Problems

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Total results29,185 problems

Zoo
Hard9
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Museum Guards
Hard9
Binary search, Greedy+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Ideas
Hard9
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Nice Prefixes
Hard9
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Asteroid Rangers
Hard9
Minimum spanning tree, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Old Factory Plumbing
Hard9
Graph, Minimum spanning tree+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Affine Mess
Hard9
Geometry, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Mummy Madness
Hard9
Binary search, Geometry+2
No attempts yet
Time limit
6s
Memory limit
128 MB
Judgeable
Jack and Jill
Hard9
Binary search, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Spellcasting
Hard9
Math, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cubic Rube
Hard9
Implementation, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A to Z Numerals
Hard9
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Guard
Hard9
Geometry, Binary search+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Triangle Cuts
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Potholes
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Planning Rolling Blackouts
Hard9
Dynamic programming, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
A Broken Door
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
The Most Powerful Spell
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Old Memories
Hard9
String matching, Dynamic programming+2
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Congruent Partition of Chocolate
Hard9
Brute force, DFS+2
No attempts yet
Time limit
30s
Memory limit
128 MB
Judgeable
Twirl Around
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Kindergarten
Hard9
Graph, Binary search+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Around the Track
Hard9
Graph, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Floor Bricks
Hard9
Dynamic programming, Implementation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
ASCII Art
Hard9
Geometry, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Navi Navigation
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Two Circles in a Convex Polygon
Hard9
Geometry, Binary search+2
No attempts yet
Time limit
4s
Memory limit
128 MB
Judgeable
Giant Cover
Hard9
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tables
Hard9
Dynamic programming, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Farmer John
Hard9
Geometry, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Archery
Hard9
Math, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Teleporters
Hard9
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Amazing Robots
Hard9
BFS, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Contact
Hard9
String, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Success Probability of the Card-Pile Game
Hard9
Probability, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Version-Controlled IDE
Hard9
Tree, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Apparent Twin Primes
Hard9
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Synnerg Lifeform
Hard9
Dynamic programming, Intervals+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ballroom Lights
Hard9
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Jukebox
Hard9
String, Brute force+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Not Too Convex Hull
Hard9
Dynamic programming, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Ideal City
Hard9
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Hyperspace Routes
Hard9
Shortest path, Graph+2
No attempts yet
Time limit
5s
Memory limit
64 MB
Judgeable
Tropical Garden
Hard9
Graph, Simulation+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Yin and Yang
Hard9
Tree, Divide and conquer+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Island Travels
Hard9
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tied Down
Hard9
Geometry, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Simplifying the Farm
Hard9
Minimum spanning tree, Union-find+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bottleneck
Hard9
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Taking Turns
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cow Hopscotch
Hard9
Dynamic programming, Segment tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Largest Fence
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Casting
Hard9
Geometry, Two pointers+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Watering the Fields
Hard9
Greedy, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Forgetful Waiter
Hard9
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Warez Test
Hard9
BFS, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Winmine (Minesweeper)
Hard9
Dynamic programming, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Very Boring Homework
Hard9
Tree, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Servers
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
City Navigation
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pendulum
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cyclic Antimonotonic Permutations
Hard9
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Construct the Wall Maze
Hard9
Brute force, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mine the Gradient
Hard9
Dynamic programming, Implementation+2
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Alea iacta est
Hard9
Dynamic programming, Simulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
The Herbalists' Village
Hard9
Graph, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Downpayment
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
A Romantic Movie Outing
Hard9
Segment tree, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Lights Going On and Off
Hard9
Bit manipulation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Landing
Hard9
Geometry, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Move that Mouse AGAIN
Hard9
Segment tree, Geometry+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Fast Food
Hard9
Geometry, Divide and conquer+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Phylogenetic Tree
Hard9
Graph, Tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Checker Board
Hard9
Game theory, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Telecorp
Hard9
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Longest Paths in a Tree
Hard9
Tree, Segment tree+2
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Falling Balls
Hard9
Segment tree, Tree+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Joy of Mobile Routing
Hard9
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Prince of Persia
Hard9
Simulation, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Deformed Wheel
Hard9
Geometry, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Parallel Expectations
Hard9
Probability, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Find the Border
Hard9
Geometry, Implementation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Illumination
Hard9
Geometry, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
King's Quest
Hard9
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Exam
Hard9
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Jogger
Hard9
Tree, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Purify
Hard9
String, Trie+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Duopoly
Hard9
Dynamic programming, Greedy+1
No attempts yet
Time limit
3s
Memory limit
32 MB
Judgeable
Coloring maps
Hard9
Graph, Greedy+1
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Structural Isomers
Hard9
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Juggle with Criteria
Hard9
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Accountant Notes
Hard9
String matching, Hash map+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Hypervisor MacrOS
Hard9
Graph, Topological sort+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Suffix Array Reconstruction
Hard9
String, Greedy+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Markov Trains
Hard9
Dynamic programming, Probability+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mirror Trap
Hard9
Math, Number theory+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Dextrogyrate Camel
Hard9
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Bus Tour
Hard9
Dynamic programming, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Save the Dinosaurs
Hard9
Geometry, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Wandering Flea Trainers
Hard9
Graph, DFS+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
ZooChoose cages to empty on a circle so that the most children watching 5-cage arcs become happy, where each child needs one feared animal removed or one liked animal kept.	Hard9	Dynamic programmingBit manipulation+2	No attempts yet	2s	128 MB	Judgeable
Museum GuardsAssign each guard repeating daily intervals on half-hour boundaries within their availability and minute limits so the minimum number of guards on duty is maximized.	Hard9	Binary searchGreedy+2	No attempts yet	5s	128 MB	Judgeable
IdeasFor each directed tube, find the smallest set of ideas a packet must carry while traversing it so that every reachable person still receives all ideas they need.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Nice PrefixesCount length-L strings over a K-letter alphabet where every prefix keeps all symbol counts within 2 of each other, modulo 1e9+7, with L up to 1e18.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Asteroid RangersGiven n moving points, count how many times the minimum spanning tree over all future times changes, plus the initial build.	Hard9	Minimum spanning treeGeometry+2	No attempts yet	1s	128 MB	Judgeable
Old Factory PlumbingChoose a water height so the flooded region avoids open holes unless plugged or piped, minimizing pipe distances plus 0.5 per plug.	Hard9	GraphMinimum spanning tree+2	No attempts yet	5s	128 MB	Judgeable
Affine MessGiven three integer start points and three integer end points, decide whether a snapped integer rotation, integer scaling, and integer translation map one set onto the other, and if so whether all such maps agree on the whole plane.	Hard9	GeometryMath+2	No attempts yet	2s	128 MB	Judgeable
Mummy MadnessGiven mummy start positions on an infinite grid, compute how many time steps a fleeing player survives when both sides move on a king-step grid.	Hard9	Binary searchGeometry+2	No attempts yet	6s	128 MB	Judgeable
Jack and JillChoose walking routes and timing for two people on a grid so the smallest distance between them at any whole minute is as large as possible, and report that maximum.	Hard9	Binary searchBFS+2	No attempts yet	1s	128 MB	Judgeable
SpellcastingGiven element costs, power rates, and a support tree, find the minimum time for the spell's total power to reach the target, given starting energy and continuous accumulation.	Hard9	MathGreedy+2	No attempts yet	1s	128 MB	Judgeable
Cubic RubeGiven two connected 5x5 height maps of unit cubes, decide whether the pieces can be rotated and translated in 3D to assemble a full 5x5x5 cube.	Hard9	ImplementationGeometry+2	No attempts yet	1s	128 MB	Judgeable
A to Z NumeralsConvert each positive integer up to 7e17 into its unique A to Z numeral, where letters a to r and A to R stand for powers of ten and their quintuples.	Hard9	GreedyMath+2	No attempts yet	1s	128 MB	Judgeable
GuardPlace g guards on segments so every valuable point is seen, minimizing the largest value-times-distance risk, or report too few guards.	Hard9	GeometryBinary search+2	No attempts yet	1s	128 MB	Judgeable
Triangle CutsGiven a large triangle and four small triangles as angle triples in clockwise order, decide whether three straight cuts can produce exactly those four pieces.	Hard9	GeometrySimulation+2	No attempts yet	1s	128 MB	Judgeable
PotholesPlace a straight rope across a rectangular lot without crossing any pothole so the total pothole area is split as evenly as possible, with tie-breaking rules.	Hard9	GeometrySorting+2	No attempts yet	1s	128 MB	Judgeable
Planning Rolling BlackoutsPartition an h by w grid by recursive guillotine cuts so that the heaviest set of groups left powered stays within capacity, maximizing the group count and then the reserve.	Hard9	Dynamic programmingPrefix sum+2	No attempts yet	3s	512 MB	Judgeable
A Broken DoorGiven a grid maze with card-locked doors on some walls, find the fewest cards that always suffice to reach the exit whichever single door is broken, or -1 if some broken door cuts off the exit.	Hard9	GraphShortest path+2	No attempts yet	3s	128 MB	Judgeable
The Most Powerful SpellGiven a labeled directed graph, find the lexicographically smallest string that labels a walk from the star node to the gold node, or print NO if none exists or the minimum is unbounded.	Hard9	GraphShortest path+2	No attempts yet	5s	128 MB	Judgeable
Old MemoriesGiven pieces of an original text and an altered copy with at most d edits, list all original strings whose edit distance to the copy is at most d and where every position lies inside some piece occurrence.	Hard9	String matchingDynamic programming+2	No attempts yet	10s	128 MB	Judgeable
Congruent Partition of ChocolateGiven a connected polyomino of at most 36 unit squares, decide whether it splits into two connected pieces that are congruent under rotation, reflection, and translation.	Hard9	Brute forceDFS+2	No attempts yet	30s	128 MB	Judgeable
Twirl AroundA bar inside a simple polygon rotates clockwise, pivoting on the wall whenever a new contact point appears; report the final position of one end, or the position when it jams.	Hard9	GeometrySimulation+2	No attempts yet	1s	128 MB	Judgeable
KindergartenSplit n students into three classes so nobody keeps their old teacher and every classmate sits in each other's top T, minimizing T.	Hard9	GraphBinary search+2	No attempts yet	1s	128 MB	Judgeable
Around the TrackFind the Eulerian circuit of a planar-ish graph whose total turning cost is minimized, where each degree-4 node requires choosing how to pair its incident edges.	Hard9	GraphDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
The Floor BricksCover a column-height profile of a bare floor with rotated 3x3 polyomino bricks of given prices, minimizing total cost.	Hard9	Dynamic programmingImplementation+1	No attempts yet	1s	128 MB	Judgeable
ASCII ArtRender triangles with ASCII characters, projecting 3D vertices through a camera onto an S by S screen grid with depth-based visibility.	Hard9	GeometryImplementation+2	No attempts yet	1s	128 MB	Judgeable
Navi NavigationGiven a weighted undirected graph with fruit types on nodes and multiple queries, find for each pair a shortest path that visits exactly one node of every fruit type.	Hard9	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
Two Circles in a Convex PolygonFind the largest radius R so that two non-overlapping circles of radius R fit inside a given convex polygon with N vertices.	Hard9	GeometryBinary search+2	No attempts yet	4s	128 MB	Judgeable
Giant CoverGiven axis-aligned boxes on a rectangular campus, find the minimum surface area of a convex solid above the ground that covers all boxes and is anchored to the campus boundary.	Hard9	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
TablesCount the tilings of a polyiamond on a triangular grid by isosceles trapezoids made of three unit triangles, given the shape's boundary as a sequence of grid nodes.	Hard9	Dynamic programmingGeometry+2	No attempts yet	1s	128 MB	Judgeable
Farmer JohnGiven start, goal, and up to 100 disjoint line-segment fences, find the shortest path that cannot cross any fence, touching allowed, and print the length to six decimals.	Hard9	GeometryGraph+2	No attempts yet	1s	128 MB	Judgeable
ArcheryPlace Seungwon into one of 2N gaps so that after R tournament rounds his final target number is minimized, breaking ties by the largest starting target.	Hard9	MathSimulation+2	No attempts yet	1s	128 MB	Judgeable
TeleportersPlace up to M new teleporters between given endpoints so the forced eastward walk triggers as many teleports as possible.	Hard9	GreedySorting+2	No attempts yet	1s	128 MB	Judgeable
Amazing RobotsTwo robots in separate mazes receive the same direction command each minute; guards patrol back and forth, and you must find the minimum time until both robots exit without capture.	Hard9	BFSSimulation+2	No attempts yet	1s	512 MB	Judgeable
ContactGiven a binary string and a length range [A,B], report the N largest occurrence counts and all patterns achieving each count, with output ordering rules.	Hard9	StringSorting+2	No attempts yet	1s	128 MB	Judgeable
Success Probability of the Card-Pile GameGiven n decks of k cards each shuffled into n piles, find the probability that the follow-the-number drawing game succeeds within m restarts, printed to r decimals.	Hard9	ProbabilityCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Version-Controlled IDEMaintain a versioned text buffer under insert and delete operations, answering substring queries against any past version, with all commands encoded by a running counter.	Hard9	TreeImplementation+2	No attempts yet	1s	128 MB	Judgeable
Apparent Twin PrimesFor each query (n, t), find the smallest n-digit p such that neither p nor p+2 has a prime factor at most t.	Hard9	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
Synnerg LifeformGiven rewriting rules that merge adjacent synnergs with multiplicative lifetimes, find all maximum-lifetime synnergs obtainable by fully unifying some contiguous block of each input sequence.	Hard9	Dynamic programmingIntervals+2	No attempts yet	1s	128 MB	Judgeable
Ballroom LightsGiven point lightbulbs and disjoint circular columns inside a rectangle, compute the total length of the wall perimeter that some lightbulb can reach with a straight, unblocked ray.	Hard9	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
JukeboxEach song has a title and artist; decide which artist fields to drop so the total length of shortest unique substrings over all title and remaining artist strings is minimized.	Hard9	StringBrute force+2	No attempts yet	3s	128 MB	Judgeable
Not Too Convex HullPartition the nails into B convex polygonal groups, all sharing the origin nail, minimizing the total covered area, with the origin strictly inside the global hull.	Hard9	Dynamic programmingGeometry+2	No attempts yet	1s	128 MB	Judgeable
The Ideal CityGiven N cells forming a simply connected polyomino with no holes, compute the sum of grid shortest-path distances over all pairs, modulo 1e9.	Hard9	GraphBFS+2	No attempts yet	1s	256 MB	Judgeable
Hyperspace RoutesFor each query, find every possible value of the shortest A-to-B path length as the shared hyperspace edge weight x ranges over the positive integers, then report the count and sum, or inf when unbounded.	Hard9	Shortest pathGraph+2	No attempts yet	5s	64 MB	Judgeable
Tropical GardenCount starting ponds whose deterministic non-backtracking walk (prefer the most beautiful unused-at-previous-step walkway) reaches pond P after exactly K steps, for many K.	Hard9	GraphSimulation+2	No attempts yet	5s	256 MB	Judgeable
Yin and YangOn a tree with each edge colored black or white, count paths that split at an internal vertex into two legs each having equal numbers of black and white edges.	Hard9	TreeDivide and conquer+2	No attempts yet	2s	128 MB	Judgeable
Island TravelsGiven a grid with N islands and shallow water, find the minimum total swim distance to visit every island, starting anywhere.	Hard9	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Tied DownGiven a closed polygonal rope loop and up to 10 collinear posts on its left, find the smallest set of posts to remove so the rope can be pulled free to the right.	Hard9	GeometryGraph+2	No attempts yet	1s	128 MB	Judgeable
Simplifying the FarmGiven a weighted graph where each edge length occurs at most three times, find the minimum spanning tree weight and count distinct minimum spanning trees modulo 1e9+7.	Hard9	Minimum spanning treeUnion-find+2	No attempts yet	1s	128 MB	Judgeable
BottleneckGiven a tree of one-way paths toward field 1, each with a per-time-unit cow capacity, answer K queries for the most cows that can reach field 1 by time T.	Hard9	TreeGreedy+2	No attempts yet	1s	128 MB	Judgeable
Taking TurnsTwo players alternately take bales from a line, skipping any number of earlier bales; each plays optimally and takes the leftmost optimal bale. Find each player's total.	Hard9	Dynamic programmingGreedy+2	No attempts yet	1s	128 MB	Judgeable
Cow HopscotchChoose an outbound path of jumps (each at most K squares) and a return path that only lands on squares one less than an outbound square, maximizing collected values.	Hard9	Dynamic programmingSegment tree+2	No attempts yet	1s	128 MB	Judgeable
Largest FenceGiven N grid points with no three collinear, find the size of the largest subset whose points form the vertices of a convex polygon.	Hard9	GeometryDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
CastingFor a convex polygon, count the vertex pairs whose connecting line splits it into two parts that can each be pulled out by translation.	Hard9	GeometryTwo pointers+2	No attempts yet	1s	128 MB	Judgeable
Watering the FieldsPlace 3-cell sprinklers on a fenced grid so every non-scarecrow cell is watered exactly once, choosing tracks and sprinklers by a fixed lexicographic rule.	Hard9	GreedySimulation+1	No attempts yet	1s	128 MB	Judgeable
Forgetful WaiterCustomers sit around a round table and pass pizzas left or right each turn; find the minimum number of turns until every pizza reaches the customer who ordered it.	Hard9	GraphGreedy+2	No attempts yet	1s	128 MB	Judgeable
Warez TestOn a grid of walls, boxes, and targets, find the shortest sequence of Jimmy's moves that pushes every box onto a target, breaking ties by the lexicographically smallest move string.	Hard9	BFSGraph+2	No attempts yet	1s	128 MB	Judgeable
Winmine (Minesweeper)Count the ways to place the remaining mines on the unrevealed squares so that every revealed number matches its adjacent mine count, modulo 1000003.	Hard9	Dynamic programmingGraph+2	No attempts yet	2s	512 MB	Judgeable
Very Boring HomeworkInsert N keys into a BST, lay out its ASCII drawing, and report up to 5 small rectangular fragments of the picture.	Hard9	TreeImplementation+1	No attempts yet	2s	128 MB	Judgeable
ServersGiven a weighted connected graph with server ranks at most 10, count for each server the vertices W such that no vertex closer or equally close has a larger rank, then sum.	Hard9	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
City NavigationCompute the shortest legal right-hand-side driving distance between two driveways in a numbered grid city with some road segments missing.	Hard9	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
PendulumSimulate an idealized pendulum swinging around point hooks on a wall and print the length of the periodic orbit it eventually settles into.	Hard9	GeometrySimulation+2	No attempts yet	1s	128 MB	Judgeable
Cyclic Antimonotonic PermutationsFor each n, output the lexicographically smallest permutation of 1 to n that is both antimonotonic (every middle element is a local min or max) and a single cycle when read as a pointer mapping.	Hard9	CombinatoricsMath+2	No attempts yet	2s	128 MB	Judgeable
Construct the Wall MazeGiven three wall lengths and a shortest-path string in a 6x6 grid, construct a valid maze consistent with it, choosing the lexicographically smallest answer.	Hard9	Brute forceBFS+2	No attempts yet	1s	128 MB	Judgeable
Mine the GradientGiven a grayscale grid, find the largest square subgrid whose values follow a vertical, horizontal, or diagonal uniform gradient, and report its area.	Hard9	Dynamic programmingImplementation+2	No attempts yet	10s	128 MB	Judgeable
Alea iacta estGiven a linear congruential generator, compute the maximum Yahtzee score over eleven rounds by choosing which dice to keep and which combination to score each round.	Hard9	Dynamic programmingSimulation+2	No attempts yet	2s	128 MB	Judgeable
The Herbalists' VillageGiven a friendship graph, decide whether it has a planar straight-line drawing where every vertex reaches infinity without crossing an edge.	Hard9	GraphGeometry+2	No attempts yet	1s	128 MB	Judgeable
DownpaymentGiven future monthly interest rates for m mortgage plans, binding periods, and switch penalties, find the schedule of plan choices that minimizes the total money paid, with debt rounded down each month.	Hard9	Dynamic programmingGreedy+2	No attempts yet	1s	256 MB	Judgeable
A Romantic Movie OutingMaintain a dynamic set of occupied seats across a huge theatre, answer queries for the combined field-of-vision inconvenience of two seats, and at the end find the minimum over far unoccupied seat pairs.	Hard9	Segment treeDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
The Lights Going On and OffGiven a light grid, pushing the button beside row k XORs it with the row above; count how many distinct bottom-row patterns can result from any subset and order of pushes.	Hard9	Bit manipulationMath+2	No attempts yet	1s	128 MB	Judgeable
LandingGiven up to 100000 integer points, find the largest circle whose boundary passes through at least three points and whose interior contains none, and output R^2 as a reduced fraction.	Hard9	GeometryCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Move that Mouse AGAINGiven up to 50,000 axis-aligned rectangles in a fixed bottom-to-top stacking order, process 50,000 point clicks, printing the topmost window at each point and moving it to the top of the stack.	Hard9	Segment treeGeometry+2	No attempts yet	3s	128 MB	Judgeable
Fast FoodGiven up to 50 points in a 10 by 10 square, compute for each point the area of its Voronoi cell within the square and report the percentage, rounded to nearest with halves up.	Hard9	GeometryDivide and conquer+2	No attempts yet	1s	128 MB	Judgeable
Phylogenetic TreeGiven the graph of organisms joined when their tree distance is at most 3, find the fewest edges in any phylogenetic tree that produces it.	Hard9	GraphTree+2	No attempts yet	1s	128 MB	Judgeable
Checker BoardEach row holds at most one checker per color; players slide their pieces along rows and the one who cannot move loses. Decide whether White wins, Black wins, or the game can run forever.	Hard9	Game theoryGreedy+2	No attempts yet	1s	128 MB	Judgeable
TelecorpPlace one of M module types on any subset of N teleporters, each jump skipping ahead and multiplying speed, to minimize total travel time from 0 to L.	Hard9	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Longest Paths in a TreeA rooted tree has weighted edges. Handle point updates to edge weights and queries that ask for the maximum-weight downward path from a vertex inside its subtree.	Hard9	TreeSegment tree+2	No attempts yet	5s	1024 MB	Judgeable
Falling BallsGiven slanted platforms whose endpoints move over time, find the final x-coordinate reached by a ball dropped at a given x.	Hard9	Segment treeTree+2	No attempts yet	2s	1024 MB	Judgeable
Joy of Mobile RoutingGiven grid building heights and antennas, find the shortest path from a start to a destination intersection where every visited intersection has line-of-sight to some antenna.	Hard9	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
Prince of PersiaGiven a grid room, mirrors with fixed orientations and allowed cells, and plates on walls, decide whether the light ray can reach every plate.	Hard9	SimulationGraph+2	No attempts yet	1s	128 MB	Judgeable
Deformed WheelSimulate a convex polygon rolling down a piecewise-linear hill until it comes to rest, and print the final position of its center of gravity.	Hard9	GeometrySimulation+2	No attempts yet	1s	128 MB	Judgeable
Parallel ExpectationsGiven two programs run by randomly interleaving their instructions, find the expected final value of every shared variable.	Hard9	ProbabilityDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
Find the BorderGiven a closed self-intersecting polyline, count the vertices of the border of its interior, the outer boundary enclosing all bounded regions.	Hard9	GeometryImplementation+2	No attempts yet	2s	128 MB	Judgeable
IlluminationAssign N fixed angular directions to N sources so their wedges cover the plane and the sum of projections is minimized, tie-broken lexicographically.	Hard9	GeometryCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
King's QuestFor each son, list every girl he likes such that a perfect matching still exists when he marries her.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
ExamGiven each student's distribution over exam scores, find the exact probability that the sequence of European marks from all students avoids every listed unpleasant string.	Hard9	Dynamic programmingString matching+2	No attempts yet	2s	128 MB	Judgeable
JoggerGiven the distance matrix of a tree with houses as leaves, find the leaf pair whose weighted travel time (distance times r plus internal nodes crossed times t) is largest.	Hard9	TreeGraph+2	No attempts yet	1s	128 MB	Judgeable
PurifyRepeatedly delete forbidden substrings from P, always choosing the earliest-ending occurrence and removing the shortest such forbidden word, then print what remains.	Hard9	StringTrie+2	No attempts yet	1s	64 MB	Judgeable
DuopolyGiven two sets of weighted bids on channels, where bids within one company are disjoint, pick a subset of non-conflicting bids to maximize total price.	Hard9	Dynamic programmingGreedy+1	No attempts yet	3s	32 MB	Judgeable
Coloring mapsSimulate a greedy 5-coloring where each vertex takes the smallest color not used by already colored neighbors and report failure.	Hard9	GraphGreedy+1	No attempts yet	1s	32 MB	Judgeable
Structural IsomersCount the number of distinct alkane carbon skeletons (free trees in which every node has degree at most 4) with n carbon atoms.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Juggle with CriteriaFor each of n five-symbol relation patterns (<, =, >) and a fixed length l, decide whether two permutations of length l exist whose inversion count, local inversions, LIS, longest increasing substring, and fixed points match that exact pattern.	Hard9	CombinatoricsDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Accountant NotesFor each note, find every starting row in the summary file where a renamed transcription of the note appears as consecutive rows.	Hard9	String matchingHash map+2	No attempts yet	5s	512 MB	Judgeable
Hypervisor MacrOSDecode an altered event log with a hidden reverse switch by maintaining reachability and answering whether A must precede B.	Hard9	GraphTopological sort+2	No attempts yet	5s	512 MB	Judgeable
Suffix Array ReconstructionGiven a permutation p, decide whether it is the suffix array of some lowercase string and, if so, output the lexicographically smallest such string.	Hard9	StringGreedy+2	No attempts yet	1s	512 MB	Judgeable
Markov TrainsFind the station list maximizing the chance of arriving by a deadline when each train may be cancelled and the traveler waits for the next one after a cancellation.	Hard9	Dynamic programmingProbability+1	No attempts yet	1s	128 MB	Judgeable
Mirror TrapFor each box [-x,x]x[-y,y]x[-z,z], find the maximum Manhattan distance a laser at the origin can travel before returning to the origin, avoiding edges and vertices.	Hard9	MathNumber theory+2	No attempts yet	3s	512 MB	Judgeable
Dextrogyrate CamelFind the longest closed camel route that starts at oasis 1 heading to oasis 2, always turns right by at most 180 degrees at each oasis, never crosses itself, and visits the most distinct oases.	Hard9	GeometryDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Bus TourChoose a sequence of attractions with strictly increasing construction times maximizing attractiveness collected plus Manhattan travel distance.	Hard9	Dynamic programmingSorting+2	No attempts yet	1s	128 MB	Judgeable
Save the DinosaursFor each vacant point, add it to the existing set and report the area protected by the soldiers (the region where every move gets closer to some soldier).	Hard9	GeometrySorting+2	No attempts yet	1s	128 MB	Judgeable
Wandering Flea TrainersGiven two functional graphs on n labeled nodes, decide whether some vertex relabeling makes the graphs isomorphic, i.e. the fleas' dance is identical.	Hard9	GraphDFS+2	No attempts yet	3s	128 MB	Judgeable