Interview core

Mediums from real onsites

Under construction

Still being built. Things may change

Total results3,613 problems

Beautiful Phone Numbers
Medium6
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Maximum Sum
Medium6
Prefix sum, Brute force+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Three-color repainting
Medium6
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Experiment
Medium6
Graph, Topological sort+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Forest Cutting
Medium6
Binary search, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Laying Tiles
Medium6
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Capitals
Medium6
Tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
The theater begins with the actors
Medium6
Greedy, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Longest Common Substring
Medium6
String, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bicycle Race
Medium6
Sorting, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Maxim's Triangle
Medium6
Math, Binary search+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Lawn
Medium6
Math, Geometry+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Kitchen Layout
Medium6
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Stalker
Medium6
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Two Rectangles
Medium6
Implementation, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Division
Medium6
Prefix sum, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Gathering Honey
Medium6
Prefix sum, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Two Teams
Medium6
Tree, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Gahui and Process 1
Medium6
Heap, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Contact Tracing
Medium6
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Promotion
Medium6
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Aerobatic Flight
Medium6
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Even Palindrome
Medium6
Dynamic programming, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Meeting in the Middle
Medium6
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Part Rental Log
Medium6
Hash map, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Problem Recommendation System Version 2
Medium6
Implementation, Hash map+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Treasure
Medium6
Stack, String+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mean
Medium6
Dynamic programming, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
King's Task
Medium6
Graph, BFS+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Teleports
Medium6
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Banana Box Purchases
Medium6
Simulation, Sorting+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Visiting with Gifts
Medium6
Simulation, Queue+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Changyoung and the Commute Home
Medium6
Binary search, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Kill the Pig
Medium6
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Information Merchant Hoseok
Medium6
Heap, Hash map+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Hosuk Saurus
Medium6
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dividing Candy
Medium6
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Excellent Views
Medium6
Stack, Array+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Job Allocator
Medium6
Hash map, Implementation+2
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
Lola's Schedule
Medium6
Intervals, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Small Schedule
Medium6
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
shortestpathcube
Medium6
Geometry, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Palindrome Numbers
Medium6
String, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Antibody Recognition
Medium6
BFS, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Poisonous Swamp
Medium6
Shortest path, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Mansion and Deliveries
Medium6
Dynamic programming, Greedy+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Let's Solve a Geometry Problem
Medium6
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
House Moving
Medium6
Dynamic programming, Sorting+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Rabbit Party
Medium6
Graph, Brute force+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Palindrome Generator
Medium6
Graph, BFS+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Differential Pulse Code Modulation
Medium6
Dynamic programming, Implementation+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Earn Big
Medium6
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mirror Cave
Medium6
BFS, Graph+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Defend the Bases
Medium6
Binary search, Greedy+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Marked Ancestor
Medium6
Union-find, Tree+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Reverse a Road
Medium6
Graph, Shortest path+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Vending Machine
Medium6
Dynamic programming, Greedy+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Magical Dungeon
Medium6
Shortest path, Graph
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Text Justification
Medium6
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
X-Ray Screening System
Medium6
Implementation, Brute force+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Tetrahedra
Medium6
Brute force, Geometry+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
TV Watching
Medium6
Intervals, Dynamic programming+1
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Make Friendships
Medium6
Graph, BFS+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Gather the Maps!
Medium6
Graph, BFS+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
The Secret Number
Medium6
Dynamic programming, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Missing Numbers
Medium6
Math, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Walk (small)
Medium6
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Append Sort
Medium6
Greedy, String+2
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Closest Pick
Medium6
Greedy, Sorting+2
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Data Checker
Medium6
Sorting, Intervals+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Team Building
Medium6
Array, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sudden Attack 3
Medium6
Greedy, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rabbit House
Medium6
Graph, Greedy+2
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Longest Progression
Medium6
Array, Two pointers+2
No attempts yet
Time limit
30s
Memory limit
1024 MB
Judgeable
Palindromic Crossword
Medium6
Union-find, Simulation+2
No attempts yet
Time limit
60s
Memory limit
1024 MB
Judgeable
Parking Lot
Medium6
Dynamic programming, Sorting+2
No attempts yet
Time limit
15s
Memory limit
512 MB
Judgeable
I Want to Get Home Fast!
Medium6
Shortest path, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Baeknam's Travel Preparation
Medium6
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Aging
Medium6
Simulation, Heap+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rescue Mission
Medium6
Array, Math+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Making a Square
Medium6
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Reversing Roads
Medium6
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
A Careful Approach
Medium6
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Treasure Hunter
Medium6
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hanoi Tower K
Medium6
Recursion, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Staying Hydrated
Medium6
Math, Greedy+2
No attempts yet
Time limit
Not set
Memory limit
1024 MB
Judgeable
Web Browser 1
Medium6
Simulation, Stack+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Team Battle
Medium6
Math, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
A Sorting Problem
Medium6
Sorting, Greedy+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Watering
Medium6
Greedy, Sliding window+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Escape Room
Medium6
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
git mv
Medium6
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Painting roofs
Medium6
Graph, Matrix+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Divisible Inversions
Medium6
Array, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Double Rainbow
Medium6
Two pointers, Sliding window+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Trio
Medium6
Hash map, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Identical Scarves
Medium6
Sorting, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Red-Black Tree
Medium6
Dynamic programming, Tree+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Interstellar Fantasy
Medium6
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Miswritten DFS
Medium6
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Beautiful Phone NumbersGiven a 7-digit phone number, split the digits with hyphens into groups of 2 to 4 digits so that the total pattern-based beauty score is maximized, and print the best split with its score.	Medium6	Dynamic programmingString+2	No attempts yet	2s	1024 MB	Judgeable
Maximum SumGiven an m by n grid of integers, find the axis-aligned rectangle with the largest sum along its border and print that sum plus the corner coordinates.	Medium6	Prefix sumBrute force+2	No attempts yet	2s	1024 MB	Judgeable
Three-color repaintingRecolor every vertex of a graph with a color different from its current one so that no edge joins two vertices of the same color.	Medium6	GraphDFS+2	No attempts yet	2s	1024 MB	Judgeable
ExperimentSchedule n stages with precedence constraints, each needing one of two devices, to minimize the number of switches between devices.	Medium6	GraphTopological sort+2	No attempts yet	2s	1024 MB	Judgeable
Forest CuttingTwo lumberjacks cut A and B trees per day but rest every K-th and M-th day; find the first day the total felled reaches X.	Medium6	Binary searchMath+2	No attempts yet	1s	1024 MB	Judgeable
Laying TilesCount tilings of a 2 by n corridor with 1x2 and 1x1 tiles, given some 1x1 tiles already placed, modulo 1e9+7.	Medium6	Dynamic programmingCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
CapitalsGiven a tree of n cities, count the triples of cities where every pair is exactly d roads apart.	Medium6	TreeDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
The theater begins with the actorsGiven M acts, each listing actors who performed, find for every actor the earliest act after which the actor can be matched to a portrait.	Medium6	GreedyImplementation+1	No attempts yet	1s	1024 MB	Judgeable
Longest Common SubstringGiven up to 1000 lowercase strings of length at most 100, find the length of the longest substring that appears in every string.	Medium6	StringDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Bicycle RaceEach cyclist starts at position x_i with constant speed v_i; find the time t when the spread between the frontmost and rearmost cyclist is smallest, and that spread.	Medium6	SortingBinary search+2	No attempts yet	2s	512 MB	Judgeable
Maxim's TriangleGiven a sequence of probe frequencies and whether each is closer to or farther from an unknown value, find the min and max possible value of that unknown.	Medium6	MathBinary search+2	No attempts yet	2s	512 MB	Judgeable
LawnCount the integer lattice points inside an axis-aligned rectangle that also lie within distance r of a given point.	Medium6	MathGeometry+2	No attempts yet	2s	512 MB	Judgeable
Kitchen LayoutCount the ways to split distinct cabinet types into two groups and order each group along one of the two kitchen walls.	Medium6	Dynamic programmingCombinatorics+2	No attempts yet	2s	1024 MB	Judgeable
StalkerGiven K undirected graphs on N vertices, find the fewest graph switches needed to walk from vertex 1 to vertex N, starting with no graph loaded.	Medium6	GraphBFS+2	No attempts yet	2s	1024 MB	Judgeable
Two RectanglesGiven a grid of black and white cells, decide whether the black cells form exactly two non-overlapping axis-aligned rectangles, and if so, label them with 'a' and 'b'.	Medium6	ImplementationBrute force+2	No attempts yet	2s	512 MB	Judgeable
DivisionCount ways to cut a sequence into four nonempty contiguous parts with equal sums, allowing negative values.	Medium6	Prefix sumHash map+2	No attempts yet	1s	512 MB	Judgeable
Gathering HoneyPlace two bees and one hive on distinct positions in a row; each bee collects honey from every cell it passes (start cell excluded, shared cells counted twice), and you maximize the total.	Medium6	Prefix sumGreedy+2	No attempts yet	1s	512 MB	Judgeable
Two TeamsGiven a rooted tree of employees with signed skill values, pick two disjoint teams led by different employees to maximize the total skill of both.	Medium6	TreeDynamic programming	No attempts yet	2s	512 MB	Judgeable
Gahui and Process 1Simulate a priority scheduler that each second picks the process with the largest priority (ties broken by smallest id), then bumps every other process's priority by 1 and decrements the chosen one's remaining time, printing the chosen id for T seconds.	Medium6	HeapSimulation+2	No attempts yet	1s	512 MB	Judgeable
Contact TracingGiven daily meetings, initial infections, and test results on day 101, label each person as certainly infected, certainly healthy, or unknown.	Medium6	GraphBFS+2	No attempts yet	1s	256 MB	Judgeable
PromotionGiven n daily packages, each covering a subset of m object types at a fixed price, find the cheapest set of packages whose union covers all m types.	Medium6	Dynamic programmingBit manipulation+2	No attempts yet	1s	512 MB	Judgeable
Aerobatic FlightGiven an N by M grid of scores, find a climb from the bottom-left cell moving only up or right and a descent from the switch cell to the bottom-right cell moving only down or right that maximize the sum of visited cells.	Medium6	Dynamic programmingPrefix sum+1	No attempts yet	1s	512 MB	Judgeable
Even PalindromeSplit the sequence into the maximum number of contiguous parts, each of even length and equal to its own reverse, or report -1 if impossible.	Medium6	Dynamic programmingHash map+2	No attempts yet	1s	512 MB	Judgeable
Meeting in the MiddleGiven a directed weighted graph and a set of K home cities, pick every city X such that the maximum over all homes of the round-trip distance to X and back is minimized, printing the chosen city numbers in ascending order.	Medium6	GraphShortest path+2	No attempts yet	1s	512 MB	Judgeable
Part Rental LogParse a chronological log of borrow and return events, match them per person and part, and sum fines for rentals that exceed the allowed period, then print nicknames in lexicographic order.	Medium6	Hash mapString+2	No attempts yet	1s	512 MB	Judgeable
Problem Recommendation System Version 2Maintain a problem list supporting add and remove, plus queries for the hardest or easiest problem by category, overall, or above or below a difficulty threshold.	Medium6	ImplementationHash map+2	No attempts yet	1s	512 MB	Judgeable
TreasureRepeatedly delete the first run of exactly K equal consecutive letters until no such run remains, and print the final string.	Medium6	StackString+2	No attempts yet	1s	512 MB	Judgeable
MeanRepeatedly merge two adjacent numbers into the floor of their mean until one number remains; find the largest possible final value.	Medium6	Dynamic programmingMath+2	No attempts yet	1s	512 MB	Judgeable
King's TaskGiven a permutation of 1 to 2n, find the fewest swaps of adjacent pairs or of the two halves needed to sort it, or report that sorting is impossible.	Medium6	GraphBFS+2	No attempts yet	3s	512 MB	Judgeable
TeleportsGiven n points, each teleport reflects your position across it; decide whether you can reach the target point from the start.	Medium6	GraphBFS+2	No attempts yet	2s	256 MB	Judgeable
Banana Box PurchasesSimulate Gru's account: at each shipping time buy if affordable, otherwise try to pay the higher price at delivery, and count purchases.	Medium6	SimulationSorting+2	No attempts yet	2s	256 MB	Judgeable
Visiting with GiftsSimulate m gift visits where each visitor gives their earliest received gift, or buys a new one if they hold none, and report whether the host receives a gift they originally bought.	Medium6	SimulationQueue+2	No attempts yet	2s	256 MB	Judgeable
Changyoung and the Commute HomeGiven an N by N grid of elevations, find the smallest possible value of the maximum absolute elevation difference along a path from the top-left cell to the bottom-right cell, moving up, down, left, or right.	Medium6	Binary searchBFS+2	No attempts yet	2s	512 MB	Judgeable
Kill the PigA bird flies along a parabola until the player taps, then continues along the tangent line; find the tap time so the path passes through the pig, or report Ok or Impossible.	Medium6	GeometryMath+2	No attempts yet	2s	256 MB	Judgeable
Information Merchant HoseokProcess queries where gorillas gain information values and Hoseok buys the b most valuable pieces from a named gorilla, and report the total value bought.	Medium6	HeapHash map+2	No attempts yet	2s	512 MB	Judgeable
Hosuk SaurusA cow moves on a grid where allowed directions cycle with the move number (any, vertical only, horizontal only); find the minimum total cell shock from start to exit.	Medium6	GraphShortest path+2	No attempts yet	1s	512 MB	Judgeable
Dividing CandyGiven N boxes whose candy counts are powers of 2, decide whether the boxes can be split into two nonempty groups whose sums are both powers of 2.	Medium6	MathGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Excellent ViewsFor each building i, count buildings j such that no building within distance \|i-j\| of i is taller than Hj.	Medium6	StackArray+2	No attempts yet	1s	1024 MB	Judgeable
Job AllocatorProcess machine connect, disconnect, and job query events, counting connected machines that hold at least the requested counts of each resource type.	Medium6	Hash mapImplementation+2	No attempts yet	1.5s	1024 MB	Judgeable
Lola's ScheduleChoose the earliest first-dose time T within 480 minutes that minimizes how many of the recurring doses at T, T+X, T+2X, ... fall inside Lola's non-overlapping activities.	Medium6	IntervalsMath+2	No attempts yet	1s	1024 MB	Judgeable
Small ScheduleGiven M identical machines, S jobs of length 1 and L jobs of length Q, find the minimum makespan to schedule all jobs.	Medium6	Binary searchGreedy+2	No attempts yet	1s	512 MB	Judgeable
shortestpathcubeFind the shortest path along the surface of a 100 by 100 by 100 cube from a given surface point to the opposite corner.	Medium6	GeometryShortest path+2	No attempts yet	1s	512 MB	Judgeable
Palindrome NumbersGiven up to 50 positive integers of at most 80 digits, output for each the smallest decimal palindrome that is greater than or equal to it.	Medium6	StringGreedy+2	No attempts yet	1s	512 MB	Judgeable
Antibody RecognitionGiven two grids, decide whether the second can result from picking one start cell, flooding its monochromatic connected component, and repainting that whole component one color.	Medium6	BFSDFS+2	No attempts yet	1s	1024 MB	Judgeable
Poisonous SwampOn a 100x100 grid with one non-poisonous rectangle, find the minimum total damage (entries into swamp cells) to visit N destinations in order.	Medium6	Shortest pathGraph+2	No attempts yet	8s	512 MB	Judgeable
Mansion and DeliveriesDeliveries arrive at sorted times; each round trip to the door costs 2M, so pick a subset of deliveries to answer while maximizing time spent in the study up to T.	Medium6	Dynamic programmingGreedy+2	No attempts yet	10s	512 MB	Judgeable
Let's Solve a Geometry ProblemGiven a fraction p/q, find the smallest base b >= 2 in which p/q has a finite (terminating) expansion.	Medium6	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
House MovingGiven a permutation of weights, move pieces to any position at cost equal to the piece's weight so the final order is sorted; minimize total cost.	Medium6	Dynamic programmingSorting+2	No attempts yet	3s	512 MB	Judgeable
Rabbit PartyChoose a subset of rabbits to maximize the sum over guests of the minimum friendliness toward any other guest; uninvited pairs have friendliness 0.	Medium6	GraphBrute force+2	No attempts yet	5s	512 MB	Judgeable
Palindrome GeneratorFind the longest palindrome made of dictionary words where each consecutive word pair is an allowed transition. Print 0 if none exists and -1 if the length is unbounded.	Medium6	GraphBFS+1	No attempts yet	5s	512 MB	Judgeable
Differential Pulse Code ModulationGiven a codebook of step values and a signal, choose a code per sample so the reconstructed signal stays within 0 to 255 and minimizes the sum of squared errors against the input.	Medium6	Dynamic programmingImplementation+2	No attempts yet	8s	512 MB	Judgeable
Earn BigGiven N boxes and N names in a random permutation, compute the probability that every element lies in a cycle of length at most M.	Medium6	CombinatoricsDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Mirror CaveTwo people move on two W by H grids with mirrored directions, one blocked mover stays put, and the task asks whether they can occupy the two destination cells at the same time.	Medium6	BFSGraph+2	No attempts yet	8s	512 MB	Judgeable
Defend the BasesGiven troops with positions and speeds and a set of bases, find the minimum time so every base is reached by at least one troop, or report it is impossible.	Medium6	Binary searchGreedy+2	No attempts yet	8s	512 MB	Judgeable
Marked AncestorOn a rooted tree, process mark and query operations where each query asks for the nearest marked ancestor of a node, then report the sum of all query answers.	Medium6	Union-findTree+2	No attempts yet	8s	512 MB	Judgeable
Reverse a RoadGiven a directed graph, allow reversing at most one edge and report the shortest S to T distance and the smallest-numbered edge to reverse (0 if none helps).	Medium6	GraphShortest path+2	No attempts yet	8s	512 MB	Judgeable
Vending MachineGiven up to 10 coin denominations and a target M up to 100000, find the minimum number of operations where each operation outputs at most one coin of each denomination.	Medium6	Dynamic programmingGreedy+2	No attempts yet	8s	512 MB	Judgeable
Magical DungeonFind the maximum hit points Arthur can have when reaching room t from room s, where HP is capped at H and must stay above zero along the way.	Medium6	Shortest pathGraph	No attempts yet	8s	512 MB	Judgeable
Text JustificationSplit a sequence of word widths into lines no wider than the paper, minimizing a per-line cost that is absolute except on the last line.	Medium6	Dynamic programmingPrefix sum+2	No attempts yet	8s	512 MB	Judgeable
X-Ray Screening SystemGiven an X-ray projection grid of at most 7 labeled materials, decide whether every material region is a solid rectangle, otherwise report SUSPICIOUS.	Medium6	ImplementationBrute force+2	No attempts yet	8s	512 MB	Judgeable
TetrahedraGiven up to 15 stick lengths, choose 6 sticks to form the edges of a tetrahedron and maximize its volume.	Medium6	Brute forceGeometry+2	No attempts yet	8s	512 MB	Judgeable
TV WatchingPick each program to watch live or record so that the live picks and the recorded picks each have no time overlap, maximizing the total score.	Medium6	IntervalsDynamic programming+1	No attempts yet	8s	512 MB	Judgeable
Make FriendshipsGiven Isaac's available days and each friend's available days, find the largest set of friends he can date on distinct days.	Medium6	GraphBFS+2	No attempts yet	8s	512 MB	Judgeable
Gather the Maps!Each person is free on some subset of days 1 to 30; find the earliest day by which repeated pairwise meetings can collect all map fragments at one person.	Medium6	GraphBFS+2	No attempts yet	8s	512 MB	Judgeable
The Secret NumberIn a grid of digits and letters, find the largest number spelled by a path of digits that only moves right or down, ignoring paths with letters.	Medium6	Dynamic programmingArray+2	No attempts yet	2s	512 MB	Judgeable
Missing NumbersGiven a sales table with some entries missing but all row and column totals intact, decide whether the missing values are uniquely determined and print them in order, otherwise print NO.	Medium6	MathGraph+2	No attempts yet	2s	512 MB	Judgeable
Walk (small)Given an undirected unweighted graph, find the sum of the shortest S-to-E path (lexicographically smallest) and the shortest E-to-S path that avoids all vertices used on the forward trip.	Medium6	GraphBFS+2	No attempts yet	1s	1024 MB	Judgeable
Append SortGiven a fixed list of integers, append digits to the right of each number so the list becomes strictly increasing, using the fewest total append operations.	Medium6	GreedyString+2	No attempts yet	10s	1024 MB	Judgeable
Closest PickGiven N sold tickets with values in 1..K, pick two integers to maximize the fraction of values in 1..K that your tickets are strictly closest to.	Medium6	GreedySorting+2	No attempts yet	10s	1024 MB	Judgeable
Data CheckerGiven N circles centered on the x-axis, decide whether every pair is either disjoint or nested, so no two circles intersect.	Medium6	SortingIntervals+2	No attempts yet	1s	1024 MB	Judgeable
Team BuildingGiven N developers in a line with powers, pick two so that the gap between them times the smaller power is maximized.	Medium6	ArrayTwo pointers+2	No attempts yet	1s	1024 MB	Judgeable
Sudden Attack 3Given attack powers where a winner absorbs the loser's power, decide whether player 1 can be the last survivor under some order of fights.	Medium6	GreedySorting+2	No attempts yet	2s	1024 MB	Judgeable
Rabbit HouseGiven a grid of heights, add the fewest boxes so that every pair of side-adjacent cells differs in height by at most 1.	Medium6	GraphGreedy+2	No attempts yet	Not set	1024 MB	Judgeable
Longest ProgressionGiven an array, replace at most one element and find the length of the longest contiguous arithmetic subarray.	Medium6	ArrayTwo pointers+2	No attempts yet	30s	1024 MB	Judgeable
Palindromic CrosswordFill as many dots as possible in a crossword grid so that every maximal horizontal and vertical word is a palindrome, and report the count and final grid.	Medium6	Union-findSimulation+2	No attempts yet	60s	1024 MB	Judgeable
Parking LotAssign N drivers to distinct parking spaces among 1..M so that the total distance from each driver's preferred space is minimized.	Medium6	Dynamic programmingSorting+2	No attempts yet	15s	512 MB	Judgeable
I Want to Get Home Fast!Given directed subway lines with travel times and departure intervals, find the earliest arrival time at station N when departing station 1 at time 0.	Medium6	Shortest pathGraph+2	No attempts yet	1s	512 MB	Judgeable
Baeknam's Travel PreparationFor each bag capacity, choose a subset of items with total weight at most the capacity that maximizes the packed value, then output the bag whose value-to-capacity ratio is highest.	Medium6	Dynamic programmingGreedy+2	No attempts yet	1s	512 MB	Judgeable
AgingSimulate a priority scheduler with aging: at each step run the available process with highest current priority, breaking ties by running time then index, and report the run order.	Medium6	SimulationHeap+2	No attempts yet	2s	1024 MB	Judgeable
Rescue MissionFor each starting coach, find the shortest prefix of coaches whose prisoner counts can be split into 10 equal nonnegative integer parts; output the prefix length or -1.	Medium6	ArrayMath+2	No attempts yet	2s	1024 MB	Judgeable
Making a SquareGiven n distinct positive integers, count ordered pairs (i, j) such that a_i^2 + a_j is a perfect square.	Medium6	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
Reversing RoadsGiven a directed graph, decide if it is strongly connected; if not, find the earliest input edge whose reversal makes it strongly connected, or report that no single reversal works.	Medium6	GraphDFS+2	No attempts yet	2s	1024 MB	Judgeable
A Careful ApproachGiven up to 8 planes each with a landing window, choose landing times and an order that maximize the smallest gap between consecutive landings.	Medium6	Binary searchGreedy+2	No attempts yet	2s	1024 MB	Judgeable
Treasure HunterGiven k treasure cells in an m by n grid, find the minimum number of monotone right/down paths from (1,1) to (m,n) that together cover every treasure.	Medium6	SortingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Hanoi Tower KGiven n disks on the first peg, print the peg pair moved at step K in the minimal Tower of Hanoi solution.	Medium6	RecursionDivide and conquer+2	No attempts yet	1s	1024 MB	Judgeable
Staying HydratedChoose integer coordinates minimizing the sum of Manhattan distances to K axis-aligned rectangles, breaking ties by smallest x then smallest y.	Medium6	MathGreedy+2	No attempts yet	Not set	1024 MB	Judgeable
Web Browser 1Simulate a browser's back, forward, access, and compress operations on a bounded cache, then report the current page and the back and forward stacks.	Medium6	SimulationStack+2	No attempts yet	1s	512 MB	Judgeable
Team BattleGiven two n-member teams with integer skills, compute the expected value of A's score minus B's score over a uniformly random pairing, where the winner of a match scores the squared skill difference.	Medium6	MathSorting+2	No attempts yet	1s	1024 MB	Judgeable
A Sorting ProblemGiven a permutation of 1 to n, you may swap two elements only when their values differ by 1; find the minimum number of such swaps to sort the array.	Medium6	SortingGreedy+2	No attempts yet	3s	1024 MB	Judgeable
WateringEach day water A consecutive pots adding B moisture, then every pot loses 1; find the latest day the first plant can die with optimal watering.	Medium6	GreedySliding window+2	No attempts yet	1s	512 MB	Judgeable
Escape RoomOn a grid of digits where 0 cells are walls, find two reachable cells whose shortest-path distance is maximum and report the largest sum of their digits, or 0 if none exists.	Medium6	BFSGraph+2	No attempts yet	1s	512 MB	Judgeable
git mvGiven two Unix paths, output the shortest string of the form A{B => C}D that rewrites the source path into the destination path.	Medium6	StringImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Painting roofsGiven a grid of two colors, recolor the fewest cells so that the grid becomes bipartite by parity, i.e. every side-adjacent pair differs.	Medium6	GraphMatrix+2	No attempts yet	1s	256 MB	Judgeable
Divisible InversionsGiven a permutation of 1 to n, count pairs i < j where p[i] is a multiple of p[j].	Medium6	ArrayMath+2	No attempts yet	2s	512 MB	Judgeable
Double RainbowGiven a color sequence and k colors, find the shortest contiguous block that contains every color and whose complement also contains every color, or print 0.	Medium6	Two pointersSliding window+2	No attempts yet	1s	1024 MB	Judgeable
TrioCount the sets of three numbers from a list of four-digit numbers (no zero digits) where each digit position is either all equal or all distinct across the three.	Medium6	Hash mapCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
Identical ScarvesGiven n scarf lengths and k moments (one row knit or unravelled per moment), find the largest count of scarves that can be made equal in length within k total operations.	Medium6	SortingGreedy+2	No attempts yet	1s	256 MB	Judgeable
Red-Black TreeColor the vertices of a binary rooted tree red or black so no red-red edge exists and every root-to-void path has the same black count, or say Impossible.	Medium6	Dynamic programmingTree+1	No attempts yet	2s	1024 MB	Judgeable
Interstellar FantasyGiven a sphere obstacle and two points outside or on it, find the shortest path length from s to t that never enters the sphere.	Medium6	GeometryMath+2	No attempts yet	1s	256 MB	Judgeable
Miswritten DFSGiven a binary tree and a huge K, find the K-th node visited by a buggy pre-order DFS that recurses into the left child twice, without simulating all visits.	Medium6	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable