Problems

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Total results29,423 problems

Equilateral Dominoes
Hard8
Backtracking, Geometry+2
No attempts yet
Time limit
15s
Memory limit
128 MB
Judgeable
Game Rigging
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Highway Construction
Hard8
Tree, Binary search+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A Reasonable Ranking
Hard8
Graph, Topological sort+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Burns' Rods
Hard8
Implementation, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rectangles Too!
Hard8
Sorting, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
The 2 x 2 x 2 Rubik's Cube
Hard8
BFS, Simulation+2
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Globulous Gumdrops
Hard8
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Censorship
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
RSI: Two-Finger Numeric Typing
Hard8
Dynamic programming
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Planet Hunting
Hard8
Geometry, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
2D Matrix
Hard8
Hash map, Sorting+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Vigenère Cipher
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
5s
Memory limit
64 MB
Judgeable
Cover All Points with Three Squares
Hard8
Binary search, Greedy+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Cyclic Rotation Cipher
Hard8
String, Sorting+1
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
One-Way Roads
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Byephone
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
3 MB
Judgeable
Painting Patterns
Hard8
Geometry, Prefix sum+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Necklace
Hard8
Dynamic programming, Greedy
No attempts yet
Time limit
1s
Memory limit
16 MB
Judgeable
Downtown One-Way Streets
Hard8
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Collision of Asteroids
Hard8
Geometry, Binary search+1
No attempts yet
Time limit
1s
Memory limit
16 MB
Judgeable
Union Area of Triangles
Hard8
Geometry, Segment tree+2
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Cakes
Hard8
Greedy, Sorting+1
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Encoding
Hard8
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Three Bit Computer Strikes Back
Hard8
Graph, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Increasing Subsequences
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
4s
Memory limit
128 MB
Judgeable
Battleship
Hard8
Greedy, Backtracking+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Grid
Hard8
Geometry, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Log Analysis
Hard8
Array, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Distinct Digits
Hard8
BFS, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Red Chips, Green Chips
Hard8
Game theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Corridor
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
KBTU Party
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Panda Land 5: Panda Programming Language
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Almost Clear
Hard8
Geometry, Binary search+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Walaweh
Hard8
Recursion, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Worst Locations
Hard8
Tree, Geometry+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Counting BST
Hard8
Combinatorics, Tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Playing With Stones
Hard8
Game theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fire Drill
Hard8
Dynamic programming, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Road Accident
Hard8
Geometry, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Harder Sokoban Problem
Hard8
BFS, Graph+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Fool Game
Hard8
Game theory, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hamming Sequence
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Garlands
Hard8
Binary search, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Knowledge for the Masses
Hard8
Greedy, Prefix sum+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
YAPTCHA
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Museum Tour
Hard8
Graph, Simulation+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Morphing is fun
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Counting Heaps
Hard8
Combinatorics, Tree+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Closest Point
Hard8
Divide and conquer, Sorting+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Johnny and the Quadratic Equation
Hard8
Number theory, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Prison rearrangement
Hard8
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Picnic
Hard8
Geometry, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Arithmetic Rectangle
Hard8
Dynamic programming, Array+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Bytean Road Race
Hard8
Graph, DFS+2
No attempts yet
Time limit
3s
Memory limit
64 MB
Judgeable
Ants
Hard8
Math, Simulation+2
No attempts yet
Time limit
3s
Memory limit
8 MB
Judgeable
Bits Generator
Hard8
Math, Number theory+2
No attempts yet
Time limit
3s
Memory limit
64 MB
Judgeable
Intelligence Quotient
Hard8
Graph, Combinatorics+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Cave
Hard8
Tree, DFS+2
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Ternary Trees
Hard8
Tree, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Firefighter
Hard8
Graph, Tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Greedy Farmers
Hard8
Graph, Game theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Curious Prince
Hard8
Geometry, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Hallucinogenic Carnations
Hard8
Geometry, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tetris
Hard8
Dynamic programming, Matrix+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Radio
Hard8
Geometry, Array
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Showy Self-Defense
Hard8
Graph, Game theory+2
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Beer Numbers
Hard8
String, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Equivalent Knight Moves
Hard8
Math, Number theory
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Fibonacci Sums
Hard8
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Special Forces Manoeuvres
Hard8
Geometry, Binary search+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Vending Machine
Hard8
Dynamic programming, Greedy
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Evaluation of an Expression
Hard8
Math, Number theory+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Shut Down the Machines
Hard8
Dynamic programming, Graph+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Catching Moles
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Gates
Hard8
Implementation, Greedy+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Fruit Chicken
Hard8
Tree, Binary search+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
C-algae
Hard8
Graph, Divide and conquer+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Maximal Orders of Permutations
Hard8
Number theory, Greedy+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Numerals of the Przesmyks
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Motorways
Hard8
Graph, Sorting+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Trinomial
Hard8
Math, Number theory+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Connections
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Sums
Hard8
Number theory, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Resort
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Skiers
Hard8
Graph, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
B-Smooth Numbers
Hard8
Number theory, Segment tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pawn
Hard8
Number theory, Math+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Green Game
Hard8
Game theory, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Peaceful Commission
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Island
Hard8
Tree, DFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Necklaces
Hard8
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
City Tour
Hard8
Graph, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Automorphisms
Hard8
Combinatorics, Math+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Triple-Arm Crane
Hard8
Greedy, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Labyrinth of Wells
Hard8
Graph, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
P-Broken-Line
Hard8
BFS, Graph+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Polygons
Hard8
Game theory, Tree+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Empty Cuboids
Hard8
Sorting, Two pointers+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Equilateral DominoesGiven up to 6 equilateral dominoes with pip values 1 to 6, tile a connected subset on the triangular grid to maximize shared edges between adjacent matching ends.	Hard8	BacktrackingGeometry+2	No attempts yet	15s	128 MB	Judgeable
Game RiggingGiven a set of players, a subset of friends, and known guaranteed match-up outcomes, decide whether a friend can be made to win the elimination tournament.	Hard8	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Highway ConstructionChoose a path in a weighted tree so that the maximum distance from any node to the path is minimized, and report that distance.	Hard8	TreeBinary search+2	No attempts yet	1s	128 MB	Judgeable
A Reasonable RankingGiven a complete tournament's win-loss table, find the lexicographically smallest ranking in which each higher player is connected to each lower player through a chain of intermediate wins.	Hard8	GraphTopological sort+2	No attempts yet	1s	128 MB	Judgeable
Burns' RodsGiven the six colors on each of N slices plus both end caps, decide whether some sequence of 180-degree twists makes labels share a color exactly when they share a face.	Hard8	ImplementationSimulation+2	No attempts yet	1s	128 MB	Judgeable
Rectangles Too!Find the longest chain of rectangles where each rectangle lies strictly below and to the left of the next one.	Hard8	SortingDynamic programming+1	No attempts yet	3s	128 MB	Judgeable
The 2 x 2 x 2 Rubik's CubeGiven a scrambled 2x2x2 Rubik's cube, compute the minimum number of 90-degree turns needed to solve it.	Hard8	BFSSimulation+2	No attempts yet	10s	1024 MB	Judgeable
Globulous GumdropsGiven spheres of radii r_i and a tube of diameter d, find the shortest cylinder length holding them all.	Hard8	GeometryDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
CensorshipGiven a text and a filter word set, remove occurrences repeatedly to make the shortest possible result and report its length.	Hard8	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
RSI: Two-Finger Numeric TypingGiven a digit string, type it on a two-finger keypad in the fewest time units, keeping the left finger always in a strictly smaller column than the right.	Hard8	Dynamic programming	No attempts yet	1s	128 MB	Judgeable
Planet HuntingGiven the moon's positions at three times and the planet's period, find the star to planet distance by solving for the orbital phase.	Hard8	GeometryMath+1	No attempts yet	1s	128 MB	Judgeable
2D MatrixSplit N points into two disjoint non-empty sets, each centrally symmetric, and print every division's two centres in lexicographic order.	Hard8	Hash mapSorting+2	No attempts yet	1s	64 MB	Judgeable
Vigenère CipherGiven a ciphertext and pair frequencies, find the key length-K shift maximizing the total frequency of adjacent plaintext letter pairs.	Hard8	Dynamic programmingString+1	No attempts yet	5s	64 MB	Judgeable
Cover All Points with Three SquaresFind the smallest integer side length d so that three axis-aligned d×d squares can cover all N given points.	Hard8	Binary searchGreedy+2	No attempts yet	2s	64 MB	Judgeable
Cyclic Rotation CipherReconstruct the original lowercase string from its Burrows-Wheeler transform index i and last column R.	Hard8	StringSorting+1	No attempts yet	1s	32 MB	Judgeable
One-Way RoadsDecide whether the undirected streets of a graph can all be oriented so that each required ordered pair stays reachable from the first to the second.	Hard8	GraphDFS+2	No attempts yet	2s	64 MB	Judgeable
ByephoneFind the longest common subsequence of two strings up to length 10000 within 3MB of memory, breaking ties by the lexicographically smallest result.	Hard8	Dynamic programmingString+2	No attempts yet	2s	3 MB	Judgeable
Painting PatternsCount grid cells painted black by up to N rectangle operations, each applying one of three periodic patterns under OR overlap.	Hard8	GeometryPrefix sum+2	No attempts yet	2s	64 MB	Judgeable
NecklaceGiven a target cyclic bead order and a removal order from a pin, minimize the largest number of beads held aside while building the necklace from both ends.	Hard8	Dynamic programmingGreedy	No attempts yet	1s	16 MB	Judgeable
Downtown One-Way StreetsOrient every edge of an undirected planar graph to minimize the maximum outdegree over all vertices.	Hard8	GraphGreedy+2	No attempts yet	1s	128 MB	Judgeable
Collision of AsteroidsGiven two moving convex hulls in 3D, decide whether they overlap at some past or future time.	Hard8	GeometryBinary search+1	No attempts yet	1s	16 MB	Judgeable
Union Area of TrianglesGiven right isosceles triangles with axis-parallel legs and hypotenuse of slope -1, compute the area of their union.	Hard8	GeometrySegment tree+2	No attempts yet	1s	32 MB	Judgeable
CakesSchedule dough preparation and single-oven baking for N cakes so that all finish as early as possible.	Hard8	GreedySorting+1	No attempts yet	1s	32 MB	Judgeable
EncodingFind the shortest encoding length for a target string under dynamic coding, where a changing marker toggles between verbatim and interpreted modes.	Hard8	Dynamic programmingString	No attempts yet	1s	128 MB	Judgeable
Three Bit Computer Strikes BackGiven up to 5 functions on states 0..n-1, decide whether some composition of them maps every state to 0.	Hard8	GraphMath+1	No attempts yet	1s	128 MB	Judgeable
Increasing SubsequencesCount permutations of 1..N whose longest increasing subsequence has length exactly B, modulo 1,000,000,000.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	4s	128 MB	Judgeable
BattleshipFire order over a 10x10 grid is given; place the ten standard ships without touching so the game lasts as long as possible.	Hard8	GreedyBacktracking+2	No attempts yet	2s	256 MB	Judgeable
GridGiven n points, decide whether there exist an axis-aligned grid of evenly spaced lines and a straight line whose intersection set is exactly those points.	Hard8	GeometryMath+2	No attempts yet	1s	128 MB	Judgeable
Log AnalysisMaintain a volatile log under insertions in the middle, block deletions, and queries asking how many distinct event types appear in a position range.	Hard8	ArraySegment tree+2	No attempts yet	2s	256 MB	Judgeable
Distinct DigitsFor each n up to 65536, find the smallest positive multiple of n whose decimal digits use as few distinct digits as possible.	Hard8	BFSNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Red Chips, Green ChipsWith r red and g green chips, players alternately remove k chips of one color where k divides the other color's count; decide the winner under optimal play.	Hard8	Game theoryMath+2	No attempts yet	1s	128 MB	Judgeable
CorridorFind the largest radius of a sphere that can travel west to east through a corridor, where point pillars and the two side walls block it.	Hard8	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
KBTU PartyCount the ways to choose r disjoint acquainted girl-boy pairs when girl j knows exactly the first 2j-1 boys, modulo 2946859.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Panda Land 5: Panda Programming LanguageReorder up to 18 functions to satisfy call-before-use ordering, minimizing a move cost weighted by line counts, or report impossibility.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
Almost ClearGiven two disjoint convex polygons A and B and a point C outside both, decide whether B hides none, part, or all of A as seen from C.	Hard8	GeometryBinary search+2	No attempts yet	1s	128 MB	Judgeable
WalawehEach Walaweh list W_L is built from W_{L-1} by a fixed 8-step cycle of append/prepend and optional reversal operations; convert between (length, index) and the binary string. The recursion only needs O(log N) work per level, but the reversal and leading-zero handling make the index bit-mapping non-obvious.	Hard8	RecursionBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
Worst LocationsGiven a perfect binary tree and two distance-from-leaf descriptions, decide whether some pair of matching vertices sits farther than Z apart.	Hard8	TreeGeometry+2	No attempts yet	1s	128 MB	Judgeable
Counting BSTCount insertion sequences of distinct values from 1..M that build a BST with the same shape as a given sequence, modulo 1000003.	Hard8	CombinatoricsTree+2	No attempts yet	1s	128 MB	Judgeable
Playing With StonesA subtraction game on piles where each move removes at most half a pile; decide if the first player wins, with pile sizes up to 2e18.	Hard8	Game theoryMath+2	No attempts yet	1s	128 MB	Judgeable
Fire DrillPlan rescues in a multi-floor grid so the total points collected within the time limit is maximized, where a laden move costs double.	Hard8	Dynamic programmingGraph+1	No attempts yet	1s	128 MB	Judgeable
Road AccidentFind which quarter-part of each car (corner plus adjacent side halves) first touches the other car during straight-line motion before impact.	Hard8	GeometrySimulation+1	No attempts yet	1s	128 MB	Judgeable
Harder Sokoban ProblemChoose player and container start cells to maximize the minimum Sokoban moves needed to push the container onto the single destination cell.	Hard8	BFSGraph+2	No attempts yet	5s	128 MB	Judgeable
Fool GameGiven a trump suit and both hands, find the lowest-ranked opening card that forces the defender to take, assuming optimal defense.	Hard8	Game theoryDFS+2	No attempts yet	1s	128 MB	Judgeable
Hamming SequenceGiven three primes and an index i, find the i-th smallest number greater than 1 whose prime factors all lie among those three primes.	Hard8	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
GarlandsSplit a weighted sequence of n pieces into m segments of even length, each half-segment at most d pieces, minimizing the maximum half-segment weight.	Hard8	Binary searchDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Knowledge for the MassesEach row's racks keep their order and can shift left or right at cost 1 per rack; find the cheapest passage position and all positions attaining it.	Hard8	GreedyPrefix sum+2	No attempts yet	1s	512 MB	Judgeable
YAPTCHAFor each query n, compute the sum of floor(((3k+6)!+1)/(3k+7) - floor((3k+6)!/(3k+7))) over k from 1 to n. The sum equals the count of primes among 3k+7 for k=1..n, so precompute primes up to 3n+7 and prefix counts.	Hard8	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
Museum TourGiven a connected graph with max degree 3 and a fixed cyclic door order per room, count starting rooms whose edge-following walk eventually traverses every corridor.	Hard8	GraphSimulation+2	No attempts yet	1s	512 MB	Judgeable
Morphing is funGiven color mutation rules, decide whether every fixed-height cell eventually stops changing color over the nights.	Hard8	GraphDFS+2	No attempts yet	1s	512 MB	Judgeable
Counting HeapsCount the number of ways to label a rooted tree with 1..n so each node is smaller than its parent, modulo a possibly composite m.	Hard8	CombinatoricsTree+2	No attempts yet	5s	128 MB	Judgeable
Closest PointFor each of N points, output the squared distance to the nearest other point.	Hard8	Divide and conquerSorting+2	No attempts yet	3s	128 MB	Judgeable
Johnny and the Quadratic EquationDecide whether a quadratic congruence modulo 2^32 has a solution in x.	Hard8	Number theoryMath+1	No attempts yet	1s	512 MB	Judgeable
Prison rearrangementGiven a bipartite conflict graph between two prisons of size m, find the largest k <= m/2 so that k prisoners can be swapped across while keeping every conflicting pair apart.	Hard8	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
The PicnicGiven up to 99 points, find the largest convex polygon whose vertices are points and whose interior contains no other point.	Hard8	GeometryDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Arithmetic RectangleGiven an n by m grid of integers, find the largest rectangle in which every row and every column forms an arithmetic sequence, and output its area in unit squares.	Hard8	Dynamic programmingArray+2	No attempts yet	3s	128 MB	Judgeable
Bytean Road RaceGiven a planar south/east DAG from node 1 to node n, answer queries asking whether some monotone path passes through both given crossings.	Hard8	GraphDFS+2	No attempts yet	3s	64 MB	Judgeable
AntsGiven a tree tour as a 2n-bit sequence, compute the exact time when the two ants walking in opposite directions turn around for the second time, as a reduced fraction.	Hard8	MathSimulation+2	No attempts yet	3s	8 MB	Judgeable
Bits GeneratorCount how many of the m possible seeds make a floor-mod pseudorandom generator output a given bit string of length n.	Hard8	MathNumber theory+2	No attempts yet	3s	64 MB	Judgeable
Intelligence QuotientGiven a bipartite acquaintance graph and IQ values, choose a clique (subsets of both sides where every cross pair is acquainted) maximizing total IQ.	Hard8	GraphCombinatorics+2	No attempts yet	3s	128 MB	Judgeable
CaveGiven a tree of n nodes, find every k such that the tree splits into k connected parts of equal size.	Hard8	TreeDFS+2	No attempts yet	3s	256 MB	Judgeable
Ternary TreesLabel the leaves of a complete ternary tree so that, given a fixed query order, the leaf values stay hidden until every leaf is asked.	Hard8	TreeRecursion+2	No attempts yet	1s	128 MB	Judgeable
FirefighterOn a graph with max degree 3, fire spreads one step per hour while one house can be protected each hour; maximize houses kept safe.	Hard8	GraphTree+2	No attempts yet	1s	128 MB	Judgeable
Greedy FarmersAssign each node the smallest Grundy number absent from its neighbors, maximizing the count of nodes that get infinity (-1).	Hard8	GraphGame theory+2	No attempts yet	1s	128 MB	Judgeable
The Curious PrinceFind the shortest path along the surface of a convex polyhedron between two given points.	Hard8	GeometryShortest path+2	No attempts yet	1s	128 MB	Judgeable
Hallucinogenic CarnationsFor each of up to 10000 polygons, sum the carnations in grid parcels whose area at least half lies inside the polygon.	Hard8	GeometryPrefix sum+1	No attempts yet	1s	128 MB	Judgeable
TetrisCount ways to fully tile a 4-by-n board with seven Tetris pieces (long piece has 3 cells), given some cells of the first row already covered, modulo 10^6.	Hard8	Dynamic programmingMatrix+2	No attempts yet	1s	128 MB	Judgeable
RadioGiven a circle and a simple polygon, compute the area of the polygon's interior that lies inside the circle.	Hard8	GeometryArray	No attempts yet	1s	128 MB	Judgeable
Showy Self-DefenseGiven n game states, each with optional A/B moves to other states, decide if for every attacker start there is a distinct defender start that can mirror every move.	Hard8	GraphGame theory+2	No attempts yet	10s	128 MB	Judgeable
Beer NumbersDecide whether a positive integer is the only one that can produce its row of binary mugs under any choice of which mug position means 1 and which reading direction.	Hard8	StringCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Equivalent Knight MovesGiven integer move vectors, find the unique Hermite Normal Form basis of the 2D lattice they generate.	Hard8	MathNumber theory	No attempts yet	3s	128 MB	Judgeable
Fibonacci SumsGiven two Zeckendorf representations of positive integers, compute the Zeckendorf representation of their sum.	Hard8	GreedyMath+2	No attempts yet	1s	128 MB	Judgeable
Special Forces ManoeuvresDiscs cover the plane; find the smallest prefix of the given order whose union already covers the entire plane, or report NIE if no prefix does.	Hard8	GeometryBinary search+2	No attempts yet	3s	512 MB	Judgeable
Vending MachineGiven snack prices, stocks, and a budget, choose purchases so that each buy also dispenses one free snack of every cheaper kind still in stock, maximizing total value received.	Hard8	Dynamic programmingGreedy	No attempts yet	1s	128 MB	Judgeable
Evaluation of an ExpressionCount assignments of values to variables modulo a prime that make a given sparse polynomial expression zero, output modulo 30011.	Hard8	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Shut Down the MachinesGiven devices that either shut down alone with a strong shock or reactivate a multiset of other devices with a cheaper weak shock, find the minimum total power, counting each activation separately.	Hard8	Dynamic programmingGraph+1	No attempts yet	1s	256 MB	Judgeable
Catching MolesChoose at most k holes to shoot on a circle; each shot removes the target's moles and pushes neighbors' moles outward, maximizing the total removed.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	256 MB	Judgeable
GatesEach gate outputs the majority state of its inputs (0, 1/2, or 1); decide for every gate whether its state is the same across all valid circuit states.	Hard8	ImplementationGreedy+2	No attempts yet	3s	128 MB	Judgeable
Fruit ChickenA tree has shops at one end and houses at the other, separated by a single bridge edge; assign each open shop a distinct house minimizing the time until all couriers arrive, with no two couriers sharing a road at once.	Hard8	TreeBinary search+2	No attempts yet	3s	128 MB	Judgeable
C-algaeDecide whether each given undirected graph can be built from single vertices by disjoint union and complete join.	Hard8	GraphDivide and conquer+2	No attempts yet	3s	128 MB	Judgeable
Maximal Orders of PermutationsFor each n, find the smallest partition of n whose parts have the maximum possible LCM, then output the lexicographically smallest permutation with those cycle lengths.	Hard8	Number theoryGreedy+2	No attempts yet	3s	512 MB	Judgeable
Numerals of the PrzesmyksConvert numerals over {- , +} with at most m1 consecutive minuses into their rank-ordered representation under the bound m2.	Hard8	CombinatoricsMath+2	No attempts yet	1s	128 MB	Judgeable
MotorwaysAssign each of k motorway chords to one of two sides so that no two chords on the same side interleave, choosing the lexicographically smallest assignment.	Hard8	GraphSorting+1	No attempts yet	1s	128 MB	Judgeable
TrinomialFor each query, output the coefficient of x^i in (x^2+x+1)^n modulo 3, with n up to 10^15.	Hard8	MathNumber theory+2	No attempts yet	3s	128 MB	Judgeable
ConnectionsGiven a directed weighted graph, answer queries asking the length of the k-th shortest walk from c to d, counting equal-length walks separately.	Hard8	GraphShortest path+2	No attempts yet	3s	128 MB	Judgeable
SumsGiven a set A of positive integers and queries b, decide for each b whether it can be written as an unlimited sum of elements of A.	Hard8	Number theoryDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
ResortFind the path from a start clearing to any base clearing that minimizes leftover card points, where track edges are free but lift edges cost points and require enough balance.	Hard8	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
SkiersGiven a planar DAG whose edges leave clearings in west-to-east order, find the minimum number of downhill paths that cover every edge.	Hard8	GraphDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
B-Smooth NumbersCount B-smooth numbers (no prime factor above B) in the interval [n, n+m], with n up to 2e9, m up to 1e8, and B up to 1e6.	Hard8	Number theorySegment tree+2	No attempts yet	1s	128 MB	Judgeable
PawnGiven horizontal and vertical step sizes, count lattice cells reachable from (1,1) inside an axis-aligned rectangle.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Green GameOn a bipartite board where Ann and Billy alternately move a pawn, find all starting fields from which Ann can force the first repeated field's cycle to contain a green field.	Hard8	Game theoryGraph+2	No attempts yet	1s	128 MB	Judgeable
Peaceful CommissionPick exactly one deputy from each of n pairs, avoiding forbidden deputy pairs, and print the lexicographically smallest valid choice or NIE.	Hard8	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
IslandGiven all pairwise shortest tolls among the n seaside triangles, recover the adjacency structure and edge weights of the underlying border tree.	Hard8	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
NecklacesDecide whether two run-length compressed string descriptions encode the same circular necklace up to rotation.	Hard8	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
City TourGiven a connected 4-regular multigraph with an object on each edge, decide whether some closed Eulerian tour starting at an edge midpoint never lets accumulated interest drop below zero.	Hard8	GraphGreedy+2	No attempts yet	1s	128 MB	Judgeable
AutomorphismsGiven a permutation of n vertices, count tournaments (complete oriented graphs) that the permutation preserves as an automorphism, modulo 1000.	Hard8	CombinatoricsMath+2	No attempts yet	3s	128 MB	Judgeable
Triple-Arm CraneGiven p, q, n, find the lexicographically smallest sequence of triple placements (x, x+p or x+q, x+p+q) that covers wagons 1..n exactly once.	Hard8	GreedyMath+2	No attempts yet	1s	128 MB	Judgeable
The Labyrinth of WellsGiven a colored DAG where each room has three outgoing wells, find the minimum number of rooms in a DAG producing the same color sequence for every path.	Hard8	GraphDynamic programming+1	No attempts yet	3s	128 MB	Judgeable
P-Broken-LineFind the minimum number of axis-parallel unit-free segments in an orthogonal polyline from A to B that avoids all n given axis-parallel obstacles.	Hard8	BFSGraph+2	No attempts yet	3s	512 MB	Judgeable
PolygonsA convex polygon is triangulated, one triangle is black; players alternately cut off an ear triangle, and whoever removes the black triangle wins. Decide if the first player wins.	Hard8	Game theoryTree+2	No attempts yet	1s	128 MB	Judgeable
Empty CuboidsGiven up to 5000 integer points, find the largest axis-aligned box anchored at the origin whose strict interior contains none of the points, and output its volume.	Hard8	SortingTwo pointers+2	No attempts yet	3s	128 MB	Judgeable