Interview core

Mediums from real onsites

Under construction

Still being built. Things may change

Total results3,613 problems

Super Cheap Party Rooms
Medium7
Intervals, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Graph Automata Player
Medium7
Matrix, Math+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Comfortable String
Medium7
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Matrix Game
Medium7
Game theory, Greedy+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Running
Medium7
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Breaking Walls and Moving 3
Medium7
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Red Blue Spanning Tree 2
Medium7
Graph, Minimum spanning tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Wand
Medium7
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Why the Mole Came Up to Jeongbo Island
Medium7
Tree, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Laboratory 3
Medium7
BFS, Backtracking+2
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Fine Dust, Goodbye!
Medium7
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Newcomer and Veteran
Medium7
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Delicious Pineapple Pizza
Medium7
Binary search, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Linear-Feedback Shift Register
Medium7
Bit manipulation, Math+2
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Kaka and Bebe
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
2.5s
Memory limit
512 MB
Judgeable
Infinite Booster
Medium7
Dynamic programming, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Depressing Vacation
Medium7
Dynamic programming, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
K-th Parenthesis String
Medium7
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Multiples of Primes
Medium7
Combinatorics, Math+2
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Jinwoo's Moon Trip (Large)
Medium7
Dynamic programming, Matrix+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Hop Game
Medium7
Dynamic programming, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Knapsack Packing
Medium7
Sorting, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Research Productivity Index
Medium7
Dynamic programming, Probability+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gluttonous Goop
Medium7
Geometry, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Jammed Gym
Medium7
Dynamic programming, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Beer Mugs
Medium7
Bit manipulation, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Big Company Seungbeom's
Medium7
Tree, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Taxed Editor
Medium7
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hidden Words
Medium7
Backtracking, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Thread Knots
Medium7
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Know your Aliens
Medium7
Math, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Allergic Aron
Medium7
Tree, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pixels
Medium7
Greedy, Implementation+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Commute Circuit
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Letter Wheels
Medium7
String, Brute force+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Stock Exchange
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Jumping Junipers
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Balance
Medium7
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Songwriter
Medium7
Greedy, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Tic-tac-toe
Medium7
Game theory, Simulation+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Block, Stock and Two Smoking Galaxy Notes
Medium7
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Factory
Medium7
Geometry, Math+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Lost Array
Medium7
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Company Merging
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
School Olympiad
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Perfect Squares
Medium7
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hyungon's Blind Date
Medium7
Greedy, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Multitap Scheduling 2
Medium7
Greedy, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mind the Gap
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Chemistry Experiment
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Arrow Maze (Normal)
Medium7
Graph, BFS+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Force Fields
Medium7
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Typing Practice
Medium7
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Permutation Sort
Medium7
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Arriving on Time
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hide and Seek
Medium7
Tree, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Scheduler
Medium7
Simulation, Heap+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Build More 2020's!
Medium7
Greedy, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Planet X
Medium7
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Planetbacke
Medium7
DFS, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Shortsighted
Medium7
Prefix sum, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Easter Gift
Medium7
Sorting, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Returning Lights To Box
Medium7
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Kinky Word Searches
Medium7
DFS, Backtracking+2
No attempts yet
Time limit
6s
Memory limit
1024 MB
Judgeable
Weighty Tomes
Medium7
Dynamic programming, Binary search+2
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Statues
Medium7
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bloodseeker
Medium7
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Digit Sum
Medium7
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Clay Shooting Game
Medium7
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cities
Medium7
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Flight Collision
Medium7
Stack, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Stock
Medium7
Greedy, Heap+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Electrician Cowboy Joe
Medium7
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Investigating Imposters
Medium7
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pekka's Amusement
Medium7
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gahui's Sweet Potato Eating
Medium7
BFS, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Physical Distancing
Medium7
Geometry, Union-find+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Luna Likes Love
Medium7
Greedy, Stack+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Boats
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Crisis at the Wedding
Medium7
Greedy, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Balancing a Graph
Medium7
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Summer Camp Mornings Come Early
Medium7
Probability, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Fastest Route
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Restrictive Filesystem
Medium7
Implementation, Simulation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Dial Lock
Medium7
Dynamic programming, Greedy+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Up Above the World So High
Medium7
Geometry, Brute force+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Oil Company
Medium7
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Water Pipe Construction
Medium7
Graph, Shortest path+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Push!!
Medium7
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tower View
Medium7
Stack, Array+2
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Crossing the Stepping Stones (large)
Medium7
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
3-Second Sort
Medium7
Greedy, Implementation+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Demand-Responsive Bus
Medium7
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Festival
Medium7
Intervals, Heap+2
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Logistical Warehouse 2
Medium7
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Diamond Hands
Medium7
Greedy, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Power of ALPS
Medium7
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bundling
Medium7
Trie, Tree+2
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable
Catch Some
Medium7
Dynamic programming, Greedy+1
No attempts yet
Time limit
30s
Memory limit
1024 MB
Judgeable
Flattening
Medium7
Dynamic programming, Greedy+1
No attempts yet
Time limit
20s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Super Cheap Party RoomsManage a row of N rooms across new/in/out queries, placing each new room in the leftmost gap of size Y and cleaning it when its guests leave.	Medium7	IntervalsSimulation+2	No attempts yet	1s	512 MB	Judgeable
Graph Automata PlayerGiven a Boolean graph update rule and a state at time 0, decide whether a state at time -T exists and is unique, by inverting the adjacency matrix over GF(2).	Medium7	MatrixMath+1	No attempts yet	10s	512 MB	Judgeable
Comfortable StringCount how many substrings of a bracket string are both correctly balanced and symmetric under reversal with bracket swap.	Medium7	Dynamic programmingString+2	No attempts yet	1s	512 MB	Judgeable
Matrix GameGiven an N by M matrix, it asks who wins a take-away game where a move subtracts 1 to K from the leftmost nonzero entry of some row.	Medium7	Game theoryGreedy+2	No attempts yet	0.5s	512 MB	Judgeable
RunningOn a grid with walls, each move slides 1 to K empty cells in one of four directions; find the minimum number of moves from start to goal.	Medium7	BFSGraph+2	No attempts yet	1s	512 MB	Judgeable
Breaking Walls and Moving 3Find the shortest path from the top-left to the bottom-right of a grid, where up to K walls can be broken during daytime and day/night alternate with each move or wait.	Medium7	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Red Blue Spanning Tree 2Given a connected undirected graph whose edges are red or blue, decide whether some spanning tree uses exactly k blue edges, and print one if it does.	Medium7	GraphMinimum spanning tree+2	No attempts yet	1s	128 MB	Judgeable
WandGiven M duels with fixed winners, in any order, decide which wizards can hold the wand (initially with wizard 1) after all duels.	Medium7	GraphDFS+2	No attempts yet	1s	512 MB	Judgeable
Why the Mole Came Up to Jeongbo IslandOn a weighted tree, sum the minimum edge weight over all unordered pairs of vertices.	Medium7	TreeUnion-find+2	No attempts yet	2s	512 MB	Judgeable
Laboratory 3Given a grid with walls and up to 10 viruses, choose M of them to activate simultaneously and minimize the time until the virus fills every empty cell, or print -1.	Medium7	BFSBacktracking+2	No attempts yet	0.25s	512 MB	Judgeable
Fine Dust, Goodbye!Simulate T seconds of dust diffusion on a grid plus the circular wind from a two-cell air purifier, then sum the remaining dust.	Medium7	SimulationImplementation+2	No attempts yet	1s	512 MB	Judgeable
Newcomer and VeteranGiven a directed reporting graph on N participants where newcomers speak truth and veterans lie, find the maximum possible number of veterans.	Medium7	GraphDFS+2	No attempts yet	2s	256 MB	Judgeable
Delicious Pineapple PizzaPair each pineapple with a dough to make N pizzas, maximizing the smallest XOR value over all pairs.	Medium7	Binary searchBit manipulation+2	No attempts yet	1s	256 MB	Judgeable
Linear-Feedback Shift RegisterGiven the 36 feedback bits of an LFSR and up to 64 output bits, decide whether some 36-bit initial state produces them, and print the lexicographically smallest such state.	Medium7	Bit manipulationMath+2	No attempts yet	1.5s	256 MB	Judgeable
Kaka and BebeFind a path from vertex 0 to N-1 whose total Kaka and total Bebe are each at most 1000, minimizing the product of the two totals.	Medium7	GraphShortest path+2	No attempts yet	2.5s	512 MB	Judgeable
Infinite BoosterOn an N by M grid of booster counts, move only right or down within the count of the cell you last stopped on, minimizing the number of stopping cells from (1,1) to (N,M).	Medium7	Dynamic programmingGraph+2	No attempts yet	1s	512 MB	Judgeable
Depressing VacationPlace N ordered appointments within M vacation days to minimize the total squared depression, where each idle day lowers the mood by 1.	Medium7	Dynamic programmingImplementation+2	No attempts yet	1s	512 MB	Judgeable
K-th Parenthesis StringFind the K-th valid balanced parenthesis string of length N in lexicographic order, or -1 if fewer than K+1 exist.	Medium7	Dynamic programmingCombinatorics+2	No attempts yet	0.25s	512 MB	Judgeable
Multiples of PrimesGiven up to 10 distinct primes and a limit M up to 1e12, count the natural numbers at most M divisible by at least one listed prime.	Medium7	CombinatoricsMath+2	No attempts yet	0.25s	512 MB	Judgeable
Jinwoo's Moon Trip (Large)Find the cheapest path from any cell in the top row to any cell in the bottom row of an N x M grid, where no two consecutive moves may use the same direction.	Medium7	Dynamic programmingMatrix+2	No attempts yet	1s	256 MB	Judgeable
Hop GameStart in row 1 of an N x M grid and jump to later rows within Manhattan distance D, multiplying the two cells' values and adding to the score; maximize the total when reaching row N.	Medium7	Dynamic programmingImplementation+1	No attempts yet	1s	256 MB	Judgeable
Knapsack PackingGiven the multiset of all 2^n subset sums of n unknown non-negative weights, reconstruct the weights in non-decreasing order or report impossible.	Medium7	SortingGreedy+2	No attempts yet	2s	512 MB	Judgeable
Research Productivity IndexChoose any subset of n papers with known acceptance probabilities to maximize the expected value of a^a/s, where s is the subset size and a the number accepted.	Medium7	Dynamic programmingProbability+2	No attempts yet	1s	1024 MB	Judgeable
Gluttonous GoopGiven an r by c grid of fungus cells and k steps, each step expands the fungus to all 8 neighbors, and the fungus grows past the grid; count occupied cells at the end.	Medium7	GeometryMath+2	No attempts yet	3s	512 MB	Judgeable
Jammed GymGiven a required sequence of machine types and stations placed on a unit circle, find the minimum total walking distance to visit stations in that order.	Medium7	Dynamic programmingGeometry+2	No attempts yet	2s	512 MB	Judgeable
Beer MugsGiven a string of N characters over 20 brands, find the longest substring that is a palindrome after permuting it freely.	Medium7	Bit manipulationHash map+2	No attempts yet	2s	512 MB	Judgeable
Big Company Seungbeom'sGiven a rooted tree of employees, pick a matching of edges where each node touches at most one chosen edge, maximizing the sum of products of endpoint skill values.	Medium7	TreeDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Taxed EditorGiven book lengths and deadlines, find the smallest integer reading speed so that at most m books finish after their deadline.	Medium7	Binary searchGreedy+2	No attempts yet	2s	512 MB	Judgeable
Hidden WordsGiven a grid of up to 10x10 letters and up to 100,000 query words of length at most 10, count how many words can be traced through adjacent, non-repeating cells.	Medium7	BacktrackingDFS+2	No attempts yet	2s	512 MB	Judgeable
Thread KnotsPlace one integer knot on each of n given intervals so that the smallest gap between any two knots is maximized, and print that optimum.	Medium7	Binary searchGreedy+2	No attempts yet	1s	512 MB	Judgeable
Know your AliensGiven a human/alien label for each even number 2 to 2N, build the lowest-degree monic or anti-monic integer polynomial whose sign at 2i matches the label.	Medium7	MathDivide and conquer+2	No attempts yet	2s	512 MB	Judgeable
Allergic AronGiven a weighted tree, choose a connected set of edges maximizing (number of edges) times (minimum edge weight in the set).	Medium7	TreeUnion-find+2	No attempts yet	1s	512 MB	Judgeable
PixelsGiven a target black and white grid, find which switches to press so that each press flips a cell and its four orthogonal neighbors to match the target.	Medium7	GreedyImplementation+2	No attempts yet	3s	512 MB	Judgeable
Commute CircuitGiven a weighted undirected city graph, the office at node 0, and up to 10 employee homes, find the length of the shortest closed route that starts at the office, visits every home, and returns.	Medium7	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Letter WheelsThree cyclic strings over {A,B,C}; rotate each independently to make every column have three distinct letters, minimizing total rotation steps.	Medium7	StringBrute force+2	No attempts yet	3s	512 MB	Judgeable
Stock ExchangeArrange a given multiset of N daily prices to maximize profit, starting with one share and cash, buying and selling fractional shares each day, and selling everything by the end.	Medium7	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Jumping JunipersMove each tree to a distinct positive integer position within its allowed interval so that the total distance from the house is minimized.	Medium7	GreedySorting+2	No attempts yet	4s	512 MB	Judgeable
BalanceGiven an N x N matrix A, find the entrywise-minimal balanced matrix B (satisfying the additive rectangle condition) with B[i][j] >= A[i][j], and report its sum.	Medium7	Dynamic programmingGreedy+2	No attempts yet	1s	512 MB	Judgeable
SongwriterGiven a melody A, find the lexicographically smallest B with the same up/equal/down pattern as A, bounded in [L, R], and with adjacent differences at most K.	Medium7	GreedyImplementation+2	No attempts yet	1s	512 MB	Judgeable
Tic-tac-toeFor each 3x3 tic-tac-toe board, decide whether it is invalid, reachable only by non-optimal play, or reachable by two perfect players.	Medium7	Game theorySimulation+2	No attempts yet	5s	512 MB	Judgeable
Block, Stock and Two Smoking Galaxy NotesGiven a graph of effective pairs, pick a techlead and split the rest into singles or pairs such that every pair is an edge and each team has someone adjacent to the techlead.	Medium7	GraphGreedy+2	No attempts yet	1s	512 MB	Judgeable
FactoryFind any point in the plane that minimizes the sum of Euclidean distances to n given store locations, within a relative error of 1e-6.	Medium7	GeometryMath+2	No attempts yet	10s	512 MB	Judgeable
Lost ArrayGiven M constraints of the form min(X[Ai], X[Bi]) = Ci, reconstruct any array X of N positive integers that satisfies all of them.	Medium7	GraphGreedy+2	No attempts yet	1s	512 MB	Judgeable
Company MergingGiven n companies with employee salaries, repeatedly merge two companies whose maximum salaries are equal, raising every salary in a company by one uniform amount, and minimize the total raise.	Medium7	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
School OlympiadAssign n students at given coordinates to three locations with capacity limits so the total walking distance is minimized.	Medium7	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Perfect SquaresGiven a starting integer k, the sequence k, k+1, k+4, k+9, ... is formed by adding consecutive odd numbers; find the smallest nonnegative integer whose square occurs in the sequence, or report none.	Medium7	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Hyungon's Blind DateGiven N men and N women with full preference lists, find a stable matching where no man and woman both prefer each other to their assigned partners.	Medium7	GreedyHash map+2	No attempts yet	1s	512 MB	Judgeable
Multitap Scheduling 2Given a power strip with N holes and a usage sequence, find the minimum number of unplugs needed using the optimal offline replacement rule.	Medium7	GreedyHash map+2	No attempts yet	2s	512 MB	Judgeable
Mind the GapGiven n distinct positive card values, find an integer d so that the players, each playing their card exactly when its value is within d above the pile top and otherwise waiting, always place all cards in increasing order regardless of tie order.	Medium7	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Chemistry ExperimentGiven counts of K colors summing to N, arrange all N test tubes in a row so no two neighbors share a color, or report that it is impossible.	Medium7	GreedySorting+2	No attempts yet	1s	1024 MB	Judgeable
Arrow Maze (Normal)Given a grid of arrows and K sets of one clockwise and one counterclockwise rotation scroll, decide whether some sequence of moves and rotations reaches the bottom-right cell from the top-left.	Medium7	GraphBFS+2	No attempts yet	3s	512 MB	Judgeable
Force FieldsChoose exactly k axis-aligned rectangles anchored at the origin so that their common intersection has maximum area, and output that area.	Medium7	SortingGreedy+2	No attempts yet	1s	512 MB	Judgeable
Typing PracticeGiven up to six strings over the letters A to D, find the shortest string that contains every input string as a subsequence, breaking ties lexicographically.	Medium7	Dynamic programmingBit manipulation+2	No attempts yet	8s	1024 MB	Judgeable
Permutation SortEach day every value x on the board is replaced by Q[x]; find the smallest d for which the sequence P becomes sorted, or -1 if it never does.	Medium7	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Arriving on TimeGiven periodic tram lines with fixed travel times, find the latest time to leave stop 0 and still reach stop n-1 by time s.	Medium7	GraphShortest path+2	No attempts yet	2s	512 MB	Judgeable
Hide and SeekGiven a weighted tree rooted at cave 0, find the largest number of non-root vertices that a walk starting at the root with total length at most n can cover.	Medium7	TreeDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
SchedulerSimulate a priority scheduler for T seconds where the process with the largest p_i + t_i wins ties by smallest index, and report each process's total run time.	Medium7	SimulationHeap+2	No attempts yet	2s	256 MB	Judgeable
Build More 2020's!Given a string of digits 0, 1, 2, find the largest number of disjoint subsequences equal to 2020.	Medium7	GreedyString+2	No attempts yet	1s	512 MB	Judgeable
Planet XGiven a grid where some cell heights are known and adjacent cells differ by at most 1, fill in every cell whose height is forced by the constraints.	Medium7	GraphBFS+2	No attempts yet	1s	1024 MB	Judgeable
PlanetbackeGiven a grid of digit heights with at most 7 cells per height, find the longest simple path that moves between 8-neighbors and never goes to a strictly higher cell.	Medium7	DFSBacktracking+2	No attempts yet	1s	1024 MB	Judgeable
ShortsightedStart with a zero array; range-update queries add a triangular weight pattern to each position, and range-sum queries report the total modulo 1e9+7.	Medium7	Prefix sumMath+2	No attempts yet	2s	512 MB	Judgeable
Easter GiftGiven an array, find the smallest K such that repeated swaps of pairs whose values differ by at most K can sort it.	Medium7	SortingUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Returning Lights To BoxGiven initial light states and a schedule of automatic toggles, find the earliest second by which switches can make every light off.	Medium7	Binary searchGreedy+2	No attempts yet	1s	512 MB	Judgeable
Kinky Word SearchesGiven a letter grid, decide whether a target word can be traced with exactly k direction changes, where the path may reuse cells but cannot stay put.	Medium7	DFSBacktracking+2	No attempts yet	6s	1024 MB	Judgeable
Weighty TomesWith m pallets and at most n boxes, find the minimum worst-case number of drop tests to determine the box limit, and the first test size (or range).	Medium7	Dynamic programmingBinary search+2	No attempts yet	5s	1024 MB	Judgeable
StatuesGiven K statues at distinct street lights with sizes, assign them to distinct lights so sizes increase with position, minimizing total movement cost size times distance.	Medium7	Dynamic programmingSorting+2	No attempts yet	1s	512 MB	Judgeable
BloodseekerEach enemy takes t_i hits and restores h_i hit-points up to a cap of m, so the task is to decide whether Bloodseeker can kill all enemies before his hit-points reach 0.	Medium7	GreedySorting	No attempts yet	2s	512 MB	Judgeable
Digit SumGiven an integer N up to 10^20, find the smallest integer greater than N whose digits sum to the same value as N's digits.	Medium7	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Clay Shooting GameChoose an order to hit the N clays; hitting clay i in round j scores b[i]*j, but once a path is used no clay returns to it, so timing must be respected.	Medium7	Dynamic programmingBit manipulation+2	No attempts yet	1s	1024 MB	Judgeable
CitiesGiven a tree with N nodes, count the unordered pairs of cities whose unique path contains exactly K edges.	Medium7	TreeDFS+2	No attempts yet	2s	1024 MB	Judgeable
Flight CollisionGiven drones on a line with fixed positions and velocities, simulate which collide pairwise and report the indices of drones that never crash.	Medium7	StackSorting+2	No attempts yet	1s	1024 MB	Judgeable
StockEach day i you receive xi shares, may sell up to mi shares at price pi, and unsold shares expire worthless after day n. Find the maximum total profit.	Medium7	GreedyHeap+2	No attempts yet	1s	1024 MB	Judgeable
Electrician Cowboy JoeGiven two poles of heights h1, h2 at distance d and a jump limit l, minimize the total climbing distance while moving between the pole tops.	Medium7	GeometryMath+2	No attempts yet	2s	1024 MB	Judgeable
Investigating ImpostersGiven each villager's list of people they claim are not imposters, and at most k imposters in total, decide for each villager whether they could be an imposter.	Medium7	GraphDFS+2	No attempts yet	1s	1024 MB	Judgeable
Pekka's AmusementCount the arrangements of multiset cards numbered 1..N where every card numbered k+1 appears after at least one card numbered k. Total cards up to 100.	Medium7	CombinatoricsDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Gahui's Sweet Potato EatingGiven a grid with obstacles, a start cell, and sweet potatoes, find the most potatoes Gahui can eat while walking or waiting for exactly T seconds, where T is at most 10.	Medium7	BFSDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Physical DistancingGiven points in a rectangle, find the widest corridor you can walk through from one end to the other, keeping that distance from every point.	Medium7	GeometryUnion-find+2	No attempts yet	1s	256 MB	Judgeable
Luna Likes LoveGiven 2n friends in a line where each of n labels appears twice, repeatedly swap adjacent friends or remove an adjacent matching pair, and find the minimum number of actions to remove all pairs.	Medium7	GreedyStack+2	No attempts yet	2s	512 MB	Judgeable
BoatsEach boat has a fixed length and an assigned ring position; tie a boat so its ring falls anywhere on the boat, boats may touch but not overlap. Maximize the number of boats tied.	Medium7	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Crisis at the WeddingGlasses are spread unevenly over N circular tables with average 1 each; find the minimum total carry distance when a waiter walks one fixed direction, starting anywhere.	Medium7	GreedyPrefix sum+2	No attempts yet	1s	1024 MB	Judgeable
Balancing a GraphAssign integer weights to the vertices of a connected graph so every edge's endpoints sum to its given weight, minimizing the sum of absolute vertex weights.	Medium7	GraphDFS+2	No attempts yet	2s	1024 MB	Judgeable
Summer Camp Mornings Come EarlyGiven each participant's independent oversleeping probability and a directed contact graph, find the probability that calls from awake participants eventually wake everyone.	Medium7	ProbabilityGraph+2	No attempts yet	8s	512 MB	Judgeable
Fastest RouteGiven N stages and N pieces of equipment, where clearing stage i yields equipment i and each stage can be done in any order with at most one equipment, find the minimum total time to clear all stages.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	8s	512 MB	Judgeable
Restrictive FilesystemSimulate a filesystem where writes fill the first free sectors with possible fragmentation, deletes free a file, and references report which file occupies a sector.	Medium7	ImplementationSimulation+2	No attempts yet	8s	512 MB	Judgeable
Dial LockGiven two k-digit dial strings (k <= 10), find the fewest rotations where each rotation turns a contiguous block of dials by the same signed amount mod 10.	Medium7	Dynamic programmingGreedy+2	No attempts yet	8s	512 MB	Judgeable
Up Above the World So HighGiven up to 100 star positions and an angular radius, find the maximum number of stars that fit inside a circular cone of that half-angle centered at the origin.	Medium7	GeometryBrute force+2	No attempts yet	8s	512 MB	Judgeable
Oil CompanyPlace plants on grid blocks so no two share an edge, maximizing the total oil reserve collected.	Medium7	Dynamic programmingBit manipulation+2	No attempts yet	8s	512 MB	Judgeable
Water Pipe ConstructionGiven a directed weighted graph, find the minimum total cost of two paths from source s to goals g1 and g2, where the two paths may share edges whose cost is counted once.	Medium7	GraphShortest path+2	No attempts yet	8s	512 MB	Judgeable
Push!!On a grid up to 7 by 7 with pillars, find the fewest pushes to move the cargo to the goal, given the warehouseman must walk to the tile behind the cargo before each push.	Medium7	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Tower ViewFor each building, count the buildings visible to its left and right, where a shorter or equal building is hidden behind a taller one, and report the nearest visible index.	Medium7	StackArray+2	No attempts yet	1.5s	1024 MB	Judgeable
Crossing the Stepping Stones (large)Find the smallest energy limit K such that some path from stone 1 to stone N, jumping rightward, keeps every jump cost (j-i)*(1+\|Ai-Aj\|) within K.	Medium7	Binary searchGreedy+2	No attempts yet	2s	1024 MB	Judgeable
3-Second SortGiven a sequence that is not sorted, decide whether at most 3 element replacements can make it nondecreasing, and output one such sequence of operations.	Medium7	GreedyImplementation+2	No attempts yet	2s	1024 MB	Judgeable
Demand-Responsive BusMatch as many requests (passengers, max wait) to buses (capacity, arrival) as possible, where a bus fits a request if its capacity and arrival time are both at least as small or large as required.	Medium7	GreedySorting+2	No attempts yet	1s	1024 MB	Judgeable
FestivalEach attraction is open on a day interval and has a happiness value; pick one day and at most K open attractions to maximize the sum.	Medium7	IntervalsHeap+2	No attempts yet	Not set	1024 MB	Judgeable
Logistical Warehouse 2Given a tree and radius K, find the minimum number of nodes to select so every node lies within distance K of a selected node.	Medium7	TreeGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Diamond HandsGiven stock price differences at n known days, reconstruct a history of +1 and -1 streaks from day 1 to day d_n using the fewest streaks, or report impossibility.	Medium7	GreedyImplementation+2	No attempts yet	2s	512 MB	Judgeable
The Power of ALPSCount pairs i<j with (Ai^2 + Ai*Aj + Aj^2) mod P equal to K, given N up to 1e5 and prime P up to 1e9.	Medium7	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
BundlingPartition N strings into groups of exactly K to maximize the total length of the longest common prefix within each group.	Medium7	TrieTree+2	No attempts yet	20s	1024 MB	Judgeable
Catch SomeGiven N dogs at positions with colors, find the minimum travel time to observe K dogs, where Bundle starts at 0, can only observe a dog whose color matches her shirt, and may change shirts only at home.	Medium7	Dynamic programmingGreedy+1	No attempts yet	30s	1024 MB	Judgeable
FlatteningChoose heights to rebuild so the final wall has at most K adjacent unequal pairs, minimizing the number of rebuilt sections.	Medium7	Dynamic programmingGreedy+1	No attempts yet	20s	1024 MB	Judgeable