1s	256 MB	Judgeable
Federation FavoritesRead integers until -1 and print each perfect number with its divisors or state that it is not perfect.	Easy3	Number theoryImplementation	No attempts yet	1s	256 MB	Judgeable
Counting Communication GroupsCount the connected groups of camps whose circular communication areas touch or overlap.	Easy3	Union-findGeometry	No attempts yet	8s	256 MB	Judgeable
Real Estate AuctionCount the blocks of consecutive houses priced 2, 3, 4 and upward whose prices sum to exactly N.	Easy3	Sliding windowTwo pointers+1	No attempts yet	10s	256 MB	Judgeable
HenryRun the greedy unit-fraction expansion of each given fraction and print its last denominator.	Easy3	GreedyMath+1	No attempts yet	1s	256 MB	Judgeable
Algebraic TeamworkFor each given n, count the permutations of n elements that are not idempotent modulo 1000000007.	Easy3	CombinatoricsMath	No attempts yet	3s	256 MB	Judgeable
Gold RushSplit a bar of weight 2 to the n into halves with the fewest cuts so two shares of weights a and b can be formed.	Easy3	Bit manipulationMath	No attempts yet	1s	256 MB	Judgeable
RibbonAfter dropping the dirty inch at each end of every roll, find the longest common piece length that uses up every roll and count the total pieces.	Easy3	Number theory	No attempts yet	2s	256 MB	Judgeable
Tigger's bouncesCount length-K walks on an R by C grid where each step stays put or moves to a side neighbor, summed over all starts, modulo P per query.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Cookie FarmYou start at rate 2 and buy farms to reach X cookies in the least total time.	Easy3	GreedyMath	No attempts yet	10s	64 MB	Judgeable
Spiral Area DivisionGiven up to 100 points in an 80 by 80 square cut into 15 labeled pieces by alternating 3-to-1 splits, output the label containing each point.	Easy3	GeometrySimulation+1	No attempts yet	1s	64 MB	Judgeable
Word CloudCompute each word font size from its count, pack words in order into rows of width W, and output the summed row heights.	Easy3	SimulationMath	No attempts yet	1s	256 MB	Judgeable
GraveDecide whether a fixed-orientation w by h rectangle fits inside the graveyard without entering the chapel interior.	Easy3	GeometryImplementation	No attempts yet	2s	256 MB	Judgeable
Two Tower Mod 3Find the remainder of a power tower of H twos divided by 3.	Easy3	MathNumber theory	No attempts yet	1s	256 MB	Judgeable
Valid Parenthesis CountCount the distinct correct parenthesis strings of length L for each test case, modulo 1000000007.	Easy3	CombinatoricsDynamic programming+1	No attempts yet	2s	256 MB	Judgeable
Happy PrimeDecide whether each given number is both prime and happy under repeated digit-square sums, and print the result with its case number.	Easy3	SimulationHash map+1	No attempts yet	1s	256 MB	Judgeable
Eureka TheoremGiven K from 3 to 1000, print 1 when it equals the sum of exactly three triangular numbers and 0 otherwise.	Easy3	Brute forceMath	No attempts yet	1s	256 MB	Judgeable
Time TravelTwo watches losing a and b seconds per day start at midnight, and you report the first displayed time they agree on, rounded to the minute.	Easy3	Math	No attempts yet	1s	256 MB	Judgeable
XOR RangeCompute the XOR of all integers from S to F for each of up to 1000 test cases.	Easy3	Bit manipulationMath	No attempts yet	1s	256 MB	Judgeable
Goldbach's ConjectureCount and list every pair of primes that sums to each given even number up to 32000.	Easy3	Number theoryBrute force	No attempts yet	2s	256 MB	Judgeable
Skyscraper SilhouetteRebuild the skyline picture from N ground-based rectangles, mark the border cells, and report the perimeter without the ground side.	Easy3	SimulationArray+1	No attempts yet	1s	32 MB	Judgeable
Knockout RacingCount the cars whose back-and-forth motion between two points puts them inside each queried interval at the given time.	Easy3	SimulationMath	No attempts yet	1s	256 MB	Judgeable
Multiple of 30Rearrange all digits of N into the largest number divisible by 30, or print -1 when impossible.	Easy3	SortingMath	No attempts yet	1s	256 MB	Judgeable
Marathon 1Run checkpoints 1 to N in order while skipping exactly one middle checkpoint to minimize the total Manhattan distance.	Easy3	GreedyArray+1	No attempts yet	1s	256 MB	Judgeable
Cable CleanupFor each test case, keep N minus 1 of the M cables that join N computers into one network and print how many cables go.	Easy3	GraphMath	No attempts yet	1s	256 MB	Judgeable
Prof. Ossama's budgetEach test case asks for the remainder when a fund N with up to one million digits is divided by X.	Easy3	MathString	No attempts yet	1s	256 MB	Judgeable
Bessie Gets EvenCount assignments of listed values to seven letters that make the product (B+E+S+S+I+E)(G+O+E+S)(M+O+O) even.	Easy3	Brute forceCombinatorics+1	No attempts yet	1s	256 MB	Judgeable
Largest Stock Price DeclineGiven up to a million prices from a sine-cosine formula, find the largest drop from an earlier price to a later one.	Easy3	ArrayGreedy+1	No attempts yet	5s	256 MB	Judgeable
Binomial Coefficient 2Compute the binomial coefficient C(N, K) modulo 10007 for N up to 1000.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Ascending NumbersCount length-N digit strings, leading zeros allowed, whose digits never decrease left to right, modulo 10007.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Palindrome in Some BaseFor each N, decide whether its base B representation is a palindrome for some B from 2 to 64.	Easy3	MathBrute force+1	No attempts yet	1s	256 MB	Judgeable
Folding CodeThe program reflects each folded corner across its fold line to find the ticked box and lists the chosen answers per question.	Easy3	GeometryImplementation	No attempts yet	2s	256 MB	Judgeable
Bobby's BetDecide whether a bet pays off by computing the binomial chance of rolling at least R on at least X of Y rolls and comparing it to the odds W.	Easy3	ProbabilityCombinatorics+1	No attempts yet	2s	256 MB	Judgeable
Geometry DartsCount how many circles, rectangles, and triangles contain each of six dart throws and name Bob, Hannah, or Tied as the winner of each game.	Easy3	GeometryBrute force	No attempts yet	1s	256 MB	Judgeable
Neurotic NetworkEvaluate the weighted sum from the leaves to the root of a tree and print FREAK OUT for an even result, else the value modulo 1,000,000,007.	Easy3	TreeDynamic programming+1	No attempts yet	1s	256 MB	Judgeable
Birds on a WireCount how many more birds can sit on a wire of length l when birds stay d apart and 6 cm from each pole.	Easy3	GreedySorting+1	No attempts yet	1s	256 MB	Judgeable
Lifting WallsChoose the fewest of up to 30 crane sites so that each of the four wall centers is within reach of a chosen crane.	Easy3	Brute forceGeometry	No attempts yet	1s	256 MB	Judgeable
FreeCellDecide whether a sorted pile of K cards can be moved using N free cells and M empty stacks.	Easy3	Math	No attempts yet	1s	256 MB	Judgeable
Numbers on a TreeGiven the height H and an L/R path from the root, compute the label of the reached node under bottom-up right-to-left numbering.	Easy3	MathBit manipulation	No attempts yet	1s	256 MB	Judgeable
Falling MugsGiven D, find nonnegative integers n1 and n2 with n2 squared minus n1 squared equal to D, smallest n1 first, or report impossible.	Easy3	Number theoryMath	No attempts yet	1s	256 MB	Judgeable
PIN Code PossibilitiesCount n-digit codes with leading zeros allowed whose digits add up to s for each test case.	Easy3	Dynamic programmingCombinatorics	No attempts yet	3s	256 MB	Judgeable
Ethel's EncryptionRecover the plaintext by computing the Caesar shift a^b modulo 26 and moving each ciphertext letter back by that amount.	Easy3	Number theoryString+1	No attempts yet	1s	256 MB	Judgeable
Covering an equilateral triangleGiven side lengths A and B with A divisible by B, compute the minimum number of side-B equilateral triangles that cover a side-A equilateral triangle.	Easy3	MathGeometry	No attempts yet	1s	256 MB	Judgeable
Roots! Really?Decide for each quadratic equation whether a real root lies inside the given closed interval.	Easy3	Math	No attempts yet	1s	256 MB	Judgeable
Largest inscribed rectangleGiven radius R and bound B, find the largest area of a rectangle inscribed in the circle whose shorter side is at most B.	Easy3	MathGeometry	No attempts yet	2s	256 MB	Judgeable
A Serious Reading ProblemGiven C, W, L and P per test case, print C raised to W times L times P in full, treating 0 to the 0 as 1.	Easy3	MathImplementation	No attempts yet	1s	256 MB	Judgeable
Safe ZoneCount the K-step walks on segments 0 to N-1 with forced turns at the ends that finish inside segments P to Q.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Counting Primes in a RangeCount the primes between m and n inclusive for each blank-line separated test case.	Easy3	Number theoryPrefix sum	No attempts yet	1s	256 MB	Judgeable
Maximum Number of DivisorsYou answer each query with the largest divisor count among integers from 1 to N that are not multiples of P.	Easy3	Number theoryPrefix sum	No attempts yet	1s	256 MB	Judgeable
The Owl and the FoxGiven N, find the largest integer below N whose digit sum is exactly one less than the digit sum of N.	Easy3	MathGreedy	No attempts yet	1s	256 MB	Judgeable
Milestone CounterMatch the recorded pass times against milestone positions to count feasible speeds and list each possible first gap.	Easy3	Brute forceMath	No attempts yet	1s	256 MB	Judgeable
Sum of Three PrimesRead each odd K between 7 and 999 and print the lexicographically smallest triple of primes summing to K, or 0.	Easy3	Number theoryBrute force	No attempts yet	1s	256 MB	Judgeable
Positive Con SequencesFill the missing entry of each four-term sequence with a number from 1 to 10000 that makes it arithmetic or geometric, or output -1.	Easy3	MathBrute force	No attempts yet	1s	256 MB	Judgeable
Compositions Missing a SequenceCount the ordered compositions of n that use no part from the arithmetic progression starting at m with step k.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Stepping StonesMaximize the number of landed stones when jump lengths grow by at least one each time and the last landing is stone N.	Easy3	MathBinary search	No attempts yet	1s	256 MB	Judgeable
BlurBlur a binary image up to nine times with a wrapping 3 by 3 average and count how many distinct gray values remain.	Easy3	SimulationMatrix+1	No attempts yet	2s	256 MB	Judgeable
Space JunkTwo spheres drift on straight paths at constant speeds, and you compute the first instant their surfaces touch or report no collision.	Easy3	MathGeometry	No attempts yet	4s	256 MB	Judgeable
Prime factorizationPrint the prime factors of N up to 10,000,000 in ascending order, repeating each factor by multiplicity.	Easy3	Number theory	No attempts yet	1s	256 MB	Judgeable
Minho and KanghoTwo people walk straight lines at constant speeds over the same time span, and the program prints the smallest distance between them to ten decimal places.	Easy3	GeometryMath	No attempts yet	1s	256 MB	Judgeable
Segment and PointFind the closest point on segment AB to point C in 3D and print the distance with ten decimals.	Easy3	GeometryMath	No attempts yet	1s	256 MB	Judgeable
Settlement OfficeReport each row or column sum in a grid holding x plus y, zeroing that row or column after each query.	Easy3	Hash mapMath	No attempts yet	1s	256 MB	Judgeable
Shuffling AlongGiven a deck size and shuffle type, count how many repeated perfect shuffles restore the original order.	Easy3	SimulationMath	No attempts yet	1s	256 MB	Judgeable
Even? Odd?Decide for each of up to 100 numbers up to 1e18 whether its divisor count is odd or even.	Easy3	Number theoryMath	No attempts yet	2s	256 MB	Judgeable