Math and counting

Number theory, combinatorics, and geometry

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Total results13,164 problems

The Easiest Problem Is This One
Easy3
Brute force, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Complicated Route
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Too Much Water
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ball Bearings
Easy3
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hardware
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Goldbach's Conjecture
Easy3
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Add Backward Numbers
Easy3
Math, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Chances of Winning
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Don't pass me the ball!
Easy3
Combinatorics, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Aromatic Numbers
Easy3
String, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mouse Journey
Easy3
Dynamic programming, Matrix+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Who Has Seen the Wind
Easy3
Math, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Up and Down
Easy3
Simulation, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Punchy
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Global Warming
Easy3
String matching, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cool Numbers
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
GPS Text Entry
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cell-Phone Messaging
Easy3
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Maternity
Easy3
Implementation, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
RSA Numbers
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Picture Perfect
Easy3
Math, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Students' Council Breakfast
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Numbers That Read the Same Upside Down
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Slot Machines
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Deficient, Perfect, and Abundant
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Train Swapping
Easy3
Array, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Trimmed and Corrected Mean
Easy3
Sorting, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Arithmetic Sequence
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hobbiton Farms
Easy3
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Millennium
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rectangle
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Making shortest-path test data
Easy3
Implementation, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Class
Easy3
Implementation, Matrix+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Carpets
Easy3
Geometry, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Harmony: Parallel Fifths
Easy3
Implementation, Array+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Harmony
Easy3
Implementation, Brute force+2
No attempts yet
Time limit
7s
Memory limit
1024 MB
Judgeable
Aliens' Socks
Easy3
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Alien Socks
Easy3
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pyramids
Easy3
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Encryption
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Equations
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Laundry
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
A DP Problem
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Skew Binary
Easy3
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Number Steps
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polynomial Remainder Operation
Easy3
Math, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Undercut
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Currency Exchange
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ride My Bicycle
Easy3
Sorting, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sequence
Easy3
Math, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Untidy Desktops
Easy3
Geometry, Brute force
No attempts yet
Time limit
7s
Memory limit
128 MB
Judgeable
Box
Easy3
Implementation, Sorting+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Factoring a Polynomial
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Prehistoric Operating Systems
Easy3
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Incomplete chess boards
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Yeehaa!
Easy3
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cramer's Rule
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Kingdom Subdivision
Easy3
Geometry, Math+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Circle Drawing
Easy3
Simulation, Geometry+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Big Number
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Supermarket
Easy3
Sorting, Array+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sequences without Stammers
Easy3
String, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Table and Chairs
Easy3
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rectilinear Polygon With Area Equal to Its Vertex Count
Easy3
Implementation, Geometry+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Rectangles
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Computation of a Road Network Plan
Easy3
Tree, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Can You Exponentiate?
Easy3
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Postcard
Easy3
Combinatorics, Array
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
List
Easy3
Math, Array
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Smallest Missing Multiple
Easy3
Hash map, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Smallest Perfect-Square Multiple
Easy3
Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grasshopper
Easy3
Greedy, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Grasshopper 2
Easy3
Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Divisor Set Inclusion
Easy3
Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Cheerful Monkey
Easy3
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gym
Easy3
Math, Number theory
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pocket Money
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Perfect Memory
Easy3
Math, Array
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Konduktor
Easy3
Math, Simulation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hektor's Test Answers
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Class Pairings
Easy3
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Stone Game
Easy3
Game theory, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Encoding
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Point Numbers
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Password
Easy3
Combinatorics, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gas
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rectangle Coloring
Easy3
Union-find, Geometry
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Goldbach's Conjecture
Easy3
Number theory, Two pointers
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Fence
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lexicographic rank of a permutation
Easy3
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Primality Test
Easy3
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Biorhythms
Easy3
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Approximate String Matching
Easy3
String matching, Brute force+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Integer Rectangles
Easy3
Brute force, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bishop's minimum moves
Easy3
Geometry, Brute force
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Flowers instead of a tree
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fun with fractions
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bomb Defusal
Easy3
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Where's the Rainbow
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Wiretap Device
Easy3
Math, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
The Easiest Problem Is This OneFor each positive integer N up to 100000, find the smallest multiplier p greater than 10 such that N and N*p have the same decimal digit sum.	Easy3	Brute forceMath+2	No attempts yet	1s	128 MB	Judgeable
Complicated RouteParse a route of step counts in eight compass directions, sum the displacement, and print the final point and its distance from the origin to three decimals.	Easy3	ImplementationMath+2	No attempts yet	1s	128 MB	Judgeable
Too Much WaterGiven a property point, compute the hour when the growing semicircle centered at the origin first covers it, using the fixed 50 square meters per hour rate.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Ball BearingsGiven the inner diameter of an outer ring, the ball diameter, and the minimum gap between neighboring balls, find the maximum number of balls that fit.	Easy3	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
HardwareExpand each house-number order into individual numbers, count how many times each digit 0-9 appears, and print the per-digit totals plus the grand total.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Goldbach's ConjectureFor each even n below 2^15, count the unordered pairs of primes that sum to n, stopping at a terminating 0.	Easy3	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
Add Backward NumbersAdd two numbers whose digits are given in reverse order, printing the sum with its digits also reversed and no leading zeroes.	Easy3	MathString+2	No attempts yet	1s	128 MB	Judgeable
Chances of WinningGiven results of some games among four teams, count the outcomes of the remaining games where team T ends with strictly more points than every other team.	Easy3	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Don't pass me the ball!Given the scorer's jersey number J, count the ordered increasing 4-tuples of distinct jersey numbers ending at J.	Easy3	CombinatoricsMath	No attempts yet	2s	512 MB	Judgeable
Aromatic NumbersGiven a string alternating Arabic digits and Roman numeral letters, sum each digit times its Roman value, subtracting a pair when the next Roman value is larger.	Easy3	StringImplementation+1	No attempts yet	2s	512 MB	Judgeable
Mouse JourneyCount monotone right/down paths on an R by C grid from (1,1) to (R,C) that avoid K blocked cat cells.	Easy3	Dynamic programmingMatrix+1	No attempts yet	2s	512 MB	Judgeable
Who Has Seen the WindGiven humidity h and a time limit M, evaluate the quartic altitude formula hour by hour and report the first hour the balloon's altitude drops to zero or below.	Easy3	MathSimulation+2	No attempts yet	2s	512 MB	Judgeable
Up and DownTwo walkers repeat a forward/backward step cycle; after s steps, report whose distance from the start is greater, or Tied.	Easy3	SimulationMath+2	No attempts yet	2s	512 MB	Judgeable
PunchySimulate a tiny two-variable language, running the given instructions in order until a stop opcode, and print each requested variable value.	Easy3	SimulationImplementation+1	No attempts yet	2s	512 MB	Judgeable
Global WarmingGiven a sequence of temperatures, find the length of the shortest period of the sequence of consecutive differences, allowing the final repetition to be truncated.	Easy3	String matchingBrute force+2	No attempts yet	2s	512 MB	Judgeable
Cool NumbersCount integers in [a, b] that are both a perfect square and a perfect cube, meaning perfect sixth powers.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
GPS Text EntryGiven a fixed 5x6 letter grid, compute the total cursor moves to type a string starting from 'A' and then reach 'enter'.	Easy3	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
Cell-Phone MessagingGiven words, compute the typing time on a phone keypad where each press takes 1 second and switching between letters on the same key adds a 2-second pause.	Easy3	ImplementationString+2	No attempts yet	1s	128 MB	Judgeable
MaternityGiven the two alleles each parent carries for five genes, decide for each baby whether its five visible traits could result from that pairing.	Easy3	ImplementationCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
RSA NumbersCount how many integers in an inclusive range below 1000 have exactly four divisors, then print the count in a fixed sentence.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Picture PerfectFor each C, find the factor pair (W, H) with W*H = C closest to a square, and report the smallest perimeter along with W and H.	Easy3	MathBrute force+2	No attempts yet	1s	128 MB	Judgeable
The Students' Council BreakfastGiven four ticket prices and a target amount, list every non-negative count combination that hits the target, count them, and report the fewest tickets needed.	Easy3	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Numbers That Read the Same Upside DownCount how many integers in the interval [m, n] stay the same when rotated 180 degrees, using the digit map 0, 1, 8, 6, 9.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Slot MachinesSimulate a gambler who cycles through three slot machines with fixed payout periods and stops when she runs out of quarters, and report the total number of plays.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Deficient, Perfect, and AbundantFor each integer, sum its proper divisors and classify it as deficient, perfect, or abundant.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
Train SwappingFor each test case, count the inversions of a permutation of 1..L, the minimum number of adjacent swaps needed to sort the train.	Easy3	ArraySorting+2	No attempts yet	1s	128 MB	Judgeable
Trimmed and Corrected MeanGiven N judge scores and an integer K, sort the scores, then output the trimmed mean that drops K from each end and the corrected mean that replaces those extremes with the nearest kept value, both rounded to two decimals.	Easy3	SortingPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
Arithmetic SequenceGiven a sequence, decide whether consecutive differences are equal and, if so, print the next five terms in the exact required format.	Easy3	ImplementationMath+1	No attempts yet	1s	128 MB	Judgeable
Hobbiton FarmsFor each test case, decide whether a circle and an axis-aligned rectangle share at least one point.	Easy3	GeometryImplementation+1	No attempts yet	1s	128 MB	Judgeable
MillenniumGiven a birthdate in a fictional 10-month calendar with alternating 19 and 20 day months, find days until year 1000, month 1, day 1.	Easy3	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
RectangleRepeatedly cut the largest possible square from an n by m rectangle and count how many squares result.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Making shortest-path test dataPrint the prescribed shortest-path test graph: a chain with a computed number of self-loops at vertex 0, plus Q queries from V-1 to 0.	Easy3	ImplementationGraph+2	No attempts yet	1s	128 MB	Judgeable
ClassGiven a grid of digits, sum each cell's average absolute difference from its up to four orthogonal neighbors, and print the total with four decimals.	Easy3	ImplementationMatrix+2	No attempts yet	1s	1024 MB	Judgeable
CarpetsGiven up to three axis-aligned rectangles, find the total area of their union.	Easy3	GeometryImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Harmony: Parallel FifthsGiven N pairs of simultaneous two-voice pitches, list every position i where the voices form a perfect fifth (interval 5 mod 12) at both i and i+1 and both voices move.	Easy3	ImplementationArray+2	No attempts yet	3s	1024 MB	Judgeable
HarmonyGiven K voices over N note rows, list every pair of consecutive rows and voice pair that forms a parallel fifth (both voices move and stay 7 semitones apart mod 12).	Easy3	ImplementationBrute force+2	No attempts yet	7s	1024 MB	Judgeable
Aliens' SocksFind the minimum number of socks to draw so that at least k of one color are guaranteed, given the counts per color.	Easy3	GreedyMath+1	No attempts yet	1s	1024 MB	Judgeable
Alien SocksGiven counts of socks in s colors, find the smallest number of socks to draw to guarantee k socks of one color, or -1 if impossible.	Easy3	MathGreedy+1	No attempts yet	1s	1024 MB	Judgeable
PyramidsGiven N blocks, repeatedly take out the largest triangular number that fits, and print the resulting pyramid heights in decreasing order.	Easy3	GreedyMath+2	No attempts yet	1s	1024 MB	Judgeable
EncryptionGiven a string encrypted with the rule x -> x^3 mod 29 + 1, recover and print the original symbols.	Easy3	ImplementationMath+2	No attempts yet	1s	1024 MB	Judgeable
EquationsGiven sums of each number paired with the last number, plus the total sum, recover all N original numbers.	Easy3	MathImplementation+1	No attempts yet	1s	1024 MB	Judgeable
LaundryGiven colors partitioned into washable groups and counts of clothes per color, find how many machine loads of capacity M are needed.	Easy3	MathImplementation+2	No attempts yet	1s	1024 MB	Judgeable
A DP ProblemParse each linear equation without parentheses, solve for x, and report the floored solution or whether it is impossible or an identity.	Easy3	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Skew BinaryConvert each decimal number into its unique skew binary representation, printed as the sorted ranks of its nonzero digits.	Easy3	MathGreedy+2	No attempts yet	1s	128 MB	Judgeable
Number StepsGiven a point, print the number written there by a fixed boustrophedon path over the plane, or No Number if the point is empty.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Polynomial Remainder OperationMultiply two binary polynomials over GF(2) and print the remainder modulo a third polynomial, all given as bit strings.	Easy3	MathBit manipulation+1	No attempts yet	1s	128 MB	Judgeable
UndercutScore a five-round card game where players reveal numbered cards each round, applying undercut and tie rules, and print both totals.	Easy3	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
Currency ExchangeGiven a 5x5 exchange-rate table where every conversion rounds to the nearest hundredth, simulate each trip and report the final dollar amount rounded to cents.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Ride My BicycleCompute the ratio of each of the 21 front and back gear pairs, round to two decimals, and print them sorted by ratio then chain ring.	Easy3	SortingImplementation+1	No attempts yet	1s	128 MB	Judgeable
SequenceGiven up to five strictly increasing numbers, find the smallest base at most 10 in which their values, read as base-b numerals, form an arithmetic sequence.	Easy3	MathBrute force	No attempts yet	1s	128 MB	Judgeable
Untidy DesktopsGiven n axis-aligned rectangles, count how many overlap at least one other rectangle, boundaries included.	Easy3	GeometryBrute force	No attempts yet	7s	128 MB	Judgeable
BoxGiven six rectangles that can be rotated, decide whether they form the three pairs of opposite faces of a rectangular box.	Easy3	ImplementationSorting+1	No attempts yet	2s	128 MB	Judgeable
Factoring a PolynomialGiven a polynomial with integer coefficients of degree at most 20, decide whether it is irreducible over the reals.	Easy3	MathImplementation+1	No attempts yet	1s	512 MB	Judgeable
Prehistoric Operating SystemsCount binary strings of length n with no two adjacent D's, where D means DOORS and O means any other brand, for up to 40 test values of n.	Easy3	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Incomplete chess boardsFor each pair of removed squares on an 8x8 board, decide whether the remaining 62 squares can be tiled by 31 dominoes.	Easy3	Math	No attempts yet	1s	128 MB	Judgeable
Yeehaa!Given the large circle radius R and the count n of equal small circles packed around the inside rim, compute the small circle radius r.	Easy3	GeometryMath+1	No attempts yet	1s	128 MB	Judgeable
Cramer's RuleGiven several 3x3 linear systems, compute four determinants by Cramer's rule and either print the unique solution rounded to three decimals or report none.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Kingdom SubdivisionGiven a simple polygon's integer vertices, output half its area as a reduced fraction p/q.	Easy3	GeometryMath+1	No attempts yet	2s	256 MB	Judgeable
Circle DrawingPaint circles onto a grid, later circles overwriting earlier ones, then print the final color of every pixel.	Easy3	SimulationGeometry+1	No attempts yet	3s	128 MB	Judgeable
Big NumberFor each m up to 10^7, print the number of decimal digits in m factorial.	Easy3	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
SupermarketFind the k-th smallest value among n amounts spent, with values bounded by 100000.	Easy3	SortingArray+2	No attempts yet	1s	128 MB	Judgeable
Sequences without StammersPrint the smallest alphabet size for which a square-free (stammer-free) string of length n exists.	Easy3	StringCombinatorics+1	No attempts yet	3s	128 MB	Judgeable
Table and ChairsGiven a rectangular tabletop A by B and square chairs of side K, find the maximum number of non-overlapping chairs whose backrest lies along a table edge.	Easy3	MathGreedy+1	No attempts yet	1s	128 MB	Judgeable
Rectilinear Polygon With Area Equal to Its Vertex CountGiven n, print a canonical rectilinear polygon outline with n vertices and area n, or NIE when n is odd or below 4.	Easy3	ImplementationGeometry+2	No attempts yet	5s	128 MB	Judgeable
RectanglesCount axis-aligned rectangles on an n by m grid of points whose perimeter is at least p.	Easy3	MathBrute force+1	No attempts yet	1s	128 MB	Judgeable
Computation of a Road Network PlanGiven the number of cities n and a target diameter d, print a specific tree: a path of length d with all remaining cities hung off its middle vertex.	Easy3	TreeImplementation+1	No attempts yet	1s	128 MB	Judgeable
Can You Exponentiate?Given a and b up to 1e9, print the last decimal digit of a^b.	Easy3	MathNumber theory+1	No attempts yet	1s	128 MB	Judgeable
PostcardCount the contiguous segments that keep at least one mountain of height m or more after trimming both ends.	Easy3	CombinatoricsArray	No attempts yet	1s	512 MB	Judgeable
ListAfter moving the last k numbers of 1 to n to the front, sum the entries from position i to position j.	Easy3	MathArray	No attempts yet	1s	512 MB	Judgeable
Smallest Missing MultipleFind the smallest positive multiple of k that is absent from the given set of n distinct integers.	Easy3	Hash mapMath	No attempts yet	1s	512 MB	Judgeable
Smallest Perfect-Square MultipleRead n and print the smallest multiple of n that is a perfect square.	Easy3	Number theory	No attempts yet	1s	128 MB	Judgeable
GrasshopperThe grasshopper crosses width x with the fewest jumps, starting at length s and halving each later jump rounded down, with 1 always allowed.	Easy3	GreedySimulation+1	No attempts yet	1s	128 MB	Judgeable
Grasshopper 2Decide whether jumps of lengths s, s/2, s/4, and so on can reach or pass distance x in finitely many jumps.	Easy3	Math	No attempts yet	1s	128 MB	Judgeable
Divisor Set InclusionDecide for each pair whether every divisor of a also divides b, which holds exactly when a divides b.	Easy3	Number theory	No attempts yet	1s	128 MB	Judgeable
The Cheerful MonkeyStarting from one closed cage in a circle of n, repeated jumps of length d open each landing cage until a repeat, and you count the opened cages.	Easy3	Number theoryMath	No attempts yet	1s	128 MB	Judgeable
GymCount the integers from 1 to n that are multiples of a or of b.	Easy3	MathNumber theory	No attempts yet	1s	128 MB	Judgeable
Pocket MoneyFor each test case, compare the sum and the product of the given numbers and print which is larger or whether they tie.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Perfect MemorySplit an even-length integer sequence into a palindrome and an antipalindrome that add up to it, or print NIE when parity forbids it.	Easy3	MathArray	No attempts yet	2s	128 MB	Judgeable
KonduktorCount how many times each of N compartments is visited during the first K steps of a back-and-forth walk starting at compartment 1.	Easy3	MathSimulation	No attempts yet	2s	128 MB	Judgeable
Hektor's Test AnswersFor each N, print the N-th letter of Hektor's 12-letter cycle over A to D formed by two steps forward and one step back.	Easy3	SimulationMath	No attempts yet	1s	128 MB	Judgeable
Class PairingsCount the ways to split N students into pairs for each test case and print the result modulo 1000.	Easy3	CombinatoricsMath	No attempts yet	1s	128 MB	Judgeable
The Stone GamePlayers alternately remove 1 to K of N stones, and the player taking the last stone wins each test case.	Easy3	Game theoryMath	No attempts yet	1s	128 MB	Judgeable
EncodingCount binary strings of length n that start with 1 and contain no adjacent ones for up to 100 queries.	Easy3	Dynamic programmingCombinatorics	No attempts yet	1s	128 MB	Judgeable
Point NumbersThe program converts two diagonal point numbers back to coordinates, adds them, and prints the number of the sum.	Easy3	MathImplementation	No attempts yet	1s	256 MB	Judgeable
PasswordFind the K-th password in lexicographic order whose letters appear in the same column of both 6 by 5 grids, or print NO.	Easy3	CombinatoricsSorting+1	No attempts yet	1s	128 MB	Judgeable
GasYou split M integer units across n tubes with linear outputs so every tube yields the same gas amount, or report 0 when impossible.	Easy3	Brute forceMath	No attempts yet	1s	128 MB	Judgeable
Rectangle ColoringCount the groups of overlapping rectangles where touching edges count as overlap and each group gets one color.	Easy3	Union-findGeometry	No attempts yet	1s	128 MB	Judgeable
Goldbach's ConjectureGiven an even number n, print the two primes that sum to n with the smallest gap between them.	Easy3	Number theoryTwo pointers	No attempts yet	2s	256 MB	Judgeable
FenceScale the given convex polygon to enclose the target area and report the resulting fence length.	Easy3	GeometryMath	No attempts yet	1s	128 MB	Judgeable
Lexicographic rank of a permutationGiven a permutation of the letters a to h, print its 1-based position in lexicographic order.	Easy3	CombinatoricsMath	No attempts yet	1s	128 MB	Judgeable
Primality TestDecide whether each of up to 10 numbers up to 100000000 is prime and print YES or NO.	Easy3	Number theoryMath	No attempts yet	1s	128 MB	Judgeable
BiorhythmsGiven one peak day for each of the 23, 28, and 33 day cycles and a date d, find the days from d to the next day when all three peak together.	Easy3	Number theoryMath	No attempts yet	1s	128 MB	Judgeable
Approximate String MatchingFor each word pair, try every offset, keep the largest count of matching letters, and print twice that count over the total length as a reduced fraction.	Easy3	String matchingBrute force+1	No attempts yet	1s	128 MB	Judgeable
Integer RectanglesFind the smallest wide integer rectangle larger than the given one when ordered by diagonal length and then height.	Easy3	Brute forceMath	No attempts yet	1s	128 MB	Judgeable
Bishop's minimum movesDecide whether a bishop can reach a target square and print the shortest route, breaking ties by lexicographic order.	Easy3	GeometryBrute force	No attempts yet	1s	128 MB	Judgeable
Flowers instead of a treeChoose the vase whose solid-of-revolution volume is closest to the target volume.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Fun with fractionsAdd up to 999 mixed numbers, integers, or fractions per test case and print each sum in lowest terms as a mixed number.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Bomb DefusalDecode up to 8 digits from 5 rows of ASCII art and print BEER!! only when every digit is valid and the value is divisible by 6.	Easy3	ImplementationMath	No attempts yet	1s	128 MB	Judgeable
Where's the RainbowGiven the height of a semicircular rainbow and the viewing angle to its top, compute the distance from the origin to the nearest point of the arc.	Easy3	GeometryMath	No attempts yet	1s	128 MB	Judgeable
Wiretap DeviceFind the one device whose received power exceeds six times the background noise plus every other device's power, or print NOISE.	Easy3	MathArray	No attempts yet	1s	128 MB	Judgeable