Interview core

Mediums from real onsites

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Total results3,617 problems

Queries are not locks
Medium5
Segment tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Escape the Ghost House
Medium5
BFS, Simulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Wiing Wiing
Medium5
Sorting, Geometry
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Flooding
Medium5
Array, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Group Project
Medium5
Sorting, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
A Slightly Slow but Kind Friend
Medium5
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Shortest Circuit
Medium5
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Alley
Medium5
Stack, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
DJ Gigs
Medium5
Dynamic programming, Shortest path+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Haybale Distribution
Medium5
Sorting, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Cowntact Tracing 2
Medium5
Greedy, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Liars
Medium5
Array, Prefix sum
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mirror Brackets
Medium5
Stack, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Graph Theory
Medium5
Segment tree, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Days of the week
Medium5
Matrix, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Complete Road
Medium5
Math, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Equipment
Medium5
Greedy, Union-find+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Recover the Sequence
Medium5
Graph, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tourism Product
Medium5
Binary search, Prefix sum
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Keep Climbing
Medium5
Stack, Sliding window+1
No attempts yet
Time limit
0.7s
Memory limit
1024 MB
Judgeable
Mice
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
TV Game
Medium5
Dynamic programming, Matrix
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Shooting
Medium5
Sorting, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Training
Medium5
Dynamic programming, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Soccer Tournament
Medium5
Dynamic programming, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Distinct Digits
Medium5
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Toy Dog
Medium5
Math, Hash map+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Compare Continued Fractions
Medium5
Math, Array
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Candies
Medium5
Heap, Simulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The Pool for Lucky Ones
Medium5
Greedy, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bridge Building
Medium5
Binary search, Greedy
No attempts yet
Time limit
5.5s
Memory limit
1024 MB
Judgeable
Urban geography
Medium5
Two pointers, Union-find+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Overload Prevention
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Military Enlistment
Medium5
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
String Graph Matching
Medium5
Sliding window, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Sinchon Merger Plan
Medium5
Linked list, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Carrot Click Game
Medium5
Dynamic programming, Greedy
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Card game
Medium5
Dynamic programming, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Supporting everyone
Medium5
Graph, BFS
No attempts yet
Time limit
0.25s
Memory limit
1024 MB
Judgeable
DP (Large)
Medium5
Dynamic programming, Binary search
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Wine Tasting
Medium5
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pho Restaurant
Medium5
Greedy, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Lefties vs. Righties
Medium5
Dynamic programming, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Graduation Table
Medium5
Graph, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Special Student Council President Replacement
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Reserved Seating 1
Medium5
Sorting, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Split the GSHS 2
Medium5
Dynamic programming, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
78 stairs descent contest
Medium5
Dynamic programming, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Phoenix Locks the Door
Medium5
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Construct a Graph
Medium5
Graph, Shortest path
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
MR.DR String
Medium5
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
First Bus
Medium5
Graph, Shortest path
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
The Beauty of Fireworks
Medium5
Dynamic programming, Tree+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Inequality Puzzle
Medium5
Graph, Topological sort
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Insung Lake Park
Medium5
Prefix sum, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Simple Permutation Problem
Medium5
Stack, Array
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Snowflake Tanghulu
Medium5
Hash map, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bubble Bubble
Medium5
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Yeongil Land
Medium5
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
EDF
Medium5
Greedy, Heap+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The K512 Cup Begins!
Medium5
Dynamic programming, Bit manipulation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Stacking Sticks
Medium5
Segment tree, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Binary Grid
Medium5
Dynamic programming, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dihedral Group
Medium5
String matching, Array
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
2024
Medium5
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sudoku
Medium5
Array, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
September
Medium5
Tree, Array+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Tightly Packed
Medium5
Math, Brute force
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Nightmare Brother
Medium5
Brute force, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Street Lamps
Medium5
Heap, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Merge Not Sort
Medium5
Greedy, Array+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Hiring Workers
Medium5
Prefix sum, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rock-Paper-Scissors
Medium5
Hash map, String
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Heater on the Farm
Medium5
Binary search, Array+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Card Game (Hard)
Medium5
Greedy, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Moving Freely
Medium5
Binary search, Math+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Communication System Performance Degradation
Medium5
Brute force, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Baseball
Medium5
Sorting, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Mountain
Medium5
Array, Two pointers
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Consecutive lectures are hard (Easy)
Medium5
Dynamic programming, Prefix sum
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Random Multi-Match
Medium5
String, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Secret of the Sequence (Hard)
Medium5
Divide and conquer, Recursion+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Rectangular Dry Land
Medium5
Matrix, Stack+1
No attempts yet
Time limit
7s
Memory limit
1024 MB
Judgeable
Weekend Gardening
Medium5
Dynamic programming, Probability
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fixing the Tournament
Medium5
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Speed Ups
Medium5
Dynamic programming, Sorting
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
I Am Going to Get Rich!
Medium5
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Harmony
Medium5
Dynamic programming, Array
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Daedong Yeojido Roads
Medium5
Minimum spanning tree, Union-find+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
I Want to Turn Back Time
Medium5
Binary search, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Deck Operations and Queries
Medium5
Tree, Stack+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Keunseong, Get to Work
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Too Hot!
Medium5
BFS, Graph+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gift Selection
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Fireworks
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Charging
Medium5
Segment tree, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Treasure Hunt
Medium5
Graph, Shortest path
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Business Magic
Medium5
Array, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Disbursement on Quarantine Policy
Medium5
Probability, Brute force+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Interference
Medium5
Prefix sum, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Queries are not locksGiven a string with single-character updates, answer range queries for the number of subsequences equal to ROCK, modulo 1000000007.	Medium5	Segment treeDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Escape the Ghost HouseFind the minimum time for Seokjun to walk from the entrance to the exit on a grid without entering the line of sight of any rotating ghost.	Medium5	BFSSimulation+1	No attempts yet	2s	1024 MB	Judgeable
Wiing WiingSort N points around Hyeok by the angle of a counterclockwise rotating ray from him, with nearer people first when two share a direction.	Medium5	SortingGeometry	No attempts yet	2s	1024 MB	Judgeable
FloodingGiven heights and queries (l, r, x), count the maximal runs of heights strictly above x that lie within positions l to r.	Medium5	ArraySorting+1	No attempts yet	2s	1024 MB	Judgeable
Group ProjectSplit N students with distinct IDs into pairs and one triple so that the sum of each team's max-min ID gap is minimized.	Medium5	SortingDynamic programming	No attempts yet	1s	512 MB	Judgeable
A Slightly Slow but Kind FriendFind the shortest route that leaves the university, visits each neighborhood once, and returns, while each photo follows its ordering constraint.	Medium5	Dynamic programmingBit manipulation+1	No attempts yet	1s	512 MB	Judgeable
Shortest CircuitGiven a grid of two-wire and single-wire knobs, find the fewest 90-degree spins that connect the two end knobs.	Medium5	Shortest pathGraph+1	No attempts yet	1s	1024 MB	Judgeable
AlleyGiven floats in street order, decide whether a single dead-end alley used as a stack can sort them by license plate.	Medium5	StackGreedy+1	No attempts yet	1s	1024 MB	Judgeable
DJ GigsDoug starts at venue 1 at time 0 and picks non-overlapping gigs, accounting for road travel times between venues, to maximize total pay.	Medium5	Dynamic programmingShortest path+2	No attempts yet	8s	1024 MB	Judgeable
Haybale DistributionGiven N barn positions and Q pairs (a, b), find for each pair the minimum total haybale waste when choosing a delivery point y in [0, 10^6].	Medium5	SortingPrefix sum+2	No attempts yet	2s	1024 MB	Judgeable
Cowntact Tracing 2Find the fewest starting infected cows that, spreading to adjacent cows each night, produce the given infected bitstring.	Medium5	GreedyDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
LiarsGiven N statements that each claim at least k or at most k people are lying, list every number of liars that makes the statements consistent.	Medium5	ArrayPrefix sum	No attempts yet	2s	1024 MB	Judgeable
Mirror BracketsGiven a string of mirror letters and brackets, apply the reflections until no brackets remain and print the final string.	Medium5	StackString+1	No attempts yet	1s	1024 MB	Judgeable
Graph TheoryRemove one edge from an n-cycle so that the largest shortest-path distance over m given vertex pairs is as small as possible.	Medium5	Segment treeGraph+1	No attempts yet	1s	1024 MB	Judgeable
Days of the weekEach button shifts its linked universes forward one weekday (mod 7). Decide whether every weekday configuration is reachable, and print an unreachable one if not.	Medium5	MatrixMath+1	No attempts yet	1s	1024 MB	Judgeable
Complete RoadGiven hole positions and segment length m, find the fewest damaged segments over all start offsets k from 1 to m, and list every k that reaches it.	Medium5	MathPrefix sum+1	No attempts yet	1s	1024 MB	Judgeable
EquipmentAssign each child a distinct kit from their interval [L_i, R_i], or report NO if no such assignment exists.	Medium5	GreedyUnion-find+1	No attempts yet	1s	1024 MB	Judgeable
Recover the SequenceGiven sums a_i + a_j for some index pairs, recover the hidden positive integer sequence a_0 through a_{n-1}.	Medium5	GraphMath+1	No attempts yet	1s	1024 MB	Judgeable
Tourism ProductGiven N beauty values, find the largest median over all contiguous segments of at least two attractions.	Medium5	Binary searchPrefix sum	No attempts yet	1s	1024 MB	Judgeable
Keep ClimbingGiven a sequence A, find the smallest window size k so that the sliding-window maxima of A form a non-decreasing sequence.	Medium5	StackSliding window+1	No attempts yet	0.7s	1024 MB	Judgeable
MiceGiven mice and cheese positions on a line, find the movement direction and the fewest hungry mice under two eating rules.	Medium5	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
TV GameFind the maximum sum of digits a ball collects while falling down a board, along with the starting column and one path that reaches it.	Medium5	Dynamic programmingMatrix	No attempts yet	1s	1024 MB	Judgeable
ShootingFind the smallest starting skill that lets a shooter, hitting the highest reachable target on each of at most M shots, reach a total score of A.	Medium5	SortingBinary search+1	No attempts yet	1s	1024 MB	Judgeable
TrainingPick at least one training from each situation so the total time stays within M hours and is as large as possible. Print -1 if no valid plan exists.	Medium5	Dynamic programmingArray	No attempts yet	1s	1024 MB	Judgeable
Soccer TournamentSelect 11 players, exactly one goalkeeper and at least one each of striker, midfielder, and defender, to maximize the sum of their assigned preference scores.	Medium5	Dynamic programmingGreedy	No attempts yet	1s	1024 MB	Judgeable
Distinct DigitsCount the integers in [A, B], where B can be up to 10^100, whose decimal digits are all distinct and have no leading zeros.	Medium5	Dynamic programmingBit manipulation+1	No attempts yet	1s	1024 MB	Judgeable
Toy DogGiven a move string S repeated K times, decide whether a walk starting at the origin returns to the origin after its first step.	Medium5	MathHash map+1	No attempts yet	1s	1024 MB	Judgeable
Compare Continued FractionsGiven two finite continued fractions, decide whether the rational number x is less than, equal to, or greater than y.	Medium5	MathArray	No attempts yet	2s	1024 MB	Judgeable
CandiesGiven n counts and a bonus of up to y for bobo 1, find the most candies bobo 1 can hold after m rounds, where each round the minimum (ties to the smallest label) gets x.	Medium5	HeapSimulation+1	No attempts yet	1s	1024 MB	Judgeable
The Pool for Lucky OnesGiven swimmer counts per lane, move single swimmers to adjacent lanes to minimize how many swimmers remain in the lanes with the maximum count.	Medium5	GreedyArray	No attempts yet	1s	1024 MB	Judgeable
Bridge BuildingGiven x logs of length a and y logs of length b, split them into l rows to maximize the smallest row total.	Medium5	Binary searchGreedy	No attempts yet	5.5s	1024 MB	Judgeable
Urban geographyPick a set of roads that keeps all districts connected while minimizing the gap between the most expensive and cheapest kept road, then print their numbers.	Medium5	Two pointersUnion-find+2	No attempts yet	2s	1024 MB	Judgeable
Overload PreventionGiven power strips with their socket counts, K wall outlets, and M devices with maximum strip-depth limits, find the most devices that can receive power.	Medium5	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
Military EnlistmentGiven daily volunteer points and a blood donation that blocks the next D days, find the fewest donations needed to reach at least M points, or -1 if impossible.	Medium5	Dynamic programmingPrefix sum+1	No attempts yet	1s	1024 MB	Judgeable
String Graph MatchingCount the substrings of T whose set of adjacent letter pairs is exactly the given set of M directed edges.	Medium5	Sliding windowString+1	No attempts yet	2s	1024 MB	Judgeable
Sinchon Merger PlanGiven N strings and the sequence of pairs where one string is appended to another and emptied, output the final merged string.	Medium5	Linked listString+1	No attempts yet	2s	1024 MB	Judgeable
Carrot Click GameGiven N speed effects with costs A_i and speed gains B_i, find the most carrots Eric can hold after K seconds of clicking and buying.	Medium5	Dynamic programmingGreedy	No attempts yet	2s	1024 MB	Judgeable
Card gameFind the fewest single-card moves to group the hand by suit with each suit sorted by number, and put the cyan cards last in increasing order.	Medium5	Dynamic programmingBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Supporting everyoneEach country is either supported with a pin for 1 or has its flag colours bought at 1 per colour; find the minimum total cost.	Medium5	GraphBFS	No attempts yet	0.25s	1024 MB	Judgeable
DP (Large)For each queried problem, find the longest subsequence of problems whose numbers and difficulties both strictly increase and that includes it.	Medium5	Dynamic programmingBinary search	No attempts yet	4s	1024 MB	Judgeable
Wine TastingPick K of N wines and order them so the sum of perceived tastes is maximized, where a step up from a worse wine to a better one counts as the difference.	Medium5	GreedySorting	No attempts yet	1s	512 MB	Judgeable
Pho RestaurantGiven n tables of binary dish orders, find the fewest contestants to move so every table serves one dish type.	Medium5	GreedyImplementation	No attempts yet	2s	1024 MB	Judgeable
Lefties vs. RightiesGiven T topics and N experts labeled rightie or leftie, pick at least one expert per topic with equal numbers of each label, minimizing the total interviewed.	Medium5	Dynamic programmingArray	No attempts yet	1s	1024 MB	Judgeable
Graduation TableGiven friend pairs with bribe values at a circular table where each person has at most two friends, choose which pairs to seat together to maximize total bribes.	Medium5	GraphGreedy	No attempts yet	1s	1024 MB	Judgeable
Special Student Council President ReplacementGiven N groups with vote counts and a total budget M, find the largest budget the Student Council can keep without being impeached.	Medium5	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
Reserved Seating 1Given the heights of M students who want each of N rows, decide whether every student can sit in a preferred row so that no column's view is blocked.	Medium5	SortingGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Split the GSHS 2Count the ways to split students 1 to N into consecutive groups, where each group's size is an endpoint leader's A plus 1, modulo 1e9+7.	Medium5	Dynamic programmingArray	No attempts yet	1s	1024 MB	Judgeable
78 stairs descent contestFind the maximum total score of a path from step 1 to step N, where opening chest i needs the previous visited step to be at least H_i+B_i tall.	Medium5	Dynamic programmingBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Phoenix Locks the DoorGiven N dials showing letters, find the lexicographically smallest string after turning single dials exactly K times, with each turn advancing a letter and wrapping Z to A.	Medium5	GreedyString+1	No attempts yet	1s	1024 MB	Judgeable
Construct a GraphGiven an N x N distance matrix, build a connected weighted graph whose shortest-path distances match it with minimum total edge weight, or report -1 if none exists.	Medium5	GraphShortest path	No attempts yet	1s	1024 MB	Judgeable
MR.DR StringCount the length-N uppercase strings that contain MRDR as a subsequence, modulo 1,000,000,007.	Medium5	CombinatoricsMath+1	No attempts yet	1s	1024 MB	Judgeable
First BusFind the minimum time to travel from building 1 to building N, where sidewalks work anytime but buses on roads can only be taken from time K onward.	Medium5	GraphShortest path	No attempts yet	2s	1024 MB	Judgeable
The Beauty of FireworksGiven a tree with weight W_i on each node, pick one node a so that the sum of W_b times the distance from a to every other node b is maximized.	Medium5	Dynamic programmingTree+1	No attempts yet	3s	1024 MB	Judgeable
Inequality PuzzleFill an N by N grid with each integer from 1 to N^2 once so that every adjacent pair satisfies its given < or > sign.	Medium5	GraphTopological sort	No attempts yet	2s	1024 MB	Judgeable
Insung Lake ParkGiven a ring of fork paths a_i and gate spurs b_i, find the longest walk between two different gates that never reuses a path.	Medium5	Prefix sumArray	No attempts yet	1s	1024 MB	Judgeable
Simple Permutation ProblemCount position pairs i < j in a permutation where both values are larger than every element strictly between them.	Medium5	StackArray	No attempts yet	1s	1024 MB	Judgeable
Snowflake TanghuluGiven fruit positions and candidate endpoints, find the most fruits one skewer from (0, 0) to a candidate endpoint can pierce.	Medium5	Hash mapMath+2	No attempts yet	2s	512 MB	Judgeable
Bubble BubbleGiven distinct integers, find the fewest operations to sort them using adjacent swaps, where one whole-array reversal (allowed once) also counts as one operation.	Medium5	ArraySorting+1	No attempts yet	1s	1024 MB	Judgeable
Yeongil LandFind the longest directed route from the gate that rides each of N rides (N up to 9) exactly once and returns to the gate.	Medium5	Dynamic programmingBit manipulation+1	No attempts yet	1s	1024 MB	Judgeable
EDFGiven N existing jobs and M jobs arriving later, simulate earliest-deadline-first scheduling with preemption and report whether all jobs finish, and the finish time if they do.	Medium5	GreedyHeap+1	No attempts yet	1s	1024 MB	Judgeable
The K512 Cup Begins!Starting from 0, use all N add-scrolls and M multiply-scrolls in some order to find the maximum final luck value.	Medium5	Dynamic programmingBit manipulation	No attempts yet	1s	512 MB	Judgeable
Stacking SticksDrop 1x4 horizontal and 4x1 vertical blocks onto columns, then report the highest block height at a given x coordinate.	Medium5	Segment treeSorting+1	No attempts yet	1s	512 MB	Judgeable
Binary GridFind the largest binary number spelled by the digits along a right-or-down path from the top-left to the bottom-right of a 0/1 grid.	Medium5	Dynamic programmingGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Dihedral GroupCheck whether the sequence t appears as a contiguous block in some rotation or reflection of the circular labeling d.	Medium5	String matchingArray	No attempts yet	1s	2048 MB	Judgeable
2024Decide whether a digit string can be built from English digit words, where each word is either a digit or a repeat count for the next word's digit.	Medium5	Dynamic programmingString	No attempts yet	1s	1024 MB	Judgeable
SudokuAfter each of M writes into an N^2 by N^2 grid, print 1 if the grid is a valid sudoku with special squares, otherwise print 0.	Medium5	ArrayImplementation	No attempts yet	2s	1024 MB	Judgeable
SeptemberGiven M recorded orders of leaf deletions in a rooted tree, find the largest K such that all records agree on which nodes fall on each of the K days.	Medium5	TreeArray+1	No attempts yet	1s	1024 MB	Judgeable
Tightly PackedGiven N widgets, find the fewest empty cells in a W by H box with H/2 <= W <= 2H that holds all N widgets.	Medium5	MathBrute force	No attempts yet	1s	1024 MB	Judgeable
Nightmare BrotherGiven N hints placing substrings in a length-M string, with at most one hint false, print the unique possible string, -1 if none exists, or -2 if several do.	Medium5	Brute forceString+1	No attempts yet	2s	1024 MB	Judgeable
Street LampsGiven lamp positions on a line, list the K smallest distances from integer positions 0 to L to the nearest lamp, in increasing order.	Medium5	HeapSorting+1	No attempts yet	2s	1024 MB	Judgeable
Merge Not SortSplit a permutation of 1 to 2N into two length-N arrays A and B so that the merge routine outputs it, or report -1 if no split works.	Medium5	GreedyArray+1	No attempts yet	2s	1024 MB	Judgeable
Hiring WorkersCount contiguous groups of workers with equal numbers of task 1 and task 2 workers whose efficiency sums differ by at most K.	Medium5	Prefix sumHash map+1	No attempts yet	2s	1024 MB	Judgeable
Rock-Paper-ScissorsFind the fewest rounds in which Pidol's moves leave between 1 and K friends, and print the moves that achieve it.	Medium5	Hash mapString	No attempts yet	1s	1024 MB	Judgeable
Heater on the FarmGiven N cows in a line with frozen degrees a_j, place one heater on a cow so the largest a_j times its distance to the heater is as small as possible, and print that value.	Medium5	Binary searchArray+1	No attempts yet	2s	1024 MB	Judgeable
Card Game (Hard)Given health H and a set of attack values that grows by one card per query, find the fewest cards whose attacks sum to at least H, or -1 if impossible.	Medium5	GreedyBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Moving FreelyGiven obstacles on a number line, count the positions Huynh can reach after T one-meter moves from P without stepping on an obstacle.	Medium5	Binary searchMath+1	No attempts yet	4s	1024 MB	Judgeable
Communication System Performance DegradationGiven a grid with one base station and M nodes, find the largest value of path loss minus bounding box area when exactly K1 nodes (day) or K2 nodes (night) are activated.	Medium5	Brute forceGreedy+1	No attempts yet	1s	1024 MB	Judgeable
BaseballGiven batted ball positions and candidate fence radii, count the foul balls, infield balls, and home runs for each radius.	Medium5	SortingBinary search+1	No attempts yet	1s	1024 MB	Judgeable
MountainCount the contiguous subarrays that never decrease before a peak and never increase after it, with N up to 500000.	Medium5	ArrayTwo pointers	No attempts yet	1s	1024 MB	Judgeable
Consecutive lectures are hard (Easy)Count the timetables that include every mandatory period and whose longest run of consecutive chosen periods is exactly k, modulo 1e9+7.	Medium5	Dynamic programmingPrefix sum	No attempts yet	1s	1024 MB	Judgeable
Random Multi-MatchGiven a cyclic A/B string, sum the number of games each best-of-g match plays, starting from position s and wrapping around the board games.	Medium5	StringPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
Secret of the Sequence (Hard)Given a sequence where a_2i and a_2i+1 are linear functions of a_i, find the sum of the first 2^k-1 terms modulo 1e9+7.	Medium5	Divide and conquerRecursion+1	No attempts yet	1s	1024 MB	Judgeable
Rectangular Dry LandGiven a binary grid of wet and dry cells, find the area of the largest rectangle made only of dry cells.	Medium5	MatrixStack+1	No attempts yet	7s	1024 MB	Judgeable
Weekend GardeningFind the probability that buying plants one at a time, each drawn from the remaining stock, keeps the running total within the budget range from L to H.	Medium5	Dynamic programmingProbability	No attempts yet	1s	1024 MB	Judgeable
Fixing the TournamentGiven n and your team's rank r in a bracket of 2^n single-elimination teams, find the latest round your team can reach when you choose every pairing.	Medium5	MathGreedy	No attempts yet	1s	1024 MB	Judgeable
Speed UpsGiven speed-up boosts at fixed meter marks, find the fastest finishing time when a taken boost blocks any other boost until it ends.	Medium5	Dynamic programmingSorting	No attempts yet	2s	1024 MB	Judgeable
I Am Going to Get Rich!Given N dial digits, find the smallest resulting number after exactly M turns, where each turn adds 1 to one digit modulo 10.	Medium5	GreedyString+1	No attempts yet	1s	1024 MB	Judgeable
HarmonyChoose trainings within time N to maximize energy, doubling it when the harmony sum is 0, then print that harmony sum and energy.	Medium5	Dynamic programmingArray	No attempts yet	2s	1024 MB	Judgeable
Daedong Yeojido RoadsBuild a minimum-cost road network that connects all places, breaking cost ties by road-type priority, and report the count and cost of each road type.	Medium5	Minimum spanning treeUnion-find+2	No attempts yet	1s	1024 MB	Judgeable
I Want to Turn Back TimeGiven N days and a powered-on array A, find the minimum T so that at most K jumps of T days back, each taken on a powered day, get you from day N to day 1.	Medium5	Binary searchDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Deck Operations and QueriesProcess N deck actions (push, pop, restore to an earlier action's state, print the card sum) and output the sum for each print.	Medium5	TreeStack+1	No attempts yet	2s	1024 MB	Judgeable
Keunseong, Get to WorkTrash is added at tree coordinates, and each clear query walks to the nearest remaining tree, with ties going to the smaller coordinate. Output the total distance walked.	Medium5	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
Too Hot!Find the fewest moves from house S to meeting place E on a grid where discomfort rises outdoors, falls indoors, and must stay below 100.	Medium5	BFSGraph+1	No attempts yet	1s	1024 MB	Judgeable
Gift SelectionGiven gift sizes, box sizes, and the boxes taken by K earlier winners, find the largest gift you can take from the largest remaining box over all valid assignments.	Medium5	GreedySorting+1	No attempts yet	2s	1024 MB	Judgeable
FireworksGiven firecracker brilliances and a threshold K, find the most shows you can build from single or paired firecrackers, each at least K and in non-decreasing order.	Medium5	GreedySorting+1	No attempts yet	1s	1024 MB	Judgeable
ChargingEach plug request takes the smallest empty port numbered at least i, and each unplug query reports which action filled that port.	Medium5	Segment treeImplementation+1	No attempts yet	2s	1024 MB	Judgeable
Treasure HuntFor each island x, find the maximum of v_y minus the cheapest sea route cost from x to any island y.	Medium5	GraphShortest path	No attempts yet	4s	1024 MB	Judgeable
Business MagicPick one interval to double, and negate each negative store outside it, to maximize the total profit for next month.	Medium5	ArrayDynamic programming	No attempts yet	2s	1024 MB	Judgeable
Disbursement on Quarantine PolicyGiven a seat grid with known infections and 50% uncertain ones, find the expected total quarantine days modulo 1e9+7.	Medium5	ProbabilityBrute force+1	No attempts yet	2s	1024 MB	Judgeable
InterferenceEach wave adds a period-4 pattern of +a and -a over an interval, and each query asks for the summed height at one position.	Medium5	Prefix sumMath+1	No attempts yet	1s	1024 MB	Judgeable