Interview core

Mediums from real onsites

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Total results3,613 problems

Dark Tunnel
Medium5
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Being a Celebrity Is Hard
Medium5
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Tribal War
Medium5
Combinatorics, Math+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Carpool Matching
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Crazy_aRcade_Good
Medium5
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Next Greater Element
Medium5
Stack, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Stars Falling from the Sky: 1, 2, ..., R-L+1 of Them
Medium5
Prefix sum, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Segment Intersection 1
Medium5
Geometry, Math+2
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Backdoor
Medium5
Shortest path, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
FLEX
Medium5
Dynamic programming, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sum of Divisors
Medium5
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Course Basket
Medium5
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Go Stone Jump
Medium5
Backtracking, Matrix+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Promoting a Club
Medium5
Tree, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Brazilian Popcorn Marathon
Medium5
Binary search, Greedy+2
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Strings
Medium5
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Analogue Cluster
Medium5
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Summer Trip
Medium5
String, Two pointers+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Palindrome
Medium5
String, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Four Squares
Medium5
Dynamic programming, Math+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Efficient Exchange
Medium5
Dynamic programming, Greedy+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Find my Family
Medium5
Array, Prefix sum+2
No attempts yet
Time limit
7s
Memory limit
512 MB
Judgeable
Ballpark Estimate
Medium5
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Zoo
Medium5
Graph, BFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Snail List
Medium5
Linked list, Array+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
String Currency
Medium5
Greedy, Implementation+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Save the Princess!
Medium5
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Course Selection
Medium5
Dynamic programming, Array+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Retribution!
Medium5
Greedy, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Musical Chairs
Medium5
Simulation, Queue+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Typo
Medium5
Hash map, String+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Meow Factor 2
Medium5
String, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fishmongers
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Keyboards in Concert
Medium5
Dynamic programming, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Pokémon Ice Maze
Medium5
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drop The Byte!
Medium5
Implementation, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Snowball
Medium5
Math, Prefix sum+2
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Dessert
Medium5
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Fire on Field
Medium5
Brute force, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
What's Mine is Mine
Medium5
Dynamic programming, Sorting+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Levenshtein Distance
Medium5
String, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Balanced Animals
Medium5
Sorting, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
From A to B
Medium5
Greedy, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Alphabet Animals
Medium5
Hash map, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cheese Game
Medium5
Dynamic programming, Array
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Election Meddling
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Move & Meet
Medium5
Math, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Accurate Movement
Medium5
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Managing Difficulties
Medium5
Hash map, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Height Profile
Medium5
Array, Two pointers+1
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Inverted Deck
Medium5
Array, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Kitesurfing
Medium5
Graph, Shortest path+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Matches
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Black Friday
Medium5
Two pointers, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Word Memorization
Medium5
Bit manipulation, Hash map+2
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Riyuna Likes Sailor Uniforms
Medium5
Greedy, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Rush Hour Puzzle
Medium5
BFS, Simulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Length of Bundle Rope
Medium5
Greedy, Heap+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Speeding
Medium5
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Saba1000kg
Medium5
Graph, Union-find+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Buying Ramen (Small)
Medium5
Greedy, Dynamic programming+2
No attempts yet
Time limit
0.5s
Memory limit
32 MB
Judgeable
Minjun, Masan, and Gunwoo
Medium5
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Teleport Station
Medium5
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
SHOP
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
BNKQ
Medium5
Simulation, Heap+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Wise Knight
Medium5
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Competitive Contagion
Medium5
BFS, Simulation+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Stacking Blocks Together
Medium5
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Building a Large Number
Medium5
Greedy, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
DNA evolution
Medium5
String, String matching
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binomial
Medium5
Combinatorics, Bit manipulation+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Palindrome
Medium5
String, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Unstable Substances
Medium5
Graph, Dynamic programming+2
No attempts yet
Time limit
1.2s
Memory limit
256 MB
Judgeable
Attaching Stickers
Medium5
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Iguana Instructions
Medium5
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Multiverse I
Medium5
Sorting, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Favorite Colors
Medium5
Union-find, Graph
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Gravity
Medium5
Simulation, BFS+1
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Octopus
Medium5
Graph, Implementation
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Euclid
Medium5
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bar "Duck"
Medium5
Two pointers, Array
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Elections
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Bracket Strings
Medium5
String, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
A Really Odd Sequence
Medium5
Array, Dynamic programming+2
No attempts yet
Time limit
6s
Memory limit
512 MB
Judgeable
Waiter's Problem
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Highly Composite Permutations
Medium5
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Apple Tree
Medium5
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Toy Car Race
Medium5
Math, Binary search+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Prime Game
Medium5
Dynamic programming, Game theory+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Reversing Strings
Medium5
Greedy, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Minimum Number of Conference Rooms
Medium5
Sorting, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Escape Room
Medium5
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Meeting Room Scheduling 4
Medium5
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Sirtet
Medium5
Simulation, BFS+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mountains
Medium5
Array, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Experimental Charges
Medium5
Union-find, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
How Many Tests
Medium5
Implementation, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Different digits
Medium5
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Typing Trouble
Medium5
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Birthday
Medium5
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Dark TunnelStreetlights sit at fixed positions along a tunnel from 0 to N, each lighting H units left and right; find the smallest integer H that covers the whole road.	Medium5	Binary searchGreedy+2	No attempts yet	1s	256 MB	Judgeable
Being a Celebrity Is HardGiven a weighted undirected graph and two starting nodes, pick a meeting node minimizing the sum of both shortest distances and breaking ties by Jiheon's distance then index.	Medium5	Shortest pathGraph+1	No attempts yet	1s	256 MB	Judgeable
Tribal WarGiven N tribes where listed pairs are allied and all other pairs are hostile, count the number of triples that are all allied or all hostile.	Medium5	CombinatoricsMath+2	No attempts yet	3s	512 MB	Judgeable
Carpool MatchingEach passenger has a destination point and each driver accepts a closed interval of destinations; match the maximum number of passenger-driver pairs.	Medium5	GreedySorting+2	No attempts yet	3s	512 MB	Judgeable
Crazy_aRcade_GoodGiven a 10x10 board with bombs and a start cell, find the fewest moves to reach a cell not sharing a row or column with any bomb.	Medium5	BFSGraph+2	No attempts yet	1s	256 MB	Judgeable
Next Greater ElementFor each element of a sequence, output the nearest greater value to its right, or -1 if none exists.	Medium5	StackArray+2	No attempts yet	1s	512 MB	Judgeable
Stars Falling from the Sky: 1, 2, ..., R-L+1 of ThemMaintain an array where a range update adds 1,2,...,R-L+1 to positions L..R, and point queries ask the current total at one index.	Medium5	Prefix sumArray+2	No attempts yet	1s	512 MB	Judgeable
Segment Intersection 1Given the integer endpoints of two segments, decide whether the segments intersect, using orientation tests with no three input points collinear.	Medium5	GeometryMath+2	No attempts yet	0.25s	512 MB	Judgeable
BackdoorFind the shortest travel time from junction 0 to junction N-1 in an undirected weighted graph, where every intermediate junction marked visible is blocked and only the Nexus may be entered.	Medium5	Shortest pathGraph+2	No attempts yet	2s	512 MB	Judgeable
FLEXDistribute M extra ten-thousand-won units among N days to minimize the sum of squared drops between consecutive daily spends.	Medium5	Dynamic programmingGreedy+2	No attempts yet	2s	512 MB	Judgeable
Sum of DivisorsGiven N up to 10^6 and 10^5 test cases, compute g(N), the sum of the divisor sums f(y) for all y from 1 to N.	Medium5	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Course BasketGiven seat caps and two rounds of course requests per student, decide which courses each student gets, breaking ties by student order within each round.	Medium5	ImplementationSimulation+2	No attempts yet	2s	256 MB	Judgeable
Go Stone JumpGiven an N by N board of walls, empty cells, and stones, decide whether repeated jumps over adjacent stones can leave exactly one stone.	Medium5	BacktrackingMatrix+1	No attempts yet	1s	256 MB	Judgeable
Promoting a ClubGiven a forest, choose the fewest vertices so that every vertex is either chosen or adjacent to a chosen one (minimum dominating set on a forest).	Medium5	TreeDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
Brazilian Popcorn MarathonSplit a row of popcorn bags into at most C contiguous segments, minimizing the maximum segment sum given each competitor eats at most T per second.	Medium5	Binary searchGreedy+2	No attempts yet	1.5s	512 MB	Judgeable
StringsBuild strings by concatenating earlier strings or slicing a substring, then output the sum of ASCII codes of the final string modulo 1e9+7, without materializing the possibly huge string.	Medium5	Dynamic programmingString+2	No attempts yet	2s	512 MB	Judgeable
Analogue ClusterGiven n vertices with widths and c edges, recolor the fewest vertices so every edge joins equal widths, per connected component.	Medium5	GraphGreedy+2	No attempts yet	1s	512 MB	Judgeable
Summer TripGiven a string of event types, count contiguous substrings of length at least two whose first and last characters are distinct and each appears only once in the substring.	Medium5	StringTwo pointers+2	No attempts yet	3s	1024 MB	Judgeable
PalindromeFor each string, print 0 if it is a palindrome, 1 if deleting one character makes it a palindrome, or 2 otherwise.	Medium5	StringTwo pointers+2	No attempts yet	1s	512 MB	Judgeable
Four SquaresGiven n up to 50,000, print the minimum number of perfect squares whose sum equals n.	Medium5	Dynamic programmingMath+2	No attempts yet	0.5s	512 MB	Judgeable
Efficient ExchangeGiven a payment amount, minimize the total number of power-of-10 coins exchanged in both directions, allowing both sides to give change.	Medium5	Dynamic programmingGreedy+2	No attempts yet	3s	512 MB	Judgeable
Find my FamilyFor each photo, decide whether some arrangement lets Alice (taller than you) stand left of you and Bob (taller than both) stand right of you.	Medium5	ArrayPrefix sum+2	No attempts yet	7s	512 MB	Judgeable
Ballpark EstimateGiven n up to 1e18, print the closest number that has a single non-zero digit, breaking ties toward the larger value.	Medium5	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
ZooGiven an R by C grid of T, B, and * footprints, find the minimum number of animals that could have left them.	Medium5	GraphBFS+1	No attempts yet	2s	512 MB	Judgeable
Snail ListA linked list has a tail node N pointing back to node V, forming one cycle. For each query K, report the value stored in the node reached after moving K steps from node 1.	Medium5	Linked listArray+2	No attempts yet	1s	256 MB	Judgeable
String CurrencyFind the lexicographically smallest string of length N over A-Z, where letter values 1 to 26 sum to exactly X, or print ! if impossible.	Medium5	GreedyImplementation+1	No attempts yet	1s	256 MB	Judgeable
Save the Princess!Given an N by M grid with walls and one sword cell, find the minimum steps from (1,1) to (N,M) within T, where the sword lets the hero pass through walls afterward.	Medium5	BFSGraph+2	No attempts yet	1s	256 MB	Judgeable
Course SelectionChoose courses with given importance and study time so total time stays within N and total importance is maximized.	Medium5	Dynamic programmingArray+2	No attempts yet	1s	512 MB	Judgeable
Retribution!Assign tar repositories and feather storehouses to judges one at a time by repeatedly taking the closest remaining pair, breaking ties by lowest index, and report the total distance.	Medium5	GreedyImplementation+2	No attempts yet	2s	512 MB	Judgeable
Musical ChairsSimulate the Josephus elimination where each eliminated person's own number k sets the next count length, and print the last survivor.	Medium5	SimulationQueue+2	No attempts yet	1s	512 MB	Judgeable
TypoGiven a dictionary of unique words, print each word that becomes another dictionary word after deleting exactly one character, in input order.	Medium5	Hash mapString+2	No attempts yet	6s	512 MB	Judgeable
Meow Factor 2Given a lowercase string, find the minimum number of insert, delete, replace, or adjacent swap operations needed to make "meow" appear as a substring.	Medium5	StringDynamic programming	No attempts yet	2s	512 MB	Judgeable
FishmongersAssign each fish to a fishmonger with a weight limit and per-kilogram price so total earnings are maximized.	Medium5	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Keyboards in ConcertGiven n keyboards, the sets of notes each can play, and the note sequence of a tune, find the minimum number of keyboard switches needed to play the whole tune.	Medium5	Dynamic programmingHash map+2	No attempts yet	1s	512 MB	Judgeable
Pokémon Ice MazeIn an ice maze where a full glide over ice counts as one move, find the fewest moves from each cell to the goal, or -1 if unreachable.	Medium5	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Drop The Byte!Given a hex string and a sequence of type sizes (char 2 digits, int 8, long_long 16), split the string and print each piece as a decimal value.	Medium5	ImplementationString+2	No attempts yet	1s	256 MB	Judgeable
SnowballSnowballs form at each altitude with size 1 and multiply by x each centimeter they descend; find the total size of all snowballs modulo 1e9+7.	Medium5	MathPrefix sum+2	No attempts yet	0.5s	256 MB	Judgeable
DessertEach day pick one of M desserts to maximize total satisfaction, where repeating the same dessert halves that day's value (rounded down).	Medium5	Dynamic programmingGreedy+2	No attempts yet	1s	256 MB	Judgeable
Fire on FieldDefine a sequence where each term is the smallest positive integer that avoids forming an arithmetic progression with any earlier pair at equal spacing, and print the n-th term.	Medium5	Brute forceImplementation+1	No attempts yet	1s	512 MB	Judgeable
What's Mine is MinePick non-overlapping ore intervals to maximize total value, where each interval's value is its duration times its mineral's price.	Medium5	Dynamic programmingSorting+2	No attempts yet	0.5s	512 MB	Judgeable
Levenshtein DistanceGiven an alphabet and a string s, list every distinct string over that alphabet whose Levenshtein distance from s is exactly 1, sorted alphabetically.	Medium5	StringBrute force+2	No attempts yet	1s	512 MB	Judgeable
Balanced AnimalsFind the smallest integer threshold t that splits the animals by weight into two groups of equal total weight, handling ties at t by pairing them off.	Medium5	SortingPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
From A to BGiven two integers a and b, find the minimum number of operations (divide an even number by two, or add one) needed to turn a into b.	Medium5	GreedyBit manipulation+2	No attempts yet	1s	512 MB	Judgeable
Alphabet AnimalsGiven the previous animal and a list of unused names, pick a playable name that leaves the next player with no valid move, preferring that over any playable name.	Medium5	Hash mapImplementation+2	No attempts yet	2s	512 MB	Judgeable
Cheese GameGiven n cheese slices with deliciousness values, Alice and Bob alternately eat sets of non-adjacent slices; find the maximum total Alice can get under optimal play.	Medium5	Dynamic programmingArray	No attempts yet	2s	512 MB	Judgeable
Election MeddlingGiven each district's vote counts per party, find the minimum number of voters to bribe so party 1 wins a strict majority of districts, each by a strict margin.	Medium5	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Move & MeetTwo pieces start at given grid cells and each must make exactly d orthogonal steps; decide whether some cell can be the common endpoint, and print one.	Medium5	MathImplementation+2	No attempts yet	2s	512 MB	Judgeable
Accurate MovementTwo bars of lengths a and b sit on parallel rails in a 2 by n box; move one bar at a time keeping the short bar between the long bar's stoppers, and find the fewest moves to shift both from one side to the other.	Medium5	MathGreedy+1	No attempts yet	2s	512 MB	Judgeable
Managing DifficultiesCount triples of increasing indices i < j < k where a[j] - a[i] equals a[k] - a[j], so a[i] + a[k] = 2*a[j].	Medium5	Hash mapCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Height ProfileGiven heights at each integer kilometre, find the longest interval whose average incline is at least each queried grade, or report impossible if none exists.	Medium5	ArrayTwo pointers+1	No attempts yet	6s	512 MB	Judgeable
Inverted DeckGiven a sequence, find one contiguous segment whose reversal makes the whole sequence non-decreasing, or report that no such segment exists.	Medium5	ArrayGreedy+2	No attempts yet	5s	512 MB	Judgeable
KitesurfingFind the minimum time for Nora to reach the finish by surfing open water or jumping up to d metres over islands, each jump costing t seconds.	Medium5	GraphShortest path+1	No attempts yet	4s	512 MB	Judgeable
MatchesAssign N participants to rooms 1..N so that the number of participants whose passport number equals their room number is maximized.	Medium5	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
Black FridayGiven up to 5000 distinct item weights, decide whether 1, 2, or 3 of them sum exactly to a target C.	Medium5	Two pointersSorting+2	No attempts yet	1s	1024 MB	Judgeable
Word MemorizationTrack which letters are currently remembered and, after each forget or recall query, report how many dictionary words contain only remembered letters.	Medium5	Bit manipulationHash map+2	No attempts yet	4s	1024 MB	Judgeable
Riyuna Likes Sailor UniformsGiven N shirt widths and M collar widths, a collar of width c fits a shirt of width w if w/2 <= c <= 3w/4 or w <= c <= 5w/4; find the maximum number of valid shirt-collar pairs.	Medium5	GreedyTwo pointers+2	No attempts yet	1s	256 MB	Judgeable
Rush Hour PuzzleFind the fewest steps to slide the red car (id 1) out of the right exit of row 3 on a 6x6 board, or print -1 if it needs more than 10.	Medium5	BFSSimulation+1	No attempts yet	2s	1024 MB	Judgeable
Length of Bundle RopeGiven the sizes of n parcels, repeatedly join two bundles at a time and pay the sum of their sizes, finding the total cost that ties everything into one bundle for the least rope.	Medium5	GreedyHeap+2	No attempts yet	2s	1024 MB	Judgeable
SpeedingGiven positions and times of a car at checkpoints, find the largest integer speed the car must have reached at some moment.	Medium5	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Saba1000kgGiven an undirected graph and many vertex subsets, count the connected components induced by each subset. Each subset is queried independently.	Medium5	GraphUnion-find+1	No attempts yet	2s	512 MB	Judgeable
Buying Ramen (Small)Buy exactly Ai packs from each factory using 1-pack, 2-pack, or 3-pack deals with different costs, minimizing total money.	Medium5	GreedyDynamic programming+2	No attempts yet	0.5s	32 MB	Judgeable
Minjun, Masan, and GunwooGiven an undirected weighted graph, check whether vertex P lies on some shortest path from vertex 1 to vertex V.	Medium5	GraphShortest path+2	No attempts yet	1s	256 MB	Judgeable
Teleport StationGiven N points in a line, edges between x-1 and x+1, plus M teleport connections, find the shortest time from S to E.	Medium5	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
SHOPGiven an amount to return and a limited supply of each bill denomination, choose bills of the highest denominations so the total equals the amount.	Medium5	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
BNKQCustomers arrive over time and each joins the shortest counter queue; find the total time until the last customer finishes being served.	Medium5	SimulationHeap+2	No attempts yet	2s	512 MB	Judgeable
Wise KnightGiven a knight's start square on an N by N board, find the minimum knight moves to reach each of M target squares.	Medium5	BFSGraph+2	No attempts yet	1s	256 MB	Judgeable
Competitive ContagionSimulate a grid where each cell's virus spreads to four neighbors every second, with lower-numbered viruses spreading first and blocking others, then report the virus at one cell after S seconds.	Medium5	BFSSimulation+2	No attempts yet	1s	256 MB	Judgeable
Stacking Blocks TogetherEach of N students offers a set of distinct block sizes, at most one block per student is used, and we count subsets of students whose chosen blocks sum to exactly H modulo 10007.	Medium5	Dynamic programmingPrefix sum+2	No attempts yet	1s	256 MB	Judgeable
Building a Large NumberGiven N and a digit set K (size 1 to 3), find the largest number at most N whose digits all come from K.	Medium5	GreedyBacktracking+2	No attempts yet	1s	256 MB	Judgeable
DNA evolutionGiven the Z-array of an unknown DNA string over A, C, G, and T, find the lexicographically smallest string that produces it, or report Impossible.	Medium5	StringString matching	No attempts yet	2s	512 MB	Judgeable
BinomialGiven a sequence, count ordered pairs (i, j) where the binomial coefficient C(a_i, a_j) is odd, using the Lucas theorem bit condition.	Medium5	CombinatoricsBit manipulation+2	No attempts yet	5s	512 MB	Judgeable
PalindromeGiven a binary string, find the fewest moves of one character to the end that turn it into a palindrome, or report -1 if that is impossible.	Medium5	StringGreedy+1	No attempts yet	1s	512 MB	Judgeable
Unstable SubstancesEach substance conflicts with exactly one other; choose a subset with no conflicting pair to maximize total weight.	Medium5	GraphDynamic programming+2	No attempts yet	1.2s	256 MB	Judgeable
Attaching StickersPlace each sticker in order on a rectangular laptop, trying rotations 0, 90, 180, 270 and picking the topmost then leftmost valid spot; output the total filled cells.	Medium5	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
Iguana InstructionsGiven an n by n grid with blocked cells, find the minimum number of straight-line moves (direction plus distance) to walk from the top-left to the bottom-right.	Medium5	BFSGraph+2	No attempts yet	1s	512 MB	Judgeable
Multiverse ITwo universes are equal when their size arrays induce the same ordering and tie pattern. Replace each array by its rank pattern and count equal pairs.	Medium5	SortingHash map+2	No attempts yet	1s	512 MB	Judgeable
Favorite ColorsCows that admire the same cow must share a color; assign colors to maximize the count of distinct colors, lexicographically smallest.	Medium5	Union-findGraph	No attempts yet	1s	512 MB	Judgeable
GravityEach 4-connected group of # cells falls straight down until it reaches the floor or lands on another piece. The task is to print the final grid.	Medium5	SimulationBFS+1	No attempts yet	1.5s	256 MB	Judgeable
OctopusGiven an octopus-shaped graph with one extra edge added, find the two endpoints of that extra edge.	Medium5	GraphImplementation	No attempts yet	2s	256 MB	Judgeable
EuclidGiven three points in 3D space, find a point minimizing the sum of Euclidean distances to all three.	Medium5	GeometryMath+2	No attempts yet	1s	512 MB	Judgeable
Bar "Duck"Trash pieces on a table of length L must be flung off within T seconds using at most E energy; find the longest clean gap that can be made.	Medium5	Two pointersArray	No attempts yet	5s	256 MB	Judgeable
ElectionsChoose the fewest polling stations to cancel so that candidate n's total votes are not strictly greater than every other candidate's total.	Medium5	GreedySorting+2	No attempts yet	3s	512 MB	Judgeable
Bracket StringsGiven a string of brackets and wildcards, find the fewest characters to delete so the rest can become a balanced bracket string.	Medium5	StringDynamic programming	No attempts yet	1s	256 MB	Judgeable
A Really Odd SequenceGiven a sequence of integers, find the maximum sum of a contiguous subarray whose length is odd.	Medium5	ArrayDynamic programming+2	No attempts yet	6s	512 MB	Judgeable
Waiter's ProblemGiven tip amounts that decay by one per minute of waiting, choose a serving order to maximize the total tips collected.	Medium5	GreedySorting+2	No attempts yet	1s	512 MB	Judgeable
Highly Composite PermutationsFind a permutation of 1 to n whose every prefix sum is a composite number, or report that none exists.	Medium5	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Apple TreeGiven N target heights, decide whether a 1-unit and a 2-unit watering can, used simultaneously on trees (or together on one tree), can reach exactly those heights.	Medium5	GreedyMath+2	No attempts yet	1s	1024 MB	Judgeable
Toy Car RaceFind the smallest booster distance Z (at most Y, whole meters per second for one second) so your car finishes the X-meter race strictly faster than every other car.	Medium5	MathBinary search+2	No attempts yet	1s	256 MB	Judgeable
Prime GameGiven A and k, find the start x that lets Bob win the most of the k prime subtraction games from x to x+k-1, and output that win count with the smallest such x.	Medium5	Dynamic programmingGame theory+2	No attempts yet	1s	256 MB	Judgeable
Reversing StringsFor each string choose to reverse it or not so the sequence becomes lexicographically sorted, and output the lexicographically smallest such 0-1 choice string.	Medium5	GreedyString+2	No attempts yet	1s	256 MB	Judgeable
Minimum Number of Conference RoomsGiven N meetings with start and end times, find the minimum number of rooms so that no two overlapping meetings share a room, where a meeting may start exactly when another ends.	Medium5	SortingGreedy+2	No attempts yet	2s	256 MB	Judgeable
Escape RoomGiven an M by N grid of integers, start at (1,1) and jump from cell value x to any cell (a,b) with a*b=x, staying inside the grid; decide if (M,N) is reachable.	Medium5	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Meeting Room Scheduling 4Choose a set of non-overlapping meetings, where touching endpoints are allowed, to maximize the total number of attendees.	Medium5	Dynamic programmingSorting+2	No attempts yet	1s	256 MB	Judgeable
SirtetConnected groups of filled cells fall straight down as rigid objects until each lands on the bottom row or on another object. Print the final grid.	Medium5	SimulationBFS+1	No attempts yet	2s	512 MB	Judgeable
MountainsCount triples x < y < z where the middle mountain y is strictly taller than both mountain x and mountain z.	Medium5	ArrayCombinatorics+2	No attempts yet	2s	256 MB	Judgeable
Experimental ChargesParticles carry unknown plus or minus charges; process attract/repel observations online and answer whether a queried pair must attract, must repel, or is unconstrained.	Medium5	Union-findGraph+2	No attempts yet	2s	512 MB	Judgeable
How Many TestsGiven some surviving file names (equal length, digits only), find the minimum and maximum possible original test count n consistent with the zero-padding naming rule.	Medium5	ImplementationMath+2	No attempts yet	1s	512 MB	Judgeable
Different digitsGiven n up to 10^18, find the smallest integer strictly greater than n whose decimal digits have no two adjacent equal digits.	Medium5	GreedyMath+2	No attempts yet	1s	512 MB	Judgeable
Typing TroubleDecide whether t can be produced from s when stray Home presses split s into blocks that are each placed at the front of the line.	Medium5	Dynamic programmingString+1	No attempts yet	1s	512 MB	Judgeable
BirthdayGiven a list of candidate dates and a three-line dialogue between the day-knower and month-knower, determine the unique birthday consistent with all statements.	Medium5	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable