Interview core

Mediums from real onsites

Under construction

Still being built. Things may change

Total results3,613 problems

Pants On Fire
Medium5
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Finding Your Coach
Medium5
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Life on a Torus
Medium5
Simulation, Hash map+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Extending Rock-Paper-Scissors
Medium5
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Signal
Medium5
Implementation, Array+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
PPAP
Medium5
Stack, String+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Demerit Points (DemeritPoints)
Medium5
Simulation, String+2
No attempts yet
Time limit
0.1s
Memory limit
32 MB
Judgeable
Engineering Calculator
Medium5
Recursion, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Drawing
Medium5
Math, Brute force+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Blog
Medium5
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Longest Increasing Palindromic Subsequence
Medium5
String, Two pointers+1
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
A Great Way
Medium5
Graph, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Execution Time
Medium5
Dynamic programming, Graph+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
I Have Few Friends (Large)
Medium5
String matching, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Jumping King Jelly (Small)
Medium5
DFS, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Adding 1, 2, 3 (9)
Medium5
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Two Coins
Medium5
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rectangles
Medium5
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
DSHS Bank
Medium5
Math, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
GCC Min Max Expression
Medium5
Stack, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Math Problem
Medium5
Math, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Population Movement
Medium5
Simulation, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Magic Weapon
Medium5
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Passport Control
Medium5
Queue, Stack+2
No attempts yet
Time limit
0.2s
Memory limit
512 MB
Judgeable
H to O
Medium5
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
A Prize No One Can Win
Medium5
Array, Sorting+2
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Fishermen
Medium5
Array, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Die
Medium5
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Flute
Medium5
Implementation, Brute force+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Sheba's Amoebas
Medium5
DFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sharing the Snacks
Medium5
Binary search, Greedy+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Amusement Park
Medium5
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Seungbeom Corporation
Medium5
Tree, DFS+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Illiteracy
Medium5
BFS, Graph+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Area Rug
Medium5
Prefix sum, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Judy and the Carrot Farm
Medium5
Implementation, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Sheep Rescue Operation
Medium5
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Jake and Cake
Medium5
Brute force, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Dual Channel VHF Radio
Medium5
Math, Implementation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Gazua
Medium5
Math, Number theory+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Making a Palindrome
Medium5
String matching, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Meet at One Point!
Medium5
Geometry, Math
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Small Penalty
Medium5
Sorting, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Lipschitz Constant
Medium5
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Building a Field
Medium5
Hash map, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cheap Trips
Medium5
Dynamic programming, Greedy
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Friendship Fee
Medium5
Union-find, Graph+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary String
Medium5
String, Greedy+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Achievements
Medium5
Two pointers, Array+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hard Drive
Medium5
Greedy, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Kleptography
Medium5
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Left and Right
Medium5
Greedy, Stack+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Email Destruction
Medium5
String, Hash map+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Guest Student
Medium5
Array, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Geunwoo's Diary Decorating
Medium5
Math, Greedy+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Defile
Medium5
Greedy, Sorting
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
House Numbers
Medium5
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
American Tour
Medium5
Graph, Shortest path+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Magnus
Medium5
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Teamwork
Medium5
Dynamic programming, Array
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Convention II
Medium5
Heap, Simulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Japan Sinks
Medium5
Sorting, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Where is the Boundary
Medium5
Prefix sum, Array+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Surface Area of Cubes
Medium5
Hash map, Math+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Junior
Medium5
Hash map, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
So You Like Your Food Hot?
Medium5
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Root Game
Medium5
Game theory, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Nim Game 3
Medium5
Game theory, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Uukjeo
Medium5
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bomberman 2
Medium5
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String Guessing
Medium5
String, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Array Rotation 1
Medium5
Matrix, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rotating an Array 2
Medium5
Matrix, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Two Dots
Medium5
DFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rotating an Array 3
Medium5
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Divide by 3, Multiply by 2
Medium5
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Two Stickers
Medium5
Implementation, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
BFS Special Judge
Medium5
BFS, Tree+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Escaping the Moving Maze
Medium5
BFS, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Restore the Array
Medium5
Matrix, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Value of Array B
Medium5
Array, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pretty Average Primes
Medium5
Number theory, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Icy Perimeter
Medium5
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mountain View
Medium5
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sleepy Cow Sorting
Medium5
Greedy, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Great Revegetation (Bronze)
Medium5
Graph, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Pipe Move 2
Medium5
Dynamic programming, Implementation+2
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Placing Two Crosses
Medium5
Brute force, Implementation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Escape the Maze
Medium5
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Subsequence with the Largest Maximum-Minimum Difference
Medium5
Two pointers, Array+2
No attempts yet
Time limit
0.5s
Memory limit
256 MB
Judgeable
Contest
Medium5
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Operations
Medium5
Segment tree, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Gahui's Remainder Sequence Game (Small)
Medium5
Stack, Array+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Fence Planning
Medium5
Union-find, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Bucket Brigade
Medium5
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Game of Death
Medium5
Graph, Simulation+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Cowburger Kitchen Worker
Medium5
Dynamic programming, Greedy+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Largest Sum Decreasing Subsequence
Medium5
Dynamic programming, Array+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Drug Investigation Unit
Medium5
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Making the Number N
Medium5
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Pants On FireGiven n true statements of the form "a are worse than b" that form a partial order, classify each of m queries as Fact, Alternative Fact, or Pants on Fire by transitive reachability.	Medium5	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
Finding Your CoachGiven your coach number and the coach counts to its left and right, decide whether the ticketed coach is here, certainly left, certainly right, or ambiguous.	Medium5	MathImplementation	No attempts yet	2s	512 MB	Judgeable
Life on a TorusSimulate Conway's Life on a wrapped 8x8 torus and find the smallest repeat period reached after any transient.	Medium5	SimulationHash map+1	No attempts yet	2s	512 MB	Judgeable
Extending Rock-Paper-ScissorsLabel n elements so every element beats exactly half the others, and print one ordered winner-loser line for each unordered pair.	Medium5	MathImplementation	No attempts yet	2s	512 MB	Judgeable
SignalDecode a 5-row pixel strip into digits: 3-column glyphs except 1, separated by blank columns.	Medium5	ImplementationArray+1	No attempts yet	1s	512 MB	Judgeable
PPAPDecide whether a length-1000000 string of P and A is generated from P by replacing a P with PPAP at each step.	Medium5	StackString+1	No attempts yet	1s	512 MB	Judgeable
Demerit Points (DemeritPoints)Simulate a student's demerit events encoded as base-36 chars, tracking accumulated points and quotient-by-10 crossing, and output total expulsion weeks plus weapon or permanent marker.	Medium5	SimulationString+2	No attempts yet	0.1s	32 MB	Judgeable
Engineering CalculatorEvaluate an integer arithmetic expression with precedence, right-associative exponentiation and square root, and truncation toward zero for incomplete roots and divisions.	Medium5	RecursionMath+2	No attempts yet	1s	256 MB	Judgeable
DrawingGiven n brightness values, decide whether some real a and positive real b make floor(a + b*k) equal every value.	Medium5	MathBrute force+2	No attempts yet	1s	256 MB	Judgeable
BlogGiven a string of R, G, and B, find the minimum number of contiguous same-color paint operations needed to build it.	Medium5	Dynamic programmingString+2	No attempts yet	1s	256 MB	Judgeable
Longest Increasing Palindromic SubsequenceGiven up to 10^5 integers, find the longest contiguous subarray that is a palindrome whose values strictly rise from both ends toward the center.	Medium5	StringTwo pointers+1	No attempts yet	1.5s	512 MB	Judgeable
A Great WayFind the cheapest path from node 1 to node N, where an edge costs c + d*max(0,e-10), breaking ties by fewer waypoints.	Medium5	GraphShortest path+1	No attempts yet	1s	128 MB	Judgeable
Execution TimeGiven ranks and operating speeds of n computers in a chain of ranks, compute when the whole task finishes using transmission time (i-j)^2 between machines.	Medium5	Dynamic programmingGraph+1	No attempts yet	2s	128 MB	Judgeable
I Have Few Friends (Large)Find whether keyword K appears in S as an exact substring, digits and all, and print 1 or 0.	Medium5	String matchingString+1	No attempts yet	1s	128 MB	Judgeable
Jumping King Jelly (Small)Given an N by N board with jump numbers, move only right or down from the top-left and reach the bottom-right, or report failure.	Medium5	DFSBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Adding 1, 2, 3 (9)Count ordered compositions of n into parts 1, 2, and 3 that use at most m terms, and output each count modulo 1,000,000,009.	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Two CoinsMove both coins together with four direction buttons and find the shortest press sequence that drops exactly one coin off the board.	Medium5	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
RectanglesChoose pairs of sticks (each possibly shortened by at most 1) as opposite sides of rectangles, maximizing the total area.	Medium5	GreedySorting+2	No attempts yet	2s	512 MB	Judgeable
DSHS BankPick the branch minimizing the total taxicab distance to all others, breaking ties by smallest branch number.	Medium5	MathSorting+2	No attempts yet	2s	512 MB	Judgeable
GCC Min Max ExpressionEvaluate an expression containing the <? (min) and >? (max) operators plus + and -, respecting precedence, left associativity, and parentheses.	Medium5	StackImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Math ProblemFor each N, find the smallest X such that N plus the digit sum of X equals X, or report -1 if none exists.	Medium5	MathImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Population MovementRepeat until stable: open borders whose population difference is L to R, compute each connected union's floored mean population, and count the days with any change.	Medium5	SimulationBFS+2	No attempts yet	2s	512 MB	Judgeable
Magic WeaponCount triples of details, one per color, where the red number's first and last digits match the green's last digit and the blue's first digit, and all three model numbers differ.	Medium5	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Passport ControlDecide whether a given exit permutation can arise from a FIFO arrival line feeding k desk queues, each holding an arrival-ordered subsequence.	Medium5	QueueStack+2	No attempts yet	0.2s	512 MB	Judgeable
H to OCount each atom's total from the input formula multiplied by k and from the output formula, then divide each element's counts to find the smallest quotient, the output count.	Medium5	StringHash map+2	No attempts yet	1s	512 MB	Judgeable
A Prize No One Can WinPick a largest subset of item prices such that no pair has a sum strictly greater than X, and print its size.	Medium5	ArraySorting+2	No attempts yet	1.5s	512 MB	Judgeable
FishermenCount for each fisherman how many fish satisfy \|x - a\| + y <= l, given fish and fishermen positions on a line.	Medium5	ArraySorting+1	No attempts yet	1s	512 MB	Judgeable
DieClassify a 3x3 grid of o and : as one of the five standard die faces 1-5, up to rotation, or output unknown if it matches none.	Medium5	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable
FluteGiven four scrambled lamp grids whose lit lamps may include burned-out (dark) ones, output the earliest valid time matching each grid as a digit pattern.	Medium5	ImplementationBrute force+1	No attempts yet	1s	512 MB	Judgeable
Sheba's AmoebasCount closed loops of # pixels in an m by n image, where loops may be nested but never touch or overlap.	Medium5	DFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Sharing the SnacksGiven M children and N snack sticks, find the maximum integer length where cutting gives every child one equal piece, or 0 if impossible.	Medium5	Binary searchGreedy+1	No attempts yet	1s	256 MB	Judgeable
Amusement ParkCitizens at various blocks must reach block 0 by taxi (A per block, one rider) or by sharing a bus (B won, up to 40 riders, one pick-up point). Find the minimum total cost.	Medium5	Dynamic programmingSorting+2	No attempts yet	1s	256 MB	Judgeable
Seungbeom CorporationMaintain balances on a company mentor tree while updates add a value to one employee and every employee below them.	Medium5	TreeDFS+1	No attempts yet	1s	256 MB	Judgeable
IlliteracyGiven two 8-icon sequences over A-F where clicking an icon deterministically mutates the whole sequence, find the shortest click sequence turning the start into the target, or -1.	Medium5	BFSGraph+2	No attempts yet	5s	512 MB	Judgeable
Area RugCount dirty cells under an s-by-s rug at every placement on an n-by-n grid, then report how many placements cover each possible count.	Medium5	Prefix sumArray+2	No attempts yet	2s	512 MB	Judgeable
Judy and the Carrot FarmPlace as many non-adjacent carrots as possible on an N by N grid given one preset cell, and print the resulting field.	Medium5	ImplementationGreedy+2	No attempts yet	1s	128 MB	Judgeable
Sheep Rescue OperationGiven a tree rooted at 1 with sheep or wolf counts per node, find the maximum number of sheep that can reach node 1 along unique paths while each wolf eats at most one entering sheep.	Medium5	TreeGreedy+2	No attempts yet	1s	256 MB	Judgeable
Jake and CakeCut a row cake at the fewest boundaries so each person gets N/4 strawberries and N/4 kiwis, and output one such cutting.	Medium5	Brute forceImplementation+2	No attempts yet	1s	128 MB	Judgeable
Dual Channel VHF RadioGiven two stored frequencies, the active channel, and a target, find the fewest button presses to receive the target using direct entry, UP steps, or DOWN steps, plus channel switching.	Medium5	MathImplementation+1	No attempts yet	1s	512 MB	Judgeable
GazuaEach test case gives K; decide if K equals a sum of at least two consecutive integers in 1 to K-1, printing "Gazua" on yes and "GoHanGang" on no.	Medium5	MathNumber theory+1	No attempts yet	1s	512 MB	Judgeable
Making a PalindromeFind the largest odd-length palindrome centered at index i, then answer each query by dropping the rest of the N cards.	Medium5	String matchingDynamic programming+1	No attempts yet	1s	512 MB	Judgeable
Meet at One Point!Given triangle side lengths and two cevian foot offsets along two sides, find the third offset using Ceva's theorem for the concurrent cevians.	Medium5	GeometryMath	No attempts yet	1s	512 MB	Judgeable
Small PenaltyPick one card from each of three players so the max minus min of the chosen numbers is as small as possible, and report that range.	Medium5	SortingTwo pointers+1	No attempts yet	1s	512 MB	Judgeable
Lipschitz ConstantGiven N points (x, f(x)), the Lipschitz constant is the maximum slope between adjacent points after sorting by x.	Medium5	GeometrySorting+1	No attempts yet	2s	512 MB	Judgeable
Building a FieldGiven N points on a circle with arc lengths between consecutive points, decide whether four trees are the vertices of some rectangle.	Medium5	Hash mapGeometry+2	No attempts yet	2s	512 MB	Judgeable
Cheap TripsOrder trips cannot be reordered and take no gaps; plan discounts across 120-minute windows to minimize total cost.	Medium5	Dynamic programmingGreedy	No attempts yet	2s	512 MB	Judgeable
Friendship FeeFind the cheapest way to become friends with everyone by paying each student a friend fee and using the friend-of-a-friend rule; output the minimum cost or "Oh no" when it exceeds k.	Medium5	Union-findGraph+1	No attempts yet	2s	512 MB	Judgeable
Binary StringDelete the fewest bits from a binary string so the remaining subsequence keeps no leading zeros and has value at most K.	Medium5	StringGreedy+2	No attempts yet	0.5s	512 MB	Judgeable
AchievementsGiven practice days and a budget of paid days, find the longest run of consecutive days where the number of skipped days does not exceed the budget.	Medium5	Two pointersArray+1	No attempts yet	1s	512 MB	Judgeable
Hard DriveBuild a length-n bit string where fixed-zero positions stay zero, bit 1 and bit n are pinned, and the number of adjacent bit changes is exactly c.	Medium5	GreedyImplementation+1	No attempts yet	2s	512 MB	Judgeable
KleptographyRecover an autokey ciphertext's plaintext when only its last n letters are known, using the known tail to decrypt backwards through the keystream.	Medium5	ArrayImplementation+1	No attempts yet	2s	512 MB	Judgeable
Left and RightFind the lexicographically smallest permutation of 1..n whose consecutive moves match the given L/R string.	Medium5	GreedyStack+1	No attempts yet	2s	512 MB	Judgeable
Email DestructionGiven n, k and k distinct shuffled email subjects of repeated 'Re: ' prefixes plus letters, decide whether exactly n emails could have existed before deletion.	Medium5	StringHash map+1	No attempts yet	3s	512 MB	Judgeable
Guest StudentGiven a weekly class schedule and k, find the shortest consecutive span of days covering exactly k class days.	Medium5	ArraySimulation+2	No attempts yet	2s	512 MB	Judgeable
Geunwoo's Diary DecoratingGiven N up to 10^9, find how many sticker packs (one of each digit 0-9) are needed so every integer from 0 to N can be written while reusing stickers between numbers.	Medium5	MathGreedy+1	No attempts yet	1s	256 MB	Judgeable
DefileGiven N honor scores, find the fewest unit decrements so that the repeated decrement process removes every member, with each step removing at least one.	Medium5	GreedySorting	No attempts yet	1.5s	512 MB	Judgeable
House NumbersGiven the first house number m, find the smallest n and the house x whose left and right neighbours' numbers sum equally.	Medium5	MathNumber theory+2	No attempts yet	1s	512 MB	Judgeable
American TourFind the shortest walk from node 1 to node N that passes through node 2, where no road may be repeated but nodes may be revisited.	Medium5	GraphShortest path+1	No attempts yet	1s	256 MB	Judgeable
MagnusDelete any letters from a length-N uppercase word so the kept letters contain as many disjoint subsequences "HONI" as possible, and print that maximum.	Medium5	GreedyString+1	No attempts yet	1s	512 MB	Judgeable
TeamworkPartition cows in a row into blocks of at most K so each block contributes its maximum times block size; maximize the sum.	Medium5	Dynamic programmingArray	No attempts yet	2s	512 MB	Judgeable
Convention IISimulate a single-server queue where queued cows are served by strict priority instead of arrival order, and find the largest start time minus arrival time.	Medium5	HeapSimulation+1	No attempts yet	2s	512 MB	Judgeable
Japan SinksRaise the sea level through the section heights and track how maximal runs of above-level sections merge; report the largest island count seen.	Medium5	SortingUnion-find+2	No attempts yet	2s	512 MB	Judgeable
Where is the BoundaryGiven m binary strings of length n, cut the line between two prefectures and label each side east or west to minimize mismatches. Report the two prefectures meeting at the best cut, choosing the westernmost one on ties.	Medium5	Prefix sumArray+2	No attempts yet	5s	512 MB	Judgeable
Surface Area of CubesGiven an A x B x C block of unit cubes with N cubes removed (including interior ones), compute the total surface area including surfaces of interior cavities.	Medium5	Hash mapMath+2	No attempts yet	5s	512 MB	Judgeable
JuniorGiven names in birth order with optional junior or iii suffixes, count people who have no earlier possible parent under the naming rules, which is the number of families.	Medium5	Hash mapString+1	No attempts yet	2s	512 MB	Judgeable
So You Like Your Food Hot?Given monthly profit and per-item profits for pita and pizza, find all nonnegative integer pairs whose profit equals the total and list them by pita count, or none.	Medium5	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Root GameFor each N, decide who wins the subtraction game where a move subtracts any perfect square from a running total and taking the last square wins.	Medium5	Game theoryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Nim Game 3Given Nim pile sizes, count how many first moves (choosing a pile and removing stones) leave the opponent in a losing position.	Medium5	Game theoryBit manipulation+2	No attempts yet	1s	512 MB	Judgeable
UukjeoGiven N word lengths, build binary words of those lengths where no word is a prefix of another, or report -1 if it is impossible.	Medium5	GreedySorting+1	No attempts yet	1s	512 MB	Judgeable
Bomberman 2Simulate Bomberman's bomb placement and explosion cycles on a grid and print the state after N seconds, handling N up to 10^9.	Medium5	SimulationImplementation+2	No attempts yet	2s	512 MB	Judgeable
String GuessingGiven all 2N-2 prefixes and suffixes of a hidden string, recover the string and label each input line as prefix or suffix in order.	Medium5	StringHash map+2	No attempts yet	2s	512 MB	Judgeable
Array Rotation 1Rotate each concentric ring of an N by M matrix counterclockwise R times, then print the resulting matrix.	Medium5	MatrixSimulation+2	No attempts yet	1s	512 MB	Judgeable
Rotating an Array 2Rotate each concentric layer of an N by M matrix one cell counterclockwise, R times, and print the final matrix.	Medium5	MatrixSimulation+2	No attempts yet	1s	512 MB	Judgeable
Two DotsGiven a grid of colored dots, decide whether any cycle of four or more same-colored dots exists, where consecutive dots touch by an edge.	Medium5	DFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Rotating an Array 3Apply a sequence of up to 1000 operations (vertical flip, horizontal flip, quarter rotations, and quadrant swaps) to an N by M array and print the final arrangement.	Medium5	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable
Divide by 3, Multiply by 2Given a shuffled copy B of the sequence produced by a divide-by-3, multiply-by-2 game, reconstruct the original order A.	Medium5	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
Two StickersGiven an H by W grid and N rectangles that may rotate, place two non-overlapping rectangles inside and maximize their total area.	Medium5	ImplementationBrute force+2	No attempts yet	2s	512 MB	Judgeable
BFS Special JudgeGiven a tree and a permutation of its vertices, decide whether the permutation can be produced by a BFS traversal starting from vertex 1.	Medium5	BFSTree+2	No attempts yet	2s	512 MB	Judgeable
Escaping the Moving MazeAn 8x8 board with walls that shift down one row each second; decide if a character moving first each second can reach the top-right cell.	Medium5	BFSSimulation+2	No attempts yet	2s	512 MB	Judgeable
Restore the ArrayRecover grid A from grid B, where B is built by overlapping A with A shifted down X and right Y so overlapping cells are summed.	Medium5	MatrixSimulation+2	No attempts yet	2s	512 MB	Judgeable
Value of Array BSwap at most one pair of rows or columns in an N by M grid to maximize the sum of all 2 by 2 block sums.	Medium5	ArrayGreedy+2	No attempts yet	2s	512 MB	Judgeable
Pretty Average PrimesFor each N, print two primes whose average is N, which means finding a prime pair that sums to 2N.	Medium5	Number theoryBrute force+2	No attempts yet	1s	512 MB	Judgeable
Icy PerimeterFind the connected component of '#' cells with the largest area, breaking ties by smallest perimeter, where perimeter counts all edges touching non-component cells including holes.	Medium5	GraphDFS+2	No attempts yet	2s	512 MB	Judgeable
Mountain ViewCount how many mountain peaks are not covered by any other 45-degree right-triangle mountain with its base on the x-axis.	Medium5	GeometrySorting+2	No attempts yet	2s	512 MB	Judgeable
Sleepy Cow SortingGiven a permutation of 1..N, repeatedly move the front cow any number of paces back; find the minimum number of steps to reach sorted order.	Medium5	GreedyArray+2	No attempts yet	2s	512 MB	Judgeable
The Great Revegetation (Bronze)Assign each of N pastures one of 4 grass types so that every listed pair differs, choosing the lexicographically smallest N-digit answer.	Medium5	GraphGreedy+2	No attempts yet	2s	512 MB	Judgeable
Pipe Move 2Count the ways to push a 2-cell pipe (horizontal, vertical, or diagonal) across an N by N grid so its end reaches (N, N), keeping all covered cells empty.	Medium5	Dynamic programmingImplementation+2	No attempts yet	0.5s	512 MB	Judgeable
Placing Two CrossesGiven a small grid of '.' and '#', place two non-overlapping crosses made of '#' cells and maximize the product of their areas.	Medium5	Brute forceImplementation+2	No attempts yet	2s	512 MB	Judgeable
Escape the MazeEach cell holds a direction to the next cell; count how many starting cells eventually leave the N by M grid.	Medium5	GraphDFS+2	No attempts yet	1s	512 MB	Judgeable
Subsequence with the Largest Maximum-Minimum DifferenceGiven a sequence, find the shortest contiguous segment whose max minus min equals the largest such difference over all segments.	Medium5	Two pointersArray+2	No attempts yet	0.5s	256 MB	Judgeable
ContestGiven N intervals with start time, end time, and prize money, choose non-overlapping contests (end must not touch the next start) to maximize total prize.	Medium5	Dynamic programmingSorting+2	No attempts yet	1s	256 MB	Judgeable
OperationsMaintain a sparse integer array under point add, point reset, and range sum queries, printing the whole-array sum after each update.	Medium5	Segment treePrefix sum+2	No attempts yet	2s	512 MB	Judgeable
Gahui's Remainder Sequence Game (Small)Maintain a sequence under push and pop from the back, and for each type-3 query report the shortest suffix whose values cover every residue 0 to mod-1, or -1 if impossible.	Medium5	StackArray+1	No attempts yet	1s	256 MB	Judgeable
Fence PlanningConnect cows into groups given moo pairs, then find the axis-aligned rectangle of smallest perimeter that fully contains one group.	Medium5	Union-findGraph+2	No attempts yet	2s	512 MB	Judgeable
Bucket BrigadeOn a fixed 10x10 grid with one barn, one lake, and one blocked rock, find the fewest empty squares to occupy so a chain of cows links the lake to the barn.	Medium5	BFSGraph+2	No attempts yet	2s	512 MB	Judgeable
Game of DeathGiven a fixed pointing map for N people, find the smallest positive M so that starting at person 0 and following M pointers ends on person K.	Medium5	GraphSimulation+2	No attempts yet	2s	256 MB	Judgeable
Cowburger Kitchen WorkerWith M cheeseburgers and K fries available, pick the largest subset of orders, each requiring some of each item, that fits within both limits.	Medium5	Dynamic programmingGreedy+2	No attempts yet	3s	512 MB	Judgeable
Largest Sum Decreasing SubsequenceGiven a sequence, find a strictly decreasing subsequence with the maximum possible sum and print that sum.	Medium5	Dynamic programmingArray+2	No attempts yet	1s	256 MB	Judgeable
Drug Investigation UnitGiven a directed supply graph and a set of arrested suppliers, count how many remaining suppliers still receive drugs from some origin.	Medium5	GraphDFS+2	No attempts yet	1s	256 MB	Judgeable
Making the Number NCount how many digit-by-digit sequences build the number N when each new digit is attached to the left or right end.	Medium5	Dynamic programmingString+2	No attempts yet	1s	256 MB	Judgeable