Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Pancake sorting
Medium4
BFS, Brute force
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Walking
Medium4
Dynamic programming, Sorting
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Card Shuffling
Medium4
Simulation, Queue
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Housing
Medium4
Dynamic programming, Combinatorics
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Triball Ranking
Medium4
Topological sort, Graph+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
4SUM
Medium4
Hash map
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Balanced Teams
Medium4
Brute force, Backtracking
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Claws
Medium4
Tree, DFS
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Paths
Medium4
BFS, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lexical
Medium4
Combinatorics, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rank
Medium4
Graph, DFS
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Coin
Medium4
Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Triangles made from lines
Medium4
Hash map, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Auto-Complete
Medium4
Trie, Sorting
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Colorful Chain
Medium4
Sliding window, Hash map+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Lottery 2
Medium4
Greedy, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Lazy Polar Bear
Medium4
Sliding window, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Decorating the Pastures
Medium4
BFS, Graph
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tourism
Medium4
Shortest path, Math
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
JOI emblem
Medium4
Brute force, Matrix
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Tickets
Medium4
Bit manipulation, Recursion
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Counting Inversions
Medium4
Divide and conquer, Sorting
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Troyangles
Medium4
Dynamic programming, Matrix
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Gates
Medium4
Shortest path, Graph
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Intersection Points
Medium4
Geometry, Implementation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Hacking
Medium4
Shortest path, Graph+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Man in the Middle
Medium4
DFS, Graph
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Hiking
Medium4
Shortest path, Graph+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Turtle Elder
Medium4
Tree, Dynamic programming
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Button Bashing
Medium4
BFS, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Counting Substhreengs
Medium4
Prefix sum, Math
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Algorithms Final Exam
Medium4
Segment tree, Prefix sum
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Exploration Team
Medium4
Graph, Queue
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Uncompressing Compressed Words
Medium4
Recursion, Stack+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Human Cannonball
Medium4
Shortest path, Graph
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Ternarian Weights
Medium4
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Trapezoid Walkway
Medium4
Shortest path, Graph
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Flowery Trails
Medium4
Shortest path, Graph
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Push-Ups
Medium4
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Diamonds
Medium4
Dynamic programming
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Ambiguous Encodings
Medium4
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Silk Road
Medium4
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Train Travel
Medium4
Prefix sum, Greedy
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
XOR triplets 2
Medium4
Brute force, Bit manipulation
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
ACM
Medium4
Prefix sum, Brute force
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Cow Hopscotch
Medium4
Dynamic programming, Matrix
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Airport
Medium4
Union-find, Greedy
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Palindrome?
Medium4
Dynamic programming, Intervals
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Next permutation
Medium4
Array, Two pointers
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Previous Permutation
Medium4
Array
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Remainder Subarray Count
Medium4
Prefix sum, Hash map
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Range Add and Range Sum
Medium4
Segment tree
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Classroom assignment
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sliding Window Minimum
Medium4
Sliding window, Queue
No attempts yet
Time limit
2.4s
Memory limit
512 MB
Judgeable
Study Time Allocation
Medium4
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Josephus Problem 3
Medium4
Math, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
16 MB
Judgeable
Longest Increasing Subsequence
Medium4
Dynamic programming, Binary search
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Shortest string containing both
Medium4
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Jump Jump
Medium4
Dynamic programming, Greedy
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Card Game
Medium4
Dynamic programming, Game theory
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Diana and the Golden Apples
Medium4
Dynamic programming
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
The Knight's Scouting Mission
Medium4
BFS, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Troop Movement
Medium4
Minimum spanning tree, Union-find+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Torn to Pieces
Medium4
Graph, BFS
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Nurikabe
Medium4
BFS, Matrix+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Candy Store
Medium4
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
C.S.I.: P15
Medium4
DFS, String matching
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Kindergarten Excursion
Medium4
Sorting, Prefix sum
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Coast Length
Medium4
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Goods Market
Medium4
Heap, Simulation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
2-SAT Assignment
Medium4
Brute force, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Graph bridges
Medium4
DFS, Graph
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Floyd
Medium4
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Longest Prefix Match
Medium4
Trie, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Miraculous Drug
Medium4
Sliding window, Queue
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Lowest Common Ancestor
Medium4
Tree, DFS
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Lowest Common Ancestor 2
Medium4
Tree, DFS
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Large Fibonacci Number Modulo
Medium4
Matrix, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Ga
Medium4
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Icelandic Motorclubs
Medium4
Greedy, Prefix sum
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Range product queries
Medium4
Segment tree
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Popping Balloons
Medium4
Greedy, Hash map
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Word Clouds Revisited
Medium4
Dynamic programming, Prefix sum
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Competition
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Puyo Puyo
Medium4
BFS, Simulation
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Polynomial Game
Medium4
Dynamic programming, Combinatorics
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Baegyang Road Break
Medium4
Shortest path, Graph
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Mingyun's Scheme
Medium4
Dynamic programming, Binary search
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Geppetto's Pizza
Medium4
Brute force, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Excellence
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Grid Jumps
Medium4
BFS, Graph
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Two-Dimensional Range Sum
Medium4
Prefix sum, Matrix
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Points on a Segment
Medium4
Binary search, Sorting
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Smallest third number for a given lcm
Medium4
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Smallest number missing from a digit sequence
Medium4
String matching, Brute force
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Rings
Medium4
BFS, Matrix+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
The Shortest does not Mean the Simplest
Medium4
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Star triangles
Medium4
Hash map, Combinatorics
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Trading
Medium4
Segment tree, Intervals
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Multigram
Medium4
String, Hash map
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Pancake sortingSort a stack of up to 8 pancakes into descending order with the fewest suffix flips.	Medium4	BFSBrute force	No attempts yet	2s	512 MB	Judgeable
WalkingWalkers start at distinct times with fixed speeds, and a later starter who arrives earlier befriends the other; find the largest group where every pair meets.	Medium4	Dynamic programmingSorting	No attempts yet	1s	128 MB	Judgeable
Card ShufflingGiven a deck numbered from the top and a string of two shuffle moves, find the three cards at positions k-1, k and k+1 after all moves.	Medium4	SimulationQueue	No attempts yet	2s	512 MB	Judgeable
HousingCount the unordered splits of n into parts of at least 5 for n between 5 and 100.	Medium4	Dynamic programmingCombinatorics	No attempts yet	2s	512 MB	Judgeable
Triball RankingOrder all k players to satisfy every match result and return the lexicographically smallest lineup, or 0 when no lineup fits.	Medium4	Topological sortGraph+1	No attempts yet	2s	512 MB	Judgeable
4SUMPick one number from each of four sets of up to 500 integers so the four numbers sum to zero.	Medium4	Hash map	No attempts yet	2s	512 MB	Judgeable
Balanced TeamsSplit twelve cows with given skill levels into four teams of three to minimize the gap between the strongest and weakest team sums.	Medium4	Brute forceBacktracking	No attempts yet	1s	128 MB	Judgeable
ClawsCompute each hinge grade from subtree and root-path bar weights and report the largest root-to-claw sum of grades over all claws.	Medium4	TreeDFS	No attempts yet	2s	512 MB	Judgeable
PathsFind the cheapest total cost among the directed paths from node 0 to node 1 that use the fewest links.	Medium4	BFSDynamic programming	No attempts yet	2s	512 MB	Judgeable
LexicalGiven n and a permutation of 0 to n-1, compute its 1-based position in lexicographic order.	Medium4	CombinatoricsMath	No attempts yet	2s	1024 MB	Judgeable
RankCount the players that lie on a directed win cycle built from the game results.	Medium4	GraphDFS	No attempts yet	2s	1024 MB	Judgeable
CoinFind the fewest coins from unlimited denominations whose values sum to V and weights sum to W.	Medium4	Dynamic programming	No attempts yet	2s	1024 MB	Judgeable
Triangles made from linesCount how many triples of the given lines form a triangle by removing triples that contain parallel lines.	Medium4	Hash mapCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Auto-CompleteThe app prints the original index of the K-th dictionary word with each query prefix in alphabetical order, or -1.	Medium4	TrieSorting	No attempts yet	1s	128 MB	Judgeable
Colorful ChainCount the contiguous segments that hold exactly the required number of links of each listed color and no other colors.	Medium4	Sliding windowHash map+1	No attempts yet	3s	512 MB	Judgeable
Lottery 2Change as few entries as possible in a length-n sequence over 1 to k so no two adjacent entries are equal.	Medium4	GreedyArray	No attempts yet	1s	128 MB	Judgeable
Lazy Polar BearChoose a point on the line so the buckets within distance K of it hold the most ice in total.	Medium4	Sliding windowSorting+1	No attempts yet	1s	128 MB	Judgeable
Decorating the PasturesColor each connected group of pastures with two letters so neighbors differ and the count of J signs is as large as possible.	Medium4	BFSGraph	No attempts yet	1s	128 MB	Judgeable
TourismVisit the given sights in order on a grid with extra northeast diagonals and minimize the total number of road segments traveled.	Medium4	Shortest pathMath	No attempts yet	1s	128 MB	Judgeable
JOI emblemYou may change at most one cell of the letter grid, then count how many 2 by 2 blocks match the emblem, and report the largest possible count.	Medium4	Brute forceMatrix	No attempts yet	1s	256 MB	Judgeable
TicketsPrint the K-th n-bit string in reflective Gray code order for the given n and K.	Medium4	Bit manipulationRecursion	No attempts yet	1s	64 MB	Judgeable
Counting InversionsCount the pairs in a permutation of 1 to n where a larger number stands before a smaller one.	Medium4	Divide and conquerSorting	No attempts yet	1s	256 MB	Judgeable
TroyanglesCount all centered triangles of `#` cells in an N-by-N grid where row i of a height-h triangle holds 2i-1 cells.	Medium4	Dynamic programmingMatrix	No attempts yet	1s	256 MB	Judgeable
GatesFind the minimum travel time for each query pair of gates using walking and directed walkways.	Medium4	Shortest pathGraph	No attempts yet	2s	256 MB	Judgeable
Intersection PointsGiven an axis-aligned rectangle and a segment per test case, count their shared boundary points, printing 4 for infinite overlap.	Medium4	GeometryImplementation	No attempts yet	1s	256 MB	Judgeable
HackingStarting from the hacked computer, count reachable computers through dependency edges and report the longest infection time.	Medium4	Shortest pathGraph+1	No attempts yet	2s	256 MB	Judgeable
Man in the MiddleDecide whether removing some single person disconnects the connected friendship network.	Medium4	DFSGraph	No attempts yet	3s	256 MB	Judgeable
HikingFind the cheapest 8-direction path from the start to the highest cell of a height grid where flat steps cost 1 and a height change of d costs (d+1) squared.	Medium4	Shortest pathGraph+1	No attempts yet	3s	256 MB	Judgeable
Turtle ElderPick safe start and end islands in a tree so the sum of values along the path is as large as possible, staying home when the best sum is not positive.	Medium4	TreeDynamic programming	No attempts yet	5s	256 MB	Judgeable
Button BashingPress add and subtract buttons from 0, clamped between 0 and 3600, to reach a target time in the fewest presses or the nearest reachable longer time.	Medium4	BFSShortest path+1	No attempts yet	1s	256 MB	Judgeable
Counting SubsthreengsCount the contiguous digit-only substrings of S whose value is a multiple of 3.	Medium4	Prefix sumMath	No attempts yet	3s	256 MB	Judgeable
Algorithms Final ExamGiven the final order listed by midterm rank, print for each student how many midterm superiors they passed minus how many inferiors passed them.	Medium4	Segment treePrefix sum	No attempts yet	1s	256 MB	Judgeable
Exploration TeamFind the size of the largest group where every member has at least k friends inside the group.	Medium4	GraphQueue	No attempts yet	1s	256 MB	Judgeable
Uncompressing Compressed WordsExpand each nested compressed word by concatenating its parts and repeating the group n times.	Medium4	RecursionStack+1	No attempts yet	1s	256 MB	Judgeable
Human CannonballFind the fastest route from start to target by running at 5 m/s and chaining optional 50-meter cannon shots that cost 2 seconds each.	Medium4	Shortest pathGraph	No attempts yet	1s	256 MB	Judgeable
Ternarian WeightsConvert each decimal weight to balanced ternary and list which powers of three go on each pan.	Medium4	MathImplementation	No attempts yet	2s	256 MB	Judgeable
Trapezoid WalkwayFind the cheapest chain of trapezoid stones joining two given widths, where each stone links its two edge lengths at a cost tied to its area.	Medium4	Shortest pathGraph	No attempts yet	2s	256 MB	Judgeable
Flowery TrailsAdd twice the length of every trail that lies on some shortest route from point 0 to point P-1.	Medium4	Shortest pathGraph	No attempts yet	2s	256 MB	Judgeable
Push-UpsGiven a push-up total equal to the sum of running scores, find the largest final score reachable with the allowed scoring plays.	Medium4	Dynamic programming	No attempts yet	1s	256 MB	Judgeable
DiamondsFind the longest subsequence of diamonds in input order with strictly rising weight and strictly falling clarity.	Medium4	Dynamic programming	No attempts yet	5s	256 MB	Judgeable
Ambiguous EncodingsCount how many letter strings map to each digit string when A is 1 through Z at 26.	Medium4	Dynamic programmingString	No attempts yet	1s	256 MB	Judgeable
Silk RoadChoose N of M days in order for the eastward moves so the sum of distance times daily badness is smallest.	Medium4	Dynamic programming	No attempts yet	1s	256 MB	Judgeable
Train TravelCount how many times each rail is crossed and pay the cheaper of single tickets or a discount card plus cheap fares for every rail.	Medium4	Prefix sumGreedy	No attempts yet	1s	256 MB	Judgeable
XOR triplets 2Pick the largest block of consecutive integers from 1 to N with no three distinct elements xoring to zero, breaking ties by smallest start.	Medium4	Brute forceBit manipulation	No attempts yet	5s	256 MB	Judgeable
ACMSplit the task list into three nonempty consecutive blocks and assign one member to each block to minimize the summed difficulty estimates.	Medium4	Prefix sumBrute force	No attempts yet	1s	64 MB	Judgeable
Cow HopscotchCount paths from the top-left cell to the bottom-right cell that move strictly down and right onto cells of the opposite color.	Medium4	Dynamic programmingMatrix	No attempts yet	1s	256 MB	Judgeable
AirportEach arriving plane takes the largest free gate up to its limit gi, and the count stops at the first plane with no free gate.	Medium4	Union-findGreedy	No attempts yet	1s	256 MB	Judgeable
Palindrome?Answer up to a million queries asking whether a given range of the number sequence is a palindrome.	Medium4	Dynamic programmingIntervals	No attempts yet	0.5s	256 MB	Judgeable
Next permutationGiven a permutation of 1 to N, print the next permutation in lexicographic order, or -1 when the given one is the last.	Medium4	ArrayTwo pointers	No attempts yet	1s	256 MB	Judgeable
Previous PermutationGiven a permutation of 1 to N, print the permutation that comes just before it in lexicographic order, or -1 when it is the first.	Medium4	Array	No attempts yet	1s	256 MB	Judgeable
Remainder Subarray CountCount contiguous intervals whose sum is divisible by M using prefix remainder frequencies.	Medium4	Prefix sumHash map	No attempts yet	1s	256 MB	Judgeable
Range Add and Range SumProcess range additions on a sequence and print the sum of each queried range in order.	Medium4	Segment tree	No attempts yet	2s	256 MB	Judgeable
Classroom assignmentGiven N class time intervals, find the smallest number of rooms so overlapping classes never share a room.	Medium4	GreedySorting+2	No attempts yet	1s	256 MB	Judgeable
Sliding Window MinimumPrint the minimum of each window of length L ending at every position of the array.	Medium4	Sliding windowQueue	No attempts yet	2.4s	512 MB	Judgeable
Study Time AllocationDistribute up to H study hours among courses with tiered grade costs to maximize the average grade points.	Medium4	Dynamic programming	No attempts yet	1s	256 MB	Judgeable
Josephus Problem 3Find the number of the last person remaining after removing every K-th of N people seated in a circle.	Medium4	MathDynamic programming	No attempts yet	1s	16 MB	Judgeable
Longest Increasing SubsequenceFind the length of the longest strictly increasing subsequence of the given sequence.	Medium4	Dynamic programmingBinary search	No attempts yet	1s	256 MB	Judgeable
Shortest string containing bothFind the length of the shortest string that has both given strings as subsequences.	Medium4	Dynamic programmingString	No attempts yet	1s	256 MB	Judgeable
Jump JumpStarting from the first cell, find the fewest rightward jumps bounded by each cell value to reach the last cell, or -1 when unreachable.	Medium4	Dynamic programmingGreedy	No attempts yet	1s	256 MB	Judgeable
Card GameBoth players alternately take the left or right end card to maximize their own sum, and you compute the first player best total score.	Medium4	Dynamic programmingGame theory	No attempts yet	1s	256 MB	Judgeable
Diana and the Golden ApplesPick the apples with the greatest total weight so the extra carrying time stays strictly below her lead over Humperdonkey.	Medium4	Dynamic programming	No attempts yet	2s	256 MB	Judgeable
The Knight's Scouting MissionFind the shortest knight distance from (1,1) to (r,c) on an r by c board, count those routes modulo 1000000009, and report None when unreachable.	Medium4	BFSDynamic programming	No attempts yet	2s	256 MB	Judgeable
Troop MovementFind the route between two cities whose narrowest road is as wide as possible and report that width.	Medium4	Minimum spanning treeUnion-find+1	No attempts yet	2s	256 MB	Judgeable
Torn to PiecesRebuild the subway graph from the torn map pieces and print the stations on the path from the start to the destination, or no route found.	Medium4	GraphBFS	No attempts yet	2s	256 MB	Judgeable
NurikabeCheck whether each numbered island has the required size, all water cells connect, and no 2 by 2 block is all water.	Medium4	BFSMatrix+1	No attempts yet	1s	256 MB	Judgeable
Candy StoreCount the subsets of candy prices whose total is at least C for each test case, modulo 65537.	Medium4	Dynamic programming	No attempts yet	1s	256 MB	Judgeable
C.S.I.: P15Count ground-connected 8-connected flower components and isolated /\/\ bird patterns in each ASCII picture.	Medium4	DFSString matching	No attempts yet	1s	256 MB	Judgeable
Kindergarten ExcursionCount the minimum adjacent swaps needed to reorder a string of 0s, 1s, and 2s into sorted order.	Medium4	SortingPrefix sum	No attempts yet	1s	256 MB	Judgeable
Coast LengthCount the total length of borders between land and sea connected to the outside of the grid, excluding enclosed lakes.	Medium4	BFSGraph+1	No attempts yet	1s	256 MB	Judgeable
Goods MarketProcess insertions, global rent hikes, and cheapest-shop evictions, then report how many shops remain and their total rent.	Medium4	HeapSimulation	No attempts yet	1s	256 MB	Judgeable
2-SAT AssignmentDetermine whether a 2-CNF formula with up to 20 variables is satisfiable and output the lexicographically smallest satisfying assignment.	Medium4	Brute forceBit manipulation	No attempts yet	1s	256 MB	Judgeable
Graph bridgesFind every bridge in a connected undirected graph and print them sorted by endpoint.	Medium4	DFSGraph	No attempts yet	1s	256 MB	Judgeable
FloydFor every pair of n cities, compute the cheapest directed bus fare from up to 100,000 routes and print 0 where no route connects them.	Medium4	Shortest pathGraph+1	No attempts yet	1s	256 MB	Judgeable
Longest Prefix MatchGiven X bit prefixes with ids and Y destination addresses, print the id of the longest matching prefix for each address or -1.	Medium4	TrieBit manipulation	No attempts yet	1s	256 MB	Judgeable
Miraculous DrugEach hour uses the cheapest enzyme bought within the last h hours, breaking ties toward the latest hour, and reports purchase counts over a given interval.	Medium4	Sliding windowQueue	No attempts yet	1s	256 MB	Judgeable
Lowest Common AncestorGiven a rooted tree, answer each query with the number of the deepest vertex that is an ancestor of both given vertices.	Medium4	TreeDFS	No attempts yet	3s	256 MB	Judgeable
Lowest Common Ancestor 2Given a rooted tree with up to 100,000 nodes, answer up to 100,000 lowest common ancestor queries.	Medium4	TreeDFS	No attempts yet	1.5s	256 MB	Judgeable
Large Fibonacci Number ModuloGiven n up to 10^18, print the nth Fibonacci number modulo 1,000,000,007.	Medium4	MatrixDivide and conquer+1	No attempts yet	1s	256 MB	Judgeable
GaCount the empty squares White can reach by expanding from its stones through empty squares without crossing Black stones.	Medium4	BFSGraph+1	No attempts yet	1s	256 MB	Judgeable
Icelandic MotorclubsFind the smallest-numbered station from which a rider who takes all gas at every stop can complete one clockwise lap.	Medium4	GreedyPrefix sum	No attempts yet	3s	256 MB	Judgeable
Range product queriesAnswer range product queries modulo 1,000,000,007 on a sequence with point updates.	Medium4	Segment tree	No attempts yet	1s	256 MB	Judgeable
Popping BalloonsPop every balloon from left to right with the fewest rightward arrows that drop one unit after each hit.	Medium4	GreedyHash map	No attempts yet	2s	256 MB	Judgeable
Word Clouds RevisitedPlace N ordered boxes of given widths and heights into width-limited rows to minimize the sum of row heights.	Medium4	Dynamic programmingPrefix sum	No attempts yet	2s	256 MB	Judgeable
CompetitionFind the fewest seat changes that let Alice and Bob solve every solvable problem in contest order.	Medium4	GreedySorting	No attempts yet	1s	256 MB	Judgeable
Puyo PuyoCount how many chain reactions occur when groups of four or more same-color puyos pop and gravity settles the 12 by 6 field.	Medium4	BFSSimulation	No attempts yet	1s	256 MB	Judgeable
Polynomial GameFor each test case, compute the coefficient of x^N in the product of (1+x+...+x^i) for i from 1 to k.	Medium4	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Baegyang Road BreakGiven a graph with one-way and two-way roads, answer many queries for the minimum number of one-way roads to reverse to reach each destination.	Medium4	Shortest pathGraph	No attempts yet	1s	256 MB	Judgeable
Mingyun's SchemeGiven N cards in order, compute the length of the longest strictly increasing subsequence.	Medium4	Dynamic programmingBinary search	No attempts yet	1s	256 MB	Judgeable
Geppetto's PizzaCount the subsets of up to 20 ingredients that contain none of the given incompatible pairs, including the empty pizza.	Medium4	Brute forceBit manipulation	No attempts yet	1s	64 MB	Judgeable
ExcellencePair all students into teams of two so the smallest team rating sum is as large as possible.	Medium4	GreedySorting+1	No attempts yet	2s	256 MB	Judgeable
Grid JumpsFind the fewest digit-length jumps from the top-left cell to the bottom-right cell of a grid, or print IMPOSSIBLE.	Medium4	BFSGraph	No attempts yet	2s	256 MB	Judgeable
Two-Dimensional Range SumCompute the sum of each queried rectangle in an N by N table using a 2D prefix sum.	Medium4	Prefix sumMatrix	No attempts yet	1s	256 MB	Judgeable
Points on a SegmentCount how many of N distinct points fall inside each of M closed intervals on a line.	Medium4	Binary searchSorting	No attempts yet	1s	256 MB	Judgeable
Smallest third number for a given lcmFind the smallest positive integer c with lcm(a, b, c) equal to L, or output -1 when none exists.	Medium4	Number theoryMath	No attempts yet	1s	256 MB	Judgeable
Smallest number missing from a digit sequenceGiven up to 1000 digits, find the smallest non-negative integer that never occurs as a consecutive block without a leading zero.	Medium4	String matchingBrute force	No attempts yet	1s	256 MB	Judgeable
RingsLabel each tree square with its edge-step distance to the nearest empty square or the outside of the grid and print the dot-padded grid.	Medium4	BFSMatrix+1	No attempts yet	1s	256 MB	Judgeable
The Shortest does not Mean the SimplestGiven A, B and C up to 10^18, compute the remainder of A to the power B divided by C.	Medium4	Number theoryMath	No attempts yet	2s	256 MB	Judgeable
Star trianglesFor each star taken as the right-angle vertex, multiply the counts of other stars sharing its column and its row, then add the products.	Medium4	Hash mapCombinatorics	No attempts yet	2s	256 MB	Judgeable
TradingEach trader covers villages L to R with a price that rises by 1 per village, and each village reports the highest price ever asked there.	Medium4	Segment treeIntervals	No attempts yet	2s	64 MB	Judgeable
MultigramDecide whether the word splits into two or more equal anagram blocks and print the shortest such block, or -1.	Medium4	StringHash map	No attempts yet	1s	64 MB	Judgeable