Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

Rectangle Game (Small)
Medium4
Game theory, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Automated Program Analyzer
Medium4
Union-find, Hash map
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Double or One Thing
Medium4
Greedy, String
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sequence Conversion
Medium4
Prefix sum, Bit manipulation
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
SLOVA
Medium4
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Ciphertext
Medium4
Backtracking, Brute force
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Chocolate Factory
Medium4
Intervals, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Infrastructure
Medium4
Greedy, Tree+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Audi
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Stipe
Medium4
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tired Ari and Her Real Life
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Ssum Palindrome
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Swap the elements
Medium4
Sorting, Array+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
INFP Duram
Medium4
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
1, 3, 5 Segments
Medium4
Dynamic programming, Prefix sum
No attempts yet
Time limit
1.35s
Memory limit
1024 MB
Judgeable
Decisive Friday
Medium4
Dynamic programming, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Card Trading
Medium4
Prefix sum, Sorting
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Excursion to Porvoo
Medium4
Sorting, Array
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Treehouse
Medium4
Hash map, Geometry+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Permutation Sorting
Medium4
Greedy, Array
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
English Exam
Medium4
Greedy, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
String Set Combinations
Medium4
Brute force, Hash map+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Luna's Game Setup
Medium4
Combinatorics, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Too Easy
Medium4
Bit manipulation, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Let's Avoid
Medium4
Array, Prefix sum
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Intersection Construction
Medium4
Array, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Changing Cards
Medium4
Brute force, Implementation+1
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
High-Speed Number Search
Medium4
BFS, Graph+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Shout the Integers to the End
Medium4
Game theory, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Tickets
Medium4
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
What Handle Should I Pick
Medium4
Tree, BFS+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fast Ascending Number Search
Medium4
BFS, Matrix+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fast Ascending Number Search
Medium4
BFS, Graph+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Maximum Sum of Node Values in a Tree
Medium4
Tree, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Adventurer Guilds
Medium4
Union-find, Array
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Stylish Phoenix
Medium4
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Number of Differences
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Drainage
Medium4
Union-find, Array+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Merging Matryoshka Dolls
Medium4
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Flipping Bulb States
Medium4
Array, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sequence and Maximum Rise Queries
Medium4
Segment tree, Divide and conquer
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Chopsticks Game
Medium4
Game theory, Recursion+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Even and Odd Combinations
Medium4
Combinatorics, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Minimum Cost to Color a Tree
Medium4
Tree, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Score Calculation
Medium4
Math, Hash map
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Ingyeongsan
Medium4
Prefix sum, Geometry+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gene Combination
Medium4
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Word Tree
Medium4
Minimum spanning tree, Graph
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Discord Daisy Chain
Medium4
Graph, DFS+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Making Connections
Medium4
Union-find, Math
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Unique Values
Medium4
Sliding window, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hang Gliding
Medium4
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Circle Meets Square
Medium4
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
First Last Sorting
Medium4
Array, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Editor Navigation
Medium4
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Don't Break the Ice
Medium4
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dot the i's and Cross the T's
Medium4
Geometry, Brute force
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sum of a Sequence
Medium4
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Silheundeyo
Medium4
Sliding window, Two pointers
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Lemonade Stand
Medium4
Greedy, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Container Rearrangement
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Counting table of contents subheadings
Medium4
Stack, Implementation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Word Superiority Effect (Cambridge University Study)
Medium4
Hash map, String+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Typhoon Forecast
Medium4
Binary search, Geometry+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
2D Array Range Add and Range Sum
Medium4
Matrix, Prefix sum
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Abbreviated Aliases
Medium4
String, Sorting+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Cookbook Composition
Medium4
Dynamic programming, Topological sort+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Dimensional Debugging
Medium4
Graph, BFS
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Extended Braille
Medium4
Hash map, Sorting+1
No attempts yet
Time limit
8s
Memory limit
2048 MB
Judgeable
Chaotic Construction
Medium4
Array, Prefix sum+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Improving IT
Medium4
Dynamic programming, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Jesting Jabberwocky
Medium4
String, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Highest Hill
Medium4
Array, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Version History
Medium4
Simulation, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Lonely Gomgomi Has Friends
Medium4
Number theory, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hyogu and Hogyu (Easy)
Medium4
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Hyundai Mobis Software Academy
Medium4
Greedy, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Start and Link 2
Medium4
Backtracking, Brute force+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drainage Pipe Mystery
Medium4
Union-find, Sorting
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Tree and Sequence
Medium4
Greedy, Tree+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Eat Apples in Three Moves or Fewer
Medium4
Backtracking, Brute force+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Snow Removal
Medium4
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Ski race
Medium4
Array, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Backrooms
Medium4
Dynamic programming, Matrix
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hidden Node in a Binary Tree
Medium4
Tree, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Vigenère Cipher Decryption
Medium4
String matching, String
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Japanski Junak
Medium4
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Faster Microwaving
Medium4
Brute force, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Exact Change
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hanging Nests
Medium4
Tree, Recursion
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Palindrome Maker
Medium4
Dynamic programming, Array
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Rummy Score
Medium4
Backtracking, Brute force
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Simi Circles
Medium4
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Matrix Transformation
Medium4
Math, Matrix+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cut the Cake!
Medium4
Geometry, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Ants on a Stick
Medium4
Sorting, Simulation
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Factorization of Quadratic Formula
Medium4
Math, Brute force+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Stop & Go
Medium4
Simulation, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Find Palindromes
Medium4
String, Hash map+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Park
Medium4
Hash map, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Rectangle Game (Small)Given an N by N grid with N at most 9, find the maximum score Minwoo can guarantee when he colors rows, Jongjin colors columns, and each scores by the given rules.	Medium4	Game theoryBit manipulation+1	No attempts yet	1s	1024 MB	Judgeable
Automated Program AnalyzerFor each instance, decide whether all given equality and inequality constraints between variables with indices up to 1e9 can hold at the same time.	Medium4	Union-findHash map	No attempts yet	2s	1024 MB	Judgeable
Double or One ThingChoose which letters to double so the resulting string is alphabetically smallest, then print that string for each test case.	Medium4	GreedyString	No attempts yet	2s	1024 MB	Judgeable
Sequence ConversionGiven arrays a and b, find the fewest operations that xor two adjacent elements by the same value to turn a into b, or report -1 if impossible.	Medium4	Prefix sumBit manipulation	No attempts yet	3s	1024 MB	Judgeable
SLOVAGiven two permutations of the first N letters, find how many positions apart they are in the sorted list of all such permutations.	Medium4	CombinatoricsMath	No attempts yet	1s	1024 MB	Judgeable
CiphertextGiven a sorted key of K digits, list every 0/1 mask of positions where exactly X distinct positions have digits summing to Z.	Medium4	BacktrackingBrute force	No attempts yet	1s	1024 MB	Judgeable
Chocolate FactoryGiven K jobs that each occupy a range of machines, assign start minutes so overlapping jobs never share a minute, using the fewest minutes possible.	Medium4	IntervalsGreedy+2	No attempts yet	1s	1024 MB	Judgeable
InfrastructureDecide whether N cities can be joined by N-1 roads so each city i has exactly D_i roads, and print one such tree if it exists.	Medium4	GreedyTree+1	No attempts yet	1s	1024 MB	Judgeable
AudiCount the triples (X, Y, Z) with each value from 1 to N so that the spending satisfies AX > BY > C*Z, with all three totals distinct.	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
StipePick K people who are each at least as old as everyone skipped, minimizing how many people are turned away before the last dose.	Medium4	ArraySorting+1	No attempts yet	1s	1024 MB	Judgeable
Tired Ari and Her Real LifeOrder N tasks, each with a repeat count R and stress S, to minimize total stress, where earlier repetitions raise the stress of later tasks.	Medium4	GreedySorting	No attempts yet	1s	512 MB	Judgeable
Ssum PalindromeGiven N, find the fewest digits a palindrome can have while its digits sum to N (N up to 1e9).	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Swap the elementsGiven a sequence A of N integers, rearrange it by swaps so that no position keeps its original value, or report -1 if impossible.	Medium4	SortingArray+1	No attempts yet	1s	1024 MB	Judgeable
INFP DuramGiven N clothing kinds with counts d_i, decide whether everyone can stand in a circle so that no two neighbors wear the same kind.	Medium4	MathGreedy	No attempts yet	1s	1024 MB	Judgeable
1, 3, 5 SegmentsSplit a sequence of N integers into 6 contiguous segments (empty segments allowed) to maximize the sum of segments 1, 3, and 5.	Medium4	Dynamic programmingPrefix sum	No attempts yet	1.35s	1024 MB	Judgeable
Decisive FridayGiven N job durations in days, decide whether some subset of them can be ordered so the work ends exactly on Friday, 4 days after Monday.	Medium4	Dynamic programmingMath	No attempts yet	1s	1024 MB	Judgeable
Card TradingGiven buy and sell offer counts at each price, find the price that maximizes price times the number of matched trades, and report that turnover.	Medium4	Prefix sumSorting	No attempts yet	4s	1024 MB	Judgeable
Excursion to PorvooFor each car weight, find the minimum total driving time from city 1 to city n, using the fastest road each leg allows, or report impossible.	Medium4	SortingArray	No attempts yet	5s	1024 MB	Judgeable
TreehouseCount the squares, in any orientation, whose four corners all sit on tree positions among N points (N up to 2000).	Medium4	Hash mapGeometry+1	No attempts yet	3s	1024 MB	Judgeable
Permutation SortingEach element can stay as is or become N+1-x, and the task is to decide whether the sequence can be made non-decreasing.	Medium4	GreedyArray	No attempts yet	3s	1024 MB	Judgeable
English ExamGiven the answer length N and its distinct letters, print the shortest string that contains every length-N answer as a subsequence.	Medium4	GreedyImplementation	No attempts yet	2s	1024 MB	Judgeable
String Set CombinationsGiven three strings with distinct letters and an integer k, list in ascending order the length-k subsequences that appear in at least two of the three strings.	Medium4	Brute forceHash map+1	No attempts yet	1s	512 MB	Judgeable
Luna's Game SetupCount the ways to pick K of N towers with distinct heights and line them up so no tower has taller towers on both sides, modulo 1e9+7.	Medium4	CombinatoricsMath	No attempts yet	1s	1024 MB	Judgeable
Too EasyFor each query (x, y), count the ordered nonnegative pairs (a, b) with a + b = x and a XOR b = y, for up to 200000 queries.	Medium4	Bit manipulationMath	No attempts yet	2s	1024 MB	Judgeable
Let's AvoidGiven an array of N integers, find the fewest adjacent swaps so that odd and even numbers are adjacent at most once.	Medium4	ArrayPrefix sum	No attempts yet	2s	1024 MB	Judgeable
Intersection ConstructionGiven N intervals and Q queries [l, r], find the fewest intervals whose intersection is exactly [l, r], or print -1 if no selection works.	Medium4	ArrayHash map+1	No attempts yet	2s	1024 MB	Judgeable
Changing CardsFind the fewest cards to change so the numbers form an arithmetic sequence with an integer common difference, including all equal.	Medium4	Brute forceImplementation+1	No attempts yet	1.5s	1024 MB	Judgeable
High-Speed Number SearchFind the fewest walk or run moves on a 5x5 grid from a start cell to the cell holding 1, where runs stop at 7 and cannot cross -1.	Medium4	BFSGraph+1	No attempts yet	3s	512 MB	Judgeable
Shout the Integers to the EndTwo players alternately call integers up to n, each at most k above the last call and never a forbidden value. Output whether the first player wins.	Medium4	Game theoryDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
TicketsCount dog pairs where all three tickets get the pair's relative order right, or all three get it wrong.	Medium4	ArraySorting+1	No attempts yet	1s	1024 MB	Judgeable
What Handle Should I PickGiven a tree with a letter on each vertex, find the lexicographically largest string spelled by a walk from vertex 1 to a leaf.	Medium4	TreeBFS+1	No attempts yet	1s	1024 MB	Judgeable
Fast Ascending Number SearchFind the fewest moves on a 5 x 5 grid to visit cells 1 through 6 in order from a start cell, avoiding -1 cells.	Medium4	BFSMatrix+1	No attempts yet	1s	512 MB	Judgeable
Fast Ascending Number SearchGiven a 5x5 grid with walls and stopper cells (7), find the fewest moves to visit cells 1 through 6 in order from a start cell.	Medium4	BFSGraph+1	No attempts yet	3s	512 MB	Judgeable
Maximum Sum of Node Values in a TreeGiven a tree rooted at node 0 with a value on each node, find the maximum sum of values over a connected set of nodes that includes the root.	Medium4	TreeDynamic programming+1	No attempts yet	3s	512 MB	Judgeable
Adventurer GuildsGuilds merge into alliances and gain or lose adventurers, and each query asks for the total adventurers in the alliance shared by two guilds, or -1 if none.	Medium4	Union-findArray	No attempts yet	3s	1024 MB	Judgeable
Stylish PhoenixGiven counts of masks, T-shirts, and pants by color, find the longest run of valid daily outfits with no same-colored T-shirt on consecutive days.	Medium4	MathGreedy	No attempts yet	1s	1024 MB	Judgeable
Number of DifferencesGiven N, choose N distinct integers in [1, 10^9] so the number of distinct pairwise differences is maximized or minimized, and print an example for each.	Medium4	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
DrainageMerge cities into groups with each project query, then count the cities in groups whose total rainfall exceeds their total drainage capacity.	Medium4	Union-findArray+1	No attempts yet	1s	1024 MB	Judgeable
Merging Matryoshka DollsGiven N dolls of various sizes, nest empty dolls inside larger empty dolls to find the fewest dolls that can remain.	Medium4	GreedySorting+1	No attempts yet	1s	512 MB	Judgeable
Flipping Bulb StatesGiven bulbs with brightness values and on/off states, flip one contiguous segment once to maximize the total brightness of the bulbs that are on.	Medium4	ArrayDynamic programming	No attempts yet	1s	512 MB	Judgeable
Sequence and Maximum Rise QueriesGiven a sequence, process point updates and report the maximum value of a_j - a_i with i at most j inside a query range.	Medium4	Segment treeDivide and conquer	No attempts yet	1s	512 MB	Judgeable
Chopsticks GameGiven the starting finger counts A and B (1 to 4 each), decide whether the first player Yongtae wins the one-hand chopsticks game under optimal play.	Medium4	Game theoryRecursion+1	No attempts yet	1s	512 MB	Judgeable
Even and Odd CombinationsFor each n from 1 to 50, build a bijection between even-size and odd-size subsets of {1..n} and print the matching element of the other set for a given one.	Medium4	CombinatoricsBit manipulation+1	No attempts yet	2s	1024 MB	Judgeable
Minimum Cost to Color a TreePaint each vertex of a tree white or black so that no two adjacent vertices are both black, at the minimum total cost.	Medium4	TreeDynamic programming+1	No attempts yet	3s	512 MB	Judgeable
Score CalculationGiven an array, find the maximum total of digit sums of products a_i times a_j over pairs i less than j, each pair scoring once.	Medium4	MathHash map	No attempts yet	1s	1024 MB	Judgeable
IngyeongsanFor each query, sum the stamina cost along the straight path between two huts, where uphill, flat, and downhill segments have different weights.	Medium4	Prefix sumGeometry+1	No attempts yet	2s	1024 MB	Judgeable
Gene CombinationGiven N genes made of two uppercase letters, find which letters can be the phenotype (the larger letter) of a gene formed by combining two different genes, and list them in order.	Medium4	ImplementationMath	No attempts yet	1s	512 MB	Judgeable
Word TreeFind the smallest possible largest edge cost among all trees that connect n equal-length words, where edge cost is the sum of letter differences.	Medium4	Minimum spanning treeGraph	No attempts yet	1s	1024 MB	Judgeable
Discord Daisy ChainCount the channels from which a message posted there reaches every other channel, given the directed forwarding edges from bots.	Medium4	GraphDFS+1	No attempts yet	1s	1024 MB	Judgeable
Making ConnectionsAdd connections between computers one at a time and, for each query, print the average of squared component sizes as a reduced fraction.	Medium4	Union-findMath	No attempts yet	3s	1024 MB	Judgeable
Unique ValuesCount the contiguous subarrays of a given array in which no value appears more than once.	Medium4	Sliding windowTwo pointers+1	No attempts yet	1s	1024 MB	Judgeable
Hang GlidingGiven overlapping timed tasks with point values and each pilot's success probabilities, find each pilot's best expected score and print the top 3 pilots.	Medium4	Dynamic programmingSorting+2	No attempts yet	1s	1024 MB	Judgeable
Circle Meets SquareGiven a circle and an axis-aligned square, determine whether they overlap in positive area, touch at a single point, or do not meet.	Medium4	GeometryMath	No attempts yet	1s	1024 MB	Judgeable
First Last SortingGiven a permutation of 1 to n, find the fewest first/last moves needed to sort it into increasing order.	Medium4	ArrayImplementation	No attempts yet	1s	1024 MB	Judgeable
Editor NavigationGiven the line lengths of a text file and two cursor positions, find the fewest arrow key presses needed to move the cursor from the current position to the desired one.	Medium4	BFSGraph+1	No attempts yet	1s	1024 MB	Judgeable
Don't Break the IceCount the attempted moves that target an ice block already knocked off the board, where each knockout can cause a chain of further falls.	Medium4	SimulationImplementation	No attempts yet	1s	1024 MB	Judgeable
Dot the i's and Cross the T'sCount the groups of four points that form a T shape, where M is the midpoint of AB, CM equals AB in length, and CM is perpendicular to AB.	Medium4	GeometryBrute force	No attempts yet	1s	1024 MB	Judgeable
Sum of a SequenceGiven S and T up to 10^7, compute the sum of a_i from i=S to T, where a_i adds (-1) raised to each divisor d of i.	Medium4	Number theoryMath	No attempts yet	1s	1024 MB	Judgeable
SilheundeyoGiven N positive integers, find the largest sum of a contiguous block that does not exceed M.	Medium4	Sliding windowTwo pointers	No attempts yet	1s	1024 MB	Judgeable
Lemonade StandGiven daily cup demand and lemon and sugar prices, find the minimum cost of supplies so every customer gets a cup, with leftovers carried forward.	Medium4	GreedyImplementation	No attempts yet	1s	1024 MB	Judgeable
Container RearrangementGiven container counts in n slots, find the fewest containers to move so that every pair of slots differs in height by at most 1.	Medium4	GreedySorting	No attempts yet	1s	1024 MB	Judgeable
Counting table of contents subheadingsGiven the level of each heading in a table of contents, count the direct subheadings of each heading, or print -1 if the structure is invalid.	Medium4	StackImplementation	No attempts yet	1s	512 MB	Judgeable
Word Superiority Effect (Cambridge University Study)Given a dictionary of words and a sentence with scrambled inner letters, restore each word by matching first, sorted middle, and last letters.	Medium4	Hash mapString+1	No attempts yet	1s	512 MB	Judgeable
Typhoon ForecastGiven the typhoon's observed centers and radius R, classify each queried point on its day as safe, unsafe, or gori (on the boundary or outside the circle).	Medium4	Binary searchGeometry+1	No attempts yet	1s	512 MB	Judgeable
2D Array Range Add and Range SumGiven an n by n matrix, apply all rectangle add updates in order, then print the sum of each rectangle query.	Medium4	MatrixPrefix sum	No attempts yet	3s	512 MB	Judgeable
Abbreviated AliasesGiven n unique aliases of length l, find the total length of the shortest prefixes that uniquely identify each alias.	Medium4	StringSorting+1	No attempts yet	2s	2048 MB	Judgeable
Cookbook CompositionGiven each recipe as a dependency graph of timed steps, sort the recipes by the ratio of serial time to parallel critical-path time.	Medium4	Dynamic programmingTopological sort+1	No attempts yet	2s	2048 MB	Judgeable
Dimensional DebuggingCount algorithms verifiable by BFS from those with all L_i equal to 0, where algorithm A verifies B when L_B is at most H_A in every parameter.	Medium4	GraphBFS	No attempts yet	2s	2048 MB	Judgeable
Extended BrailleCount the distinct braille shapes among n dot sets, where two sets count as the same shape if one is a translation of the other.	Medium4	Hash mapSorting+1	No attempts yet	8s	2048 MB	Judgeable
Chaotic ConstructionStreet segments on a cycle close and reopen over time. For each query, report whether two open segments can reach each other without passing a closed one.	Medium4	ArrayPrefix sum+1	No attempts yet	3s	1024 MB	Judgeable
Improving ITFind the minimum net cost of keeping one CPU over n months, buying and reselling it so that each CPU is replaced within m months.	Medium4	Dynamic programmingImplementation	No attempts yet	2s	1024 MB	Judgeable
Jesting JabberwockyGiven a string of card suits, find the fewest cards to move so that every suit ends up grouped together.	Medium4	StringDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Highest HillGiven n heights, find the largest peak height, where a peak's height is the smaller of its two drops to the left and right endpoints.	Medium4	ArrayGreedy	No attempts yet	1s	1024 MB	Judgeable
Version HistoryGiven the current version N, find the longest history where each month adds a repunit with as many 1s as the previous version has digits.	Medium4	SimulationMath	No attempts yet	2s	1024 MB	Judgeable
Lonely Gomgomi Has FriendsGiven each friend's start point and allowed step lengths, decide whether the friend can reach the origin by moving axis-aligned by those lengths.	Medium4	Number theoryMath	No attempts yet	1s	1024 MB	Judgeable
Hyogu and Hogyu (Easy)Given an N by M grid of cards marked 0 or 1, decide whether all cards can be removed by pairing adjacent equal cards and sliding cards into empty neighbors.	Medium4	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
Hyundai Mobis Software AcademyPair up members into two-person teams whose ability sums reach at least M, and find the maximum number of such teams.	Medium4	GreedyTwo pointers+1	No attempts yet	1s	1024 MB	Judgeable
Start and Link 2Split N people into two equal teams to minimize the difference between the sums of pairwise ability scores of the two teams.	Medium4	BacktrackingBrute force+1	No attempts yet	2s	512 MB	Judgeable
Drainage Pipe MysteryGiven drains joined by pipes with connection probabilities, count the connected components for each threshold using only pipes with probability at least p'.	Medium4	Union-findSorting	No attempts yet	1s	512 MB	Judgeable
Tree and SequenceAssign the sequence values to the tree edges so the sum of all pairwise vertex distances is minimized, modulo 1e9+7.	Medium4	GreedyTree+1	No attempts yet	2s	1024 MB	Judgeable
Eat Apples in Three Moves or FewerGiven a 5 x 5 grid of apples and obstacles, decide whether a student starting at a given cell can eat at least 2 apples within 3 moves.	Medium4	BacktrackingBrute force+1	No attempts yet	1s	512 MB	Judgeable
Snow RemovalGiven N piles of snow, find the minimum minutes to clear them all when each minute removes 1 unit from one house or from two different houses.	Medium4	MathGreedy	No attempts yet	1s	512 MB	Judgeable
Ski raceGiven K distinct numbers up to 10^7, list the numbers that no other given number is divisible by, in ascending order.	Medium4	ArrayMath	No attempts yet	1s	1024 MB	Judgeable
BackroomsFind the maximum sum of room numbers on a path from the top left to the bottom right of an N by M grid, moving only down or right past one straight wall.	Medium4	Dynamic programmingMatrix	No attempts yet	1s	1024 MB	Judgeable
Hidden Node in a Binary TreeGiven a perfect binary search tree with one hidden node value, recover the missing value, insert X, and print the postorder traversal of the new tree.	Medium4	TreeBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Vigenère Cipher DecryptionGiven the plaintext and ciphertext, find the shortest key that maps the plaintext to the ciphertext under Vigenère encryption.	Medium4	String matchingString	No attempts yet	1.5s	256 MB	Judgeable
Japanski JunakFill a sudoku board by repeating cross-hatching, and report GRESKA if the board is illegal or a contradiction appears.	Medium4	SimulationImplementation	No attempts yet	1s	1024 MB	Judgeable
Faster MicrowavingGiven a recommended cooking time and a percent, find the digit sequence that enters a time in the allowed range with the fewest finger moves.	Medium4	Brute forceImplementation	No attempts yet	1s	1024 MB	Judgeable
Exact ChangeGiven package values in cents, find the smallest positive amount that no subset of the packages can sum to exactly.	Medium4	GreedySorting	No attempts yet	1s	1024 MB	Judgeable
Hanging NestsInsert birds into a binary search tree in arrival order and report the spot count of the node with the largest height difference between its children.	Medium4	TreeRecursion	No attempts yet	1s	1024 MB	Judgeable
Palindrome MakerFind the fewest integers to insert into a sequence so that it reads the same forwards and backwards.	Medium4	Dynamic programmingArray	No attempts yet	3s	1024 MB	Judgeable
Rummy ScoreGiven seven cards per hand, find the minimum sum of card values left outside groups of three or more cards with equal or consecutive values.	Medium4	BacktrackingBrute force	No attempts yet	1s	1024 MB	Judgeable
Simi CirclesGiven circles where each one overlaps only its neighbors in the list, find the total area their union covers in each scenario.	Medium4	GeometryMath+1	No attempts yet	1s	1024 MB	Judgeable
Matrix TransformationGiven an integer grid, decide whether repeatedly adding or subtracting 1 from both cells of an adjacent pair can turn every cell into zero.	Medium4	MathMatrix+1	No attempts yet	1s	1024 MB	Judgeable
Cut the Cake!Given a convex polygon and a horizontal cut y=Y, find the perimeters of the two pieces, smaller value first.	Medium4	GeometryImplementation	No attempts yet	1s	1024 MB	Judgeable
Ants on a StickAnts on a stick bounce off each other when they meet, and the task is to output the ant labels in the order they fall off the ends.	Medium4	SortingSimulation	No attempts yet	Not set	1024 MB	Judgeable
Factorization of Quadratic FormulaGiven integers a, b, c of ax^2 + bx + c, find integers p, q, r, s so that it equals (px + q)(rx + s), or report Impossible.	Medium4	MathBrute force+1	No attempts yet	1s	1024 MB	Judgeable
Stop & GoGiven N traffic lights on a road of length L, find the time Mr. D reaches point L, stopping at each red light he meets.	Medium4	SimulationSorting+1	No attempts yet	2s	1024 MB	Judgeable
Find PalindromesFor each input string, list every distinct palindromic substring, sorted by length, with equal lengths kept in order of first appearance.	Medium4	StringHash map+1	No attempts yet	1s	1024 MB	Judgeable
ParkCount the trees that can be seen from some horizontal or vertical path, where a tree is hidden if another tree lies between it and the path.	Medium4	Hash mapSorting+1	No attempts yet	1s	1024 MB	Judgeable