Problems

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Total results29,475 problems

Store Credit
Easy3
Array, Hash map+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Store Credit (Large)
Easy3
Hash map, Array
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
T9 Spelling
Easy3
String, Implementation+2
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
Alien Language (Small)
Easy3
String, Brute force+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Ping Pong Balls (Small)
Easy3
Simulation, BFS+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Modern Art Plagiarism (Small)
Easy3
Tree, Backtracking
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
Text Messaging Outrage (Small)
Easy3
Greedy, Sorting+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Coin maze
Easy3
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
The Fancy Tavern
Easy3
Simulation, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tic! Tac! Toe!
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Who is the final winner?
Easy3
Sorting, Simulation+2
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
One Piece
Easy3
String, String matching+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
Will the Second IUPC Go Well?
Easy3
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Peter and the Textbook
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Household Ledger (Easy)
Easy3
Prefix sum, Array
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sweet part-time job
Easy3
Sliding window, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hongjun likes FFT
Easy3
Array, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ordinary Knapsack
Easy3
Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 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
Star Pattern 23
Easy3
Implementation, Simulation+2
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
Secret Code
Easy3
Hash map, String+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
Mountains Beyond Mountains
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
1s
Memory limit
64 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 1
Easy3
Graph, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Router 3
Easy3
Graph, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Passport Checking
Easy3
Hash map, String
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Badminton Match Score
Easy3
Simulation, String+1
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Salt Bomb
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Range Sum Queries
Easy3
Prefix sum, Array
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary tree
Easy3
Tree, DFS
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bitcoin investment
Easy3
Array, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Longest non-decreasing subsegment
Easy3
Array, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Two-color coloring
Easy3
Graph, BFS+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Shuttle Run
Easy3
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Selection of Participants of an Experiment
Easy3
Sorting, Array
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Look for the Winner!
Easy3
Array, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 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
Misimplemented Dinic
Easy3
Graph, Brute force+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Trucks
Easy3
Queue, Simulation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Completing the Square
Easy3
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rune
Easy3
Sorting, String+2
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
Quality of Check Digits
Easy3
Implementation, Brute force+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Reversed Multiplication Table
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Course registration
Easy3
Queue, Hash map+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Thief of the Circular Village
Easy3
Sliding window, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Turing machine halting in ten steps
Easy3
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
256 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
Rhyming Slang
Easy3
String, Hash map+1
No attempts yet
Time limit
2s
Memory limit
512 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
Strategy Game
Easy3
Array, Simulation
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
Digital Biochemical Circuit
Easy3
Matrix, Simulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Contract Review
Easy3
String, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Collector Robot
Easy3
Simulation, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Formula 1 World Champion
Easy3
Implementation, Array+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Card Trade
Easy3
Two pointers, Array+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Peaks of a Musical Loop
Easy3
Implementation, Array+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
Hawk Eyes
Easy3
Simulation, Implementation
No attempts yet
Time limit
1s
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
Hunt the Rabbit
Easy3
Binary search, Simulation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Parliamentary Rankings
Easy3
Hash map, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hyper Rock-Scissors-Paper
Easy3
Implementation, Array+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Blackjack Dealer
Easy3
Simulation, Implementation
No attempts yet
Time limit
8s
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
Hot Air Ballooning
Easy3
Hash map, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Imena
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
32 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
Small Weird Measurements
Easy3
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dudu of English
Easy3
String, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Wildcard Anagram
Easy3
String, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Reversal
Easy3
String, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Triangle
Easy3
Divide and conquer, Recursion+1
No attempts yet
Time limit
1s
Memory limit
64 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
IOI 2017 Logo Vote
Easy3
Implementation, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Crow's Last Attack
Easy3
Simulation, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Ticket machine keyboard
Easy3
String, Simulation+2
No attempts yet
Time limit
1s
Memory limit
32 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
Password Change
Easy3
String, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Store CreditGiven a credit C and a list of item prices, find the two positions whose prices sum exactly to C and print them in increasing order.	Easy3	ArrayHash map+2	No attempts yet	5s	512 MB	Judgeable
Store Credit (Large)For each test case, find the two item positions whose prices sum to the credit C, and print the smaller position first.	Easy3	Hash mapArray	No attempts yet	5s	512 MB	Judgeable
T9 SpellingGiven messages, output the keypad press sequences that type them, inserting a space between consecutive presses on the same key.	Easy3	StringImplementation+2	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
Alien Language (Small)For each pattern of tokens (plain letters or letter groups), count how many of the D dictionary words it can match.	Easy3	StringBrute force+1	No attempts yet	5s	512 MB	Judgeable
Ping Pong Balls (Small)Given two fixed displacement vectors, simulate the chain reaction from one starting trap and count how many distinct traps fire.	Easy3	SimulationBFS+2	No attempts yet	5s	512 MB	Judgeable
Modern Art Plagiarism (Small)Decide whether the smaller tree is a connected subgraph of the larger tree, with only the shapes mattering, not the original labels.	Easy3	TreeBacktracking	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
Text Messaging Outrage (Small)Assign letters of given frequencies to at most K keys, P letters per key, to minimize total key presses; sort frequencies descending and fill positions greedily.	Easy3	GreedySorting+1	No attempts yet	5s	512 MB	Judgeable
Coin mazeFor each n, m, k, print either a hardcoded special maze for the two given triples or a wall-free grid with the base at (1,1) and coins in row-major order.	Easy3	ImplementationSimulation+2	No attempts yet	1s	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
Tic! Tac! Toe!Given the first player and the nine moves in order, report the player who first completes a row, column, or diagonal, or 0 for a draw.	Easy3	SimulationImplementation+1	No attempts yet	1s	128 MB	Judgeable
Who is the final winner?Each of N players holds M cards; every round all players play their largest remaining card and whoever plays the highest value scores a point. Report the player(s) with the most points.	Easy3	SortingSimulation+2	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
One PieceCount how many times a short uppercase pattern N appears as a substring of a longer string H, counting overlapping occurrences.	Easy3	StringString matching+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
Will the Second IUPC Go Well?Given the pen counts of N members, find the fewest members whose pens total at least M*K, or print STRESS if the total falls short.	Easy3	GreedySorting+2	No attempts yet	1s	128 MB	Judgeable
Peter and the TextbookSimulate a textbook where tearing out page i also removes page n-i+1, and answer which page sits at position p among the pages still present.	Easy3	SimulationImplementation+1	No attempts yet	2s	256 MB	Judgeable
Household Ledger (Easy)Maintain a ledger over N days with point additions and range-sum queries, printing the sum of entries from day p to day q.	Easy3	Prefix sumArray	No attempts yet	1s	512 MB	Judgeable
Sweet part-time jobJunsu can work at most m consecutive days out of n days with given daily wages; find the maximum total pay for such a window.	Easy3	Sliding windowPrefix sum+1	No attempts yet	1s	512 MB	Judgeable
Hongjun likes FFTGenerate permutations a and b with the given pseudocode, then compute c[i] = max over valid j of a[j]*b[i-j].	Easy3	ArraySimulation+1	No attempts yet	2s	512 MB	Judgeable
Ordinary KnapsackGiven N items with weights and values, pick a subset with total weight at most K to maximize total value.	Easy3	Dynamic programming	No attempts yet	2s	512 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
Star Pattern 23Infer the star-printing rule from the sample output and reproduce the pattern for a given N between 2 and 100.	Easy3	ImplementationSimulation+2	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
Secret CodeGiven a secret code with all distinct characters, score each same-length guess by counting exact position matches and characters present in the code but at a wrong position.	Easy3	Hash mapString+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
Mountains Beyond MountainsGiven column heights, a highway row, and pier rules, print the N by M picture of rock, tunnel, bridge, and pier cells exactly as specified.	Easy3	SimulationImplementation+1	No attempts yet	1s	64 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 1Print either a star-shaped router with one internal hub or a fully connected bipartite router, depending on whether N*N exceeds P_lim.	Easy3	GraphImplementation+1	No attempts yet	2s	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
Passport CheckingCount how many passport numbers on a check list appear in a list of stolen numbers, counting duplicates each time.	Easy3	Hash mapString	No attempts yet	1s	64 MB	Judgeable
Badminton Match ScoreGiven a rally-by-rally scoring string, replay a best-of-three badminton match and print each completed game's score plus the match winner.	Easy3	SimulationString+1	No attempts yet	1s	64 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
Range Sum QueriesGiven a fixed array and m range queries, print the sum of elements between two given indices for each query.	Easy3	Prefix sumArray	No attempts yet	2s	512 MB	Judgeable
Binary treeGiven each node's parent in a binary tree with n up to 20, print the height (distance from the root) of every node.	Easy3	TreeDFS	No attempts yet	2s	512 MB	Judgeable
Bitcoin investmentGiven a list of daily bitcoin prices, buy on one day and sell on that day or later to maximize the selling price minus the buying price.	Easy3	ArrayGreedy+1	No attempts yet	2s	512 MB	Judgeable
Longest non-decreasing subsegmentFind the longest contiguous non-decreasing run in a list and output its length and the sum of its elements, breaking ties by earliest start.	Easy3	ArrayImplementation+2	No attempts yet	2s	512 MB	Judgeable
Two-color coloringGiven an undirected multigraph, decide whether it is bipartite so its vertices can be colored with two colors.	Easy3	GraphBFS+1	No attempts yet	2s	256 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
Selection of Participants of an ExperimentGiven a list of student scores, find the smallest absolute difference between any two of them.	Easy3	SortingArray	No attempts yet	2s	512 MB	Judgeable
Look for the Winner!Given votes counted in order, report the earliest prefix after which one candidate's lead cannot be overtaken from remaining votes, or TIE.	Easy3	ArraySimulation+1	No attempts yet	2s	512 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
Misimplemented DinicPrint a fixed 4-vertex, 5-edge flow network; there is no input and the output is a single constant graph.	Easy3	GraphBrute force+1	No attempts yet	2s	512 MB	Judgeable
TrucksTrucks cross a one-lane bridge in order under a weight limit; find the earliest time all have finished.	Easy3	QueueSimulation	No attempts yet	1s	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
RuneFor each language, compute each rune's power as the number of maximal runs of consecutive vowels, then sort by power descending and by name ascending.	Easy3	SortingString+2	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
Quality of Check DigitsGiven a 10x10 operation table, count how many of the 10000 four-digit basic IDs let a single-digit change or an adjacent swap pass the check digit test.	Easy3	ImplementationBrute force+1	No attempts yet	1s	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
Course registrationGiven a click log of student numbers and K seats, keep each student's last click, then print the first K distinct students in that order.	Easy3	QueueHash map+1	No attempts yet	1s	256 MB	Judgeable
Thief of the Circular VillageCount the starting positions of a circular window of M houses whose total amount stays below K.	Easy3	Sliding windowPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
Turing machine halting in ten stepsSimulate a Turing machine for at most 10 steps on each query tape and report whether it reaches the halting state.	Easy3	SimulationImplementation+2	No attempts yet	1s	256 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
Rhyming SlangGiven a word and lists of rhyming endings, decide for each phrase whether its last word shares a rhyming ending with the word.	Easy3	StringHash map+1	No attempts yet	2s	512 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
Strategy GameDistribute J times R point values to players in turn order, sum each player's points, and find the highest scorer, breaking ties by last move.	Easy3	ArraySimulation	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
Digital Biochemical CircuitGiven an N-by-P table of bits, count the runs of consecutive 1s in each column whose length is at least C.	Easy3	MatrixSimulation+1	No attempts yet	1s	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
Collector RobotSimulate a robot moving on a grid with pillars, turning and stepping according to a given instruction string, and count the distinct stickers it visits.	Easy3	SimulationImplementation	No attempts yet	2s	512 MB	Judgeable
Formula 1 World ChampionGiven each driver's finishing place in every race, compute total points under several scoring systems and print the champion(s), breaking ties by listing all joint champions.	Easy3	ImplementationArray+1	No attempts yet	2s	512 MB	Judgeable
Card TradeGiven two sorted card piles, find the largest N such that Alice and Beatriz can each give away N cards of distinct kinds that the other does not own.	Easy3	Two pointersArray+1	No attempts yet	2s	512 MB	Judgeable
Peaks of a Musical LoopCount local maxima and minima in a circular sequence of samples where consecutive values differ and the first and last differ.	Easy3	ImplementationArray+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
Hawk EyesGiven a sequence of cup swaps among four positions, track where the small ball (initially at position 1) and big ball (initially at position 4) end up.	Easy3	SimulationImplementation	No attempts yet	1s	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
Hunt the RabbitFor each hidden rabbit position, print the sequence of envelope numbers a lower-middle binary search opens until it finds the rabbit.	Easy3	Binary searchSimulation	No attempts yet	2s	512 MB	Judgeable
Parliamentary RankingsGiven members and weekly action codes with point values, print the highest and lowest scores with the matching names in id order.	Easy3	Hash mapSorting+1	No attempts yet	2s	512 MB	Judgeable
Hyper Rock-Scissors-PaperGiven each player's gesture in a 15-gesture rock-paper-scissors variant, find the single gesture that beats at least one shown gesture and loses to none, or report Draw.	Easy3	ImplementationArray+2	No attempts yet	8s	512 MB	Judgeable
Blackjack DealerSimulate the dealer's blackjack hand: report blackjack, bust, or the final score after the dealer plays by fixed rules.	Easy3	SimulationImplementation	No attempts yet	8s	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
Hot Air BallooningEach trainee's flight record is an integer whose digits are the balloon types flown; count how many distinct sets of digits appear.	Easy3	Hash mapBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
ImenaSplit a book's text into N sentences and count, for each, how many words are names (uppercase first letter, lowercase rest).	Easy3	StringImplementation+1	No attempts yet	1s	32 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
Small Weird MeasurementsCount the subarrays in which the signs of consecutive differences strictly alternate (length 1 counts, equal neighbours break it).	Easy3	ArrayImplementation+1	No attempts yet	2s	512 MB	Judgeable
Dudu of EnglishApply seven ordered text transformations (lowercase, of-word replacement, vowel deletion, punctuation removal, line join, space condense, 20-char reflow) to translate English into Dudu's dialect.	Easy3	StringImplementation+1	No attempts yet	2s	512 MB	Judgeable
Wildcard AnagramGiven two equal-length strings, check whether the second is an anagram of the first after treating its asterisks as any letters.	Easy3	StringHash map+2	No attempts yet	2s	512 MB	Judgeable
ReversalApply M substring reversals to a string of up to 2.5 million characters and print the final result.	Easy3	StringImplementation+1	No attempts yet	1s	256 MB	Judgeable
TriangleRecursively subdivide a triangle into three corner triangles N-1 times and print the resulting ASCII fractal.	Easy3	Divide and conquerRecursion+1	No attempts yet	1s	64 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
IOI 2017 Logo VoteEach voter ranks up to three logos worth 3, 2, 1 points; find all logos winning on score, then first votes, then second votes.	Easy3	ImplementationSorting+1	No attempts yet	2s	512 MB	Judgeable
The Crow's Last AttackSimulate a crow that attacks around a circular line of enemies, reversing on kills, and report which enemy takes the last attack.	Easy3	SimulationImplementation	No attempts yet	2s	512 MB	Judgeable
Ticket machine keyboardGiven destination names and a pressed prefix, mark on a 4x8 grid every letter that can immediately follow the prefix in some name.	Easy3	StringSimulation+2	No attempts yet	1s	32 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
Password ChangeFind the minimum letter changes so the first K characters equal the last K characters.	Easy3	StringImplementation	No attempts yet	2s	512 MB	Judgeable