Problems

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Total results21,230 problems

The Ideal CityHard9
Graph, BFS +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Hyperspace RoutesHard9
Shortest path, Graph +2No attempts yetTime limit5sMemory limit64 MB
Judgeable
Tropical GardenHard9
Graph, Simulation +2No attempts yetTime limit5sMemory limit256 MB
Judgeable
Yin and YangHard9
Tree, Divide and conquer +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Island TravelsHard9
Graph, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Tied DownHard9
Geometry, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Simplifying the FarmHard9
Minimum spanning tree, Union-find +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
BottleneckHard9
Tree, Greedy +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Taking TurnsHard9
Dynamic programming, Greedy +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Cow HopscotchHard9
Dynamic programming, Segment tree +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Largest FenceHard9
Geometry, Dynamic programming +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
CastingHard9
Geometry, Two pointers +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Watering the FieldsHard9
Greedy, Simulation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Forgetful WaiterHard9
Graph, Greedy +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Warez TestHard9
BFS, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Winmine (Minesweeper)Hard9
Dynamic programming, Graph +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Very Boring HomeworkHard9
Tree, Implementation +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
ServersHard9
Graph, Shortest path +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
City NavigationHard9
Graph, Shortest path +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
PendulumHard9
Geometry, Simulation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Cyclic Antimonotonic PermutationsHard9
Combinatorics, Math +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
Construct the Wall MazeHard9
Brute force, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Mine the GradientHard9
Dynamic programming, Implementation +2No attempts yetTime limit10sMemory limit128 MB
Judgeable
Alea iacta estHard9
Dynamic programming, Simulation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
The Herbalists' VillageHard9
Graph, Geometry +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
DownpaymentHard9
Dynamic programming, Greedy +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
A Romantic Movie OutingHard9
Segment tree, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
The Lights Going On and OffHard9
Bit manipulation, Math +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
LandingHard9
Geometry, Combinatorics +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Move that Mouse AGAINHard9
Segment tree, Geometry +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
Fast FoodHard9
Geometry, Divide and conquer +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Phylogenetic TreeHard9
Graph, Tree +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Checker BoardHard9
Game theory, Greedy +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
TelecorpHard9
Dynamic programming, Greedy +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Longest Paths in a TreeHard9
Tree, Segment tree +2No attempts yetTime limit5sMemory limit1024 MB
Judgeable
Falling BallsHard9
Segment tree, Tree +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Joy of Mobile RoutingHard9
Graph, Shortest path +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Prince of PersiaHard9
Simulation, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Deformed WheelHard9
Geometry, Simulation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Parallel ExpectationsHard9
Probability, Dynamic programming +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Find the BorderHard9
Geometry, Implementation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
IlluminationHard9
Geometry, Combinatorics +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
King's QuestHard9
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
ExamHard9
Dynamic programming, String matching +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
JoggerHard9
Tree, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
PurifyHard9
String, Trie +2No attempts yetTime limit1sMemory limit64 MB
Judgeable
DuopolyHard9
Dynamic programming, Greedy +1No attempts yetTime limit3sMemory limit32 MB
Judgeable
Coloring mapsHard9
Graph, Greedy +1No attempts yetTime limit1sMemory limit32 MB
Judgeable
Structural IsomersHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Juggle with CriteriaHard9
Combinatorics, Dynamic programming +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Accountant NotesHard9
String matching, Hash map +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Hypervisor MacrOSHard9
Graph, Topological sort +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
Suffix Array ReconstructionHard9
String, Greedy +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Markov TrainsHard9
Dynamic programming, Probability +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Mirror TrapHard9
Math, Number theory +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
Dextrogyrate CamelHard9
Geometry, Dynamic programming +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Bus TourHard9
Dynamic programming, Sorting +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Save the DinosaursHard9
Geometry, Sorting +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Wandering Flea TrainersHard9
Graph, DFS +2No attempts yetTime limit3sMemory limit128 MB
Judgeable
BankHard9
Greedy, Math +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
SleepwalkerHard9
Recursion, Divide and conquer +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Ice rinkHard9
BFS, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
AB-wordsHard9
Tree, Hash map +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Recursive AntHard9
Divide and conquer, Recursion +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
MessengersHard9
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
TreesHard9
Array, Math +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Axes of SymmetryHard9
String matching, Geometry +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Driving ExamHard9
Graph, Dynamic programming +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
TollHard9
Graph, MathNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Isles in a Triangular GridHard9
Geometry, Brute force +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
IslandHard9
Graph, Shortest path +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
The CodeHard9
Trie, String +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
HamstersHard9
String matching, Dynamic programming +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
OnesHard9
Math, Combinatorics +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
GarbageHard9
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
PeriodicityHard9
String, Prefix sum +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Milk MultidrinkHard9
Tree, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Ski RentalHard9
Segment tree, Geometry +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Binary KnockoutHard9
Game theory, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
SpiderHard9
Geometry, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
JourneysHard9
Graph, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Computational BiologyHard9
String, Sorting +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
Hard ChoiceHard9
Graph, DFS +2No attempts yetTime limit5sMemory limit128 MB
Judgeable
FragmentsHard9
String matching, Dynamic programming +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Army TrainingHard9
Geometry, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Blindfold NimHard9
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Quasi-templateHard9
String matching, String +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
DiamondHard9
Geometry, Brute force +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
FishesHard9
Graph, Geometry +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Programming ContestHard9
Greedy, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
WatchmenHard9
Geometry, Graph +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
QuestionsHard9
Brute force, Simulation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Dragon MilkdrinkerHard9
Probability, Math +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Video PokerHard9
Brute force, Combinatorics +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
MicrochipsHard9
Graph, Number theory +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Fibonacci WordHard9
String, Dynamic programming +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
HighwaysHard9
Matrix, Segment tree +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Reconstructing the Convex PolygonHard9
Graph, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
ManhuntHard9
Graph, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Prefix-SuffixesHard9
String matching, String +1No attempts yetTime limit1sMemory limit128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
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
BankFind the lexicographically smallest four-currency reserve vector that lets a bank serve all clients in some order, where serving client i requires its remaining need in all four currencies to be covered at once.	Hard9	GreedyMath+2	No attempts yet	1s	128 MB	Judgeable
SleepwalkerA self-similar walk on a 3^k by 3^k grid is defined by a recursive rewrite; given a starting tile on the walk and a hole tile, find the number of steps until the walk reaches the hole.	Hard9	RecursionDivide and conquer+2	No attempts yet	1s	128 MB	Judgeable
Ice rinkA skater slides in straight lines across a square rink with rectilinear obstacles, stopping only at walls, and must reach the finish point in the fewest slides.	Hard9	BFSGraph+2	No attempts yet	1s	128 MB	Judgeable
AB-wordsGiven up to 1000 nice ab-words (balanced parentheses words), count the maximum subset of pairwise non-similar words under a recursive similarity relation.	Hard9	TreeHash map+2	No attempts yet	1s	128 MB	Judgeable
Recursive AntOn a 2^n by 2^n board with at most 50 forbidden cells, find for each of the four borders a cell where a recursive quarter-by-quarter Hamiltonian tour can end, or report none.	Hard9	Divide and conquerRecursion+2	No attempts yet	1s	128 MB	Judgeable
MessengersGiven a 2-connected graph, output the lexicographically smallest pair of search plans from city 1 so that for any single occupied non-capital city, both messengers together warn every city.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
TreesFor each tree, find the smallest adjacent-difference sum reachable by either keeping the row or swapping that tree with one other tree.	Hard9	ArrayMath+2	No attempts yet	1s	128 MB	Judgeable
Axes of SymmetryFor each simple polygon, count its axes of symmetry; n can reach 100000, so the check must run in near-linear time.	Hard9	String matchingGeometry+2	No attempts yet	1s	128 MB	Judgeable
Driving ExamBuild at most k new horizontal one-way streets on a grid so that the number of streets whose southern end can reach every street's northern end is maximized.	Hard9	GraphDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
TollEach selected town must charge on exactly one incident road, and no road may be charged by both endpoints. Maximize selected towns in a general graph, not necessarily the whole graph.	Hard9	GraphMath	No attempts yet	1s	128 MB	Judgeable
Isles in a Triangular GridEnumerate all non-congruent triangular-grid isles of up to ten triangles, canonicalizing each by the lexicographically smallest clockwise boundary-turn word.	Hard9	GeometryBrute force+2	No attempts yet	1s	128 MB	Judgeable
IslandGiven a convex polygon with towns on its vertices, all diagonals and sides drawn, and some segments blocked, find the shortest path from vertex n to vertex 1 using roads and their crossings.	Hard9	GraphShortest path+1	No attempts yet	1s	128 MB	Judgeable
The CodeGiven a prefix code entered via button presses, find the code words that resynchronize decoding after any loss of leading bits.	Hard9	TrieString+2	No attempts yet	1s	128 MB	Judgeable
HamstersFind the shortest lowercase string containing at least m occurrences of the given hamster names, counted with multiplicity.	Hard9	String matchingDynamic programming+2	No attempts yet	3s	512 MB	Judgeable
OnesGiven run lengths of n in binary, output run lengths of the binary form of sks(n), the total UFO count over 1 to n.	Hard9	MathCombinatorics+2	No attempts yet	3s	512 MB	Judgeable
GarbageEach street needs its state flipped or not; a route is a simple cycle, and driving a street flips it. Find the minimum total length of cycles whose symmetric difference equals the set of streets needing a flip.	Hard9	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
PeriodicityFor each name, find the lexicographically smallest bit string of the same length whose set of periods equals the name's set of periods, or XXX if none exists.	Hard9	StringPrefix sum+2	No attempts yet	1s	128 MB	Judgeable
Milk MultidrinkDecide whether a tree with n nodes has a Hamiltonian path from 1 to n where consecutive vertices stay within distance two.	Hard9	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
Ski RentalGiven daily snowfall amounts with point updates, answer queries asking for the maximum average snowfall over a consecutive run starting at a given day, reported as an irreducible fraction.	Hard9	Segment treeGeometry+1	No attempts yet	1s	128 MB	Judgeable
Binary KnockoutA coin game on a line: each coin may double its position or move one step right; the player unable to move loses. Find the k-th value of n where the second player wins.	Hard9	Game theoryMath+1	No attempts yet	1s	128 MB	Judgeable
SpiderA walk on an infinite regular seven-legged web is given as turn directions; count the web nodes strictly inside the closed polygon it traces.	Hard9	GeometryImplementation+1	No attempts yet	1s	128 MB	Judgeable
JourneysGiven m batches, each joining every town in one interval to every town in a disjoint interval, find the shortest path in highway count from town p to all towns.	Hard9	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Computational BiologyFor each query length m, find a length-m word whose every cyclic rotation appears in s, maximizing the total count of those rotations in s.	Hard9	StringSorting+2	No attempts yet	5s	128 MB	Judgeable
Hard ChoiceAfter streets are closed one by one offline, answer for each query whether two edge-disjoint paths still connect the given pair of junctions.	Hard9	GraphDFS+2	No attempts yet	5s	128 MB	Judgeable
FragmentsCount how many times each digit string appears as a contiguous substring across the decimal forms of all numbers in a union of disjoint integer intervals up to 10^18.	Hard9	String matchingDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Army TrainingGiven n points with no three collinear, answer m queries, each a simple clockwise polygon on those points, counting the points strictly inside it.	Hard9	GeometryCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Blindfold NimEach stack size is uniform on [0, a_i]; compute the probability that the first player wins a game of Nim with hidden positions where a player who overshoots a stack loses at once.	Hard9	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Quasi-templateCount the distinct words that, as substrings of v with possibly overhanging copies, can tile across the whole input; report the count and the shortest, lexicographically smallest such word.	Hard9	String matchingString+2	No attempts yet	1s	128 MB	Judgeable
DiamondGiven a convex polyhedron, choose one plane cut so that the two resulting pieces have the largest combined number of faces.	Hard9	GeometryBrute force+1	No attempts yet	2s	512 MB	Judgeable
FishesGroup recorded closed routes into the fewest fish, where two routes can follow on consecutive days if the start cells touch and every point is visible 24 hours earlier.	Hard9	GraphGeometry+2	No attempts yet	2s	512 MB	Judgeable
Programming ContestGiven each participant's skill per topic, decide whether we can choose n tasks (topic and difficulty) so Byteman is the unique winner under solve-count then points ranking.	Hard9	GreedyMath+2	No attempts yet	2s	512 MB	Judgeable
WatchmenCount, for each city gutter, how many Palace gutters a walker can reach while dodging rotating watchers' lines of sight.	Hard9	GeometryGraph+2	No attempts yet	2s	512 MB	Judgeable
QuestionsSimulate a logic puzzle where princes and a sorcerer reason about a system of variable constraints over time; answer what each prince or the sorcerer knows.	Hard9	Brute forceSimulation+2	No attempts yet	1s	128 MB	Judgeable
Dragon MilkdrinkerCompute the probability that the sum of n independent uniform [m, M] yields is strictly less than h, printed truncated to d decimals.	Hard9	ProbabilityMath+2	No attempts yet	1s	128 MB	Judgeable
Video PokerFor a given video poker payout table, count how many of the 2,598,960 dealt hands make the optimal expected-value strategy discard exactly 0, 1, 2, 3, 4, and 5 cards.	Hard9	Brute forceCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
MicrochipsCount directed walks whose edge-impedance product equals I, allowing repeated vertices and edges, and report infinity when infinitely many such walks exist.	Hard9	GraphNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Fibonacci WordCount occurrences of a given binary pattern in the Fibonacci word F_m and count distinct subwords occurring at least that many times, mod 20062006, with m up to 1e9.	Hard9	StringDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
HighwaysMaintain a layered graph where each province has a few cities and highway lane counts change over time, answering route-count queries modulo d after each update.	Hard9	MatrixSegment tree+1	No attempts yet	1s	128 MB	Judgeable
Reconstructing the Convex PolygonGiven all edges and non-crossing diagonals of a convex polygon with shuffled vertex labels, recover the cyclic boundary order, with vertex 1 first and the smallest possible second vertex.	Hard9	GraphImplementation+1	No attempts yet	1s	128 MB	Judgeable
ManhuntGiven a connected undirected graph where the bandit moves to a different city each night, find the minimum number of days for a search schedule that guarantees capture, or report impossibility.	Hard9	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Prefix-SuffixesCount proper borders summed over all substrings of a given lowercase word of length up to 10^5.	Hard9	String matchingString+1	No attempts yet	1s	128 MB	Judgeable