Strings and text

Parsing, matching, and tries

Under construction

Still being built. Things may change

Total results3,614 problems

Antisymmetry
Hard8
String, Hash map+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Tree Rotations 2
Hard8
Divide and conquer, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A Horrible Poem
Hard8
String, Number theory+2
No attempts yet
Time limit
8s
Memory limit
128 MB
Judgeable
Prefixuffix
Hard8
String, String matching+2
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Transformations
Hard8
String, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Shortest Period
Hard8
String, String matching+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Turns
Hard8
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Almost Conjugates
Hard8
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cyclic Numbers
Hard8
String matching, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Gordian Dances
Hard8
Math, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ciąg
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Folding the Map
Hard8
Simulation, Divide and conquer+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Three-Bit Computers
Hard8
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
General Bytor
Hard8
Brute force, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ritual
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
The Fibonacci Game
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Mutations
Hard8
String matching, Hash map+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Train
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Drzewa
Hard8
Tree, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Text Algorithms
Hard8
Dynamic programming, String matching
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pandora
Hard8
Geometry, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Digital Onion
Hard8
Combinatorics, Recursion+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Rotate and Rewrite
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
15s
Memory limit
128 MB
Judgeable
Fragment Reassembly
Hard8
Backtracking, String matching+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fine Dining Restaurant
Hard8
String matching, Trie+1
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Correcting Curiosity
Hard8
String matching, String+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Passwords
Hard8
String matching, String
No attempts yet
Time limit
7s
Memory limit
128 MB
Judgeable
Tandem Repeats
Hard8
String matching, Divide and conquer
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Kkunglish
Hard8
Segment tree, String matching
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Dictionary
Hard8
Trie, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Moves on an Infinite Binary Tree
Hard8
Dynamic programming, Tree+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
C(O|W|A*RD*|S)* CROSSWORD Puzzle
Hard8
Backtracking, String matching
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
RNA
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Eunki's DNA Molecules
Hard8
Math, String+1
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Criminals
Hard8
String matching, Greedy+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Hari Merdeka
Hard8
Dynamic programming, String matching
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Out of context
Hard8
Dynamic programming, String matching
No attempts yet
Time limit
10s
Memory limit
256 MB
Judgeable
Virus synthesis
Hard8
Dynamic programming, String matching
No attempts yet
Time limit
20s
Memory limit
256 MB
Judgeable
Integer in Integer
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Ancient Scrolls
Hard8
Greedy, String+1
No attempts yet
Time limit
8s
Memory limit
256 MB
Judgeable
Revenge of the ants 2
Hard8
String matching, Sorting+2
No attempts yet
Time limit
5s
Memory limit
256 MB
Judgeable
Evolution in Parallel
Hard8
Graph, BFS+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Make a superpalindrome
Hard8
String, Recursion+1
No attempts yet
Time limit
1s
Memory limit
16 MB
Judgeable
Selling Numbers
Hard8
Backtracking, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Just a Quiz
Hard8
Dynamic programming, Trie+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Bracket Strings
Hard8
Combinatorics, Number theory+2
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Finding a Grayscale Image
Hard8
String matching, Matrix+1
No attempts yet
Time limit
10s
Memory limit
512 MB
Judgeable
Text Processor
Hard8
String matching, Sliding window+1
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Substrings
Hard8
Graph, DFS+2
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Round words
Hard8
Dynamic programming, String
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Birthday Numbers II
Hard8
Math, Recursion+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Counting palindromes
Hard8
String matching, Segment tree+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Swapping the Stones
Hard8
Greedy, String matching+1
No attempts yet
Time limit
2s
Memory limit
32 MB
Judgeable
Alphabet Blocks and Passwords
Hard8
Backtracking, String matching+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Trie Sharding
Hard8
Dynamic programming, Trie+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Fair and Square (Large2)
Hard8
Math, String+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Wildcard (Large)
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
The Great Mixing Song Festival
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Shades of the town
Hard8
String matching, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hongjun Likes Strings
Hard8
String, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Lot of Games
Hard8
Trie, Game theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Maximum substring cost
Hard8
String, Sorting+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Substring Count
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Flipping a Bit String
Hard8
Dynamic programming, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Counting strings with LCS n-1
Hard8
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fewest letters for a suffix array
Hard8
String, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Calculation mistake
Hard8
Segment tree, String+1
No attempts yet
Time limit
3s
Memory limit
256 MB
Judgeable
Password
Hard8
String, Sorting+2
No attempts yet
Time limit
4s
Memory limit
512 MB
Judgeable
Big Number Multiplication
Hard8
Math, String+1
No attempts yet
Time limit
3s
Memory limit
512 MB
Judgeable
Pseudo Palindrome
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Good Substrings
Hard8
String, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
New Store Name
Hard8
String, Brute force+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Substitution Cipher Key
Hard8
Greedy, Sorting+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Palindromes and Queries
Hard8
Segment tree, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
What Next
Hard8
Implementation, Simulation+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Revenge of the Champernowne Constant
Hard8
String, Math+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Subsets whose lexicographic order matches
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Palindrome cipher decryption
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Favorite music
Hard8
String matching, Trie+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Exam
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
1.5s
Memory limit
512 MB
Judgeable
Game of Matchings
Hard8
String matching, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Dictionary Game
Hard8
Game theory, Trie+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Arranging Hat
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Passwords
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Binary Code
Hard8
Trie, Greedy+2
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Kids Designing Kids
Hard8
Implementation, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
K-th good string
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Substring appearing twice
Hard8
String, Binary search+2
No attempts yet
Time limit
6s
Memory limit
128 MB
Judgeable
Zvonimir
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Permutations that contain a word
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Expression
Hard8
Implementation, Recursion+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rhyme
Hard8
String, Trie+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Osmosmjerka
Hard8
Math, String matching+2
No attempts yet
Time limit
4s
Memory limit
256 MB
Judgeable
String array
Hard8
String matching, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
f(X) = A + X + B + X + C
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Integeregex (Large)
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
String Table
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Piano
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Palindromes and Queries 2
Hard8
String, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Period of a Slot Machine
Hard8
String matching, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
AntisymmetryCount how many contiguous substrings of a binary string are antisymmetric, meaning each character differs from its mirror-position partner.	Hard8	StringHash map+2	No attempts yet	3s	512 MB	Judgeable
Tree Rotations 2Given a binary tree with distinct leaf labels, rotations swap children at any node; find the minimum possible inversion count of the leaf sequence.	Hard8	Divide and conquerRecursion+2	No attempts yet	1s	128 MB	Judgeable
A Horrible PoemGiven a string and substring queries, find the length of the shortest full period of each substring, where a full period divides the substring into equal repeats.	Hard8	StringNumber theory+2	No attempts yet	8s	128 MB	Judgeable
PrefixuffixGiven a string t, find the maximum length L, at most n/2, such that the length-L prefix and the length-L suffix of t are cyclic rotations of each other.	Hard8	StringString matching+2	No attempts yet	3s	512 MB	Judgeable
TransformationsGiven two binary strings of length n, decide whether disjoint ab and ba fragments can be swapped repeatedly to turn the first string into the second.	Hard8	StringMath+2	No attempts yet	1s	128 MB	Judgeable
The Shortest PeriodDelete exactly one letter from a string to minimize the length of the shortest period of the resulting word.	Hard8	StringString matching+2	No attempts yet	5s	128 MB	Judgeable
TurnsFor each starting position, find how many turns must be observed before the position on the map becomes uniquely determined.	Hard8	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
Almost ConjugatesDecide whether two length-n words are almost conjugates and, if so, list every rotation of the first that differs from the second in exactly one position.	Hard8	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
Cyclic NumbersFind the smallest B >= n that is a multiple m*A (1<=m<=k) of some k-digit number A whose multiples 1..k are all cyclic rotations.	Hard8	String matchingMath+2	No attempts yet	1s	128 MB	Judgeable
Gordian DancesGiven a sequence of S (string swap) and R (quarter-turn) moves, find the minimum number of further moves that returns the dance to a horizontal, parallel, untangled state.	Hard8	MathString+2	No attempts yet	1s	128 MB	Judgeable
CiągBajtek needs the shortest string over the given alphabet that is not a subsequence of the word, and the lexicographically smallest among shortest such strings.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	128 MB	Judgeable
Folding the MapDecide whether an n by m map with convex or concave creases folds to one square.	Hard8	SimulationDivide and conquer+1	No attempts yet	1s	128 MB	Judgeable
Three-Bit ComputersThe task is to decide whether a target string over a, b and c can be built from uninitialized cells with the two pair operations.	Hard8	Dynamic programmingString	No attempts yet	1s	128 MB	Judgeable
General BytorGiven two permutations of n unit types and m cyclic position-shift orders, find the shortest (then lexicographically smallest) sequence of at most 10 orders that transforms the start into the target.	Hard8	Brute forceString+2	No attempts yet	1s	128 MB	Judgeable
RitualCount the subsequences of a long digit string that form a palindrome divisible by 666, then report ((count - 1) mod 666) + 1.	Hard8	Dynamic programmingString+2	No attempts yet	1s	128 MB	Judgeable
The Fibonacci GameDetermine whether the first player wins a game that erases Fibonacci words only from the right end of a given a/b string.	Hard8	String matchingDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
MutationsAnswer many queries whether a fragment of the second array matches a fragment of the first after changing all copies of one value.	Hard8	String matchingHash map+1	No attempts yet	1s	128 MB	Judgeable
TrainSum over all n! orders of the wagon strings the number of occurrences of their concatenation in t.	Hard8	Dynamic programmingString matching+1	No attempts yet	1s	128 MB	Judgeable
DrzewaFor each node of a labeled rooted tree, find the leaf below it whose downward label string is lexicographically largest, breaking ties by smaller leaf number.	Hard8	TreeGreedy+2	No attempts yet	1s	128 MB	Judgeable
Text AlgorithmsMove a pawn from the bottom-right to the top-left of a grid where left and up steps cost 1 and diagonal steps are free when row and column colors match.	Hard8	Dynamic programmingString matching	No attempts yet	1s	128 MB	Judgeable
PandoraGiven the left/right turn sequence of a rectilinear polygon, count the coordinate axes it is monotone with respect to.	Hard8	GeometryString	No attempts yet	1s	128 MB	Judgeable
Digital OnionGiven a balanced parentheses string, output the string that comes next in the defined price order.	Hard8	CombinatoricsRecursion+1	No attempts yet	1s	128 MB	Judgeable
Rotate and RewriteDecide whether two rotatable integer sequences can be reduced to a common sequence by substring rewrite rules and report the greatest such length.	Hard8	Dynamic programmingString matching+1	No attempts yet	15s	128 MB	Judgeable
Fragment ReassemblyArrange the given text fragments so neighbors share an exact overlap and print the joined text in lines of at most 72 characters.	Hard8	BacktrackingString matching+1	No attempts yet	1s	128 MB	Judgeable
Fine Dining RestaurantFor each banned serial number, count the digit comparisons the described naive left-to-right substring search performs against the concatenated string A.	Hard8	String matchingTrie+1	No attempts yet	3s	128 MB	Judgeable
Correcting CuriosityGiven two strings, find the length of the shortest substitution command that rewrites the first into the second.	Hard8	String matchingString+1	No attempts yet	2s	256 MB	Judgeable
PasswordsFind the longest prefix length and suffix length from two distinct set strings whose repetitions coincide.	Hard8	String matchingString	No attempts yet	7s	128 MB	Judgeable
Tandem RepeatsCount substrings of even length whose first half equals the second half in each DNA string.	Hard8	String matchingDivide and conquer	No attempts yet	1s	128 MB	Judgeable
KkunglishFor each query range, the program reports the case-insensitive occurrence of T with the most case differences, or -1 if none, then flips the case of the range.	Hard8	Segment treeString matching	No attempts yet	2s	128 MB	Judgeable
DictionaryGiven up to 50 short words, find the fewest vertices of an edge-labeled tree whose downward paths contain every word.	Hard8	TrieString matching+2	No attempts yet	1s	128 MB	Judgeable
Moves on an Infinite Binary TreeStarting from the node reached by S, count the distinct nodes reachable by following any subsequence of T on an infinite binary tree.	Hard8	Dynamic programmingTree+1	No attempts yet	2s	128 MB	Judgeable
C(O\|W\|ARD\|S)* CROSSWORD PuzzleFill a 2 to 4 by 2 to 4 grid with capital letters so each row and column matches its regex clue, and report the unique solution, none, or ambiguous.	Hard8	BacktrackingString matching	No attempts yet	10s	128 MB	Judgeable
RNAReport the longest contiguous block shared by both RNA strings whose parenthesis marks balance.	Hard8	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
Eunki's DNA MoleculesFor every pair of N DNA strings, decide whether four two-way substring swaps can rewrite one into the other.	Hard8	MathString+1	No attempts yet	5s	256 MB	Judgeable
CriminalsFind every house where two given color sequences appear as subsequences on the left and right with both walkers sharing one home color outside.	Hard8	String matchingGreedy+1	No attempts yet	2s	256 MB	Judgeable
Hari MerdekaChoose a string over priced letters with total cost within the budget to maximize the summed scores of all occurrences of the given words.	Hard8	Dynamic programmingString matching	No attempts yet	3s	256 MB	Judgeable
Out of contextFor each text line, print the longest substring the given grammar generates, breaking ties by earliest position, or NONE.	Hard8	Dynamic programmingString matching	No attempts yet	10s	256 MB	Judgeable
Virus synthesisBuild each DNA string over A, C, G, and T from empty using single-letter attachments or mirrored duplication in the fewest operations.	Hard8	Dynamic programmingString matching	No attempts yet	20s	256 MB	Judgeable
Integer in IntegerCount how many times C appears as a (possibly overlapping) substring in the decimal writings of all integers from A to B, modulo 1000000007.	Hard8	Dynamic programmingString matching+1	No attempts yet	10s	128 MB	Judgeable
Ancient ScrollsRecover the lexicographically smallest string within Hamming distance d of three given strings, or print -1 when no such string exists.	Hard8	GreedyString+1	No attempts yet	8s	256 MB	Judgeable
Revenge of the ants 2Labeled ants walk both ways on a circular rail and bounce on collision; compute when each ant is back at its start with its initial direction.	Hard8	String matchingSorting+2	No attempts yet	5s	256 MB	Judgeable
Evolution in ParallelDecide whether every fossil sequence fits into one of two chains in which each sequence is a subsequence of the next one and of the living species sequence.	Hard8	GraphBFS+1	No attempts yet	2s	256 MB	Judgeable
Make a superpalindromeGiven a lowercase string, find the smallest superpalindrome of the same length that comes after it in lexicographic order.	Hard8	StringRecursion+1	No attempts yet	1s	16 MB	Judgeable
Selling NumbersCount how many D-digit strings, with leading zeros allowed, have exactly the memorability score S defined by palindromic and repeated substrings.	Hard8	BacktrackingCombinatorics+1	No attempts yet	2s	256 MB	Judgeable
Just a QuizTeresa interrupts randomly drawn known questions at chosen words to maximize expected correct answers within t seconds.	Hard8	Dynamic programmingTrie+1	No attempts yet	1s	256 MB	Judgeable
Bracket StringsFor each queried length L, count bracket strings that match the incorrect or aperiodic filters chosen by flags p and q, modulo m.	Hard8	CombinatoricsNumber theory+2	No attempts yet	10s	512 MB	Judgeable
Finding a Grayscale ImageCount the R by C windows of A that equal B after a linear brightness change of the form p times A plus q.	Hard8	String matchingMatrix+1	No attempts yet	10s	512 MB	Judgeable
Text ProcessorCount the distinct substrings inside each fixed-width window of a lowercase string for many queries.	Hard8	String matchingSliding window+1	No attempts yet	1s	256 MB	Judgeable
SubstringsOrder all given strings as the consecutive length-L windows of one string of length L+N-1 and print the lexicographically smallest such string.	Hard8	GraphDFS+2	No attempts yet	2s	256 MB	Judgeable
Round wordsGiven two words of length up to 2000, pick a rotation or reversal of each to maximize the LCS length and print that maximum.	Hard8	Dynamic programmingString	No attempts yet	2s	128 MB	Judgeable
Birthday Numbers IIAdd up the products of every neighboring pair among the integers between x and y that use only the digits 3, 5 and 8, and report the total modulo 19980305.	Hard8	MathRecursion+2	No attempts yet	1s	256 MB	Judgeable
Counting palindromesCount the palindromic substrings fully contained in each query interval of a lowercase string.	Hard8	String matchingSegment tree+2	No attempts yet	2s	64 MB	Judgeable
Swapping the StonesMove stones along empty arcs of a circular shore so black and white stones exchange position sets with minimum total carry distance, or report impossibility.	Hard8	GreedyString matching+1	No attempts yet	2s	32 MB	Judgeable
Alphabet Blocks and PasswordsArrange A to Z into the lexicographically smallest permutation with none of the given passwords appearing as a contiguous block.	Hard8	BacktrackingString matching+1	No attempts yet	5s	512 MB	Judgeable
Trie ShardingSplit the strings among N labeled non-empty servers to maximize the total trie node count and report the maximum and the count of optimal splits modulo 1e9+7.	Hard8	Dynamic programmingTrie+1	No attempts yet	5s	512 MB	Judgeable
Fair and Square (Large2)Count numbers in each interval [A, B] that read the same forwards and backwards and equal the square of such a number.	Hard8	MathString+1	No attempts yet	5s	512 MB	Judgeable
Wildcard (Large)Given two filenames A and B, find the shortest star pattern that matches A but not B, breaking ties by fewer stars then lexicographic order.	Hard8	Dynamic programmingString matching+1	No attempts yet	5s	512 MB	Judgeable
The Great Mixing Song FestivalPartition the given songs into groups of exactly c songs each within a year span of m, maximizing the total length of the longest common substring in each group.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	5s	128 MB	Judgeable
Shades of the townGiven several integer patterns and one shade array, count every occurrence where a contiguous block equals a pattern scaled by a positive real factor.	Hard8	String matchingMath	No attempts yet	1s	1024 MB	Judgeable
Hongjun Likes StringsFor each of up to 100000 queries, find the shortest substring of a fixed string S that contains both given short patterns A and B, allowing overlap.	Hard8	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
A Lot of GamesGiven a trie of strings, play the prefix-building game k times with the loser starting next; report who wins the last game.	Hard8	TrieGame theory+2	No attempts yet	2s	512 MB	Judgeable
Maximum substring costGiven a string T, find the maximum of length times number of occurrences over all substrings S of T.	Hard8	StringSorting+2	No attempts yet	2s	512 MB	Judgeable
Substring CountCount length-L lowercase strings that contain exactly C of N given words (N at most 6, L at most 50) as substrings, modulo 1,000,000,009.	Hard8	Dynamic programmingString matching+2	No attempts yet	2s	512 MB	Judgeable
Flipping a Bit StringGiven a binary string and a divisor M of its length, find the minimum number of operations (single flip, prefix flip of a multiple of M, or suffix flip of a multiple of M) to make all characters 1.	Hard8	Dynamic programmingGreedy+1	No attempts yet	2s	512 MB	Judgeable
Counting strings with LCS n-1Count length-n strings over the first m letters whose longest common subsequence with a given string S has length exactly n-1.	Hard8	Dynamic programmingCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Fewest letters for a suffix arrayGiven a permutation that is a suffix array, find the minimum number of distinct letters needed for a string that realizes exactly this suffix array.	Hard8	StringGreedy+2	No attempts yet	2s	512 MB	Judgeable
Calculation mistakeMaintain a string of digits and plus or minus signs under range replacements, and evaluate the arithmetic value of any substring with the calculator's operator rules.	Hard8	Segment treeString+1	No attempts yet	3s	256 MB	Judgeable
PasswordGiven a length-N string, collect all distinct substrings meeting four counts (length, digits, specials, uppercase), sort them lexicographically, and print the middle one.	Hard8	StringSorting+2	No attempts yet	4s	512 MB	Judgeable
Big Number MultiplicationMultiply two non-negative integers of up to 300,000 digits each and print the exact product without leading zeros.	Hard8	MathString+1	No attempts yet	3s	512 MB	Judgeable
Pseudo PalindromeGiven a string w and a rational theta, split w into the fewest substrings that are each a theta-palindrome (form uvu^R with enough border), or report 0.	Hard8	Dynamic programmingString matching+1	No attempts yet	2s	512 MB	Judgeable
Good SubstringsCount how many distinct substrings of a binary string appear twice at non-overlapping positions.	Hard8	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
New Store NameSplit each of two short strings into two non-overlapping contiguous pieces so that A+C equals B+D, and output the lexicographically smallest longest result.	Hard8	StringBrute force+1	No attempts yet	2s	512 MB	Judgeable
Substitution Cipher KeyGiven N distinct words and a target permutation, find the lexicographically smallest substitution cipher key that sorts the encrypted words into that order, or report none.	Hard8	GreedySorting+2	No attempts yet	1s	64 MB	Judgeable
Palindromes and QueriesSupport range character assignments and count palindromic substrings of length at most K inside a queried range.	Hard8	Segment treeString+2	No attempts yet	2s	512 MB	Judgeable
What NextGiven a prefix of an NZPC Speak program cut at an arbitrary point, list the symbols that can legally come next, respecting declarations, masking, and partial names.	Hard8	ImplementationSimulation+2	No attempts yet	2s	512 MB	Judgeable
Revenge of the Champernowne ConstantGiven a digit string S of length up to 100, find the 1-indexed position of its first occurrence in the Champernowne constant 0.123456789101112...	Hard8	StringMath+2	No attempts yet	8s	512 MB	Judgeable
Subsets whose lexicographic order matchesCount non-empty subsets of the integers from A to B whose numeric order equals their lexicographic decimal order, modulo P.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	8s	512 MB	Judgeable
Palindrome cipher decryptionFor each string, find its longest palindromic subsequence and output the lexicographically smallest one among those of maximal length.	Hard8	Dynamic programmingString+2	No attempts yet	8s	512 MB	Judgeable
Favorite musicGiven n note strings and q pairs, find the shortest string containing both given fragments as contiguous substrings, allowing overlap.	Hard8	String matchingTrie+2	No attempts yet	1s	256 MB	Judgeable
ExamGiven each student's fixed semester points and a distribution of exam points, find the probability that the grade string avoids all forbidden substrings.	Hard8	Dynamic programmingString matching+2	No attempts yet	1.5s	512 MB	Judgeable
Game of MatchingsCount substrings of S that match pattern P under a bijective letter-to-number mapping, where distinct numbers must get distinct letters.	Hard8	String matchingString+2	No attempts yet	2s	512 MB	Judgeable
Dictionary GameWords are destroyed by prefix cuts; after each insertion into the dictionary, report which player wins the impartial game under optimal play.	Hard8	Game theoryTrie+2	No attempts yet	5s	512 MB	Judgeable
Arranging HatEach of n m-digit strings may have individual digits rewritten; find the minimum number of digit changes so the sequence becomes nondecreasing.	Hard8	Dynamic programmingGreedy+2	No attempts yet	5s	512 MB	Judgeable
PasswordsCount length A to B alphanumeric passwords with mixed case and a digit that avoid blacklist substrings, where digits can stand in for similar letters.	Hard8	Dynamic programmingString matching+2	No attempts yet	2s	512 MB	Judgeable
Binary CodeEach of n binary words has at most one unreadable bit; decide whether the ?s can be filled so no word is a prefix of another.	Hard8	TrieGreedy+2	No attempts yet	2s	2048 MB	Judgeable
Kids Designing KidsGiven three grid pictures, find the translation of the second that makes the XOR of the first two match the third, up to translation.	Hard8	ImplementationString matching+2	No attempts yet	2s	512 MB	Judgeable
K-th good stringGiven a bracket string S, list the distinct good strings that appear as subsequences in lexicographic order and print the K-th one.	Hard8	Dynamic programmingString+1	No attempts yet	2s	512 MB	Judgeable
Substring appearing twiceGiven a string and at most K letter replacements, maximize the length of the longest substring that occurs at two different starting positions, allowing overlap.	Hard8	StringBinary search+2	No attempts yet	6s	128 MB	Judgeable
ZvonimirFind the minimum number of operations (type one letter, or copy a contiguous block of already typed text and append it) to produce string X.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
Permutations that contain a wordCount distinct permutations of A that contain B as a contiguous substring, modulo 10007.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
ExpressionParse a two-dimensional rendering of nested fractions, additions, multiplications, and divisions, then print the reduced value as a fraction.	Hard8	ImplementationRecursion+2	No attempts yet	2s	512 MB	Judgeable
RhymeGiven N distinct words, find the longest sequence using each word at most once where consecutive words rhyme: their longest common suffix has length at least the longer word's length minus one.	Hard8	StringTrie+2	No attempts yet	1s	256 MB	Judgeable
OsmosmjerkaGiven a letter block tiled infinitely in all directions, pick a random start square and one of 8 directions twice, and report the probability that the two read words of length K match, as a reduced fraction.	Hard8	MathString matching+2	No attempts yet	4s	256 MB	Judgeable
String arrayCount strings S of length 1 to W such that the repeated periodic filling of X matches the given patch F at the fixed offset.	Hard8	String matchingNumber theory+1	No attempts yet	2s	512 MB	Judgeable
f(X) = A + X + B + X + CCount occurrences of pattern F in the K-fold string expansion f(X)=A+X+B+X+C applied to S, modulo 1e9+7.	Hard8	String matchingDynamic programming+2	No attempts yet	2s	512 MB	Judgeable
Integeregex (Large)Count integers in [A, B] whose decimal form (no leading zeros) matches a small regular expression over digits.	Hard8	Dynamic programmingString+2	No attempts yet	5s	512 MB	Judgeable
String TableBuild a table whose cells are huge concatenated strings defined by comparing neighbors, then print 50 characters from a given position of the final cell.	Hard8	Dynamic programmingString+2	No attempts yet	2s	512 MB	Judgeable
PianoGiven N equally likely piano tones, find the expected number of presses until a fixed M-tone sequence appears, for every prefix of it.	Hard8	String matchingDynamic programming+2	No attempts yet	1s	64 MB	Judgeable
Palindromes and Queries 2Given a string and queries, each query asks how many palindromic substrings start at a given index with length at least a given value.	Hard8	StringString matching+2	No attempts yet	2s	512 MB	Judgeable
Period of a Slot MachineGiven a sequence of n outcomes, find k and p minimizing k+p (ties by smaller p) such that T[i+p]=T[i] for all i>k with i+p<=n.	Hard8	String matchingImplementation+1	No attempts yet	2s	512 MB	Judgeable