Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,152 problems

Estimated-Floccinaucinihilipilificated
Hard8
Game theory, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Inversion Number Squared
Hard8
Probability, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
The Five Heroes' Swords
Hard8
Dynamic programming, Game theory+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Recurrence and Period
Hard8
Number theory, Matrix+1
No attempts yet
Time limit
0.5s
Memory limit
512 MB
Judgeable
Sum of five squares
Hard8
Math, Number theory
No attempts yet
Time limit
5.555s
Memory limit
555 MB
Judgeable
Fibonacci Half Sequence
Hard8
Math, Recursion+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Scallion, Not Eggplant
Hard8
Game theory, Graph+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
An Ordinary String Problem
Hard8
Combinatorics, Graph+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Video Surveillance
Hard8
Sorting, Two pointers+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Moving Stones
Hard8
Game theory, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Garden
Hard8
Two pointers, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Divide
Hard8
Number theory, Math
No attempts yet
Time limit
1.8s
Memory limit
1024 MB
Judgeable
Fork
Hard8
Dynamic programming, Probability
No attempts yet
Time limit
0.15s
Memory limit
1024 MB
Judgeable
Sorting
Hard8
Number theory, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fast Interpreter
Hard8
Bit manipulation, Array+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Costume Problems
Hard8
Combinatorics, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gigaskeletons
Hard8
Dynamic programming, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Perfect Triangle Covering
Hard8
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magical clock
Hard8
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
x
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Tree House
Hard8
Math, Greedy+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Decreasing Growth Rate Tragedy 2
Hard8
Geometry, Prefix sum+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hyeoncheol's Blind Date
Hard8
Dynamic programming, Probability+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Socks Pairing Probability for Dongwoo and Tsundere Jaewoo
Hard8
Probability, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Delivery Robot
Hard8
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mousetraps
Hard8
Geometry, Divide and conquer+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Silver Chain
Hard8
Geometry, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magic Mine
Hard8
Binary search, Greedy+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Cat Goose and the Random Matrix
Hard8
Matrix, Prefix sum+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Chariot Race
Hard8
Shortest path, Dynamic programming+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Puzzle
Hard8
Matrix, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Faceted Glasses
Hard8
Geometry, Binary search+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Game
Hard8
Game theory, Number theory+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Mavis and Dracula
Hard8
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Light Bulb Sequence
Hard8
Number theory, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Lazybugs and the Fence
Hard8
String matching, Number theory+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Break, Don't Build
Hard8
Graph, Geometry+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
2048
Hard8
Dynamic programming, Matrix+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Rafiki's Test
Hard8
String, Math+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Chino's Latte Art
Hard8
Geometry, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
BlueTube Park
Hard8
Number theory, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Fence
Hard8
Geometry, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Knights
Hard8
Array, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Inheritance
Hard8
Geometry, Brute force
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Harry Potter and the Railway
Hard8
Graph, DFS+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Stones
Hard8
Bit manipulation, Dynamic programming+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Magic Potions
Hard8
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Maxima
Hard8
Combinatorics, Matrix+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Game
Hard8
Graph, Shortest path+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Villa of Emblem Shape
Hard8
Geometry, Implementation
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Fair Deal of Dice
Hard8
Divide and conquer, Sorting+2
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Choreography
Hard8
Array, Simulation+1
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
Bring Down the Sky Grading Server
Hard8
Game theory, Simulation+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
One Hit
Hard8
Greedy, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Hey Google, Drive!
Hard8
Graph, BFS+1
No attempts yet
Time limit
60s
Memory limit
1024 MB
Judgeable
Love Potion
Hard8
Combinatorics, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Splitting Segments
Hard8
Binary search, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Magical BF 2
Hard8
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Linesweeper
Hard8
Segment tree, Math+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Cake cutting
Hard8
Geometry, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Maximum sum of GCDs
Hard8
Dynamic programming, Number theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hard Linear Algebra Problem
Hard8
Matrix, Linked list+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Gold Digging
Hard8
Dynamic programming, Probability+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Reflected Copy Tree
Hard8
Tree, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Perfect Triples
Hard8
Bit manipulation, Math
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
SNUPC Game
Hard8
Game theory, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
BX Bet
Hard8
Game theory, Trie+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Grow Measure Cut Repeat
Hard8
Segment tree, Implementation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Wrong Queue
Hard8
Array, Binary search+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Gadget Construction
Hard8
Geometry, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Introversion
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Distance Permutation
Hard8
Combinatorics, Dynamic programming+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Knight Game
Hard8
Game theory, Graph+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gacha 101
Hard8
Probability, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Convex Polygon MST
Hard8
Graph, Minimum spanning tree+1
No attempts yet
Time limit
7s
Memory limit
1024 MB
Judgeable
Pool
Hard8
Probability, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Depth First Search
Hard8
Tree, DFS+2
No attempts yet
Time limit
6s
Memory limit
1024 MB
Judgeable
Reversi
Hard8
Game theory, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Aperiodic Appointments
Hard8
String, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Factor-Full Tree
Hard8
Number theory, Tree+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Rigged Lottery
Hard8
String, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Analyzing Contracts
Hard8
Geometry, Segment tree+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Health in Hazard
Hard8
Geometry, Binary search+1
No attempts yet
Time limit
3.5s
Memory limit
1024 MB
Judgeable
International Travel
Hard8
Geometry, Brute force
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Intersegment Activation
Hard8
Bit manipulation, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Royal Problem
Hard8
Graph, Bit manipulation+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Plane stretching
Hard8
Geometry, Two pointers+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
Starry Night (Hard)
Hard8
Prefix sum, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Instant Noodles
Hard8
Hash map, Number theory
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Hosting KCPC
Hard8
Geometry, Sorting+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Secret Swap
Hard8
Union-find, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Not So Distant Strings
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Random Walks in a Big City
Hard8
Graph, BFS+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Astronomy
Hard8
Geometry, Math+1
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Yet Another Coin Problem
Hard8
Dynamic programming, Number theory
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Find the Disobedient Child
Hard8
Math, Binary search
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Chapaev on a Tree
Hard8
Tree, Game theory+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Farm
Hard8
Geometry, Graph+1
No attempts yet
Time limit
0.7s
Memory limit
2048 MB
Judgeable
Hanyang Cherry Picking Contest
Hard8
Tree, Game theory+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pipelined
Hard8
Greedy, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Estimated-FloccinaucinihilipilificatedFind Heeseung's full priority order over N gift candidates by playing the alternating pick game with him, using at most 2048 queries.	Hard8	Game theoryBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Inversion Number SquaredGiven a_i copies of each value i from 1 to n, find the expected square of the inversion count of a uniformly random arrangement, modulo 998244353.	Hard8	ProbabilityCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
The Five Heroes' SwordsGiven five disjoint sets of possible attack powers, find the fewest hardness tests needed in the worst case to identify the strongest sword.	Hard8	Dynamic programmingGame theory+1	No attempts yet	5s	1024 MB	Judgeable
Recurrence and PeriodGiven a prime p and the recurrence x_n = ax_{n-1} + bx_{n-2} mod p, find the lexicographically smallest (S, T) where the sequence becomes periodic with period T from index S.	Hard8	Number theoryMatrix+1	No attempts yet	0.5s	512 MB	Judgeable
Sum of five squaresGiven n up to 10^10, count the signed integer 4-tuples and 5-tuples whose squares sum to n.	Hard8	MathNumber theory	No attempts yet	5.555s	555 MB	Judgeable
Fibonacci Half SequenceFor n up to 10^18, find the lexicographically smallest sequence a with a[a[n]] = f[n], where f is 1, 2, 3, 5, ...; print -1 if a[n] exceeds 10^18.	Hard8	MathRecursion+1	No attempts yet	2s	1024 MB	Judgeable
Scallion, Not EggplantGiven a grid of 가, 지, 대, 파, and ☆ tiles, decide whether Scallion, Aubergine, or neither wins the alternating move game under optimal play.	Hard8	Game theoryGraph+1	No attempts yet	2s	1024 MB	Judgeable
An Ordinary String ProblemFor each string, count the non-empty strings over a, b, c that have the same number of every length-2 substring, modulo 10^9 + 7.	Hard8	CombinatoricsGraph+1	No attempts yet	2s	1024 MB	Judgeable
Video SurveillanceGiven k image cells on a grid that wraps around in both directions, find the smallest bounding box reachable by cyclic shifts and the fewest button presses needed to reach it.	Hard8	SortingTwo pointers+1	No attempts yet	1s	1024 MB	Judgeable
Moving StonesGiven a row of white stones, black stones, and empty cells, decide which team wins when each turn moves one of its stones forward one cell under optimal play.	Hard8	Game theoryMath	No attempts yet	2s	1024 MB	Judgeable
GardenFind the smallest axis-aligned rectangle that contains at least one artwork of each kind, where type A repeats with period D in both directions and type B in one.	Hard8	Two pointersSegment tree+2	No attempts yet	2s	1024 MB	Judgeable
DivideCount pairs (a, b) with a up to p and b up to q where a*b/(a+b) is an integer between 1 and n.	Hard8	Number theoryMath	No attempts yet	1.8s	1024 MB	Judgeable
ForkGiven P, N, L, and R, find the minimum expected number of key presses to finish typing a fixed N-character string into two random shells.	Hard8	Dynamic programmingProbability	No attempts yet	0.15s	1024 MB	Judgeable
SortingRecover a hidden permutation of 1 to N using as few position comparisons as possible, with unlimited checks of whether a difference is divisible by any d.	Hard8	Number theorySorting+1	No attempts yet	1s	1024 MB	Judgeable
Fast InterpreterGiven array a and a copy b, repeat a program of m shift-then-xor/and/or steps p times (p up to 1e9) and print the final b.	Hard8	Bit manipulationArray+1	No attempts yet	3s	1024 MB	Judgeable
Costume ProblemsGiven n limb types, m head types, and random orders of a limbs and b heads, find the expected number of distinct costumes modulo 1073676287.	Hard8	CombinatoricsMath+1	No attempts yet	1s	1024 MB	Judgeable
GigaskeletonsSplit n skeletons with bone counts up to 2e5 into LCM-wide groups so the sum of each group's LCM is minimal, then print the groups.	Hard8	Dynamic programmingNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Perfect Triangle CoveringGiven triangle tiles with legs 2^a_i, for each plaza side 2^b find the largest tile size that can cover it exactly, or -1 if impossible.	Hard8	GreedyMath+1	No attempts yet	2s	1024 MB	Judgeable
Magical clockGiven a clock with 720t divisions whose minute hand resets when it catches the hour hand, find the fewest ticks between two hand states for each query, or -1.	Hard8	Number theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
xCount the connected vertex subsets of a tree that contain at least one vertex of each of the m skill colors, modulo 998244353.	Hard8	TreeDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Tree HouseGiven n floors of cross-shaped 5-room layouts and m staircases between adjacent floors, find the minimum total distance over all pairs of rooms.	Hard8	MathGreedy+1	No attempts yet	2s	1024 MB	Judgeable
Decreasing Growth Rate Tragedy 2Given N daily growth readings rounded to 0.001 cm, find the largest constant growth rate that can produce them, or report Impossible.	Hard8	GeometryPrefix sum+1	No attempts yet	1s	1024 MB	Judgeable
Hyeoncheol's Blind DateSplit n consecutive laundry items into baskets to minimize the expected washing time, where a basket of total weight g takes g^2 and each extra basket adds c.	Hard8	Dynamic programmingProbability+1	No attempts yet	1s	1024 MB	Judgeable
Socks Pairing Probability for Dongwoo and Tsundere JaewooGiven n sock types and m random draws, find the probability that the floor sock count after m trials equals the count at the start.	Hard8	ProbabilityMath+1	No attempts yet	2s	1024 MB	Judgeable
Delivery RobotGiven a start point and a target point, build a sequence of at most 10^6 rotation commands around two towers, or report -1 if none exists.	Hard8	Number theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
MousetrapsGiven n points, remove one so the convex hull of the remaining points has minimum area, and print twice that area.	Hard8	GeometryDivide and conquer+1	No attempts yet	2s	1024 MB	Judgeable
Silver ChainDecide whether two closed polylines cover exactly the same segments with the same multiplicities, so that one can be bent into the other.	Hard8	GeometryImplementation	No attempts yet	2s	1024 MB	Judgeable
Magic MineGiven pillar heights differing by at most 1, remove exactly t meters total to maximize the lowest final height, keeping adjacent differences at most 1. Output that minimum height.	Hard8	Binary searchGreedy+1	No attempts yet	2s	1024 MB	Judgeable
Cat Goose and the Random MatrixGiven a random n by m table with entries modulo p, find the largest-sum submatrix whose sum is divisible by p.	Hard8	MatrixPrefix sum+2	No attempts yet	3s	1024 MB	Judgeable
Chariot RaceFind the minimum time for a closed route that visits the checkpoints v1 to vk in order, where each turn at an intersection takes time based on the angle.	Hard8	Shortest pathDynamic programming+2	No attempts yet	8s	1024 MB	Judgeable
PuzzleDrop a grid figure straight onto an obstacle at a chosen horizontal shift to maximize adjacent pairs where an obstacle cell sits left of a figure cell.	Hard8	MatrixMath+1	No attempts yet	1s	1024 MB	Judgeable
Faceted GlassesFind the common water level in n glasses, each with a convex polygon base, so that the total poured volume equals v.	Hard8	GeometryBinary search+1	No attempts yet	2s	1024 MB	Judgeable
GameTwo players divide their own numbers A and B by a divisor up to C, keeping gcd above 1 with the other number. Print who wins.	Hard8	Game theoryNumber theory+1	No attempts yet	2s	1024 MB	Judgeable
Mavis and DraculaGiven A and B, find the largest lcm(A, x) over all integers x from 1 to B.	Hard8	Number theoryMath+1	No attempts yet	2s	1024 MB	Judgeable
Light Bulb SequenceCounts the bulbs still on after k rounds, where round i flips every bulb whose number is divisible by i, with n at most 10k.	Hard8	Number theoryMath	No attempts yet	2s	1024 MB	Judgeable
Lazybugs and the FenceFor each lazybug count i, find the fewest shift commands that paint exactly the '#' boards of the fence, or report -1 if impossible.	Hard8	String matchingNumber theory+1	No attempts yet	2s	1024 MB	Judgeable
Break, Don't BuildGiven a 2-regular geometric graph on n points, remove one incident edge per point so that the remaining edges form a non-crossing set, or report NO.	Hard8	GraphGeometry+1	No attempts yet	2s	1024 MB	Judgeable
2048Count the 16-color h by w grids where no two side-adjacent cells share a color, modulo 1,000,000,007, for h up to 6 and w up to 10^18.	Hard8	Dynamic programmingMatrix+1	No attempts yet	2s	1024 MB	Judgeable
Rafiki's TestFind the base x and modulus p of a polynomial string hash by querying the hash of chosen strings in an interactive session.	Hard8	StringMath+2	No attempts yet	2s	1024 MB	Judgeable
Chino's Latte ArtConstruct a simple polygon with exactly 100000 vertices that is heart-shaped, symmetric about line AB, with coordinates within 2,000,000 in absolute value.	Hard8	GeometryImplementation+1	No attempts yet	1s	1024 MB	Judgeable
BlueTube ParkFor each A_i, find the smallest index j (j not equal to i) whose value is closest in prime-operation distance, where each multiply or divide by a prime counts as one step.	Hard8	Number theoryHash map+1	No attempts yet	2s	1024 MB	Judgeable
FenceGiven a convex polygon and one interior post, find a maximum-area polygon whose vertices are these posts, with no other post strictly inside it.	Hard8	GeometryDynamic programming	No attempts yet	2s	1024 MB	Judgeable
KnightsGiven n knights in a line and m position swaps, count pairs where the shorter knight stands in front, modulo 1e9+7, with n up to 1e18.	Hard8	ArrayImplementation+1	No attempts yet	2s	1024 MB	Judgeable
InheritanceSplit n watchtowers into two convex polygons with disjoint hulls so that the difference of their areas is minimal, or report -1 if impossible.	Hard8	GeometryBrute force	No attempts yet	2s	1024 MB	Judgeable
Harry Potter and the RailwayAssign each railway a distinct spell number from 1 to m so that every station's incident spell numbers have gcd 1, or report IMPOSSIBLE.	Hard8	GraphDFS+1	No attempts yet	2s	1024 MB	Judgeable
StonesCount the sets of distinct stone segments, each with binary value at most k, whose flips turn an all-white row into the binary number n, modulo 1e9+7.	Hard8	Bit manipulationDynamic programming+1	No attempts yet	2s	1024 MB	Judgeable
Magic PotionsGiven n substances with a bottles each, pick pairs of different substances to make the most potions, breaking ties by favoring 1+2, then 1+3, 1+4, and so on.	Hard8	GreedyMath+1	No attempts yet	2s	1024 MB	Judgeable
MaximaCount permutations of 1 to n with exactly k maxima, where n is up to 10^15 and the answer is taken modulo 239.	Hard8	CombinatoricsMatrix+1	No attempts yet	2s	1024 MB	Judgeable
GameGiven a road network where a road of length c holds c-1 villages, decide which of two alternating players reaches the capital first.	Hard8	GraphShortest path+1	No attempts yet	2s	1024 MB	Judgeable
Villa of Emblem ShapeGiven a simple polygon, decide whether translated copies of it (no rotation or reflection) can be overlaid to form a convex polygon.	Hard8	GeometryImplementation	No attempts yet	8s	1024 MB	Judgeable
Fair Deal of DiceGiven dice with custom face values, pick m of n dice and split them between two players to minimize the expected squared difference of their face sums.	Hard8	Divide and conquerSorting+2	No attempts yet	8s	1024 MB	Judgeable
ChoreographyApply cyclic shifts, pair swaps, and permutation moves to a line of dancers, then report where a given dancer stands after each prefix of moves.	Hard8	ArraySimulation+1	No attempts yet	0.5s	1024 MB	Judgeable
Bring Down the Sky Grading ServerFor each scenario, decide whether the hacker can drop the server's computing power to 0 or below when the chairman plays optimally.	Hard8	Game theorySimulation+1	No attempts yet	4s	1024 MB	Judgeable
One HitEach skill maps attack x to a*x+b, and the task asks for the fewest skill uses that take starting attack x to at least boss HP y, or -1.	Hard8	GreedyMath+1	No attempts yet	2s	1024 MB	Judgeable
Hey Google, Drive!Given a grid of walls and hazards, list each start and finish pair the car can reach with probability near 1 despite random command swaps.	Hard8	GraphBFS+1	No attempts yet	60s	1024 MB	Judgeable
Love PotionGiven K, count the subsets of cards numbered 1 to 2023K whose sum is coprime with 2023, modulo 10^9+7.	Hard8	CombinatoricsNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Splitting SegmentsGiven N segments, find the shortest [A, B] that covers at least half of every segment after exactly K splits, where each split cuts a segment in two.	Hard8	Binary searchGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Magical BF 2Write an N by N BF grid that leaves x mod 7 in cell M0 for input x up to 200, whether the grid is read by rows or by columns.	Hard8	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
LinesweeperAfter each single-cell change to the top row, the task is to say whether a given bottom cell must hold a mine, must be empty, is undetermined, or the top row has no valid bottom row.	Hard8	Segment treeMath+1	No attempts yet	4s	1024 MB	Judgeable
Cake cuttingGiven an M by N cake cut into unit squares, plus slanted cuts that form squares of area S at slope Q/P, count the resulting pieces.	Hard8	GeometryNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Maximum sum of GCDsSplit a fixed sequence of pile sizes into contiguous shelves of at least D piles each (or empty) to maximize the sum of each shelf's GCD.	Hard8	Dynamic programmingNumber theory+1	No attempts yet	1s	1024 MB	Judgeable
Hard Linear Algebra ProblemGiven two invertible matrices A and B over a prime field, count the columns i where swapping column i between them keeps both invertible, for each cyclic shift of A.	Hard8	MatrixLinked list+1	No attempts yet	1s	1024 MB	Judgeable
Gold DiggingGiven pits with a breakdown chance, an extraction rate, and gold amounts, find the best expected gold when one machine is assigned to one pit per day.	Hard8	Dynamic programmingProbability+1	No attempts yet	4s	1024 MB	Judgeable
Reflected Copy TreeGiven a tree with N nodes, reflected-copy it K times and print the sum of all pairwise distances modulo 10^9+7.	Hard8	TreeDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Perfect TriplesGiven n up to 1e16, find the n-th element of a sequence built by repeatedly appending the lexicographically smallest unused triple with XOR zero.	Hard8	Bit manipulationMath	No attempts yet	2s	1024 MB	Judgeable
SNUPC GameGiven token counts on five cells with forward moves and a U-to-S loop, decide if the first player wins, loses, or the game never ends.	Hard8	Game theoryMath	No attempts yet	1s	1024 MB	Judgeable
BX BetTwo players alternately add a chosen earlier opponent number to their own, digit-wise mod 10, and the task is to find the winner from both notebooks.	Hard8	Game theoryTrie+1	No attempts yet	2s	1024 MB	Judgeable
Grow Measure Cut RepeatProcess a sequence of tent-shaped watering updates, height caps, and point queries on 100000 trees, printing each measured height.	Hard8	Segment treeImplementation+1	No attempts yet	2s	1024 MB	Judgeable
Wrong QueueEach pop removes the elements at fixed positions A_1 to A_N at once, and for each query the task asks for the value at index x after D pops.	Hard8	ArrayBinary search+1	No attempts yet	3s	1024 MB	Judgeable
Gadget ConstructionCount subsets of at least 4 cogs whose convex hull alternates colors around its vertices, with interior cogs of any color, modulo 1e9+7.	Hard8	GeometryDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
IntroversionGiven a row of 2n slots with some dishes fixed, count the ways to fill the empty slots so each type appears twice and no two equal types are adjacent, modulo 1e9+7.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	3s	1024 MB	Judgeable
Distance PermutationGiven K, count the permutations of 1 to N that the walk can produce, where the first element lies between L and R.	Hard8	CombinatoricsDynamic programming+1	No attempts yet	5s	1024 MB	Judgeable
Knight GameGiven a knight on an H by W board, decide whether Alice or Bob wins when both alternately move the knight to unvisited squares.	Hard8	Game theoryGraph+1	No attempts yet	2s	1024 MB	Judgeable
Gacha 101Balls labeled 1 to N are drawn uniformly at random, and the task asks for the probability that the string s ever contains 101 as a substring, modulo 998244353.	Hard8	ProbabilityCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
Convex Polygon MSTGiven a convex polygon's vertices, find the spanning tree whose edges, weighted by squared Euclidean length, have the maximum total weight.	Hard8	GraphMinimum spanning tree+1	No attempts yet	7s	1024 MB	Judgeable
PoolFind the probability that the largest all-safe rectangle touching the bottom of an N by 1001 grid is exactly K cells, given safe probability x/y.	Hard8	ProbabilityDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
Depth First SearchCount subsets of the m extra edges so that tree T, plus the chosen edges, is a DFS tree from one of the k special vertices.	Hard8	TreeDFS+2	No attempts yet	6s	1024 MB	Judgeable
ReversiFor each N by M board, decide whether the second player with 1x1 stones wins, loses, or draws against a first player placing 2x1 dominoes under optimal play.	Hard8	Game theoryCombinatorics+1	No attempts yet	1s	512 MB	Judgeable
Aperiodic AppointmentsCount the ones in a binary string of length N, where each new bit is 1 exactly when the string ends in a K-th power of some nonempty block.	Hard8	StringString matching+1	No attempts yet	1s	1024 MB	Judgeable
Factor-Full TreeGiven a rooted tree of up to 60 vertices, assign each vertex a number up to 10^18 so that x_v divides x_u exactly when v is an ancestor of u.	Hard8	Number theoryTree+1	No attempts yet	1s	1024 MB	Judgeable
Rigged LotteryGiven k, c, and a ticket of length k, find the shortest sequence over 1 to c that contains every length-k sequence as a subsequence except that ticket.	Hard8	StringCombinatorics+1	No attempts yet	2s	1024 MB	Judgeable
Analyzing ContractsClients are added with an end day and daily revenue, and each supplier query asks for the maximum profit from matching an available client to that supplier.	Hard8	GeometrySegment tree+1	No attempts yet	1s	1024 MB	Judgeable
Health in HazardGiven N half-plane cuts through a plane with a den at the origin, find the first cut after which no point on the circle of radius D is reachable.	Hard8	GeometryBinary search+1	No attempts yet	3.5s	1024 MB	Judgeable
International TravelGiven three pin circles for a plug and three hole circles for a socket, decide whether the plug can be rigidly moved so each pin fits a matching hole, with the earth pin fixed.	Hard8	GeometryBrute force	No attempts yet	2s	1024 MB	Judgeable
Intersegment ActivationInteractive task: flip interval barriers one at a time, reading the visible-cell count after each flip, until every barrier is inactive.	Hard8	Bit manipulationMath+1	No attempts yet	2s	1024 MB	Judgeable
Royal ProblemGiven a directed graph with XOR-weighted edges, find the XOR of the XORs of all walks from a to b, or report -1 if infinitely many walks have nonzero XOR.	Hard8	GraphBit manipulation+2	No attempts yet	3s	1024 MB	Judgeable
Plane stretchingGiven n points, for each scale factor alpha, multiply every x-coordinate by alpha and output the largest distance between any two points.	Hard8	GeometryTwo pointers+1	No attempts yet	10s	1024 MB	Judgeable
Starry Night (Hard)Given N stars with brightness that fades by Manhattan distance, find the total brightness summed over every cell in a given rectangle.	Hard8	Prefix sumMath+1	No attempts yet	1s	512 MB	Judgeable
Instant NoodlesGiven a bipartite graph with weights on the right side, find the gcd of the sums of right-vertex values covered by each nonempty subset of left vertices.	Hard8	Hash mapNumber theory	No attempts yet	2s	1024 MB	Judgeable
Hosting KCPCGiven three point sets, sum over every triple (one point from each set) the squared side lengths plus or minus twice the signed triangle area, modulo 1e9+7.	Hard8	GeometrySorting+1	No attempts yet	1s	1024 MB	Judgeable
Secret SwapCount the distinct final card arrangements reachable by swapping two cards whose values have bitwise AND at most K/2, modulo 1e9+7.	Hard8	Union-findBit manipulation+1	No attempts yet	2s	1024 MB	Judgeable
Not So Distant StringsGiven a digit string s and k, output the k-th length-n digit string when all strings are sorted by digit distance to s, then lexicographically.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Random Walks in a Big CityGiven a connected road network, find the fewest minutes a student is guaranteed to reach home when random turns are adversarial, or -1 if they can wander forever.	Hard8	GraphBFS+1	No attempts yet	5s	1024 MB	Judgeable
AstronomyGiven 2n star points, find an integer point off all stars where every line through it holds either zero or exactly two stars, or report No.	Hard8	GeometryMath+1	No attempts yet	5s	1024 MB	Judgeable
Yet Another Coin ProblemGiven N coin types with counts and values, decide whether some choice of coins sums to exactly X, and print the number of each coin type used if so.	Hard8	Dynamic programmingNumber theory	No attempts yet	2s	1024 MB	Judgeable
Find the Disobedient ChildGiven N children who each returned up to K emeralds over several days, find the fewest days needed to identify the one child who sold all of theirs.	Hard8	MathBinary search	No attempts yet	3s	1024 MB	Judgeable
Chapaev on a TreeFor each vertex as Root, count the games on its descendants where Marina moves first and flicks checkers toward the root, then report how many she wins.	Hard8	TreeGame theory+2	No attempts yet	2s	1024 MB	Judgeable
FarmGiven a rectilinear farm boundary and pest locations, find the fewest pairwise disjoint axis-aligned rectangles inside the farm that cover every pest.	Hard8	GeometryGraph+1	No attempts yet	0.7s	2048 MB	Judgeable
Hanyang Cherry Picking ContestTwo players alternately take tree vertices by moving to a child of the last taken vertex, and the task is to find the winner under optimal play.	Hard8	TreeGame theory+1	No attempts yet	1s	1024 MB	Judgeable
PipelinedFind the minimum seconds for N cars, each with stage count s_i, to pass through the slot [0,1) when each car's interval moves by its own length every second.	Hard8	GreedyMath+1	No attempts yet	1s	1024 MB	Judgeable