Problems

Pick a problem, code in the editor, and watch the judge run real test cases. The archive is open to browse

Under construction

Still being built. Things may change

Total results29,458 problems

Boat
Medium4
Greedy, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Ancient Discs
Medium4
BFS, Brute force+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Outstanding Outcome
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Dale 'n' Chip
Medium4
String, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Fastest Thing Alive
Medium4
Dynamic programming, Matrix
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Distribution Center
Medium4
BFS, Matrix+1
No attempts yet
Time limit
4s
Memory limit
2048 MB
Judgeable
Gardening
Medium4
Tree, DFS+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Icarus' Rebirth
Medium4
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Excursion
Medium4
Tree, Dynamic programming+1
No attempts yet
Time limit
7s
Memory limit
2048 MB
Judgeable
Darts
Medium4
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Sanghyeon's Math Study Plan
Medium4
Binary search, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
TAIDADA
Medium4
Greedy, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Password
Medium4
Greedy, Implementation+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Pretty-Print the Spiral
Medium5
Math, Matrix+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Finding a Perfect Square
Medium5
Brute force, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
High-Rise Buildings
Medium5
Geometry, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Cocktail
Medium5
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Lamps
Medium5
Hash map, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Base-36 Number
Medium5
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Digit Swap
Medium5
BFS, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Dice
Medium5
Implementation, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Water Bottles
Medium5
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Expandable Beautiful Triangles
Medium5
Brute force, Geometry+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Going Home
Medium5
Math, Geometry+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Range Digit Sum
Medium5
Math, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Lexicographically Largest Sort
Medium5
Greedy, Array+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Tower Floor Display
Medium5
Math, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Cargo Loading
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Unknown Sentence
Medium5
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Digit 8
Medium5
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hotel
Medium5
Dynamic programming, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
IQ Test
Medium5
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Connecting a Road Graph
Medium5
Graph, Union-find+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Maximum Sum
Medium5
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Prefix
Medium5
Trie, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Four Primes
Medium5
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Tree Diameter
Medium5
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Exercise
Medium5
Greedy, Simulation+1
No attempts yet
Time limit
2s
Memory limit
16 MB
Judgeable
Decreasing Numbers
Medium5
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sausage Sharing
Medium5
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cutting to a Triangle
Medium5
Geometry, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Number of Participants
Medium5
Math, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Survivable Diagnostic Rules
Medium5
Graph, DFS+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Hongjun Programming Contest
Medium5
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Party
Medium5
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Head Taps
Medium5
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Farm Management
Medium5
BFS, DFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Good Numbers
Medium5
Two pointers, Array+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Dictionary
Medium5
Combinatorics, Greedy+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Wall-Breaking Maze
Medium5
BFS, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Partial Rectangles
Medium5
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Finding Notebook Owners
Medium5
Graph, DFS+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
K-th Number
Medium5
Binary search, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Advertisement
Medium5
String matching, String
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Run, Hongjun
Medium5
Sliding window, Queue+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
X and K
Medium5
Bit manipulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Repeating a Number
Medium5
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hopping Frog
Medium5
BFS, Graph+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Fixed-Length Reversal Sort
Medium5
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Solving Problems
Medium5
Dynamic programming, Graph+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Two String Masks
Medium5
String, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Tangled Electric Wires
Medium5
Dynamic programming, Binary search+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tablature Transposition
Medium5
Greedy, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Watering Fields
Medium5
Minimum spanning tree, Graph+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Array Value
Medium5
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Minsik-First Search
Medium5
DFS, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Yogurt Expiration Date
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Paper Folding
Medium5
Two pointers, Simulation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Switches
Medium5
Segment tree, Intervals+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sum of an Arithmetic Sequence
Medium5
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Woodcutter Dasom
Medium5
Brute force, Simulation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
New Album
Medium5
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Broken Calculator
Medium5
Backtracking, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sunday Morning Date
Medium5
Shortest path, BFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Dividing a Rectangle into Three
Medium5
Prefix sum, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sevi Game
Medium5
Probability, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Library
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Gap Pair Sequence
Medium5
Backtracking, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Underscores
Medium5
Greedy, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Collecting Gems
Medium5
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Duel
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Divisible by Its Digits
Medium5
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
End of the Spiral
Medium5
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Shortest Path Through Required Vertices
Medium5
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Make a Periodic String
Medium5
String, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Substring Picking Game
Medium5
Game theory, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
String Exchange
Medium5
Sliding window, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sejun and Sebi's War
Medium5
Greedy, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Triangle Subsequence
Medium5
Sorting, Two pointers+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Birds
Medium5
Math, Simulation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
World Conquest
Medium5
Binary search, Greedy+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Roads of the Northern Country
Medium5
Tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
History
Medium5
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Youngsik's Finger
Medium5
Math, Binary search+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Counting Crossing Edges
Medium5
Sorting, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
New Year Party
Medium5
Dynamic programming, Tree+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Ominsik Number
Medium5
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Making the Best Team
Medium5
Dynamic programming, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sungji's Birthday Party
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
City Division Plan
Medium5
Minimum spanning tree, Union-find+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
BoatFind the fewest boat crossings needed to ferry all residents across the river, where the boat carries at most two people within a weight limit.	Medium4	GreedyTwo pointers+1	No attempts yet	1s	2048 MB	Judgeable
Ancient DiscsGiven a permutation of 1 to n (n at most 10), find the fewest operations that split it into four blocks and reorder them as C, A, D, B to sort it.	Medium4	BFSBrute force+1	No attempts yet	3s	2048 MB	Judgeable
Outstanding OutcomeGiven a frozen scoreboard with pending submissions, find the lowest rank our team can end up at after the unfreeze.	Medium4	GreedySorting+1	No attempts yet	1s	2048 MB	Judgeable
Dale 'n' ChipFor each sublist of chipmunks with fixed Rock, Paper, or Scissors plays, find the largest circle where every chipmunk wins once and loses once.	Medium4	StringPrefix sum+1	No attempts yet	2s	2048 MB	Judgeable
Fastest Thing AliveFind a route from a blank cell in the first row to a blank cell in the last row, moving down one row per step and shifting at most one lane left or right.	Medium4	Dynamic programmingMatrix	No attempts yet	2s	2048 MB	Judgeable
Distribution CenterGiven a grid of walls, empty squares, and destinations, mark each square X if a crate there can never be pushed to a destination, otherwise O.	Medium4	BFSMatrix+1	No attempts yet	4s	2048 MB	Judgeable
GardeningGiven a tree encoded as a string of labels and child lists, print the node labels in the order they are chopped when always removing the leftmost leaf.	Medium4	TreeDFS+1	No attempts yet	1s	2048 MB	Judgeable
Icarus' RebirthFind the fewest steps from the first to the last character of a word, where a step moves one index or jumps to the nearest same letter left or right.	Medium4	BFSGraph+1	No attempts yet	1s	2048 MB	Judgeable
ExcursionGiven a tree with a value on each node, find the maximum sum of values along a simple path that includes at least one node.	Medium4	TreeDynamic programming+1	No attempts yet	7s	2048 MB	Judgeable
DartsGiven n darts as rays in 3D, count how many hit the elliptical board centered at the origin with axes h and v.	Medium4	GeometryMath	No attempts yet	1s	2048 MB	Judgeable
Sanghyeon's Math Study PlanFind the smallest constant daily problem count x so that the total favorability over N days, where each day's value is piecewise linear in x, is at least L.	Medium4	Binary searchArray	No attempts yet	1s	1024 MB	Judgeable
TAIDADAPick N distinct integers from 1 to M so that no two of them XOR to K, or report -1 when that is impossible.	Medium4	GreedyMath	No attempts yet	1s	1024 MB	Judgeable
PasswordGiven the password length n, find the minimum and maximum number of non-letter characters a valid password of that length can contain.	Medium4	GreedyImplementation+1	No attempts yet	2s	2048 MB	Judgeable
Pretty-Print the SpiralCompute values on an infinite counterclockwise number spiral and print a rectangular sub-grid with aligned, minimal-width spacing.	Medium5	MathMatrix+2	No attempts yet	2s	128 MB	Judgeable
Finding a Perfect SquareFrom a grid of digits, pick cells whose row and column indices each form an arithmetic sequence, concatenate the digits, and find the largest perfect square possible.	Medium5	Brute forceMath+2	No attempts yet	2s	128 MB	Judgeable
High-Rise BuildingsGiven the heights of N buildings in a row, find the maximum number of other buildings visible in a straight line of sight from any single building.	Medium5	GeometryBrute force+2	No attempts yet	2s	128 MB	Judgeable
CocktailGiven a tree of N ingredients linked by N-1 known mass ratios, compute the smallest positive integer masses that satisfy every ratio.	Medium5	TreeDFS+2	No attempts yet	2s	128 MB	Judgeable
LampsGiven an N by M lamp grid where pressing a column switch exactly K times total flips columns, find the max number of rows that end up fully lit.	Medium5	Hash mapString+2	No attempts yet	2s	128 MB	Judgeable
Base-36 NumberPick K base-36 digit symbols to replace with Z across N numbers so their sum is maximized, then output that sum in base 36.	Medium5	GreedyMath+2	No attempts yet	2s	128 MB	Judgeable
Digit SwapGiven N and exactly K digit swaps that must never leave a leading zero, find the maximum resulting number or report -1 if impossible.	Medium5	BFSBrute force+2	No attempts yet	2s	128 MB	Judgeable
DiceGiven a die net and N, stack N^3 dice into an N x N x N cube and minimize the sum of numbers on the five visible faces.	Medium5	ImplementationGreedy+2	No attempts yet	2s	128 MB	Judgeable
Water BottlesGiven N one-liter bottles and capacity K, find the minimum number of extra one-liter bottles so that merging equal amounts leaves at most K non-empty bottles.	Medium5	MathGreedy+1	No attempts yet	1s	512 MB	Judgeable
Expandable Beautiful TrianglesCount the RGB-colored triangles on an N by M grid that share two vertices with another RGB triangle of strictly larger area.	Medium5	Brute forceGeometry+2	No attempts yet	2s	128 MB	Judgeable
Going HomeCompute the minimum time to reach the origin from (X,Y) by combining unit-speed walking with fixed-length D jumps costing T seconds each.	Medium5	MathGeometry+1	No attempts yet	2s	128 MB	Judgeable
Range Digit SumSum the decimal digits of every integer from L to U, inclusive, where U can reach two billion.	Medium5	MathDynamic programming+1	No attempts yet	2s	128 MB	Judgeable
Lexicographically Largest SortGiven a distinct-integer array and a budget of at most S adjacent swaps, output the lexicographically largest array reachable within that swap budget.	Medium5	GreedyArray+1	No attempts yet	2s	128 MB	Judgeable
Tower Floor DisplayGiven an N-digit floor number shown on a lamp display where off lamps may be broken, compute the average of every floor number consistent with the lit lamps.	Medium5	MathCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Cargo LoadingGiven crane weight limits and box weights, find the minimum minutes to load all boxes with one box per crane per minute, or -1 if impossible.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
Unknown SentencePartition a sentence into segments that are anagrams of given words, minimizing total letters moved from their original word positions.	Medium5	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
Digit 8Given L and R up to 2*10^9, find the minimum number of times digit 8 appears in any integer within [L, R].	Medium5	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
HotelGiven advertising costs and customer gains for up to 20 cities with unlimited repeats, find the minimum total cost to gain at least C new customers.	Medium5	Dynamic programmingMath	No attempts yet	2s	128 MB	Judgeable
IQ TestGiven an integer sequence, decide whether an integer rule next = a*prev + b determines the next term uniquely, ambiguously, or not at all.	Medium5	MathImplementation+1	No attempts yet	2s	128 MB	Judgeable
Connecting a Road GraphGiven an adjacency matrix, find the minimum number of edge-swap operations needed to make the graph fully connected, or report -1 if impossible.	Medium5	GraphUnion-find+1	No attempts yet	2s	128 MB	Judgeable
Maximum SumAssign digits 0-9 to letters A-J that encode N numbers so that the sum of the numbers is maximized while no number has a leading zero.	Medium5	GreedyMath+2	No attempts yet	2s	128 MB	Judgeable
PrefixGiven up to 50 words, find the largest subset where no word is a prefix of another, using a trie and tree DP.	Medium5	TrieDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Four PrimesWrite a program that finds four prime numbers whose sum equals a given natural number N, or reports -1 if impossible.	Medium5	Number theoryMath+2	No attempts yet	2s	128 MB	Judgeable
Tree DiameterGiven a weighted tree with up to 100,000 vertices, compute the diameter as the maximum distance between any two vertices.	Medium5	TreeDFS+2	No attempts yet	2s	256 MB	Judgeable
ExerciseSimulate a pulse that rises by T when exercising and falls by R when resting (bounded between m and M) to find the minimum minutes needed to accumulate N exercise minutes, or report impossibility.	Medium5	GreedySimulation+1	No attempts yet	2s	16 MB	Judgeable
Decreasing NumbersGiven N, output the N-th smallest number whose decimal digits strictly decrease left to right, or -1 if it does not exist.	Medium5	CombinatoricsMath+1	No attempts yet	2s	128 MB	Judgeable
Sausage SharingGiven N identical sausages split among M critics who must each receive an equal total amount, find the minimum number of cuts required.	Medium5	Number theoryMath+1	No attempts yet	1s	128 MB	Judgeable
Cutting to a TriangleGiven a convex polygon reduced to a triangle by repeatedly cutting ears, find the maximum possible area of the final triangle among its vertices.	Medium5	GeometryBrute force+1	No attempts yet	2s	128 MB	Judgeable
Number of ParticipantsGiven N truncated (to 3 decimals) average scores from a survey with integer answers 0-10, find the smallest possible number of participants consistent with all averages.	Medium5	MathBrute force+1	No attempts yet	2s	128 MB	Judgeable
Survivable Diagnostic RulesGiven up to 200,000 two-literal rules over 20,000 boolean symptoms, decide via 2-SAT whether an assignment exists that avoids triggering any rule.	Medium5	GraphDFS+1	No attempts yet	5s	128 MB	Judgeable
Hongjun Programming ContestGiven school sizes, choose a team size k to maximize k times the number of schools whose size is divisible by k, requiring at least two such schools.	Medium5	Number theoryMath+1	No attempts yet	2s	128 MB	Judgeable
PartyGiven a directed weighted graph, compute for each village the round-trip shortest time to a fixed village X and return the maximum over all villages.	Medium5	Shortest pathGraph+1	No attempts yet	1s	128 MB	Judgeable
Head TapsGiven N numbers arranged in a circle, count for each student how many other students' numbers it evenly divides using an efficient divisor-counting technique.	Medium5	Number theoryMath+2	No attempts yet	2s	128 MB	Judgeable
Farm ManagementCount 8-directionally connected groups of equal-height cells in a grid where every outside neighbor is strictly lower.	Medium5	BFSDFS+2	No attempts yet	2s	128 MB	Judgeable
Good NumbersGiven N integers, count how many of them equal the sum of two other numbers at two different positions in the sequence.	Medium5	Two pointersArray+1	No attempts yet	2s	256 MB	Judgeable
DictionaryConstruct the K-th lexicographically smallest string made of N 'a's and M 'z's using combinatorial counting, or report -1 if K exceeds the total count.	Medium5	CombinatoricsGreedy+1	No attempts yet	2s	128 MB	Judgeable
Wall-Breaking MazeFind the minimum number of walls to break on a grid path from the top-left to the bottom-right room, moving through 4 directions.	Medium5	BFSShortest path+1	No attempts yet	1s	128 MB	Judgeable
Partial RectanglesGiven an N x M grid doubled into a 2N x 2M grid, count how many times each letter appears summed over every possible subrectangle.	Medium5	CombinatoricsMath+2	No attempts yet	2s	128 MB	Judgeable
Finding Notebook OwnersGiven student-laptop candidate pairs, compute the maximum bipartite matching to maximize the number of students who get a laptop they listed.	Medium5	GraphDFS+1	No attempts yet	2s	128 MB	Judgeable
K-th NumberFind the k-th smallest value in the N x N multiplication table using binary search with a counting function.	Medium5	Binary searchMath	No attempts yet	2s	128 MB	Judgeable
AdvertisementGiven the L characters currently visible on a scrolling sign showing an infinitely repeated text, find the minimum possible length of the original advertisement text.	Medium5	String matchingString	No attempts yet	2s	128 MB	Judgeable
Run, HongjunGiven N billboard intensities and a sight range M, output the maximum intensity within a sliding window of size 2M-1 for each valid position.	Medium5	Sliding windowQueue+1	No attempts yet	2s	256 MB	Judgeable
X and KGiven X and K, find the K-th smallest positive integer Y such that X+Y equals X OR Y, which requires placing K's bits into the zero-bit positions of X.	Medium5	Bit manipulationMath+1	No attempts yet	2s	128 MB	Judgeable
Repeating a NumberFind the minimum number of times a number N must be concatenated with itself so the resulting number is divisible by K, or report -1.	Medium5	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
Hopping FrogFind the minimum number of jumps for a frog moving between numbered stones, where each stone's value dictates allowed jump distances as multiples.	Medium5	BFSGraph+1	No attempts yet	2s	128 MB	Judgeable
Fixed-Length Reversal SortGiven a permutation of up to 8 numbers, find the minimum number of fixed-length K reversals needed to sort it, or report impossibility.	Medium5	BFSGraph+2	No attempts yet	2s	128 MB	Judgeable
Solving ProblemsGiven N interest values and a rule to move forward by 1 or 2 steps starting at problem 1, find the minimum number of problems solved before the range of solved values reaches at least V.	Medium5	Dynamic programmingGraph+2	No attempts yet	2s	128 MB	Judgeable
Two String MasksGiven two strings each containing one asterisk, find the shortest string obtainable by replacing the asterisks with (possibly empty) letter strings so both become equal, or report impossible.	Medium5	StringSimulation+2	No attempts yet	2s	128 MB	Judgeable
Tangled Electric WiresGiven a matching between left and right poles, find the minimum number of wires to cut so no two remaining wires cross, which reduces to computing N minus the longest increasing subsequence.	Medium5	Dynamic programmingBinary search+1	No attempts yet	1s	128 MB	Judgeable
Tablature TranspositionConvert a fretted-instrument tablature to a different instrument's tuning, transposing each note and picking the highest-pitched available string for it.	Medium5	GreedySimulation+2	No attempts yet	2s	128 MB	Judgeable
Watering FieldsGiven well-digging costs per field and pairwise pipe-connection costs, compute the minimum total cost to give every field water using an MST-style approach with a virtual water source.	Medium5	Minimum spanning treeGraph+1	No attempts yet	2s	128 MB	Judgeable
Array ValueFind a path from top-left to bottom-right of an N by N grid, avoiding zero cells, that minimizes the trailing zeros in the product of visited values.	Medium5	Dynamic programmingMath+2	No attempts yet	2s	128 MB	Judgeable
Minsik-First SearchImplement a DFS variant that picks the middle unvisited neighbor when their count is odd and the smallest when even, then print the first-visit order from vertex 1.	Medium5	DFSImplementation+1	No attempts yet	1s	128 MB	Judgeable
Yogurt Expiration DatePick k yogurts with maximum total amount, break ties by minimizing the chance at least one is defective, and print that incident probability as a percentage.	Medium5	GreedySorting+2	No attempts yet	2s	128 MB	Judgeable
Paper FoldingDecide whether a strip of N labeled cells can be folded so the stack reads 1 to N from top to bottom, checking labels against the shrinking strip's two ends.	Medium5	Two pointersSimulation+1	No attempts yet	2s	128 MB	Judgeable
SwitchesGiven a switch array of size N, support range flips and range count-of-on queries over M operations, best solved with a segment tree with lazy propagation.	Medium5	Segment treeIntervals+1	No attempts yet	1s	128 MB	Judgeable
Sum of an Arithmetic SequenceGiven l, r and k (2 to 5), count integers in [l, r] that can be written as the sum of the first k terms of an arithmetic sequence with positive first term and positive common difference.	Medium5	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
Woodcutter DasomChoose a single cut length for all logs to maximize total profit from selling equal-length pieces after subtracting per-cut costs.	Medium5	Brute forceSimulation+1	No attempts yet	2s	128 MB	Judgeable
New AlbumGiven song length, CD capacity, and a superstition banning CD track counts divisible by 13, find the minimum number of CDs needed to fit all songs.	Medium5	GreedyMath+1	No attempts yet	2s	128 MB	Judgeable
Broken CalculatorStarting from 1 on a calculator limited to D digits, find the largest value reachable after exactly P multiplications by digits 2-9, or report -1 if impossible.	Medium5	BacktrackingBrute force+2	No attempts yet	2s	128 MB	Judgeable
Sunday Morning DateFind a grid path from S to F that first minimizes the number of trash cells stepped on, then minimizes clean cells adjacent to trash along that path.	Medium5	Shortest pathBFS+2	No attempts yet	2s	128 MB	Judgeable
Dividing a Rectangle into ThreeSplit a digit grid into three non-overlapping rectangles covering all cells and maximize the product of their digit sums.	Medium5	Prefix sumBrute force+2	No attempts yet	2s	128 MB	Judgeable
Sevi GameGiven one roll of five dice, pick at least two dice to reroll so the expected score of a poker-dice scoring system is minimized, with ties broken lexicographically.	Medium5	ProbabilityBrute force+2	No attempts yet	2s	128 MB	Judgeable
LibraryFind the minimum total steps for a librarian starting at 0 to deliver books to their positive or negative integer positions while carrying at most M books per trip.	Medium5	GreedySorting+2	No attempts yet	2s	128 MB	Judgeable
Gap Pair SequenceConstruct the lexicographically smallest sequence where each number from a given set appears twice with exactly that many numbers between the two occurrences, or report -1 if impossible.	Medium5	BacktrackingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
UnderscoresInsert underscores between N given words (counts differing by at most 1) to reach total length M, and output the lexicographically smallest resulting string under a custom character order.	Medium5	GreedyString+1	No attempts yet	2s	128 MB	Judgeable
Collecting GemsGiven N gem weights and M bags of capacity C, determine the maximum number of gems that can be packed into the bags without exceeding capacity.	Medium5	GreedySorting	No attempts yet	2s	128 MB	Judgeable
DuelMatch N Team A fighters against N Team B fighters to maximize points, where a win scores 2, a tie scores 1, and a loss scores 0.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
Divisible by Its DigitsGiven N, find the smallest integer whose decimal digits start with N and that is divisible by every nonzero digit of N.	Medium5	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
End of the SpiralGiven an N by M grid, simulate a spiral walk that starts east from the southwest corner and turns left whenever blocked, then output the final cell's coordinates.	Medium5	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Shortest Path Through Required VerticesGiven a weighted undirected graph, find the shortest path from vertex 1 to vertex N that must pass through two specified vertices.	Medium5	Shortest pathGraph+1	No attempts yet	1s	256 MB	Judgeable
Make a Periodic StringGiven a DNA string and a bound M, find the minimum number of character edits to make the string periodic with some period length at most M.	Medium5	StringGreedy+2	No attempts yet	2s	128 MB	Judgeable
Substring Picking GamePlayers alternately subtract a value formed by a proper substring of the current number's digits, and you must find the smallest first move that forces a win, or -1 if none exists.	Medium5	Game theoryDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
String ExchangeGiven a circular string of a's and b's, find the minimum number of swaps to make all a's form one consecutive block.	Medium5	Sliding windowString+2	No attempts yet	2s	128 MB	Judgeable
Sejun and Sebi's WarGiven two armies whose weakest soldier dies each round (ties killing Sebi's soldier first), determine which side's soldier survives last.	Medium5	GreedySimulation+2	No attempts yet	2s	128 MB	Judgeable
Triangle SubsequenceGiven a sequence, find the longest subsequence where every triple of elements satisfies the triangle inequality.	Medium5	SortingTwo pointers+1	No attempts yet	2s	128 MB	Judgeable
BirdsBirds fly away in counts 1,2,3,... each second, restarting from 1 whenever the next count exceeds the birds left, and you must find total seconds until none remain.	Medium5	MathSimulation+1	No attempts yet	2s	128 MB	Judgeable
World ConquestGiven population counts for N countries, find the maximum number of size-K groups where each group's members come from distinct countries.	Medium5	Binary searchGreedy+1	No attempts yet	2s	128 MB	Judgeable
Roads of the Northern CountryGiven the edges of a weighted tree of up to 10,000 cities, compute the length of the tree's diameter (the longest path between two nodes).	Medium5	TreeGraph+2	No attempts yet	1s	128 MB	Judgeable
HistoryGiven directed precedence edges among up to 400 events, determine for each query pair whether one event's order relative to the other is fixed by transitivity.	Medium5	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Youngsik's FingerGiven an injured left-hand finger and a cap on how many times it can be used in a repeating back-and-forth counting pattern, find the largest number Youngsik can reach.	Medium5	MathBinary search+2	No attempts yet	2s	128 MB	Judgeable
Counting Crossing EdgesGiven M cross edges between two labeled vertex sets of size N, count how many unordered pairs of edges cross each other.	Medium5	SortingDivide and conquer+2	No attempts yet	2s	128 MB	Judgeable
New Year PartyPick a maximum-score guest list from a company tree so no employee and their direct manager both attend, computed with and without the root.	Medium5	Dynamic programmingTree+1	No attempts yet	2s	128 MB	Judgeable
Ominsik NumberGiven N up to one million, compute the least common multiple of all integers from 1 to N modulo 987654321.	Medium5	Number theoryMath+1	No attempts yet	2s	128 MB	Judgeable
Making the Best TeamChoose 15 players for white and 15 for black from a list of up to 1000 players to maximize the total ability sum.	Medium5	Dynamic programmingGreedy+1	No attempts yet	1s	128 MB	Judgeable
Sungji's Birthday PartyGiven N students each requiring a minimum number of other attendees to be satisfied, find the smallest group of students that can be invited so every invited student's requirement is met.	Medium5	GreedySorting+1	No attempts yet	2s	128 MB	Judgeable
City Division PlanSplit a connected weighted graph into two connected subvillages by removing edges so that the total remaining maintenance cost is minimized.	Medium5	Minimum spanning treeUnion-find+2	No attempts yet	2s	256 MB	Judgeable