Math and counting

Number theory, combinatorics, and geometry

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Total results13,164 problems

Preparing a knapsack problem
Easy3
Combinatorics, Implementation
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Resistor Circuit
Easy3
Stack, Math
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Younghoon the Prankster
Easy3
Combinatorics, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Polynesiaglot (Small 1)
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Polynesiaglot
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Polynesiaglot (Large)
Easy3
Dynamic programming, Combinatorics
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Lazy Spelling Bee (Small)
Easy3
Combinatorics, String
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Captain Hammer (Small)
Easy3
Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Hedgemony (Large)
Easy3
Simulation, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Password Retyping
Easy3
Probability, Math+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Commute War (Small)
Easy3
Probability, Simulation+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
New Calendar (Small)
Easy3
Simulation, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Equation restoration (Small)
Easy3
Brute force, String+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Mystery Square (Small)
Easy3
Brute force, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Perfect Harmony (Small)
Easy3
Number theory, Brute force
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Ratings Percentage Index
Easy3
Simulation, Math+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
RPI (Large)
Easy3
Simulation, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Grazing Goats (Small)
Easy3
Geometry, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Center of Mass of a Firefly Swarm
Easy3
Math, Geometry+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Triangle Areas (Large)
Easy3
Geometry, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
The Fancy Tavern
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Probability of winning a prize
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lunch is not the problem right now
Easy3
Bit manipulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pinocchio
Easy3
Combinatorics, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dance on the Circle
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Unusual Sequence
Easy3
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Largest Common Vertex on a Rooted Tree
Easy3
Tree, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
World Cup Betting
Easy3
Probability, Brute force
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Σ
Easy3
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Router 3
Easy3
Graph, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Salt Bomb
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Shuttle Run
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tile Decoration
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Room Assignment
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Completing the Square
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dictionary
Easy3
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Reversed Multiplication Table
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Exam Supervisors
Easy3
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Older Brother
Easy3
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
King's Heir
Easy3
Implementation, Math
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Secret Santa
Easy3
Probability, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Robot
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
The Lap Where the Backmarker Falls Behind
Easy3
Math, Simulation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Contract Review
Easy3
String, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
World Cup Draws
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Animal Lottery
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Recurrence sequence
Easy3
Dynamic programming, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Averages in Place
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
The Calculus of Ada
Easy3
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
What base is this?
Easy3
Implementation, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
FBI Universal Control Numbers
Easy3
Implementation, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sum of Pairwise Products
Easy3
Math, Array+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Candle Box
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Six Sides
Easy3
Probability, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Binary String Ordering
Easy3
Bit manipulation, Math+1
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Square Pasture
Easy3
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Three Sticks
Easy3
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Array and Operation
Easy3
Greedy, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Regular hexagon and triangles
Easy3
Geometry, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Diwali lightings
Easy3
Math, Prefix sum+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Diwali lightings (Large)
Easy3
Math, Prefix sum+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Beautiful Numbers (Small)
Easy3
Math, Brute force+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Vote (Small)
Easy3
Math, Probability+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Counting Sheep (Small)
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Coin Jam (Small)
Easy3
Brute force, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Baskin-Robbins 31
Easy3
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
The Lost Cow
Easy3
Math, Simulation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Squares in a grid square
Easy3
Math, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Palindrome in base n
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Addition and Multiplication
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Splitting the Pizza Tower (Small)
Easy3
Dynamic programming, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Riemann Sum Offset (Small)
Easy3
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
What's Your Tier?
Easy3
Probability, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Calculate!
Easy3
Bit manipulation, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Mun, Hong, An
Easy3
Implementation, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Walking to Sincheon Station, Sam (Small)
Easy3
Math, Brute force+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Hyobin's Tutoring
Easy3
Implementation, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Exactly Electrical
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Vera and Trail Building
Easy3
Greedy, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Assigning rooms
Easy3
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Broken clock
Easy3
Math, Number theory+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Nemmo Nemmo (Easy)
Easy3
Brute force, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sat Down
Easy3
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Report Card
Easy3
Brute force, Math+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
The N-th Positive Rational Number
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Polynomial Derivative (Large)
Easy3
Math, Number theory+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Coke Drinking Contest
Easy3
Math, Simulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Election
Easy3
Probability, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Password Hacking
Easy3
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Younghoon the Informatics God
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Digit frequency
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Coin change
Easy3
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Big Number
Easy3
String, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Happy Number
Easy3
Simulation, Hash map+1
No attempts yet
Time limit
0.2s
Memory limit
512 MB
Judgeable
Cezar's Blackjack
Easy3
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Falling Apart
Easy3
Dynamic programming, Game theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Time is of the Essence
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
DRM Messages
Easy3
String, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Unloaded Die
Easy3
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Star Arrangements
Easy3
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Preparing a knapsack problemRead t up to 1e18 and print k = 300 with sixty 1s plus extra elements chosen by greedy binomial decomposition so exactly t subsets sum to 300.	Easy3	CombinatoricsImplementation	No attempts yet	1s	32 MB	Judgeable
Resistor CircuitCompute the equivalent resistance of a nested series-parallel resistor circuit described by a bracketed string.	Easy3	StackMath	No attempts yet	1s	64 MB	Judgeable
Younghoon the PranksterGiven a digit string where 1 and 6 are interchangeable and 2 and 7 are interchangeable, print its k-th candidate in lexicographic order or -1.	Easy3	CombinatoricsString	No attempts yet	1s	128 MB	Judgeable
Polynesiaglot (Small 1)Count length-L words over C consonants and V vowels in which each consonant is directly followed by a vowel, modulo 1000000007.	Easy3	Dynamic programmingCombinatorics	No attempts yet	5s	512 MB	Judgeable
PolynesiaglotCount length-L strings over C consonants and V vowels with no adjacent consonants and no trailing consonant, modulo 1e9+7.	Easy3	Dynamic programmingCombinatorics	No attempts yet	5s	512 MB	Judgeable
Polynesiaglot (Large)Count length-L words over C consonants and V vowels where every consonant is followed by a vowel, modulo 1e9+7.	Easy3	Dynamic programmingCombinatorics	No attempts yet	5s	512 MB	Judgeable
Lazy Spelling Bee (Small)Count distinct words formed by replacing each letter with itself or an adjacent letter of the target word.	Easy3	CombinatoricsString	No attempts yet	5s	512 MB	Judgeable
Captain Hammer (Small)Given launch speed and target distance, compute the smallest launch angle in degrees that lands exactly on the target.	Easy3	Math	No attempts yet	5s	512 MB	Judgeable
Hedgemony (Large)Simulate one left-to-right pass that trims each bush to the average of its neighbors when taller, then report the final height of bush N-1 with six decimals.	Easy3	SimulationMath	No attempts yet	5s	512 MB	Judgeable
Password RetypingGiven per-character correctness odds, pick backspaces or a restart to minimize expected keystrokes to finish the password.	Easy3	ProbabilityMath+1	No attempts yet	5s	512 MB	Judgeable
Commute War (Small)Walk the single chain of hourly rides from home to the office, adding each wait, ride time, and geometric checkpoint delay for the expected arrival time.	Easy3	ProbabilitySimulation+1	No attempts yet	5s	512 MB	Judgeable
New Calendar (Small)Given months per year, days per month and days per week, count calendar rows when each month starts after the previous month and never shares a row.	Easy3	SimulationMath	No attempts yet	5s	512 MB	Judgeable
Equation restoration (Small)Fill each ? in an addition or subtraction equation with a digit so the equation holds and the whole string is lexicographically smallest.	Easy3	Brute forceString+1	No attempts yet	5s	512 MB	Judgeable
Mystery Square (Small)Fill each ? in the binary string with 0 or 1 so the result is a perfect square.	Easy3	Brute forceMath	No attempts yet	5s	512 MB	Judgeable
Perfect Harmony (Small)Pick the smallest frequency between L and H that divides or is divided by every given frequency, or report NO.	Easy3	Number theoryBrute force	No attempts yet	5s	512 MB	Judgeable
Ratings Percentage IndexGiven the win-loss matrix of every team, compute each team's RPI from win percentages and opponents' averages and print each as a reduced fraction.	Easy3	SimulationMath+1	No attempts yet	5s	512 MB	Judgeable
RPI (Large)Compute every team RPI rating from the win-loss schedule using own, opponents, and opponents-of-opponents win rates.	Easy3	SimulationMath	No attempts yet	5s	512 MB	Judgeable
Grazing Goats (Small)Each of the two disks centered at the poles must cover the bucket point, and the answer is the overlap area of the smallest such disks.	Easy3	GeometryMath	No attempts yet	5s	512 MB	Judgeable
Center of Mass of a Firefly SwarmAverage the fireflies' positions and velocities to get the swarm's center of mass, then find the closest approach to the origin for t >= 0.	Easy3	MathGeometry+2	No attempts yet	5s	512 MB	Judgeable
Triangle Areas (Large)Given N, M and A, print the canonical triangle (0,0), (N,1), (w,h) with area A/2, or IMPOSSIBLE when A exceeds N*M.	Easy3	GeometryMath+2	No attempts yet	5s	512 MB	Judgeable
The Fancy TavernTwo cards hit each other simultaneously until at least one dies; decide which card survives.	Easy3	SimulationMath	No attempts yet	1s	128 MB	Judgeable
Probability of winning a prizeGiven a and b, a comment's position is uniform on a+1 to b; find the probability it is a perfect square and print the reduced fraction.	Easy3	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Lunch is not the problem right nowConvert between an IPv8 address (eight octets) and the 64-bit unsigned integer formed by concatenating their bytes.	Easy3	Bit manipulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
PinocchioCount the ordered 4-tuples of distinct positions in S whose letters are A, C, G, T in some fixed assignment.	Easy3	CombinatoricsMath	No attempts yet	2s	512 MB	Judgeable
Dance on the CircleSimulate N men dancing around a circle of N women through rotation moves and adjacent swaps, then report which man faces each woman at the end.	Easy3	SimulationImplementation+1	No attempts yet	2s	512 MB	Judgeable
Unusual SequenceGiven n and k, decide whether a permutation of 1..n has exactly k indices with gcd(i, A_i) > 1 and print the constructed sequence.	Easy3	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Largest Common Vertex on a Rooted TreeFor two nodes in a complete binary tree numbered heap-style, find the deepest common ancestor k and print 10k.	Easy3	TreeMath+1	No attempts yet	2s	512 MB	Judgeable
World Cup BettingGiven N at most 10 matches with hit probabilities and odds, find the probability that a fixed-fraction bettor ends with more money than he started.	Easy3	ProbabilityBrute force	No attempts yet	1s	32 MB	Judgeable
ΣSum Si/Ni over M dice and print the result modulo the prime 1,000,000,007 using modular inverses.	Easy3	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Router 3Build a router with g groups per layer by printing 2Ng directed edges from inputs to internal nodes and from internal nodes to outputs.	Easy3	GraphImplementation+2	No attempts yet	2s	512 MB	Judgeable
Salt BombGiven two clock times, compute how long the arm waits, treating an earlier target as the next day; print the wait in hh:mm:ss.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Shuttle RunGiven the total distance Jihun can run, report which of the 5 m cone intervals he collapses in.	Easy3	MathImplementation+1	No attempts yet	1s	128 MB	Judgeable
Tile DecorationGiven N, compute the perimeter of the rectangle formed by N spiral tiles whose side lengths follow the Fibonacci sequence, starting at 1, 1, 2, 3, 5, 8.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Room AssignmentCount students by grade and gender, then combine grades 1-2 into one pool and split grades 3-6 by gender, computing rooms as ceil(count/K).	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Completing the SquareGiven three corners of a square in any order, compute the coordinates of the missing fourth corner.	Easy3	GeometryMath	No attempts yet	1s	512 MB	Judgeable
DictionaryFor each of the given 9-letter permutations of a through i, report its 1-based rank in lexicographic order.	Easy3	CombinatoricsMath+1	No attempts yet	2s	512 MB	Judgeable
Reversed Multiplication TableFor a multiple N, reverse the decimal digits of N1 through NK and print the largest resulting value, dropping leading zeros.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Exam SupervisorsEach room needs one chief who covers B candidates plus enough assistants covering C each, so sum 1 + ceil(max(0, Ai - B) / C) over all rooms.	Easy3	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
Older BrotherGiven an integer q up to 1e9, decide whether q is a prime power, printing yes or no.	Easy3	Number theoryMath	No attempts yet	2s	512 MB	Judgeable
King's HeirGiven the king's death date and each son's birth date, find the youngest son whose 18th birthday is on or before the death date, or print -1.	Easy3	ImplementationMath	No attempts yet	2s	256 MB	Judgeable
Secret SantaFor a uniformly random permutation of N names, compute the probability that at least one resident draws their own name, rounded to 8 decimals; N can reach 10^12.	Easy3	ProbabilityMath+2	No attempts yet	2s	512 MB	Judgeable
RobotFollow TURN and MOVE commands from the origin facing east, print the final coordinates, or -1 if any move leaves the square.	Easy3	SimulationImplementation+1	No attempts yet	1s	512 MB	Judgeable
The Lap Where the Backmarker Falls BehindGiven lap times X (fast) and Y (slow), find the leader's lap number when the leader first laps the slowest driver.	Easy3	MathSimulation	No attempts yet	2s	512 MB	Judgeable
Contract ReviewFor each test case, delete every occurrence of the broken digit D from the huge integer N, then print the remaining number with leading zeros stripped.	Easy3	StringImplementation+1	No attempts yet	2s	512 MB	Judgeable
World Cup DrawsGiven each team's total points and the number of games played, work out how many of those games ended in a draw.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Animal LotteryGiven a bet value, a chosen number, and a drawn number, compute the largest prize based on how many trailing digits match.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Recurrence sequenceCompute the n-th term of a self-convolution recurrence where t(n) sums t(i)*t(n-1-i) for i from 0 to n-1, with n up to 35.	Easy3	Dynamic programmingMath+2	No attempts yet	5s	512 MB	Judgeable
Averages in PlaceGiven N, print the one fixed N x N table whose row and column averages each land inside their own row and column, with -1 for N=2.	Easy3	ImplementationMath+2	No attempts yet	1s	64 MB	Judgeable
The Calculus of AdaGiven n values of a polynomial at evenly spaced inputs, find the degree of the minimal-degree polynomial and its value at the next input using finite differences.	Easy3	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
What base is this?For each digit string, print its value read as octal, decimal, and hexadecimal; if it has an 8 or 9, print 0 for the octal value.	Easy3	ImplementationMath+2	No attempts yet	2s	512 MB	Judgeable
FBI Universal Control NumbersParse a 9-character UCN, map confusable letters to their digit characters, verify the weighted mod-27 check digit, and print the base-10 value of the first eight digits.	Easy3	ImplementationMath+1	No attempts yet	2s	512 MB	Judgeable
Sum of Pairwise ProductsGiven N integers, sum the products of every pair of distinct positions.	Easy3	MathArray+2	No attempts yet	1s	256 MB	Judgeable
Candle BoxGiven Rita's age gap D and the candle totals R and T, find how many of Theo's candles sit in Rita's box.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Six SidesGiven the six faces of two dice, find the probability that the first die shows the higher value, ignoring ties by rethrowing.	Easy3	ProbabilityMath+1	No attempts yet	1s	512 MB	Judgeable
Binary String OrderingPrint all 2^N binary strings of length N in the order given by the binary reflected Gray code formula i XOR floor(i/2).	Easy3	Bit manipulationMath+1	No attempts yet	1s	64 MB	Judgeable
Square PastureGiven two non-overlapping axis-aligned rectangles, find the smallest area of an axis-aligned square that covers both.	Easy3	GeometryMath	No attempts yet	2s	512 MB	Judgeable
Three SticksGiven three stick lengths, shorten them to positive integers so they form a non-degenerate triangle with the largest possible perimeter.	Easy3	GreedyMath+2	No attempts yet	2s	512 MB	Judgeable
Array and OperationGiven an array and a fixed K, decide if adding K to elements any number of times can turn it into a permutation of 1 to N.	Easy3	GreedyHash map+2	No attempts yet	2s	512 MB	Judgeable
Regular hexagon and trianglesChoose three non-crossing diagonals of a regular hexagon to maximize the smallest of the four resulting triangles' areas, for side length L.	Easy3	GeometryGreedy+1	No attempts yet	2s	512 MB	Judgeable
Diwali lightingsGiven a pattern S repeated infinitely and a range [I, J], count how many bulbs in that range are blue.	Easy3	MathPrefix sum+2	No attempts yet	5s	512 MB	Judgeable
Diwali lightings (Large)Given a pattern string repeated forever, count how many blue bulbs appear between positions I and J in the infinite sequence.	Easy3	MathPrefix sum+2	No attempts yet	5s	512 MB	Judgeable
Beautiful Numbers (Small)For each N, find a base B > 1 where N is written with only the digit 1, preferring the base with the most 1 digits.	Easy3	MathBrute force+2	No attempts yet	5s	512 MB	Judgeable
Vote (Small)Given N supporters of A and M of B, find the probability that A leads after every vote in a random arrival order.	Easy3	MathProbability+1	No attempts yet	5s	512 MB	Judgeable
Counting Sheep (Small)Track which digits 0 to 9 appear as Bleatrix counts multiples of N, and report the last multiple or INSOMNIA if digit 9 never completes.	Easy3	SimulationImplementation+1	No attempts yet	5s	512 MB	Judgeable
Coin Jam (Small)Print the J lexicographically smallest 0/1 strings of length N whose values in bases 2 through 10 are all composite, with the smallest prime factor for each base.	Easy3	Brute forceMath+2	No attempts yet	5s	512 MB	Judgeable
Baskin-Robbins 31Given n games with parameters j and m, compute how many turns each lasts and report the earliest game with the minimum turn count.	Easy3	MathImplementation+2	No attempts yet	2s	256 MB	Judgeable
The Lost CowGiven start x and target y on a number line, simulate a doubling zig-zag search and report the total distance traveled until y is reached.	Easy3	MathSimulation	No attempts yet	2s	512 MB	Judgeable
Squares in a grid squareFor each grid side length l, count every square whose sides lie along grid lines, including tilted ones.	Easy3	MathCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Palindrome in base nFor each query, convert the decimal number A to base n and report whether its digit sequence reads the same forwards and backwards.	Easy3	MathImplementation+2	No attempts yet	1s	256 MB	Judgeable
Addition and MultiplicationFor integers a < b, multiply the triangular numbers T(k)=1+2+...+k for k from a to b, and print the result modulo 14579.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Splitting the Pizza Tower (Small)A tower of N pizzas is repeatedly split into two smaller towers, each split scoring the product of the two new heights. Find the maximum total score (N ≤ 10).	Easy3	Dynamic programmingMath+1	No attempts yet	1s	512 MB	Judgeable
Riemann Sum Offset (Small)For a linear polynomial, find the offset epsilon in [0, dx] that makes the Riemann sum equal the exact integral, or print -1.	Easy3	MathImplementation+2	No attempts yet	1s	512 MB	Judgeable
What's Your Tier?Starting at 2000 points, play 20 games with given win, loss, and draw probabilities; compute the probability of ending in each of five tiers.	Easy3	ProbabilityDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
Calculate!Given A, B and a huge count C, find the value of A after XORing B into it C times.	Easy3	Bit manipulationMath+1	No attempts yet	1s	256 MB	Judgeable
Mun, Hong, AnEach secretary adds one step to every stone in one direction from the start. Count total steps per stone modulo 3, then split P by the final blue, red, and green counts.	Easy3	ImplementationPrefix sum+2	No attempts yet	2s	256 MB	Judgeable
Walking to Sincheon Station, Sam (Small)Count N-digit numbers using only digits 0, 1, 2 that are divisible by 3 and have no leading zero.	Easy3	MathBrute force+1	No attempts yet	2s	256 MB	Judgeable
Hyobin's TutoringMultiply N matrices in the given order and print the sum of the product's entries modulo 1,000,000,007, or -1 if the shapes do not line up.	Easy3	ImplementationMath+1	No attempts yet	1s	512 MB	Judgeable
Exactly ElectricalGiven start and destination grid points and a battery charge t, decide whether a walk of exactly t unit steps connects them.	Easy3	MathImplementation+1	No attempts yet	1s	512 MB	Judgeable
Vera and Trail BuildingGiven K, follow a fixed greedy decomposition into complete blocks and print the resulting connected trail network with exactly K two-edge-disjoint paths.	Easy3	GreedyGraph+2	No attempts yet	1s	512 MB	Judgeable
Assigning roomsGiven three distinct room capacities and a student count, decide whether some nonnegative combination of the capacities sums exactly to the count.	Easy3	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
Broken clockGiven the clock-face angles of an hour hand and a minute hand in whole degrees, decide whether both can point that way at the same instant on a working clock.	Easy3	MathNumber theory+2	No attempts yet	0.5s	512 MB	Judgeable
Nemmo Nemmo (Easy)Count subsets of cells of an N by M grid, with N*M at most 25, that contain no full 2 by 2 square of chosen cells.	Easy3	Brute forceBit manipulation+2	No attempts yet	1s	512 MB	Judgeable
Sat DownGiven your two cards, count how many of the 18 choose 2 possible opponent hands you beat, and print the win probability to three decimals.	Easy3	Brute forceImplementation+2	No attempts yet	1s	256 MB	Judgeable
Report CardGiven N (x, y) points, find positive integers a and b up to 100 that minimize the sum of squared residuals of f(x) = ax + b.	Easy3	Brute forceMath+1	No attempts yet	1s	256 MB	Judgeable
The N-th Positive Rational NumberGiven N, return the N-th term of the diagonal enumeration of positive rationals where each group of constant numerator plus denominator is listed with decreasing numerator.	Easy3	MathImplementation+1	No attempts yet	1s	256 MB	Judgeable
Polynomial Derivative (Large)Given a polynomial as coefficient-exponent pairs, compute the value of its derivative at x = 2 modulo 1e9+7.	Easy3	MathNumber theory+1	No attempts yet	3s	256 MB	Judgeable
Coke Drinking ContestGiven N entrants who each drink A mL per second with fixed drinking and resting periods, find when the first entrant finishes K mL.	Easy3	MathSimulation+1	No attempts yet	1s	512 MB	Judgeable
ElectionGiven N total votes, M counted votes split as V1 and V2, and a threshold W, decide if the probability that candidate 1 wins (when each remaining vote is a fair coin) exceeds W%.	Easy3	ProbabilityMath+2	No attempts yet	1s	512 MB	Judgeable
Password HackingGiven each password's probability of being correct, find the expected number of attempts when trying passwords in the order that minimizes it.	Easy3	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Younghoon the Informatics GodCompute Younghoon's total score from N solved problems, then compare it against P scores to decide whether his rank is within the top 15%.	Easy3	MathImplementation+1	No attempts yet	2s	512 MB	Judgeable
Digit frequencyCount how many times a given digit d appears when writing every integer from 1 to n.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Coin changeFind the fewest 2 won and 5 won coins that sum to n, or report -1 when no combination works.	Easy3	GreedyMath+1	No attempts yet	2s	512 MB	Judgeable
Big NumberGiven a non-negative integer with up to a million digits, print its remainder modulo 20000303.	Easy3	StringMath+2	No attempts yet	2s	512 MB	Judgeable
Happy NumberDecide whether repeatedly summing the squares of a number's decimal digits ever reaches 1.	Easy3	SimulationHash map+1	No attempts yet	0.2s	512 MB	Judgeable
Cezar's BlackjackGiven the values of N drawn cards summing to at most 21, decide whether to draw again based on how many remaining cards exceed the gap to 21.	Easy3	ImplementationMath+2	No attempts yet	1s	64 MB	Judgeable
Falling ApartGiven up to 15 positive integers, two players alternately take one piece; find the final sums under optimal play.	Easy3	Dynamic programmingGame theory+1	No attempts yet	2s	512 MB	Judgeable
Time is of the EssenceGiven a chain of unit conversions and an amount in the smallest unit, print a rounded answer in the largest unit and a rough answer in the top two units.	Easy3	MathImplementation	No attempts yet	2s	512 MB	Judgeable
DRM MessagesSplit a string in half, rotate each half by its character sum, then merge the halves by rotating one half with the other's values.	Easy3	StringImplementation+2	No attempts yet	2s	512 MB	Judgeable
Unloaded DieGiven probabilities of the six faces of a loaded die, change one face's label so the expected value is exactly 3.5, minimizing the absolute label change.	Easy3	MathGreedy+1	No attempts yet	1s	512 MB	Judgeable
Star ArrangementsGiven S stars, list every appealing row pattern a,b where alternating rows of a and b stars use exactly S stars.	Easy3	MathBrute force+1	No attempts yet	1s	512 MB	Judgeable