Problems

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Total results21,475 problems

«Abracadabra»Hard8
String, Hash map +2No attempts yetTime limit8sMemory limit1024 MB
Judgeable
Viruses and AntivirusesHard8
Tree, DFS +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
MosaicHard8
Array, Sorting +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Another Substring Query ProblemHard8
String matching, String +2No attempts yetTime limit6sMemory limit1024 MB
Judgeable
BordersHard8
Graph, DFS +2No attempts yetTime limit4sMemory limit1024 MB
Judgeable
Passing the TowelHard8
Math, Recursion +2No attempts yetTime limit0.25sMemory limit256 MB
Judgeable
Find the Double ClassHard8
Combinatorics, Math +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Wizard Shark and BlizzardHard8
Simulation, Implementation +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Math HomeworkHard8
Number theory, Math +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Jumping MachineHard8
Combinatorics, Math +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Multiple Subject LessonsHard8
Dynamic programming, Combinatorics +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
TramHard8
Greedy, Sorting +2No attempts yetTime limit5sMemory limit512 MB
Judgeable
PermutationsHard8
Backtracking, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
TableHard8
Prefix sum, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Garden InformatizationHard8
Geometry, Brute force +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Digits and NumbersHard8
Dynamic programming, Math +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Commuter trains do not change tracksHard8
Graph, DFS +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Dutch PayHard8
Union-find, Greedy +2No attempts yetTime limit1sMemory limit1536 MB
Judgeable
Special Ice Breaking PenguinHard8
Tree, DFS +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Bus RidingHard8
Simulation, Implementation +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Two KnightsHard8
BFS, Graph +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Interesting NumberHard8
Dynamic programming, BFS +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Colored zerosHard8
Math, Bit manipulation +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Histogram Connectivity CountHard8
Stack, Combinatorics +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Opinion PoolHard8
Binary search, Greedy +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
ShoppingHard8
Divide and conquer, Segment tree +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
AutobahnHard8
Prefix sum, Sliding window +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
MalnaRISCHard8
Sorting, Divide and conquer +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Balanced SubsetsHard8
Dynamic programming, Implementation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
PortalsHard8
Graph, Union-find +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Swap Swap SortHard8
Sorting, Hash map +2No attempts yetTime limit3sMemory limit512 MB
Judgeable
SecretHard8
Divide and conquer, Implementation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Quarantine MathHard8
Number theory, Math +2No attempts yetTime limit1.25sMemory limit256 MB
Judgeable
One-way SidewalksHard8
Graph, DFS +2No attempts yetTime limit5sMemory limit256 MB
Judgeable
Mutant VaccineHard8
String, String matching +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
The Xanadu coupHard8
Tree, Dynamic programming +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
ComebackHard8
Two pointers, Sliding window +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
WalkHard8
Tree, DFS +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
GCDChel Loves GCDHard8
Dynamic programming, Greedy +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Road BuildingHard8
Geometry, Sorting +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Neo-Robin HoodHard8
Greedy, Sorting +2No attempts yetTime limit4sMemory limit256 MB
Judgeable
To be Connected, or not to be, that is the QuestionHard8
Graph, Union-find +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
High-Tech DetectiveHard8
Dynamic programming, Combinatorics +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Suffixes may Contain PrefixesHard8
String, Dynamic programming +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
String RemovalHard8
Dynamic programming, String matching +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
MaxCompHard8
Graph, Union-find +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
D-Balanced TreeHard8
Tree, DFS +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
SimpleHard8
Segment tree, Linked list +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
ConsulHard8
Divide and conquer, Brute force +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Digital ArtHard8
Sliding window, Two pointers +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
MonkeyHard8
Dynamic programming, Sorting +2No attempts yetTime limit2sMemory limit1024 MB
Judgeable
Need More T-shirts!Hard8
Number theory, Math +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Cartesian TreesHard8
Tree, Dynamic programming +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
Internet CableHard8
Geometry, Math +2No attempts yetTime limit4sMemory limit256 MB
Judgeable
HomeworkHard8
Math, Number theory +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Password decryptionHard8
Dynamic programming, Segment tree +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Minions Having FunHard8
Graph, Union-find +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
LotteryHard8
Combinatorics, Sorting +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
GameHard8
Graph, Greedy +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Network OrganizationHard8
Tree, Greedy +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Physics LabHard8
Math, Number theory +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Cryptographically Strong KeysHard8
Number theory, Math +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
TreeHard8
Tree, DFS +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Travel TaxHard8
Tree, Combinatorics +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Laying Out a NetworkHard8
Dynamic programming, Greedy +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
DepositHard8
Dynamic programming, Greedy +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
LasersHard8
Geometry, Binary search +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
WheelHard8
Dynamic programming, Probability +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Match of the CenturyHard8
Combinatorics, Math +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Forest PhenomenonHard8
Probability, Math +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
OlympiadHard8
Geometry, Brute force +2No attempts yetTime limit1sMemory limit256 MB
Judgeable
Mluran StorageHard8
Graph, Math +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Planet DefenseHard8
Math, Sorting +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
InterferenceHard8
Math, Dynamic programming +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Cipher KeyHard8
String, String matching +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Choosing ProblemsHard8
Backtracking, Bit manipulation +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Text EditorHard8
Segment tree, Stack +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Road ReformHard8
Graph, Union-find +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Time ShiftHard8
Sorting, Prefix sum +2No attempts yetTime limit3sMemory limit256 MB
Judgeable
ArchiverHard8
Dynamic programming, Greedy +1No attempts yetTime limit3sMemory limit256 MB
Judgeable
VirusesHard8
Dynamic programming, Trie +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
RailsHard8
Geometry, Hash map +2No attempts yetTime limit2sMemory limit256 MB
Judgeable
Political DevelopmentHard8
Graph, Greedy +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
RailwayHard8
Tree, Prefix sum +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
TollHard8
Graph, Dynamic programming +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Plus MinusHard8
Combinatorics, Union-find +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
RepeatsHard8
String, String matching +2No attempts yetTime limit6sMemory limit512 MB
Judgeable
Car ParkHard8
BFS, Simulation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Table 10Hard8
Backtracking, Brute force +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Gahui and the AirplaneHard8
Combinatorics, Number theory +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Beautiful MountainsHard8
Greedy, Implementation +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Fascinating PartitionsHard8
Dynamic programming, Divide and conquer +2No attempts yetTime limit2.5sMemory limit1024 MB
Judgeable
Game of SlotsHard8
Combinatorics, Greedy +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Impenetrable WallHard8
Geometry, Dynamic programming +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Driving LanesHard8
Dynamic programming, Implementation +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
twOBoOgErHard8
Math, Simulation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
XOR 5Hard8
Greedy, Implementation +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
XOR 6Hard8
Prefix sum, Greedy +2No attempts yetTime limit1sMemory limit512 MB
Judgeable
Fence PostsHard8
Prefix sum, Sliding window +2No attempts yetTime limit5sMemory limit1024 MB
Judgeable
Ski ResortHard8
Graph, Dynamic programming +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
«Abracadabra»For each pattern s, count dictionary words t where s is both a prefix and a suffix of t; word and pattern lengths are at most 50.	Hard8	StringHash map+2	No attempts yet	8s	1024 MB	Judgeable
Viruses and AntivirusesGiven two rooted trees on the same N employees, count ordered pairs (A, B) such that A is an ancestor of B in both trees.	Hard8	TreeDFS+2	No attempts yet	2s	1024 MB	Judgeable
MosaicGiven up to 100000 rectangles in a fixed order, answer range queries asking for any two pieces in the range that share no matching side length.	Hard8	ArraySorting+2	No attempts yet	1s	1024 MB	Judgeable
Another Substring Query ProblemGiven a string s and queries each with a pattern t and integer k, find the starting position of the k-th occurrence of t in s, or -1 if it occurs fewer than k times.	Hard8	String matchingString+2	No attempts yet	6s	1024 MB	Judgeable
BordersGiven a black and white grid, find the fewest connected same-color regions to outline so that every region shares a border with at least one outlined region.	Hard8	GraphDFS+2	No attempts yet	4s	1024 MB	Judgeable
Passing the TowelIn a Josephus-style circle game where the towel skips one person each pass, find the number of the person who receives the towel on the K-th pass.	Hard8	MathRecursion+2	No attempts yet	0.25s	256 MB	Judgeable
Find the Double ClassGiven M distinct rows of N section numbers, output at most M new rows so that each input row agrees with some new row in every column, yet no new row equals an input row.	Hard8	CombinatoricsMath+2	No attempts yet	1s	256 MB	Judgeable
Wizard Shark and BlizzardSimulate Blizzard spells on a spiral-indexed grid: destroy marbles, compact them along the spiral, and repeatedly explode runs of four or more, scoring exploded marble types.	Hard8	SimulationImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Math HomeworkConstruct a sequence of N integers in [1, 10^9] so that the GCD of each given subarray equals a given value at most 16, or report impossibility.	Hard8	Number theoryMath+2	No attempts yet	1s	1024 MB	Judgeable
Jumping MachineGiven n springs with jump lengths, the machine at (0,0) uses each spring once in any order, moving l up or l right; count the grid cells it can ever land on or pass over.	Hard8	CombinatoricsMath+2	No attempts yet	1s	512 MB	Judgeable
Multiple Subject LessonsCount the multisets of colored positive integers that sum to n, where two solutions match when every value has the same count in every color.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	1s	512 MB	Judgeable
TramEach passenger boards and exits at given stops and contributes ai per segment if seated or bi if standing; with M seats, maximize total satisfaction over the whole route.	Hard8	GreedySorting+2	No attempts yet	5s	512 MB	Judgeable
PermutationsGiven n distinct integers, list all permutations where adjacent elements share gcd at least k, and output the m-th one in lexicographic order or -1.	Hard8	BacktrackingDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
TableGiven the first row of an n by m table, each lower cell is the sum of the triangular region above it mod r; output the last row.	Hard8	Prefix sumDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Garden InformatizationGiven a rectangle with up to 10 axis-aligned obstacle rectangles, place one or two non-overlapping axis-aligned beds to maximize total area.	Hard8	GeometryBrute force+2	No attempts yet	2s	512 MB	Judgeable
Digits and NumbersA binary number is ugly if no smaller number reaches it by adding its own digit sum; count the ugly numbers up to n (n up to 10^18).	Hard8	Dynamic programmingMath+2	No attempts yet	2s	512 MB	Judgeable
Commuter trains do not change tracksGiven a tree and a set of simple paths, assign each vertex a value in 1..N so that values strictly increase along every path; report NO if impossible.	Hard8	GraphDFS+2	No attempts yet	1s	1024 MB	Judgeable
Dutch PayGiven merge and expense records of n travelers, compute each person's final balance and output at most n transfers that settle all debts.	Hard8	Union-findGreedy+2	No attempts yet	1s	1536 MB	Judgeable
Special Ice Breaking PenguinGiven a tree with some nodes marked as supports, break as many nodes as possible while keeping the penguin's node connected to at least two supports through unbroken ordinary nodes.	Hard8	TreeDFS+2	No attempts yet	1s	1024 MB	Judgeable
Bus RidingSimulate people riding circular bus routes, tracking boarding order by smallest route number and each transfer's one-minute wait, to report the finish time and stop or 0 0.	Hard8	SimulationImplementation+2	No attempts yet	2s	1024 MB	Judgeable
Two KnightsPlace two knights on a chessboard, move them alternately (any order) to distinct target squares without ever sharing a square, and output the minimum moves plus the actual move sequence, or -1.	Hard8	BFSGraph+2	No attempts yet	2s	1024 MB	Judgeable
Interesting NumberGiven n up to 1000, find the smallest positive integer with digit sum n that is also divisible by n.	Hard8	Dynamic programmingBFS+2	No attempts yet	2s	1024 MB	Judgeable
Colored zerosCount how many zero bits get marked when writing 1 to n in binary and flagging every k-th zero in each row.	Hard8	MathBit manipulation+2	No attempts yet	2s	512 MB	Judgeable
Histogram Connectivity CountCount choices of x_i with 0 <= x_i < h_i so that the remaining part of the histogram stays connected, modulo 1e9+7.	Hard8	StackCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Opinion PoolGiven sets of voters and a fraction p, find the largest p for which some assignment with at least one opponent still satisfies every set's support quota.	Hard8	Binary searchGreedy+2	No attempts yet	1s	1024 MB	Judgeable
ShoppingAnna sends at most 18 bits describing a range to Bruno, who replies with at most 10000 bits so she can name the cheapest item in that range.	Hard8	Divide and conquerSegment tree+2	No attempts yet	2s	256 MB	Judgeable
AutobahnEach driver stays for a time interval and owes extra fees for minutes when at least K drivers are present; choose X consecutive minutes to waive fees and maximize the waived total.	Hard8	Prefix sumSliding window+2	No attempts yet	1s	512 MB	Judgeable
MalnaRISCGiven N, output a parallel sorting network of CMPSWP comparator lines that sorts N registers, minimizing the number of parallel nanoseconds.	Hard8	SortingDivide and conquer+2	No attempts yet	1s	512 MB	Judgeable
Balanced SubsetsCount connected subsets of grass cells in an N by N grid where every row and column intersects the subset in a single contiguous run, modulo 1e9+7.	Hard8	Dynamic programmingImplementation+2	No attempts yet	1s	512 MB	Judgeable
PortalsEach vertex lists four portals grouped into two switchable pairs; pay c_v to permute a vertex's list, and find the minimum cost so all 4N (vertex, portal) locations become mutually reachable.	Hard8	GraphUnion-find+2	No attempts yet	1s	512 MB	Judgeable
Swap Swap SortMaintain a target permutation of 1..K under adjacent swaps, and after each swap report the minimum adjacent-swap count to sort the fixed array by that ordering.	Hard8	SortingHash map+2	No attempts yet	3s	512 MB	Judgeable
SecretGiven a hidden associative operation on 0..1e9 and an array, answer range-fold queries while minimizing calls to an oracle that returns x star y, especially after each query.	Hard8	Divide and conquerImplementation+2	No attempts yet	1s	512 MB	Judgeable
Quarantine MathGiven n and m up to 1e9, sum the divisor counts of all positive k with (n mod k) + (m mod k) >= k, using number theory.	Hard8	Number theoryMath+2	No attempts yet	1.25s	256 MB	Judgeable
One-way SidewalksGiven a connected undirected graph, orient each edge so that the fewest edges stay two-way while the resulting mixed graph stays strongly connected.	Hard8	GraphDFS+2	No attempts yet	5s	256 MB	Judgeable
Mutant VaccineGiven up to 100 DNA strings, find the longest substring common to all of them, breaking ties by earliest position in the first string.	Hard8	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
The Xanadu coupGiven a tree of N cameras, each with an on/off state, find the fewest button presses that toggle a node and its neighbors to turn every camera off, or report impossibility.	Hard8	TreeDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
ComebackFor each left rotation of the array, count all contiguous subsequences whose sum is at most X and report both their count and the total of their sums.	Hard8	Two pointersSliding window+2	No attempts yet	1s	512 MB	Judgeable
WalkGiven a rooted tree and an ordered list of m distinct nodes, count the shortest closed walks from the root that visit all nodes and hit the listed nodes in the given order, modulo 1e9+7.	Hard8	TreeDFS+2	No attempts yet	1s	512 MB	Judgeable
GCDChel Loves GCDGiven an array, repeatedly split off either the left floor(n/2) elements or the right ceil(n/2) elements, sum the GCDs of the removed blocks, and maximize that sum.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Road BuildingGiven n non-overlapping circles and a direction line, find the widest infinite strip parallel to that line that touches no circle and has at least one circle on each side.	Hard8	GeometrySorting+2	No attempts yet	2s	512 MB	Judgeable
Neo-Robin HoodChoose a set of politicians to rob and a disjoint set to bribe so that total stolen money covers total bribes, maximizing the number robbed.	Hard8	GreedySorting+2	No attempts yet	4s	256 MB	Judgeable
To be Connected, or not to be, that is the QuestionGiven an undirected graph with a value on each node, find the smallest threshold t such that the graph can be made connected by adding new edges between low-value and high-value nodes, each node used at most once.	Hard8	GraphUnion-find+2	No attempts yet	2s	512 MB	Judgeable
High-Tech DetectiveGiven a sequence of 2n entry and exit events where some visitor IDs are lost, count the ways to fill the zeros so each visitor enters once and exits once with proper nesting.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
Suffixes may Contain PrefixesGiven a target string and a bullet length n, choose a bullet string of length n that maximizes the sum, over all its suffixes, of the longest common prefix length between that suffix and the target.	Hard8	StringDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
String RemovalErase the whole string S using substring deletions that give scores or single-character deletions worth 1 point each, and find the maximum total score.	Hard8	Dynamic programmingString matching+2	No attempts yet	1s	512 MB	Judgeable
MaxCompFind the connected set of grid cells maximizing (max value - min value - size), over a grid up to 1000 by 1000.	Hard8	GraphUnion-find+2	No attempts yet	1s	512 MB	Judgeable
D-Balanced TreeGiven a tree with each vertex colored black or white, find the smallest D such that every vertex has another vertex of the same color within distance D, or -1 if impossible.	Hard8	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
SimpleSupport range add updates and range queries for the minimum even and maximum odd value, printing -1 for a missing parity.	Hard8	Segment treeLinked list+2	No attempts yet	1s	512 MB	Judgeable
ConsulGiven N hidden votes, use point queries and value-count queries to find a candidate with strictly more than N/3 votes, or report that none exists.	Hard8	Divide and conquerBrute force+2	No attempts yet	1s	512 MB	Judgeable
Digital ArtGiven an H by W grid of color numbers, cover one rectangle of at most S pixels to minimize the number of distinct colors still visible.	Hard8	Sliding windowTwo pointers+2	No attempts yet	1s	1024 MB	Judgeable
MonkeyGiven M allowed (x, y) handle pairs with banana counts on each handle, find the maximum total bananas collectable along a monotone path that only increases x or y.	Hard8	Dynamic programmingSorting+2	No attempts yet	2s	1024 MB	Judgeable
Need More T-shirts!Given a list where each entry is either a T-shirt count or a percentage, find every possible total number of T-shirts consistent with the list.	Hard8	Number theoryMath+2	No attempts yet	1s	512 MB	Judgeable
Cartesian TreesCount the number of distinct Cartesian trees (BST over keys 1..n, max-heap over given priorities) modulo 1e9+7, summed over test cases with total n up to 2e5.	Hard8	TreeDynamic programming+2	No attempts yet	3s	256 MB	Judgeable
Internet CableChoose a line and a distance d so that as many given points as possible lie exactly at distance d from the line; output that maximum count.	Hard8	GeometryMath+2	No attempts yet	4s	256 MB	Judgeable
HomeworkFor each triple of decimal strings x, y, z, decide whether infinitely many bases k make x times y equal z when read in base k.	Hard8	MathNumber theory+2	No attempts yet	2s	256 MB	Judgeable
Password decryptionCount the ways an encrypted digit string can be split into trinomial values for digits 0-9, reporting the count after each point update.	Hard8	Dynamic programmingSegment tree+2	No attempts yet	2s	256 MB	Judgeable
Minions Having FunFind a simple cycle in an undirected weighted graph maximizing the minimum edge weight plus the maximum edge weight on that cycle.	Hard8	GraphUnion-find+2	No attempts yet	2s	256 MB	Judgeable
LotteryCount arrays of length n with entries in 1..k such that the maximum on each of m given segments [l,r] equals a specified x.	Hard8	CombinatoricsSorting+2	No attempts yet	2s	256 MB	Judgeable
GameGiven the hint sets of n first-team and m second-team players, decide whether the first team can guarantee collecting all k hints when each first-team player may ask at most one second-team player for one hint he lacks, and if so, output the assignment.	Hard8	GraphGreedy+2	No attempts yet	2s	256 MB	Judgeable
Network OrganizationGiven a tree, find the minimum number of vertices whose distance vectors uniquely identify every vertex, and output one such set.	Hard8	TreeGreedy+2	No attempts yet	2s	256 MB	Judgeable
Physics LabGiven cold and hot vessel volumes and temperatures C and H, decide for each reported fraction p/q whether some cold and hot vessel pair can produce that mixture temperature.	Hard8	MathNumber theory+2	No attempts yet	2s	256 MB	Judgeable
Cryptographically Strong KeysGiven numbers a_i, the closure under gcd and lcm defines a set S; decide whether a query value v lies in S.	Hard8	Number theoryMath+2	No attempts yet	2s	256 MB	Judgeable
TreeStarting from a single vertex, using only edge deletion and adding pairs of leaves to a vertex of degree at most one, find the minimum operations to build a given tree, or -1.	Hard8	TreeDFS+2	No attempts yet	2s	256 MB	Judgeable
Travel TaxIn a tree of n cities, each road has a toll range [l, r]; count assignments of tolls whose total weighted income (each road weighted by how many shortest paths cross it) equals m, modulo 1e9+7.	Hard8	TreeCombinatorics+2	No attempts yet	2s	256 MB	Judgeable
Laying Out a NetworkPlace n computers and m capacity-limited switches around a circular table; connect every computer to a switch, minimizing total cable length given by circular distance.	Hard8	Dynamic programmingGreedy+2	No attempts yet	3s	256 MB	Judgeable
DepositEach year Vasily can move money between banks after paying fixed withdrawal fees, and the task is to maximize the final total after m years.	Hard8	Dynamic programmingGreedy+2	No attempts yet	2s	256 MB	Judgeable
LasersGiven n points where a laser sits at the first and refractors at the rest, find the minimum voltage a so a beam can be bent back to its start, where each turn angle is bounded by a.	Hard8	GeometryBinary search+2	No attempts yet	2s	256 MB	Judgeable
WheelEach city on a wheel graph is captured by one of two parties at random; find the expected size of the largest connected group of cities held by a single party.	Hard8	Dynamic programmingProbability+2	No attempts yet	2s	256 MB	Judgeable
Match of the CenturyGiven 2n distinct heights, randomly split into two teams of n, then order one team by decreasing height and the other by increasing height; find the expected sum of same-position height differences.	Hard8	CombinatoricsMath+2	No attempts yet	2s	256 MB	Judgeable
Forest PhenomenonFor each n by m grid, every cell ships its firewood to a uniformly random orthogonal neighbor; find the expected number of cells that end up with at least one shipment.	Hard8	ProbabilityMath+2	No attempts yet	2s	256 MB	Judgeable
OlympiadGiven three rectangles with fixed side lengths, arrange them axis-parallel so the union covers the least area, allowing overlaps.	Hard8	GeometryBrute force+2	No attempts yet	1s	256 MB	Judgeable
Mluran StorageCount the ways to 2-color isotopes 1..n so that no two masses summing to a given power-of-two critical number share a color, mod 1e9+7.	Hard8	GraphMath+2	No attempts yet	2s	256 MB	Judgeable
Planet DefenseGiven each asteroid's initial position and constant velocity, count for each queried integer time how many asteroids lie strictly within distance R of the origin.	Hard8	MathSorting+2	No attempts yet	2s	256 MB	Judgeable
InterferenceFor each received n-bit string (n up to 34) and target polynomial hash, find a string within minimum Hamming distance whose hash matches, and report the flipped bit indices.	Hard8	MathDynamic programming+2	No attempts yet	2s	256 MB	Judgeable
Cipher KeyGiven encrypted strings, recover for each the longest string s such that s is a prefix and reversed s is a suffix of some substring t, maximizing t.	Hard8	StringString matching+2	No attempts yet	2s	256 MB	Judgeable
Choosing ProblemsChoose d problems, one per difficulty level, so that every one of m topics appears exactly once across the chosen problems.	Hard8	BacktrackingBit manipulation+2	No attempts yet	2s	256 MB	Judgeable
Text EditorMaintain a string of parentheses and letters under point updates, and after each update that sets a parenthesis, report the position of its matching bracket or -1.	Hard8	Segment treeStack+2	No attempts yet	2s	256 MB	Judgeable
Road ReformCount ordered pairs (removed edge, added edge) that make the graph connected after the swap, where the added edge is not already present.	Hard8	GraphUnion-find+2	No attempts yet	2s	256 MB	Judgeable
Time ShiftGiven daily clock shifts in n cities over a year, compute the sum over all hours of the pairwise absolute differences of each city's elapsed time from the capital.	Hard8	SortingPrefix sum+2	No attempts yet	3s	256 MB	Judgeable
ArchiverAt each phase, replace the sequence of length n with one of length ceil(n/2), picking each new element from either end of its mirror pair; count a penalty whenever the two candidates differ, and minimize the total penalty.	Hard8	Dynamic programmingGreedy+1	No attempts yet	3s	256 MB	Judgeable
VirusesCount length-n strings over lowercase letters in which every position lies inside some substring that matches one of the m given virus patterns, modulo 1e9+7.	Hard8	Dynamic programmingTrie+2	No attempts yet	2s	256 MB	Judgeable
RailsGiven 2n distinct lines, pair them so each pair has two parallel lines at the same distance d, and find the smallest such d.	Hard8	GeometryHash map+2	No attempts yet	2s	256 MB	Judgeable
Political DevelopmentGiven a graph where every nonempty subset has a vertex of degree under K inside it, find the largest set of mutually disagreeing members (a maximum clique), guaranteed to be at most K.	Hard8	GraphGreedy+2	No attempts yet	2s	512 MB	Judgeable
RailwayGiven a tree and m sets of vertices, count for each tree edge how many sets contain a path covering it, and list edges covered by at least k sets.	Hard8	TreePrefix sum+2	No attempts yet	1s	512 MB	Judgeable
TollGiven a layered directed graph where every edge jumps from one block of K nodes to the next, answer queries for the cheapest path cost between two nodes, or -1 if none exists.	Hard8	GraphDynamic programming+2	No attempts yet	1s	512 MB	Judgeable
Plus MinusCount the spin grids on an N by M board, consistent with K fixed cells, where every 2 by 2 block has two pluses and two minuses, modulo 1e9+7.	Hard8	CombinatoricsUnion-find+2	No attempts yet	1s	512 MB	Judgeable
RepeatsGiven a binary string of length n, find a substring that is some seed repeated as many times as possible, and report the count, seed length, and 1-based start position.	Hard8	StringString matching+2	No attempts yet	6s	512 MB	Judgeable
Car ParkA 6x6 parking lot holds 2x1 and 3x1 cars that slide only along their long axis; find the fewest single-square moves to drive car 1 out the row-3 exit, or -1 if impossible.	Hard8	BFSSimulation+2	No attempts yet	1s	512 MB	Judgeable
Table 10Build an N by N digit table (2 <= N <= 10) where every row, column, and main diagonal reads as a distinct multiple of M with no leading zero.	Hard8	BacktrackingBrute force+2	No attempts yet	1s	512 MB	Judgeable
Gahui and the AirplaneCount the flight paths of horizontal length d that start and end at altitude 0, stay positive in between, and consist of straight constant-slope segments, modulo a prime m.	Hard8	CombinatoricsNumber theory+2	No attempts yet	1s	512 MB	Judgeable
Beautiful MountainsGiven an array where some entries are unknown, decide whether the unknown positive values can be filled so the array splits into equal-length mountains, with the last block allowed to be shorter.	Hard8	GreedyImplementation+2	No attempts yet	1s	1024 MB	Judgeable
Fascinating PartitionsFor every k from 1 to N, compute the minimum and maximum total cost of splitting the array into exactly k contiguous subarrays, where a subarray costs its maximum element.	Hard8	Dynamic programmingDivide and conquer+2	No attempts yet	2.5s	1024 MB	Judgeable
Game of SlotsAlice arranges her cards into slots first, then Bob responds; compute Alice's optimal expected score when all card values are drawn uniformly from [1, 10^18].	Hard8	CombinatoricsGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Impenetrable WallCount simple polygons through a fixed gate vertex, using tower vertices only, that strictly contain the house, are star-shaped from it, and have all tower angles convex, modulo 1e9+7.	Hard8	GeometryDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Driving LanesGiven n straightaways separated by n-1 curves whose cost grows by c per lane, find the minimum total distance from lane 1 back to lane 1, where lane changes cost k+r and must fit within a straightaway.	Hard8	Dynamic programmingImplementation+1	No attempts yet	2s	512 MB	Judgeable
twOBoOgErCount every collision (A-B or A-wall) when B of mass n kg hits resting A of mass 1 kg elastically between a wall and B, for n up to 10^6.	Hard8	MathSimulation+2	No attempts yet	1s	512 MB	Judgeable
XOR 5Given an N by N black-and-white image, write a file of rectangle XOR operations that turns an all-white screen into the image using as few operations as possible.	Hard8	GreedyImplementation+2	No attempts yet	1s	512 MB	Judgeable
XOR 6Given an N by N binary image, find the minimum number of rectangle XOR (pixel-flip) operations that produce it from an all-white screen.	Hard8	Prefix sumGreedy+2	No attempts yet	1s	512 MB	Judgeable
Fence PostsGiven post heights and per-post costs to raise or lower them by 1 cm, find the minimum total cost so that some K consecutive posts end at the same height.	Hard8	Prefix sumSliding window+2	No attempts yet	5s	1024 MB	Judgeable
Ski ResortGiven a DAG of ski courses that always descend, and lifts that always ascend and can be ridden at most K times, maximize total skiing time from S to T.	Hard8	GraphDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable