Problems

Pick a problem and write your solution in the built-in editor. The judge runs it against real test cases while you watch, and the wider archive is open to read whenever you like.

Total results1,786 problems

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Number of RectanglesGiven up to 5000 points, count axis-aligned rectangles whose four corners are all present among the points.	Medium5	Hash mapCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
SequenceFind the K-th lexicographically smallest non-decreasing sequence of N positive integers summing to M.	Medium5	BacktrackingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Theater SeatsCount permutations where each ticket holder sits in their own or adjacent seat, with VIP seats fixed and splitting the row into independent segments counted by a Fibonacci-like recurrence.	Medium5	Dynamic programmingCombinatorics+1	No attempts yet	2s	128 MB	Judgeable
Polygon PartitionsCount noncrossing dissections of a regular N-gon into all triangles or all quadrilaterals, modulo 1e9, using Catalan-like combinatorics.	Medium5	CombinatoricsDynamic programming+1	No attempts yet	2s	128 MB	Judgeable
Number of PermutationsGiven a permutation's up-down pattern, count permutations of size n sharing the same pattern, modulo 1,000,000,000.	Medium5	Dynamic programmingCombinatorics	No attempts yet	2s	128 MB	Judgeable
Sum of Powers of TwoCount the ways to write N as an unordered sum of powers of two, modulo one billion.	Medium5	Dynamic programmingMath+1	No attempts yet	2s	128 MB	Judgeable
Adjacent Bit Pair CountCount binary strings of length n whose number of adjacent 11-pairs equals a given k, for up to 1000 queries.	Medium5	Dynamic programmingCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
A Margarita Today?Count subsets of up to 30 prices whose sum is within budget D and whose leftover money cannot afford any unchosen item.	Medium5	Brute forceRecursion+1	No attempts yet	1s	128 MB	Judgeable
Counting Sanggeun's Digit FriendsGiven up to a million large integers, count pairs that share at least one decimal digit, requiring bitmask digit sets and efficient counting over 1024 subsets.	Medium5	Bit manipulationCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Pleasant WordCount ways to fill blanks in a word with uppercase letters so it avoids three consecutive vowels or consonants and contains at least one 'L'.	Medium5	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
Counting Axis-Aligned Right TrianglesCount triangles among N points where the right angle vertex has one point sharing its x-coordinate and another sharing its y-coordinate.	Medium5	Hash mapMath+1	No attempts yet	1s	128 MB	Judgeable
TripletsGiven a grid with letters placed on some cells, count how many triples of letters are collinear.	Medium5	GeometryCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Film FestivalGiven a bipartite graph of boat connections, count the number of pairs of left villages and pairs of right villages that form a complete K2,2 subgraph.	Medium5	CombinatoricsHash map+1	No attempts yet	1s	128 MB	Judgeable
Handong Does Not Want to Study!Given a functional graph where each node points to exactly one other node, find the starting node whose path visits the most distinct nodes before repeating, breaking ties by smallest index.	Medium5	GraphDFS+1	No attempts yet	1s	128 MB	Judgeable
Friends Calling PlanGiven call minutes between up to 16 employees, pair them all up to minimize total billing cost using bitmask DP over perfect matchings.	Medium5	Dynamic programmingBit manipulation+1	No attempts yet	1s	128 MB	Judgeable
PINCount pairs of 4-character PINs (from a given list) that differ in exactly D of their four positions.	Medium5	Hash mapCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Hop, HopCount, modulo 1000000, the number of ways to write n as a non-increasing sequence of jumps of length 1, 2, or 3, for n up to 1e9.	Medium5	MathDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
Enchanted MirrorDecide if bricks with fixed (real,mirror) letter pairs can be permuted so the row reads T1 and its mirror reads T2, given initial words S1,S2.	Medium5	Hash mapString+2	No attempts yet	3s	256 MB	Judgeable
History of FootballGiven final points of n (up to 8) football teams under win/draw/loss scoring, count the number of distinct match outcome assignments consistent with those totals.	Medium5	BacktrackingCombinatorics+1	No attempts yet	2s	64 MB	Judgeable
Graph MatchingCount the number of matchings (independent edge sets) of the cycle graph C_n for each given n, likely requiring big-integer arithmetic via a Lucas-sequence style recurrence.	Medium5	Dynamic programmingMath+1	No attempts yet	1s	128 MB	Judgeable
Breaking the CipherGiven plaintext, ciphertext, and block size, count permutations of size k that transform every plaintext block into the matching ciphertext block.	Medium5	CombinatoricsString+1	No attempts yet	1s	128 MB	Judgeable
The Industrial Spy's LetterGiven up to 7 digit shreds, count the distinct primes formable by arranging any subset of them (leading zeros dropped), over up to 200 test cases.	Medium5	BacktrackingCombinatorics+1	No attempts yet	1.5s	128 MB	Judgeable
I've Got Your Back(gammon)Map between 6-tuples of 15 pieces on 6 points, ordered lexicographically, and their index among the 15504 configurations.	Medium5	CombinatoricsMath+2	No attempts yet	1s	128 MB	Judgeable
SkylineCount permutations of 1..N with no increasing subsequence of length 3, modulo 1,000,000, for each N up to 1,000.	Medium5	Dynamic programmingCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
MeganominoesFor each query i, count unordered pairs of distinct tiles where one matching pair of ends touches and the two opposite ends sum to i.	Medium5	Hash mapBrute force+1	No attempts yet	1s	128 MB	Judgeable
Frosh WeekGiven n distinct student numbers in a line, find the minimum number of adjacent swaps needed to sort them into increasing order.	Medium5	SortingDivide and conquer+2	No attempts yet	1s	128 MB	Judgeable
Cantor SetGiven a decimal x between 0 and 1 that ends within 6 fractional digits, decide whether x lies in the Cantor set, that is, whether some ternary expansion of x avoids the digit 1.	Medium5	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
Team RankingsGiven up to 100 rankings of five teams, find the ranking minimizing the sum of pairwise-order disagreements, breaking ties alphabetically.	Medium5	Brute forceCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Tight WordsCount words of length n over digits 0..k where adjacent digits differ by at most 1, then print that count as a percentage rounded to five decimals.	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Know When to Hold ThemRank a set of five-card poker hands from most to least valuable, using nine standard hand categories and their tie-breakers.	Medium5	SortingImplementation+2	No attempts yet	1s	128 MB	Judgeable
PERMSFor each query (n, k), count permutations of 1..n having exactly k inversions, with n up to 18 and k up to 200.	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Great Geek Game-show 3000!Given a random permutation of N names, each contestant follows its cycle up to K steps; find the probability every cycle has length at most K.	Medium5	CombinatoricsMath+2	No attempts yet	1s	128 MB	Judgeable
SoccerCompute probability distribution of final scores after up to T seconds of a stochastic soccer simulation with passing, stealing, shooting, and absorbing states.	Medium5	ProbabilityDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Baby's BlocksGiven a multiset of letters, find the 0-based rank of a given distinct permutation among all distinct permutations in lexicographic order.	Medium5	CombinatoricsString+1	No attempts yet	1s	128 MB	Judgeable
JOI FlagCount fillings of an M by N grid with J, O, I (some cells fixed) that contain at least one L shape: J with O to its right and I below, modulo 100000.	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	5s	128 MB	Judgeable
Commute RouteCount monotone lattice paths from (1,1) to (w,h) that never turn at two consecutive intersections, modulo 100000.	Medium5	Dynamic programmingArray+2	No attempts yet	1s	128 MB	Judgeable
Listing Square Arrangements in Lexicographic OrderList every partition of n whose parts are non-increasing, and print the sequences in decreasing lexicographic order.	Medium5	BacktrackingRecursion+2	No attempts yet	1s	128 MB	Judgeable
Odd or EvenPair each red number with a blue number to minimize how many pairs sum to an even value, since Mary wins those.	Medium5	GreedyMath+2	No attempts yet	3s	128 MB	Judgeable
Computer DJGiven N labeled songs, map the k-th character of the infinite string of all words over A..Z in length-then-lex order back to its song title.	Medium5	MathCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Cow IDsFind the N-th smallest binary number that has exactly K one-bits and no leading zeros, then print it in binary.	Medium5	CombinatoricsMath+2	No attempts yet	1s	128 MB	Judgeable
Cow LineGiven N up to 20, convert between a permutation of 1..N and its lexicographic rank among all permutations, for up to 10000 queries.	Medium5	CombinatoricsMath+1	No attempts yet	1s	128 MB	Judgeable
Bovine Bridge BattleCount sets of four points that are symmetric about some center, where each point pairs with its 180-degree rotation partner.	Medium5	Hash mapGeometry+2	No attempts yet	1s	128 MB	Judgeable
Building a FenceCount the ordered ways to cut a plank of length N into four positive integer pieces whose longest piece is strictly shorter than the other three combined.	Medium5	CombinatoricsMath+2	No attempts yet	1s	128 MB	Judgeable
Cow CashCount the number of unordered ways to make an amount N using V coin denominations, where each coin can be used any number of times.	Medium5	Dynamic programmingCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Fence RepairSplit one board into N planks of given lengths; each cut costs the length of the piece being cut, so find the minimum total cost.	Medium5	GreedyHeap+2	No attempts yet	1s	128 MB	Judgeable
ATM PIN TheftGiven a sequence of observed key presses (digits and at most one backspace), count the four-digit PINs that could produce exactly that sequence of pressed keys.	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
Hopeless CoachGiven past win, draw, and loss counts, find the probability that the team earns at least P points over the next N matches.	Medium5	Dynamic programmingProbability+2	No attempts yet	1s	128 MB	Judgeable
EntropyFor each line of text, print the fixed 8-bit ASCII bit length, the optimal prefix-free Huffman bit length, and the compression ratio rounded to one decimal.	Medium5	GreedyHeap+2	No attempts yet	1s	128 MB	Judgeable
Extrapolation Using a Difference TableExtend a sequence by k steps using a polynomial difference table, always assuming the highest-order differences stay constant, and print the (n+k)-th term.	Medium5	MathDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
El DoradoCount the increasing subsequences of length exactly k in a sequence of n distinct numbers, for several test cases.	Medium5	Dynamic programmingArray+1	No attempts yet	1s	128 MB	Judgeable
A Game with MarblesEach move takes one marble from a bowl and, if it is not bowl 1, adds one marble to every lower-numbered bowl; count the total moves until all bowls are empty.	Medium5	Dynamic programmingMath+1	No attempts yet	1s	128 MB	Judgeable
Rhinoceros BeetleGiven shared community cards and each player's two hole cards, evaluate every player's best five-card poker hand and print the indices of all winners.	Medium5	ImplementationSorting+2	No attempts yet	2s	128 MB	Judgeable
Pattern GeneratorFor each (n, k) pair, print all n-bit strings with exactly k ones in decreasing numeric order, separated by blank lines.	Medium5	BacktrackingRecursion+2	No attempts yet	1s	128 MB	Judgeable
King Thrór's GoldCount the ways to choose exactly k distinct bar values summing to T, and list all solutions in lexicographic order when there are at most 20.	Medium5	Dynamic programmingBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Wonderful FoursGiven five digits, count unordered triples of distinct permutations (no leading zero) whose sum is a different valid permutation of the same digits.	Medium5	Brute forceCombinatorics+2	No attempts yet	1s	128 MB	Judgeable
GearsCount how many distinct fractions a/b exist with both a and b in the range M to N.	Medium5	MathNumber theory+2	No attempts yet	1s	1024 MB	Judgeable
Geocaching CoordinatesGiven a coordinate formula with lowercase letter slots and rules for each variable's allowed values, print every distinct resulting coordinate in lexicographic order.	Medium5	Brute forceCombinatorics+2	No attempts yet	1s	1024 MB	Judgeable
Diophantus of AlexandriaGiven n, count the pairs (x, y) with x <= y satisfying 1/x + 1/y = 1/n.	Medium5	Number theoryMath+2	No attempts yet	1s	128 MB	Judgeable
Betting SetsPartition an N by M table of probabilities into groups of one cell per column to maximize the expected number of all-heads groups.	Medium5	Dynamic programmingBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
Digit Sum Over a RangeGiven l and u up to 2e9, find the total of the digit sums of every integer in that inclusive range.	Medium5	MathDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
The History of CottonGiven n, m, and g, print the g-th m-element subset of {1,...,n} in lexicographic order.	Medium5	CombinatoricsMath+1	No attempts yet	1s	128 MB	Judgeable
Yum YumFind the minimum number of straight lines needed to cover every integer-coordinate point in an (n+1) by (m+1) grid, excluding the frog's one starting point.	Medium5	MathNumber theory+2	No attempts yet	1s	128 MB	Judgeable
ProtocolsCount the length-m strings over k symbols with no run of l equal symbols, then output floor((n/m) * log2(count)).	Medium5	Dynamic programmingCombinatorics+2	No attempts yet	3s	128 MB	Judgeable
LollobrigidaGiven a multiset of block heights, decide whether the blocks can be arranged so the sequence alternates up and down at every position.	Medium5	GreedySorting+2	No attempts yet	1s	128 MB	Judgeable
The Number of N-k-special SetsCount subsets of {1,...,n} with no two consecutive numbers whose sum exceeds k, for n up to 100.	Medium5	Dynamic programmingCombinatorics	No attempts yet	1s	128 MB	Judgeable
Monochromatic TrianglesGiven n points and a list of red edges (all other pairs are black), count the triangles whose three sides share one color.	Medium5	CombinatoricsGraph+2	No attempts yet	1s	128 MB	Judgeable
MatchesGiven m match lineups that each split n boys into two teams, decide whether every pair of boys is separated at least once.	Medium5	Bit manipulationCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
Rectangles 2Count axis-aligned rectangles with vertices on grid points of an n x m grid whose perimeter is at least p.	Medium5	MathCombinatorics+2	No attempts yet	2s	512 MB	Judgeable
BalloonsGiven stock counts for n balloon colors and m orders, decide whether each child can receive the requested number of distinct-colored balloons.	Medium5	GreedySorting+2	No attempts yet	1s	128 MB	Judgeable
ElectricityGiven k lines between n homes and m windmills on parallel lines, count subsets of non-crossing lines where every home and windmill has degree at most one, modulo r.	Medium5	Dynamic programmingSorting+1	No attempts yet	1s	128 MB	Judgeable
DiceFind the k-th non-decreasing sequence of length m with values from 1 to n, in lexicographic order.	Medium5	CombinatoricsDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Super-Fast Circular RacesGiven a directed graph where each vertex has out-degree and in-degree at most two, count the ways to cover every vertex with vertex-disjoint simple directed cycles, modulo 10000, or report NIE if impossible.	Medium5	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Neon SignCount the triples of vertices whose three connecting tubes all share the same color in a red-blue complete graph.	Medium5	CombinatoricsGraph	No attempts yet	3s	256 MB	Judgeable
HerbertCount distinct squares a robot starting at the origin can end on within n moves when each step or ninety-degree turn costs one move.	Medium5	MathCombinatorics	No attempts yet	1s	128 MB	Judgeable
The Hopeless QueueCount fillings of the movable spots with equal coin totals so every prefix keeps at least as many 50 coins as 100 coins, modulo 1000000.	Medium5	Dynamic programmingCombinatorics	No attempts yet	2s	128 MB	Judgeable
Random Walk That Never Goes NegativeCount length-2N walks from 0 back to 0 with steps of plus or minus 1 that never drop below 0, modulo 1,000,000,007.	Medium5	CombinatoricsMath	No attempts yet	2s	64 MB	Judgeable
The number of studentsFind the smallest numbers of girls and boys whose within-group and cross-group friend counts match the given a, b, c, and d.	Medium5	MathNumber theory+1	No attempts yet	2s	256 MB	Judgeable
Algorithm Final ExamCount permutations of N items in which the first k positions are all wrong.	Medium5	CombinatoricsMath	No attempts yet	1s	128 MB	Judgeable
Cut the CakeCount into how many regions the given infinite lines divide a circle.	Medium5	GeometryCombinatorics	No attempts yet	20s	128 MB	Judgeable
Farmer John has no large brown cowFind the Kth adjective combination in alphabetical order among all combinations except the N forbidden ones.	Medium5	CombinatoricsSorting	No attempts yet	1s	128 MB	Judgeable
The Alphabet StickerCount completions of a sticker pattern where each question mark becomes a visible letter and every letter forms one contiguous block.	Medium5	CombinatoricsString	No attempts yet	1s	128 MB	Judgeable
Charity Booth RentalCount the strictly increasing positive triples GP, GA and PC that sum to T for each query.	Medium5	CombinatoricsMath	No attempts yet	1s	128 MB	Judgeable
Number of LocksCount length-n strings over heights 1 to 4 that use at least three distinct heights and have an adjacent pair differing by exactly 3.	Medium5	Dynamic programmingCombinatorics	No attempts yet	1s	128 MB	Judgeable
OdometerCount the integers between X and Y whose decimal digits use one repeated digit except for a single different digit.	Medium5	Brute forceCombinatorics	No attempts yet	1s	128 MB	Judgeable
Club ScheduleCount attendance and key-passing schedules over N days where each day's leader attends and the key stays with attendees.	Medium5	Dynamic programmingCombinatorics	No attempts yet	1s	128 MB	Judgeable
Catalan SquareCompute the convolution sum S_n of Catalan numbers for a given n up to 5000 and print the exact integer.	Medium5	CombinatoricsMath	No attempts yet	1s	256 MB	Judgeable
The Kth Anagram in Alphabetical OrderGiven a word and rank K, print the Kth distinct anagram of the word in alphabetical order.	Medium5	CombinatoricsString	No attempts yet	1s	256 MB	Judgeable
Zeroing a Binary SequenceCount ordered flip sequences of exactly K moves that turn a given binary sequence into all zeroes.	Medium5	CombinatoricsDynamic programming	No attempts yet	1s	256 MB	Judgeable
Restaurant RatingsCount how many nonnegative score sheets rank no better than the given sheet under total sum first and critic order second.	Medium5	CombinatoricsDynamic programming	No attempts yet	1s	256 MB	Judgeable
Pi Day Pie DistributionCount the nondecreasing distributions of n pie pieces among k people with each person getting at least one piece.	Medium5	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Inherited diseaseFollow the birth-order path down D generations where a generation g member has g+1 children and print each breadth-first number modulo 1000000007.	Medium5	MathCombinatorics	No attempts yet	1s	16 MB	Judgeable
Uniting DepartmentsMerge departments pairwise at product-of-sizes cost and report the total cost and the number of ordered merge sequences modulo 1000000007.	Medium5	MathCombinatorics	No attempts yet	1s	256 MB	Judgeable
Attendance AwardCount length-N strings over L, O and A with at most one L and no three consecutive As for each N up to 3000.	Medium5	Dynamic programmingCombinatorics	No attempts yet	1s	256 MB	Judgeable
Next Unique-Digit NumberFind the smallest integer above N that uses no zero and repeats none of the digits 1 to 9, printing 0 when none exists.	Medium5	BacktrackingCombinatorics+1	No attempts yet	1s	256 MB	Judgeable
Football scorelinesCount the ordered scoring sequences by both teams that reach the given final score under the listed play values, modulo 1000000009.	Medium5	Dynamic programmingCombinatorics	No attempts yet	2s	256 MB	Judgeable
Krusty's BurgerCount burger combinations of size, bun, cheeses, toppings and sauces whose size plus extra-item cost is at most B.	Medium5	CombinatoricsMath	No attempts yet	1s	256 MB	Judgeable
Delicious CookieSplit every piece of a right triangle with legs a and b N times along the altitude to the hypotenuse and print the natural log of the K-th largest piece area.	Medium5	CombinatoricsGeometry+1	No attempts yet	1s	512 MB	Judgeable
Running StepsCount left-right alternating sequences of one-step and two-step strides where both legs use equal counts and twos are at least as many as ones.	Medium5	CombinatoricsMath	No attempts yet	1s	256 MB	Judgeable
Feast CoinsCount ways to reach total S with owned coins so that every chosen coin value appears the same number of times.	Medium5	Dynamic programmingCombinatorics	No attempts yet	3s	256 MB	Judgeable
Perica's PianoSort the N key values and add each value multiplied by the number of K-sets where it is the largest, modulo 1000000007.	Medium5	CombinatoricsSorting+1	No attempts yet	1s	64 MB	Judgeable