Strings and text

Parsing, matching, and tries

Under construction

Still being built. Things may change

Total results3,614 problems

Number of Expression Values
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Binary Sequence Rotation
Hard8
String matching, Sorting+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Finding a Momentum Sequence
Hard8
String, Math+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Square-Substring-Free Number
Hard8
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Easy Group Matching
Hard8
Dynamic programming, Prefix sum+1
No attempts yet
Time limit
30s
Memory limit
1536 MB
Judgeable
Message Converter
Hard8
String, Simulation+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Beautiful Word
Hard8
Greedy, Game theory+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Roman Numeral Walk
Hard8
DFS, Backtracking+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Balanced Bracket Segment
Hard8
Stack, String matching+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Martian DNA Formula
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Logo Matching
Hard8
String matching, Array+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
RLE Compression
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Vigenère Cipher Analysis
Hard8
String matching, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Unchanged Picture
Hard8
Geometry, String matching+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Insults
Hard8
String, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bundling
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Repetition-Free Formula
Hard8
Recursion, String+2
No attempts yet
Time limit
2s
Memory limit
64 MB
Judgeable
Billing Tables
Hard8
Trie, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Secret Code: Largest Number
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Term Generator
Hard8
String matching, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Proof Generator
Hard8
String matching, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Software Industry Revolution
Hard8
String matching, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
ACGU
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Genetics
Hard8
Simulation, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Stammering Aliens
Hard8
String matching, Binary search+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Matrix Calculator
Hard8
Recursion, Matrix+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Using sed
Hard8
BFS, String matching+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Keyword Search
Hard8
String matching, Bit manipulation+2
No attempts yet
Time limit
10s
Memory limit
128 MB
Judgeable
Organize Your Train
Hard8
BFS, Simulation+2
No attempts yet
Time limit
3s
Memory limit
128 MB
Judgeable
Magical Crafting
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Disjoint Regular Expressions
Hard8
Dynamic programming, BFS+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Fibonacci Word
Hard8
String matching, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Intellectual Property
Hard8
String matching, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Language Cardinality
Hard8
String, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Tail Palindrome
Hard8
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Spaghetti
Hard8
Graph, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Crypt Kicker
Hard8
Backtracking, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Barcode of Judgment
Hard8
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fill the Crossword
Hard8
Backtracking, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Ladder
Hard8
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Crosswords Insider
Hard8
Backtracking, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
GHOST
Hard8
Game theory, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
When
Hard8
Simulation, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Pattern Matching
Hard8
Dynamic programming, String matching
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
A-to-Z
Hard8
Graph, Shortest path+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Alpha of Degree k
Hard8
Graph, BFS+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Weaker than Planned
Hard8
Backtracking, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
City Merger
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Name the Crossing
Hard8
Graph, Union-find+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Infiltration
Hard8
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
DNA Copy
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Cipher
Hard8
Hash map, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Insecurity
Hard8
Bit manipulation, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Balanced Garden in a Row
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Zigzag Numbers
Hard8
Dynamic programming, Math+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Spelling Suggestion
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
12s
Memory limit
128 MB
Judgeable
Sanghak Language
Hard8
Trie, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
File Search
Hard8
String, Trie+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Code Lock
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
File Recover
Hard8
String, String matching+1
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
DNA Subsequence
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ambiguous Codes
Hard8
String, Graph+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
First!
Hard8
String, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Scrambled Letters
Hard8
String, Sorting+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Treasure
Hard8
Graph, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Milk Patterns
Hard8
String matching, Binary search+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Append
Hard8
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
L-system Substring
Hard8
String, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Xenosemantics
Hard8
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Fold
Hard8
Dynamic programming, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Careful Declaration
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
God of the Vile Baskers
Hard8
String, Sliding window+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Transforming Comets
Hard8
String matching, Geometry+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Post's Correspondence Problem
Hard8
BFS, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ransom Note
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Counting
Hard8
String matching, Trie+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Similar Polygons
Hard8
Geometry, String matching+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Similar Polygons
Hard8
Geometry, String matching+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Automatic Trading
Hard8
String, String matching+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
The Palindromes Strike Back
Hard8
Dynamic programming, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Address Matching
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
ASM
Hard8
Brute force, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Changing Phone Numbers
Hard8
String, Simulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Puzzle Out
Hard8
Backtracking, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Encoding
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
DNA Laboratory
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Missing Letters
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Identity Checker
Hard8
Math, String+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Censorship
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Vigenère Cipher
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
5s
Memory limit
64 MB
Judgeable
Cyclic Rotation Cipher
Hard8
String, Sorting+1
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Byephone
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
3 MB
Judgeable
Encoding
Hard8
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Morphing is fun
Hard8
Graph, DFS+2
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Beer Numbers
Hard8
String, Combinatorics+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Necklaces
Hard8
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Word Equations
Hard8
String, Union-find+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Words 2
Hard8
String, Recursion+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Words
Hard8
String, Dynamic programming+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Beads
Hard8
String, Hash map+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Number of Expression ValuesCount the distinct values an unspaced digit/operator string can yield when each subexpression is parsed as prefix, infix, or postfix.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
Binary Sequence RotationGiven the last column of a sorted matrix of all circular rotations of an unknown binary string, reconstruct the lexicographically smallest rotation (first row) or report impossibility.	Hard8	String matchingSorting+2	No attempts yet	2s	128 MB	Judgeable
Finding a Momentum SequenceGiven a digit string, decide if it can be split into an arithmetic progression followed by a term equal to the last progression term times some integer f, and output the minimal possible f.	Hard8	StringMath+2	No attempts yet	1s	1024 MB	Judgeable
Square-Substring-Free NumberGiven N up to 10^18, find the smallest number at least N whose decimal representation contains no perfect square as a substring.	Hard8	Dynamic programmingString matching+1	No attempts yet	1s	1024 MB	Judgeable
Easy Group MatchingGiven a text sequence and two patterns, count group-matching positions for each pattern, then find the smallest integer n that maximizes group matches for the concatenated pattern P1·n·P2 and report that count.	Hard8	Dynamic programmingPrefix sum+1	No attempts yet	30s	1536 MB	Judgeable
Message ConverterParse a MULTI markup string with tags for newline, justification, and spacing, then render it into a fixed-size character grid while detecting conflict, size, and syntax errors.	Hard8	StringSimulation+1	No attempts yet	1s	128 MB	Judgeable
Beautiful WordSimulate a turn-based letter-picking game where one player greedily takes the rightmost slip while the other picks optimally to form the lexicographically smallest possible word, then compare outcomes.	Hard8	GreedyGame theory+1	No attempts yet	1s	128 MB	Judgeable
Roman Numeral WalkFind the longest path from the grid center through empty-separated cells that spells consecutive Roman numerals starting at 1, and print the last number reached.	Hard8	DFSBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Balanced Bracket SegmentMaintain a dynamic string under prefix/suffix bracket insertions and after each insertion report the shortest valid contiguous bracket substring covering the new character.	Hard8	StackString matching+1	No attempts yet	1s	128 MB	Judgeable
Martian DNA FormulaCompress a DNA string into the shortest possible run-length style notation using nested parentheses with repeat counts.	Hard8	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
Logo MatchingGiven a permutation pattern of length n and a sequence of m distinct heights, find all starting positions where a length-n window matches the relative order pattern.	Hard8	String matchingArray+1	No attempts yet	2s	128 MB	Judgeable
RLE CompressionDecode a custom run-length encoding scheme and compute the minimum possible length of any code that decodes to the same character sequence.	Hard8	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
Vigenère Cipher AnalysisDetermine, for each candidate Vigenère key length up to K, whether the unique decrypted plaintext contains two given cribs at non-overlapping positions, and report the plaintext, ambiguous, or impossible.	Hard8	String matchingString+2	No attempts yet	1s	128 MB	Judgeable
Unchanged PictureDetermine whether two plotter-drawn vector pictures are geometrically similar under translation, rotation, and uniform scaling but no mirroring.	Hard8	GeometryString matching+1	No attempts yet	5s	128 MB	Judgeable
InsultsParse a string against a context-free grammar defining insults, then find the lexicographically next same-length valid insult or report invalid/ultimate.	Hard8	StringDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
BundlingGiven permitted bundle templates and a dependency chain among instructions, compute the minimum number of bundles to pack the sequence and, among those, the minimum number of stops needed.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	128 MB	Judgeable
Repetition-Free FormulaParse a Boolean formula that may repeat variables, determine if the underlying function is read-once, and if so print its canonical repetition-free formula.	Hard8	RecursionString+2	No attempts yet	2s	64 MB	Judgeable
Billing TablesGiven an ordered old billing table with range-based prefix rules, build the minimal prefix-only dictionary table (no prefix a prefix of another) that reproduces exactly the same plan decisions for all 11-digit numbers.	Hard8	TrieGreedy+2	No attempts yet	1s	128 MB	Judgeable
Secret Code: Largest NumberGiven a noisy string, find the largest decimal number it could decode to, either fixing one language for all digits or allowing a different language per digit, using digit-word subsequence matching.	Hard8	Dynamic programmingString matching+2	No attempts yet	3s	128 MB	Judgeable
Term GeneratorParse a formula, convert it to a normal form by expanding nested sums and products according to given rewriting rules, then implement a cyclic generator that outputs requested numbers of terms, some possibly skipped without printing, based on huge signed counters.	Hard8	String matchingRecursion+2	No attempts yet	1s	128 MB	Judgeable
Proof GeneratorConvert a logical formula to a canonical disjunctive normal form using given rewrite rules, then cyclically output the k-th next satisfying terms under given axioms for a sequence of queries.	Hard8	String matchingRecursion+2	No attempts yet	1s	128 MB	Judgeable
Software Industry RevolutionGiven a wildcard pattern (with ? and *) and a text, find the minimum-complexity substring of the text that matches the whole pattern, or report impossible.	Hard8	String matchingDynamic programming+1	No attempts yet	1s	128 MB	Judgeable
ACGUGiven an RLE-encoded RNA-like string, find the maximum number of non-crossing A-U and C-G pairs with at most K C-G pairs, exploiting the special RLE size constraints.	Hard8	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
GeneticsSimulate a topological genus-computing reduction system on circular DNA strings of paired letters to determine the resulting count of arms or legs.	Hard8	SimulationString+2	No attempts yet	1s	128 MB	Judgeable
Stammering AliensGiven a string and a minimum repeat count m, find the longest substring occurring at least m times (overlaps allowed), breaking ties by rightmost starting position, using suffix array or suffix automaton techniques.	Hard8	String matchingBinary search+1	No attempts yet	1s	128 MB	Judgeable
Matrix CalculatorParse and evaluate a matrix expression language with block matrices, transpose, indexing, and modular arithmetic, printing each assignment's resulting matrix.	Hard8	RecursionMatrix+2	No attempts yet	1s	128 MB	Judgeable
Using sedFind the minimum number of sed-style leftmost non-overlapping replacement operations needed to turn one small string into another, given up to 10 rewrite rules.	Hard8	BFSString matching+1	No attempts yet	1s	128 MB	Judgeable
Keyword SearchGiven up to 12 base strings, count positions in a text where some permutation-concatenation of all base strings occurs as a substring, treating duplicate resulting strings once.	Hard8	String matchingBit manipulation+2	No attempts yet	10s	128 MB	Judgeable
Organize Your TrainGiven a small rail-yard graph with parking lines and exchange links, compute the minimum number of sub-train moves to transform an initial arrangement of typed cars into a target arrangement.	Hard8	BFSSimulation+2	No attempts yet	3s	128 MB	Judgeable
Magical CraftingGiven binary crafting recipes with diamond costs, decide for each target string of glow stones whether it can be produced from 'A' and find the minimum diamond cost.	Hard8	Dynamic programmingGreedy+2	No attempts yet	5s	128 MB	Judgeable
Disjoint Regular ExpressionsGiven two regular expressions, decide whether any non-empty string matches both, and if so print the shortest lexicographically smallest such string.	Hard8	Dynamic programmingBFS+2	No attempts yet	2s	128 MB	Judgeable
Fibonacci WordGiven a bit pattern p and an index n up to 100, count the possibly overlapping occurrences of p inside the Fibonacci word F(n), whose length grows exponentially.	Hard8	String matchingDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
Intellectual PropertyGiven two code bases as raw strings, find the k longest maximal substrings of the JCN base that also occur in the TDP base, with exact positions and lengths.	Hard8	String matchingSorting+2	No attempts yet	1s	128 MB	Judgeable
Language CardinalityCount the distinct strings a string-rewriting grammar generates from a start string, printing Too many. if the count exceeds 1000.	Hard8	StringBFS+2	No attempts yet	1s	128 MB	Judgeable
Tail PalindromeGiven two lowercase strings a and b, find the shortest string x such that exactly one of ax, bx is a palindrome, and among ties the lexicographically smallest x.	Hard8	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
SpaghettiDecide whether two labeled Fortran IV programs run the same sequence of statements for every input, ignoring unconditional gotos and labels.	Hard8	GraphImplementation+2	No attempts yet	1s	128 MB	Judgeable
Crypt KickerDecrypt each line of a substitution cipher so every word appears in a given dictionary, choosing the lexicographically smallest result, or mask the line if none exists.	Hard8	BacktrackingString+2	No attempts yet	1s	128 MB	Judgeable
Barcode of JudgmentA barcode is a fixed 7x9 grid pattern placed somewhere in a binary image, possibly rotated; find all valid placements and decode the data bits, or report none or ambiguity.	Hard8	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Fill the CrosswordFill a crossword grid with a given word list so every slot holds a listed word exactly once and crossings match; also decide if no solution exists.	Hard8	BacktrackingTrie+2	No attempts yet	1s	128 MB	Judgeable
Word LadderGiven a vocabulary, find the longest shortest path (number of words) between any two words where a move changes, adds, or removes one letter.	Hard8	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Crosswords InsiderGiven a list of words and a crossword grid template, decide whether each word can fill one run of empty cells and output the lexicographically smallest filled grid.	Hard8	BacktrackingSimulation+2	No attempts yet	1s	128 MB	Judgeable
GHOSTGiven a GHOST position and dictionary, decide whether the computer should challenge, add the smallest safe letter, or bluff.	Hard8	Game theoryTrie+2	No attempts yet	1s	128 MB	Judgeable
WhenExecute a complete When program, an event-driven language with simultaneous Set assignments and a rotating active-clause scheduler, and print its output.	Hard8	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Pattern MatchingDecide whether digit sequences match patterns where digits match exactly and * and # stand for even and odd counts of arbitrary digits.	Hard8	Dynamic programmingString matching	No attempts yet	1s	128 MB	Judgeable
A-to-ZGiven a word dictionary, for each pair of letters find the minimum total width of a word chain where consecutive words overlap by at least two letters, and the first starts with C1, the last ends with C2.	Hard8	GraphShortest path+2	No attempts yet	1s	128 MB	Judgeable
Alpha of Degree kGiven a dictionary, answer queries asking for the shortest chain from word s to word t where each step shares a suffix-prefix overlap of length at least k, with a cap on chain length.	Hard8	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Weaker than PlannedGiven candidate plaintext words and a ciphertext message, recover the plaintext under one unknown letter-pair substitution, or report that it is not unique.	Hard8	BacktrackingString+2	No attempts yet	1s	128 MB	Judgeable
City MergerGiven up to 14 uppercase city names, find the length of the shortest string that contains every name as a consecutive substring, allowing overlaps.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	2s	128 MB	Judgeable
Name the CrossingGiven named crossings of orthogonal streets, infer an equal-strength and stronger-than relation between streets, then answer whether each queried crossing name is valid.	Hard8	GraphUnion-find+2	No attempts yet	1s	128 MB	Judgeable
InfiltrationGiven an encrypted line using a one-to-one letter substitution, recover the plaintext if exactly one consistent mapping exists using a subset of twelve known words that covers all distinct cipher letters.	Hard8	StringHash map+2	No attempts yet	1s	128 MB	Judgeable
DNA CopyGiven a source string S of length at most 18, find the minimum number of copy operations (each taking a contiguous substring of S or of the already-built target, optionally reversed) needed to assemble T.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
CipherFind the a x b subarray that occurs exactly k times (k >= 3) in an n x m character grid and list all its top-left positions in row-major order.	Hard8	Hash mapString+2	No attempts yet	1s	128 MB	Judgeable
InsecurityGiven a hexadecimal bitstring and lists of usernames and passwords, find which username concatenated with which password encrypts to that string under a growing left-shift XOR scheme.	Hard8	Bit manipulationBrute force+2	No attempts yet	1s	128 MB	Judgeable
Balanced Garden in a RowCount balanced binary strings of length N whose every substring has at most two more L than P, and find the lexicographic rank of a given string modulo M.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Zigzag NumbersCount numbers in [A, B], up to 500 digits, that are divisible by M and whose adjacent digit comparisons alternate up then down.	Hard8	Dynamic programmingMath+2	No attempts yet	2s	128 MB	Judgeable
Spelling SuggestionGiven weighted edit costs including keyboard-aware substitution and transposition, find the dictionary words closest to each query word.	Hard8	Dynamic programmingString+2	No attempts yet	12s	128 MB	Judgeable
Sanghak LanguageCount the distinct strings formed by concatenating any nonempty prefix of a Namgyu word with any nonempty suffix of a Jaehyeok word, summing over several test cases.	Hard8	TrieString+2	No attempts yet	1s	128 MB	Judgeable
File SearchCount how many non-empty subsets of the files can be exactly the result set of some substring query.	Hard8	StringTrie+2	No attempts yet	5s	128 MB	Judgeable
Code LockGiven a target lowercase string starting from all 'a', find the minimum number of moves where each move shifts a contiguous block of wheels up or down by one.	Hard8	Dynamic programmingGreedy+2	No attempts yet	1s	128 MB	Judgeable
File RecoverCount the distinct contiguous substrings that occur at least twice in a given string, for several test cases up to 100000 characters each.	Hard8	StringString matching+1	No attempts yet	5s	128 MB	Judgeable
DNA SubsequenceFind the longest common subsequence of two words where every maximal matched run must be a contiguous block of at least K characters in both words.	Hard8	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
Ambiguous CodesDecide whether a set of hexadecimal code words is ambiguous, and if so report the length of the shortest message with two distinct decodings.	Hard8	StringGraph+2	No attempts yet	1s	128 MB	Judgeable
First!Given up to 30000 strings, find every string that can become lexicographically smallest under some permutation of the 26-letter alphabet.	Hard8	StringTrie+2	No attempts yet	1s	128 MB	Judgeable
Scrambled LettersGiven N scrambled names, find for each the lowest and highest rank its original anagram could occupy in an alphabetical ordering of all cows.	Hard8	StringSorting+2	No attempts yet	1s	128 MB	Judgeable
TreasureGiven a connected graph with N nodes and N edges and max degree 4, count the distinct rooted versions of the graph up to isomorphism, where each root is a non-4-degree node.	Hard8	GraphTrie+2	No attempts yet	1s	128 MB	Judgeable
Milk PatternsGiven N integers, find the length of the longest contiguous subsequence that repeats at least K times, counting overlapping occurrences.	Hard8	String matchingBinary search+2	No attempts yet	1s	128 MB	Judgeable
AppendGiven an LZ-style encoding as a list of (back-reference, length) pairs, count how many prefix positions split it into two valid non-empty encodings whose concatenation reproduces the original string.	Hard8	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
L-system SubstringGiven a D0L system over {a,b} and a query z, decide whether z appears as a contiguous substring of some word derivable from the start word.	Hard8	StringSimulation+2	No attempts yet	1s	128 MB	Judgeable
XenosemanticsFind words over lowercase letters delimited by varying spacer letters in a bit stream, then report the distinct true words that repeat and overlap another true word.	Hard8	StringHash map+2	No attempts yet	1s	128 MB	Judgeable
FoldGiven the sequence of A/V fold directions along an unfolded paper strip, find the minimum number of all-layer folding steps that produce it.	Hard8	Dynamic programmingRecursion+2	No attempts yet	1s	128 MB	Judgeable
Careful DeclarationMerge two word sequences into the shortest common supersequence, breaking ties by choosing the lexicographically smallest result.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
God of the Vile BaskersFind the longest prefix of a string that contains no two substrings with the same multiset of k alphabetic characters, ignoring case.	Hard8	StringSliding window+2	No attempts yet	1s	128 MB	Judgeable
Transforming CometsGiven two cyclic sequences of integer points, decide whether one is a rotation, uniform positive scaling, and translation of the other, and report the matching cyclic offset.	Hard8	String matchingGeometry+2	No attempts yet	5s	512 MB	Judgeable
Post's Correspondence ProblemFind the shortest, lexicographically smallest index sequence whose A-concatenation equals its B-concatenation, under k < m.	Hard8	BFSString+2	No attempts yet	1s	128 MB	Judgeable
Ransom NoteGiven a target note and a newspaper text, find the minimum number of contiguous clips (letters and spaces only, case-insensitive, reusable) needed to paste the note.	Hard8	Dynamic programmingString+2	No attempts yet	1s	128 MB	Judgeable
Word CountingGiven a rooted tree whose edges carry letter strings, count distinct occurrences of a query word along all paths from the root to the leaves, identifying each occurrence by its start and end position.	Hard8	String matchingTrie+2	No attempts yet	1s	128 MB	Judgeable
Similar PolygonsDecide whether two polygons are similar, and if so print the square of the similarity factor as a reduced fraction and the matching vertex index in the second polygon.	Hard8	GeometryString matching+2	No attempts yet	1s	1024 MB	Judgeable
Similar PolygonsDecide whether two polygons are similar under rotation, reflection, translation, and scaling, then output the exact squared similarity ratio and the smallest matching vertex index.	Hard8	GeometryString matching+2	No attempts yet	1s	1024 MB	Judgeable
Automatic TradingGiven a string and pairs of positions, for each query find the length of the longest common prefix of the two suffixes starting at those positions.	Hard8	StringString matching+2	No attempts yet	5s	128 MB	Judgeable
The Palindromes Strike BackFor every position i, count the subsets of positions that include i and form a palindrome, then XOR all i times that count mod 1e9+7.	Hard8	Dynamic programmingCombinatorics+2	No attempts yet	2s	1024 MB	Judgeable
Address MatchingMatch each student address to a distinct teacher address with minimum total weighted edit distance, and among optimal matchings output the lexicographically smallest index sequence.	Hard8	Dynamic programmingGreedy+2	No attempts yet	3s	1024 MB	Judgeable
ASMFind the fewest add/multiply/print commands in a one-variable program whose printed concatenation matches every test's required output.	Hard8	Brute forceDynamic programming+2	No attempts yet	1s	1024 MB	Judgeable
Changing Phone NumbersGiven area codes and a sequence of rules (digit duplication, digit swap, area-code change) applied over time, answer queries transforming a phone number from one year to another.	Hard8	StringSimulation+2	No attempts yet	1s	128 MB	Judgeable
Puzzle OutGiven a dictionary and an encrypted uppercase text, recover the substitution cipher table or report no solution or multiple solutions.	Hard8	BacktrackingHash map+2	No attempts yet	1s	128 MB	Judgeable
Word EncodingGiven up to 1000 forbidden substrings of length 1 to 3, rank valid words by length then alphabetically; answer queries converting a word to its index and an index to its word.	Hard8	Dynamic programmingString matching+2	No attempts yet	1s	128 MB	Judgeable
DNA LaboratoryGiven up to 15 DNA strings, find the shortest string that contains all of them as substrings, breaking ties by lexicographic order.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	1s	128 MB	Judgeable
Missing LettersReconstruct a space-free corrupted string into words from a known vocabulary, choosing the highest-scoring word segmentation and breaking ties alphabetically.	Hard8	Dynamic programmingString+2	No attempts yet	1s	128 MB	Judgeable
Identity CheckerEach test case gives a reverse Polish expression in x with sin, cos, and tan; decide whether it equals zero wherever defined.	Hard8	MathString+2	No attempts yet	1s	128 MB	Judgeable
CensorshipGiven a text and a filter word set, remove occurrences repeatedly to make the shortest possible result and report its length.	Hard8	Dynamic programmingString+1	No attempts yet	1s	128 MB	Judgeable
Vigenère CipherGiven a ciphertext and pair frequencies, find the key length-K shift maximizing the total frequency of adjacent plaintext letter pairs.	Hard8	Dynamic programmingString+1	No attempts yet	5s	64 MB	Judgeable
Cyclic Rotation CipherReconstruct the original lowercase string from its Burrows-Wheeler transform index i and last column R.	Hard8	StringSorting+1	No attempts yet	1s	32 MB	Judgeable
ByephoneFind the longest common subsequence of two strings up to length 10000 within 3MB of memory, breaking ties by the lexicographically smallest result.	Hard8	Dynamic programmingString+2	No attempts yet	2s	3 MB	Judgeable
EncodingFind the shortest encoding length for a target string under dynamic coding, where a changing marker toggles between verbatim and interpreted modes.	Hard8	Dynamic programmingString	No attempts yet	1s	128 MB	Judgeable
Morphing is funGiven color mutation rules, decide whether every fixed-height cell eventually stops changing color over the nights.	Hard8	GraphDFS+2	No attempts yet	1s	512 MB	Judgeable
Beer NumbersDecide whether a positive integer is the only one that can produce its row of binary mugs under any choice of which mug position means 1 and which reading direction.	Hard8	StringCombinatorics+1	No attempts yet	1s	128 MB	Judgeable
NecklacesDecide whether two run-length compressed string descriptions encode the same circular necklace up to rotation.	Hard8	StringString matching+2	No attempts yet	1s	128 MB	Judgeable
Word EquationsCount the binary word assignments to variables of fixed lengths that make the two sides of a word equation equal.	Hard8	StringUnion-find+2	No attempts yet	1s	128 MB	Judgeable
Words 2Given exponents k1..kn, find the smallest m such that the concatenation of h_k(0) is a substring of h_m(0), or report NIE.	Hard8	StringRecursion+2	No attempts yet	1s	128 MB	Judgeable
WordsGiven indices k_i, decide whether the concatenation of the words h^{k_i}(0) appears as a substring of some h^m(0).	Hard8	StringDynamic programming+2	No attempts yet	1s	128 MB	Judgeable
BeadsSplit the bead string into blocks of size k (leftover dropped) and find the k that maximizes the count of distinct blocks, where a block and its reversal are the same.	Hard8	StringHash map+2	No attempts yet	1s	128 MB	Judgeable