Problems

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Total results29,355 problems

Streetlights
Hard8
Segment tree, Intervals+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mayor's House
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Volunteers
Hard8
Tree, DFS+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Toy Vending Machine
Hard8
Tree, Simulation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Names
Hard8
String, Greedy+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Robot Assembler
Hard8
String, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Ancient Dynasties
Hard8
Dynamic programming, Two pointers+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Native Expanses
Hard8
String, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Moscow Numbers
Hard8
String, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Preparing for War
Hard8
Math, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Light Stone Simulation
Hard8
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
1.5s
Memory limit
256 MB
Judgeable
Stone of Logic
Hard8
Bit manipulation, Sorting+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Space Bowling
Hard8
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
«Abracadabra»
Hard8
String, Hash map+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Viruses and Antiviruses
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mosaic
Hard8
Array, Sorting+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Another Substring Query Problem
Hard8
String matching, String+2
No attempts yet
Time limit
6s
Memory limit
1024 MB
Judgeable
Borders
Hard8
Graph, DFS+2
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Passing the Towel
Hard8
Math, Recursion+2
No attempts yet
Time limit
0.25s
Memory limit
256 MB
Judgeable
Find the Double Class
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Wizard Shark and Blizzard
Hard8
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Math Homework
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Jumping Machine
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Multiple Subject Lessons
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cutting Logs
Hard8
Geometry, Binary search
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tram
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Permutations
Hard8
Backtracking, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Table
Hard8
Prefix sum, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Garden Informatization
Hard8
Geometry, Brute force+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Digits and Numbers
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Mahjong
Hard8
Graph, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Commuter trains do not change tracks
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dutch Pay
Hard8
Union-find, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1536 MB
Judgeable
Driving Vlog
Hard8
Graph, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1536 MB
Judgeable
Inversion Statistics
Hard8
Combinatorics, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1536 MB
Judgeable
Special Ice Breaking Penguin
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bus Riding
Hard8
Simulation, Implementation+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Two Knights
Hard8
BFS, Graph+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Interesting Number
Hard8
Dynamic programming, BFS+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Colored zeros
Hard8
Math, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Histogram Connectivity Count
Hard8
Stack, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Opinion Pool
Hard8
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Endless Road
Hard8
Segment tree, Greedy+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Fake Plastic Trees 2
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Aerobatics 6
Hard8
Geometry, Greedy+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Shopping
Hard8
Divide and conquer, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Ancient Machine
Hard8
String, Greedy+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Meetings 2
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Little Red Riding Hood
Hard8
Shortest path, Graph+1
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Autobahn
Hard8
Prefix sum, Sliding window+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cigle
Hard8
Dynamic programming, Prefix sum
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
MalnaRISC
Hard8
Sorting, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Balanced Subsets
Hard8
Dynamic programming, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Portals
Hard8
Graph, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Swap Swap Sort
Hard8
Sorting, Hash map+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Secret
Hard8
Divide and conquer, Implementation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Quarantine Math
Hard8
Number theory, Math+2
No attempts yet
Time limit
1.25s
Memory limit
256 MB
Judgeable
One-way Sidewalks
Hard8
Graph, DFS+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Mutant Vaccine
Hard8
String, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
From Hacks to Snitches
Hard8
Graph, BFS+1
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
The Collection Game
Hard8
Sorting, Divide and conquer+1
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
The Xanadu coup
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Hexagonal Region
Hard8
Geometry, Shortest path+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rainforest Jump
Hard8
Tree, Union-find+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Comeback
Hard8
Two pointers, Sliding window+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Walk
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
GCDChel Loves GCD
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
XOR Sum
Hard8
Bit manipulation, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Road Building
Hard8
Geometry, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Neo-Robin Hood
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Colorful Rectangle
Hard8
Segment tree, Sorting+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
To be Connected, or not to be, that is the Question
Hard8
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
High-Tech Detective
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Suffixes may Contain Prefixes
Hard8
String, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
String Removal
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cambridge
Hard8
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
MaxComp
Hard8
Graph, Union-find+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Balanced Tree
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
D-Balanced Tree
Hard8
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Simple
Hard8
Segment tree, Linked list+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Consul
Hard8
Divide and conquer, Brute force+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Costinland
Hard8
Implementation, Bit manipulation+1
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Lanterns
Hard8
Graph, Shortest path+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Digital Art
Hard8
Sliding window, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Paint Lag
Hard8
Segment tree, Sorting+1
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Meeting Rooms
Hard8
Dynamic programming, Intervals
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Monkey
Hard8
Dynamic programming, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Street Lamps
Hard8
Segment tree, Array
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Even Electricity
Hard8
Greedy, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Need More T-shirts!
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Cartesian Trees
Hard8
Tree, Dynamic programming+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Stage Lighting
Hard8
Sliding window, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Internet Cable
Hard8
Geometry, Math+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
Homework
Hard8
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Password decryption
Hard8
Dynamic programming, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Minions Having Fun
Hard8
Graph, Union-find+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Lottery
Hard8
Combinatorics, Sorting+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Game
Hard8
Graph, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Network Organization
Hard8
Tree, Greedy+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Robot
Hard8
Sorting, Sliding window+2
No attempts yet
Time limit
8s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
StreetlightsMaintain a binary string under range set-to-0 and set-to-1 operations, and after each report how many substrings have ever been all ones at some point in time.	Hard8	Segment treeIntervals+2	No attempts yet	2s	1024 MB	Judgeable
Mayor's HouseFor each home location, find a route from city hall with at most two turns that never enters the interior of a closed rectangular block, or report NO.	Hard8	GeometrySorting+1	No attempts yet	2s	1024 MB	Judgeable
VolunteersGiven two supervision trees over n volunteers, count for each scientific member how many technical members can share a volunteer with it, and report the total.	Hard8	TreeDFS+1	No attempts yet	1s	1024 MB	Judgeable
Toy Vending MachineCoins travel a tree of tubes, choosing the wider tube (left on ties) and reducing its width by 1; count the coins needed for a coin to first reach node v.	Hard8	TreeSimulation+2	No attempts yet	1s	1024 MB	Judgeable
NamesGiven two strings, find the lexicographically largest string that is a subsequence of both, or print nothing if none exists.	Hard8	StringGreedy+1	No attempts yet	2s	1024 MB	Judgeable
Robot AssemblerGiven a string of N operation types and a memory size K, count the ways to pick a K-character cyclic memory pattern and a starting position so that the robot runs at least K+1 operations before repeating the intended sequence.	Hard8	StringPrefix sum+2	No attempts yet	1s	1024 MB	Judgeable
Ancient DynastiesLabel festival years with two dynasties so gaps between same-label festivals fit one scholar's ranges, minimizing same-dynasty transitions.	Hard8	Dynamic programmingTwo pointers+1	No attempts yet	2s	1024 MB	Judgeable
Native ExpansesGiven a string and a 0/1 table saying which letter may be deleted right after which letter, delete characters to get the lexicographically smallest result.	Hard8	StringGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Moscow NumbersGiven templates of letters and question marks, replace each ? with a Moscow digit to maximize the number's value, then print that value and the filled string.	Hard8	StringGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Preparing for WarGiven group sizes in strict order, place all soldiers in a rectangle X by Y so that adjacent different-group pairs are at most k, and find the maximum Y for each k from 0 to N-1.	Hard8	MathGreedy+2	No attempts yet	2s	256 MB	Judgeable
Light Stone SimulationGiven home positions on a number line and a light that shrinks over time, find the minimum cost to keep everyone lit until each query time t.	Hard8	Dynamic programmingPrefix sum+1	No attempts yet	1.5s	256 MB	Judgeable
Stone of LogicBuild a circuit of AND gates, using inverted inputs and as few extra bits as possible, that sorts 16 input bits into ascending order.	Hard8	Bit manipulationSorting+1	No attempts yet	1s	256 MB	Judgeable
Space BowlingGiven a triangular array of n rows of circular pins and a ball moving in a straight line, count how many pins the ball touches.	Hard8	GeometryMath+2	No attempts yet	2s	1024 MB	Judgeable
«Abracadabra»For each pattern s, count dictionary words t where s is both a prefix and a suffix of t; word and pattern lengths are at most 50.	Hard8	StringHash map+2	No attempts yet	8s	1024 MB	Judgeable
Viruses and AntivirusesGiven two rooted trees on the same N employees, count ordered pairs (A, B) such that A is an ancestor of B in both trees.	Hard8	TreeDFS+2	No attempts yet	2s	1024 MB	Judgeable
MosaicGiven up to 100000 rectangles in a fixed order, answer range queries asking for any two pieces in the range that share no matching side length.	Hard8	ArraySorting+2	No attempts yet	1s	1024 MB	Judgeable
Another Substring Query ProblemGiven a string s and queries each with a pattern t and integer k, find the starting position of the k-th occurrence of t in s, or -1 if it occurs fewer than k times.	Hard8	String matchingString+2	No attempts yet	6s	1024 MB	Judgeable
BordersGiven a black and white grid, find the fewest connected same-color regions to outline so that every region shares a border with at least one outlined region.	Hard8	GraphDFS+2	No attempts yet	4s	1024 MB	Judgeable
Passing the TowelIn a Josephus-style circle game where the towel skips one person each pass, find the number of the person who receives the towel on the K-th pass.	Hard8	MathRecursion+2	No attempts yet	0.25s	256 MB	Judgeable
Find the Double ClassGiven M distinct rows of N section numbers, output at most M new rows so that each input row agrees with some new row in every column, yet no new row equals an input row.	Hard8	CombinatoricsMath+2	No attempts yet	1s	256 MB	Judgeable
Wizard Shark and BlizzardSimulate Blizzard spells on a spiral-indexed grid: destroy marbles, compact them along the spiral, and repeatedly explode runs of four or more, scoring exploded marble types.	Hard8	SimulationImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Math HomeworkConstruct a sequence of N integers in [1, 10^9] so that the GCD of each given subarray equals a given value at most 16, or report impossibility.	Hard8	Number theoryMath+2	No attempts yet	1s	1024 MB	Judgeable
Jumping MachineGiven n springs with jump lengths, the machine at (0,0) uses each spring once in any order, moving l up or l right; count the grid cells it can ever land on or pass over.	Hard8	CombinatoricsMath+2	No attempts yet	1s	512 MB	Judgeable
Multiple Subject LessonsCount the multisets of colored positive integers that sum to n, where two solutions match when every value has the same count in every color.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
Cutting LogsFind the largest-area isosceles triangle with its base on the x-axis, centered at the origin, that fits inside every polyline section.	Hard8	GeometryBinary search	No attempts yet	2s	512 MB	Judgeable
TramEach passenger boards and exits at given stops and contributes ai per segment if seated or bi if standing; with M seats, maximize total satisfaction over the whole route.	Hard8	GreedySorting+2	No attempts yet	5s	512 MB	Judgeable
PermutationsGiven n distinct integers, list all permutations where adjacent elements share gcd at least k, and output the m-th one in lexicographic order or -1.	Hard8	BacktrackingDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
TableGiven the first row of an n by m table, each lower cell is the sum of the triangular region above it mod r; output the last row.	Hard8	Prefix sumDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Garden InformatizationGiven a rectangle with up to 10 axis-aligned obstacle rectangles, place one or two non-overlapping axis-aligned beds to maximize total area.	Hard8	GeometryBrute force+2	No attempts yet	2s	512 MB	Judgeable
Digits and NumbersA binary number is ugly if no smaller number reaches it by adding its own digit sum; count the ugly numbers up to n (n up to 10^18).	Hard8	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
MahjongGiven an m by n board of colored tile pairs, find the longest sequence of removals where each pair sits at a row end or column end, and print the colors in order.	Hard8	GraphImplementation	No attempts yet	2s	1024 MB	Judgeable
Commuter trains do not change tracksGiven a tree and a set of simple paths, assign each vertex a value in 1..N so that values strictly increase along every path; report NO if impossible.	Hard8	GraphDFS+2	No attempts yet	1s	1024 MB	Judgeable
Dutch PayGiven merge and expense records of n travelers, compute each person's final balance and output at most n transfers that settle all debts.	Hard8	Union-findGreedy+2	No attempts yet	1s	1536 MB	Judgeable
Driving VlogGiven one-way roads where entering road i at time T takes T+C_i hours, find the fastest walk from each building to building n for every exact road count j, then sum likes minus dislikes.	Hard8	GraphDynamic programming+1	No attempts yet	2s	1536 MB	Judgeable
Inversion StatisticsCount permutations of 1 to n with exactly k inversions, modulo the prime 10^6+3, for n up to 2*10^10 over up to 10 test cases.	Hard8	CombinatoricsNumber theory+1	No attempts yet	1s	1536 MB	Judgeable
Special Ice Breaking PenguinGiven a tree with some nodes marked as supports, break as many nodes as possible while keeping the penguin's node connected to at least two supports through unbroken ordinary nodes.	Hard8	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
Bus RidingSimulate people riding circular bus routes, tracking boarding order by smallest route number and each transfer's one-minute wait, to report the finish time and stop or 0 0.	Hard8	SimulationImplementation+2	No attempts yet	2s	1024 MB	Judgeable
Two KnightsPlace two knights on a chessboard, move them alternately (any order) to distinct target squares without ever sharing a square, and output the minimum moves plus the actual move sequence, or -1.	Hard8	BFSGraph+2	No attempts yet	2s	1024 MB	Judgeable
Interesting NumberGiven n up to 1000, find the smallest positive integer with digit sum n that is also divisible by n.	Hard8	Dynamic programmingBFS+2	No attempts yet	2s	1024 MB	Judgeable
Colored zerosCount how many zero bits get marked when writing 1 to n in binary and flagging every k-th zero in each row.	Hard8	MathBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Histogram Connectivity CountCount choices of x_i with 0 <= x_i < h_i so that the remaining part of the histogram stays connected, modulo 1e9+7.	Hard8	StackCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Opinion PoolGiven sets of voters and a fraction p, find the largest p for which some assignment with at least one opponent still satisfies every set's support quota.	Hard8	Binary searchGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Endless RoadGiven N segments on a line of length 10^9, output the order in which members plant, always choosing the one with the least newly covered length (ties by index).	Hard8	Segment treeGreedy+1	No attempts yet	5s	1024 MB	Judgeable
Fake Plastic Trees 2Given a vertex-weighted tree, decide for each count i from 0 to K whether deleting exactly i edges can make every component's weight sum lie in [L, R].	Hard8	TreeDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
Aerobatics 6Given N checkpoints in the plane, find a visiting order whose polyline has the largest possible minimum turning angle at its inner checkpoints.	Hard8	GeometryGreedy+1	No attempts yet	1s	512 MB	Judgeable
ShoppingAnna sends at most 18 bits describing a range to Bruno, who replies with at most 10000 bits so she can name the cheapest item in that range.	Hard8	Divide and conquerSegment tree+2	No attempts yet	2s	256 MB	Judgeable
Ancient MachineAnna sees the X, Y, Z layout and sends 0/1 bits so Bruno can remove every device in an order that maximizes good removals, using as few bits as possible.	Hard8	StringGreedy+1	No attempts yet	2s	256 MB	Judgeable
Meetings 2Given a tree of N islands, for each j find the maximum number of islands that can be optimal meeting points when j beavers are chosen.	Hard8	TreeDynamic programming+1	No attempts yet	4s	256 MB	Judgeable
Little Red Riding HoodGiven the Wolf's fixed route and his per-run times, find a path for Red from clearing 1 to clearing N that arrives before the Wolf, or report NO.	Hard8	Shortest pathGraph+1	No attempts yet	2s	64 MB	Judgeable
AutobahnEach driver stays for a time interval and owes extra fees for minutes when at least K drivers are present; choose X consecutive minutes to waive fees and maximize the waived total.	Hard8	Prefix sumSliding window+2	No attempts yet	1s	512 MB	Judgeable
CigleGiven bricks of fixed widths in a set order, build a zigzag wall that maximizes the number of points where four bricks touch.	Hard8	Dynamic programmingPrefix sum	No attempts yet	1s	512 MB	Judgeable
MalnaRISCGiven N, output a parallel sorting network of CMPSWP comparator lines that sorts N registers, minimizing the number of parallel nanoseconds.	Hard8	SortingDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
Balanced SubsetsCount connected subsets of grass cells in an N by N grid where every row and column intersects the subset in a single contiguous run, modulo 1e9+7.	Hard8	Dynamic programmingImplementation+2	No attempts yet	1s	512 MB	Judgeable
PortalsEach vertex lists four portals grouped into two switchable pairs; pay c_v to permute a vertex's list, and find the minimum cost so all 4N (vertex, portal) locations become mutually reachable.	Hard8	GraphUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Swap Swap SortMaintain a target permutation of 1..K under adjacent swaps, and after each swap report the minimum adjacent-swap count to sort the fixed array by that ordering.	Hard8	SortingHash map+2	No attempts yet	3s	512 MB	Judgeable
SecretGiven a hidden associative operation on 0..1e9 and an array, answer range-fold queries while minimizing calls to an oracle that returns x star y, especially after each query.	Hard8	Divide and conquerImplementation+2	No attempts yet	1s	512 MB	Judgeable
Quarantine MathGiven n and m up to 1e9, sum the divisor counts of all positive k with (n mod k) + (m mod k) >= k, using number theory.	Hard8	Number theoryMath+2	No attempts yet	1.25s	256 MB	Judgeable
One-way SidewalksGiven a connected undirected graph, orient each edge so that the fewest edges stay two-way while the resulting mixed graph stays strongly connected.	Hard8	GraphDFS+2	No attempts yet	5s	256 MB	Judgeable
Mutant VaccineGiven up to 100 DNA strings, find the longest substring common to all of them, breaking ties by earliest position in the first string.	Hard8	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
From Hacks to SnitchesFind the minimum number of minutes to walk from corner 1 to corner N without meeting any of K watchmen on fixed cyclic routes, or report impossible.	Hard8	GraphBFS+1	No attempts yet	4s	512 MB	Judgeable
The Collection GameSchedule at most V visits, each comparing disjoint pairs of rooms, to rank all N rooms by art value even though the museum may swap any pair you announce.	Hard8	SortingDivide and conquer+1	No attempts yet	1.5s	512 MB	Judgeable
The Xanadu coupGiven a tree of N cameras, each with an on/off state, find the fewest button presses that toggle a node and its neighbors to turn every camera off, or report impossibility.	Hard8	TreeDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Hexagonal RegionGiven a closed, simple hex-grid path of N moves, sum A + d*B over every cell in the enclosed region, where d is the distance from the start.	Hard8	GeometryShortest path+1	No attempts yet	2s	1024 MB	Judgeable
Rainforest JumpGiven distinct tree heights, find the fewest jumps to the nearest taller tree that get from some tree in one range to some tree in a later range, or report it is impossible.	Hard8	TreeUnion-find+1	No attempts yet	3s	1024 MB	Judgeable
ComebackFor each left rotation of the array, count all contiguous subsequences whose sum is at most X and report both their count and the total of their sums.	Hard8	Two pointersSliding window+2	No attempts yet	1s	512 MB	Judgeable
WalkGiven a rooted tree and an ordered list of m distinct nodes, count the shortest closed walks from the root that visit all nodes and hit the listed nodes in the given order, modulo 1e9+7.	Hard8	TreeDFS+2	No attempts yet	1s	512 MB	Judgeable
GCDChel Loves GCDGiven an array, repeatedly split off either the left floor(n/2) elements or the right ceil(n/2) elements, sum the GCDs of the removed blocks, and maximize that sum.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
XOR SumGiven n k-bit numbers, compute the sum over all pairs of (a_i XOR a_j) raised to the power x, modulo 998244353.	Hard8	Bit manipulationMath+1	No attempts yet	1s	512 MB	Judgeable
Road BuildingGiven n non-overlapping circles and a direction line, find the widest infinite strip parallel to that line that touches no circle and has at least one circle on each side.	Hard8	GeometrySorting+2	No attempts yet	2s	512 MB	Judgeable
Neo-Robin HoodChoose a set of politicians to rob and a disjoint set to bribe so that total stolen money covers total bribes, maximizing the number robbed.	Hard8	GreedySorting+2	No attempts yet	4s	256 MB	Judgeable
Colorful RectangleGiven colored points in the plane, find the minimum perimeter of an axis-parallel rectangle that contains at least one point of each of the three colors.	Hard8	Segment treeSorting+1	No attempts yet	10s	512 MB	Judgeable
To be Connected, or not to be, that is the QuestionGiven an undirected graph with a value on each node, find the smallest threshold t such that the graph can be made connected by adding new edges between low-value and high-value nodes, each node used at most once.	Hard8	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
High-Tech DetectiveGiven a sequence of 2n entry and exit events where some visitor IDs are lost, count the ways to fill the zeros so each visitor enters once and exits once with proper nesting.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Suffixes may Contain PrefixesGiven a target string and a bullet length n, choose a bullet string of length n that maximizes the sum, over all its suffixes, of the longest common prefix length between that suffix and the target.	Hard8	StringDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
String RemovalErase the whole string S using substring deletions that give scores or single-character deletions worth 1 point each, and find the maximum total score.	Hard8	Dynamic programmingString matching+2	No attempts yet	1s	512 MB	Judgeable
CambridgeGiven tasks with solve times T_i and deadlines D_i, answer for each index range whether all its tasks can be finished before their deadlines in some order.	Hard8	GreedySorting+1	No attempts yet	1s	512 MB	Judgeable
MaxCompFind the connected set of grid cells maximizing (max value - min value - size), over a grid up to 1000 by 1000.	Hard8	GraphUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Balanced TreeGiven a tree where some node colors are fixed, color the rest black or white so every node has a same-colored node within distance D, and minimize D.	Hard8	TreeDynamic programming+1	No attempts yet	2s	512 MB	Judgeable
D-Balanced TreeGiven a tree with each vertex colored black or white, find the smallest D such that every vertex has another vertex of the same color within distance D, or -1 if impossible.	Hard8	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
SimpleSupport range add updates and range queries for the minimum even and maximum odd value, printing -1 for a missing parity.	Hard8	Segment treeLinked list+2	No attempts yet	1s	512 MB	Judgeable
ConsulGiven N hidden votes, use point queries and value-count queries to find a candidate with strictly more than N/3 votes, or report that none exists.	Hard8	Divide and conquerBrute force+2	No attempts yet	1s	512 MB	Judgeable
CostinlandGiven K, build an N x M grid of X, r, d, and . cells so that exactly K Costins (clones) reach the bottom-right corner (N,M).	Hard8	ImplementationBit manipulation+1	No attempts yet	0.5s	512 MB	Judgeable
LanternsFor each lantern that works at its own peak, find the minimum cost to buy more lanterns so John can visit all peaks while always having a working one.	Hard8	GraphShortest path+1	No attempts yet	3s	1024 MB	Judgeable
Digital ArtGiven an H by W grid of color numbers, cover one rectangle of at most S pixels to minimize the number of distinct colors still visible.	Hard8	Sliding windowTwo pointers+2	No attempts yet	1s	1024 MB	Judgeable
Paint LagGiven N rectangles and M moves that each leave d stale copies on screen, count how many rectangles contain each of Q query pixels.	Hard8	Segment treeSorting+1	No attempts yet	8s	1024 MB	Judgeable
Meeting RoomsPick meetings to cancel at the lowest total penalty so the remaining ones, with overlapping or neighbor-linked meetings in separate rooms, fit into K rooms.	Hard8	Dynamic programmingIntervals	No attempts yet	1s	1024 MB	Judgeable
MonkeyGiven M allowed (x, y) handle pairs with banana counts on each handle, find the maximum total bananas collectable along a monotone path that only increases x or y.	Hard8	Dynamic programmingSorting+2	No attempts yet	2s	1024 MB	Judgeable
Street LampsGiven N lamps with heights and Q single-lamp height updates, count after each update the pairs of equal-height lamps where every lamp between them is strictly shorter.	Hard8	Segment treeArray	No attempts yet	4s	1024 MB	Judgeable
Even ElectricityChoose how much stored water to convert each day so that daily electricity output has the smallest possible max minus min.	Hard8	GreedyTwo pointers+1	No attempts yet	1s	512 MB	Judgeable
Need More T-shirts!Given a list where each entry is either a T-shirt count or a percentage, find every possible total number of T-shirts consistent with the list.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Cartesian TreesCount the number of distinct Cartesian trees (BST over keys 1..n, max-heap over given priorities) modulo 1e9+7, summed over test cases with total n up to 2e5.	Hard8	TreeDynamic programming+2	No attempts yet	3s	256 MB	Judgeable
Stage LightingFor each start i, find the smallest r such that some subset of projectors i to r, with pairwise disjoint connector sets, has total power at least Z.	Hard8	Sliding windowBit manipulation+1	No attempts yet	2s	512 MB	Judgeable
Internet CableChoose a line and a distance d so that as many given points as possible lie exactly at distance d from the line; output that maximum count.	Hard8	GeometryMath+2	No attempts yet	4s	256 MB	Judgeable
HomeworkFor each triple of decimal strings x, y, z, decide whether infinitely many bases k make x times y equal z when read in base k.	Hard8	MathNumber theory+2	No attempts yet	2s	256 MB	Judgeable
Password decryptionCount the ways an encrypted digit string can be split into trinomial values for digits 0-9, reporting the count after each point update.	Hard8	Dynamic programmingSegment tree+2	No attempts yet	2s	256 MB	Judgeable
Minions Having FunFind a simple cycle in an undirected weighted graph maximizing the minimum edge weight plus the maximum edge weight on that cycle.	Hard8	GraphUnion-find+2	No attempts yet	2s	256 MB	Judgeable
LotteryCount arrays of length n with entries in 1..k such that the maximum on each of m given segments [l,r] equals a specified x.	Hard8	CombinatoricsSorting+2	No attempts yet	2s	256 MB	Judgeable
GameGiven the hint sets of n first-team and m second-team players, decide whether the first team can guarantee collecting all k hints when each first-team player may ask at most one second-team player for one hint he lacks, and if so, output the assignment.	Hard8	GraphGreedy+2	No attempts yet	2s	256 MB	Judgeable
Network OrganizationGiven a tree, find the minimum number of vertices whose distance vectors uniquely identify every vertex, and output one such set.	Hard8	TreeGreedy+2	No attempts yet	2s	256 MB	Judgeable
RobotCount the grid cells a robot can reach from any first-row start when it moves diagonally up-left or up-right around up to 10^5 rectangular obstacles on a grid up to 10^9 by 10^9.	Hard8	SortingSliding window+2	No attempts yet	8s	256 MB	Judgeable