Strings and text

Parsing, matching, and tries

Under construction

Still being built. Things may change

Total results3,615 problems

Autocomplete
Medium7
Dynamic programming, Trie+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Equality
Medium7
Dynamic programming, Number theory+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Arithmetic Lesson
Medium7
Bit manipulation, Trie
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Restoring the array
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Restoring the Number
Medium7
Brute force, Sorting+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
x
Medium7
Game theory, String matching
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Arctic Fox Flips the Brackets
Medium7
Segment tree, String+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Spider Web Production
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Krabsburgers
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Reduce the Number of Problems
Medium7
Dynamic programming, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bella's Best Friends
Medium7
Prefix sum, Hash map+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
List
Medium7
Trie, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Melman
Medium7
String matching, String
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Bet
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Pizza Marathon
Medium7
Trie, Tree+2
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Game
Medium7
String, Union-find+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Cards
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Ancient Calendar
Medium7
Dynamic programming, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Madness
Medium7
Matrix, String matching+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Strange Digits
Medium7
Dynamic programming, Math+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
String Covering
Medium7
String matching, Dynamic programming
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Labyrinth
Medium7
Shortest path, Graph+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Clothesline
Medium7
Tree, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Balanced bracket strings
Medium7
Prefix sum, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Swapping Brackets
Medium7
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
1.5s
Memory limit
1024 MB
Judgeable
LCP Queries
Medium7
Trie, String matching+1
No attempts yet
Time limit
2.5s
Memory limit
1024 MB
Judgeable
Edit distance on table
Medium7
Dynamic programming, Graph+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
String
Medium7
String matching, Binary search+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Thwack!
Medium7
Game theory, String
No attempts yet
Time limit
5s
Memory limit
1024 MB
Judgeable
Beautiful Number
Medium7
Greedy, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Binary Game
Medium7
Game theory, Trie+2
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Open Olympiad in Design
Medium7
Binary search, Greedy+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Maggie's Homework
Medium7
Segment tree, Math+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
Gold Stimulation Also Needs a Meal First
Medium7
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Cycle Correspondence
Medium7
Array, String matching+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Stringology
Medium7
String, String matching
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Occupy the Cities
Medium7
String, Binary search+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Interesting Numbers
Medium7
Bit manipulation, Trie+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
LR
Medium7
Greedy, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Digit Translation
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
String
Medium7
String matching, Math+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dispersed parentheses
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Set Expression Transpiler
Medium7
Recursion, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Pancake Flipping
Medium7
Simulation, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Multiplication in Base N (HUGE)
Medium7
String, Math+1
No attempts yet
Time limit
10s
Memory limit
1024 MB
Judgeable
White Light 2
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Name
Medium7
Dynamic programming, String
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Central String
Medium7
String, Brute force+2
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
Harmonic Operations
Medium7
Math, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cowreography
Medium7
Greedy, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Logical Moos
Medium7
Segment tree, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Do You Know Palindrome?
Medium7
String, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
A Duel of Two Proud Geniuses
Medium7
Math, String+1
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
밤양갱
Medium7
String, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Minimum String Extraction
Medium7
Greedy, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Doubling
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
XOR Maximum
Medium7
String, Bit manipulation+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Slime Synthesis
Medium7
Dynamic programming, Intervals+1
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Tour Course
Medium7
Prefix sum, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Reducing Boredom
Medium7
Prefix sum, Greedy+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Broken Calculator
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Virus
Medium7
Segment tree, String matching
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Trainee's Letter
Medium7
String matching, Dynamic programming
No attempts yet
Time limit
3s
Memory limit
1024 MB
Judgeable
BipBop 커플
Medium7
String, String matching+2
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Hotfix
Medium7
String, String matching
No attempts yet
Time limit
8s
Memory limit
1024 MB
Judgeable
Reptile Eggs
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Disgruntled Diner
Medium7
Graph, String+1
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Covers
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Palindromic Length
Medium7
Dynamic programming, String+1
No attempts yet
Time limit
0.5s
Memory limit
2048 MB
Judgeable
Finding Keys
Medium7
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Longest Common Substring
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
5s
Memory limit
2048 MB
Judgeable
Parenthesis String Editor
Medium7
Segment tree, Linked list+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Knowns and Unknowns
Medium7
Array, String matching+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
It's Mooin' Time
Medium7
Greedy, String+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Reverse Severer
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
The Journey of the King
Medium7
String matching, Graph
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Krasan Code
Medium7
String, String matching+1
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Difficult Password
Medium7
Dynamic programming, Matrix+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Counting Is Not Fun (Easy Version)
Medium7
Dynamic programming, Combinatorics+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
Bitsets
Medium7
Bit manipulation, Prefix sum+1
No attempts yet
Time limit
3s
Memory limit
2048 MB
Judgeable
What is the most tedious part of running a contest?
Medium7
Dynamic programming, String matching+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Steganography
Medium7
String matching, Prefix sum+1
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
KSA String 2
Medium7
String, Dynamic programming+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Palindrome Sentences
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Zero Run Pattern
Hard8
String, Binary search+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Non-Repeating Word
Hard8
Backtracking, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Increasing List
Hard8
Backtracking, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Count Palindromic Word Sequences
Hard8
Dynamic programming, String matching+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Magic Stone
Hard8
Combinatorics, Dynamic programming+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Increasing Sequence
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Merge Words
Hard8
Dynamic programming, Bit manipulation+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Increasing Sequence
Hard8
Dynamic programming, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Nested Reversal Sequence
Hard8
String, Greedy+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Number Concatenation
Hard8
String matching, Binary search+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Laser
Hard8
Number theory, Math+2
No attempts yet
Time limit
5s
Memory limit
128 MB
Judgeable
Duel
Hard8
Game theory, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Palindrome Encoding
Hard8
Dynamic programming, String+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Partial DNA Substrings
Hard8
String matching, Binary search+1
No attempts yet
Time limit
2s
Memory limit
16 MB
Judgeable
Number of Trees
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Compressing a String
Hard8
Dynamic programming, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
AutocompleteCount the ways to type word s using at most k actions, where each action types a letter, deletes a letter, or accepts one of the top three autocomplete suggestions, modulo 1e9+7.	Medium7	Dynamic programmingTrie+1	No attempts yet	2s	1024 MB	Judgeable
EqualityInsert exactly k equality signs and plus (or multiply) signs into a digit string so every block has the same remainder modulo m.	Medium7	Dynamic programmingNumber theory+1	No attempts yet	3s	1024 MB	Judgeable
Arithmetic LessonApply xor or and with a value to every element of a sequence in order, and count the elements in the range [l, r] after each query.	Medium7	Bit manipulationTrie	No attempts yet	2s	1024 MB	Judgeable
Restoring the arrayDelete the fewest digits from each number so the array becomes non-decreasing, or print -1 if no deletion works.	Medium7	Dynamic programmingString+1	No attempts yet	2s	1024 MB	Judgeable
Restoring the NumberFill the ? digits of a string n (no leading zero) so that n mod m is as small as possible, and print that remainder.	Medium7	Brute forceSorting+2	No attempts yet	2s	1024 MB	Judgeable
xGiven a score and a melody, color every occurrence of the melody's suffixes in the score, then decide which player wins the turn-based game on the colored notes.	Medium7	Game theoryString matching	No attempts yet	1s	1024 MB	Judgeable
Arctic Fox Flips the BracketsApply flip, reverse, and rotate updates to a bracket string, then report the maximum number of removable () pairs in each queried range.	Medium7	Segment treeString+1	No attempts yet	3s	1024 MB	Judgeable
Spider Web ProductionFind the minimum cost to build a given string from empty using letter append, self-duplication, and last-letter deletion operations.	Medium7	Dynamic programmingString matching+1	No attempts yet	2s	1024 MB	Judgeable
KrabsburgersCount the ways to cut n ingredients into k consecutive nonempty groups whose XORs fall in the given per-customer ranges, modulo 1e9+7.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	3s	1024 MB	Judgeable
Reduce the Number of ProblemsSplit an array into contiguous segments whose adjacent lengths differ, maximizing the sum of each segment's XOR.	Medium7	Dynamic programmingBit manipulation+1	No attempts yet	1s	1024 MB	Judgeable
Bella's Best FriendsFor each guessed set of consonants, find the longest substring where every listed letter appears the same number of times.	Medium7	Prefix sumHash map+1	No attempts yet	2s	1024 MB	Judgeable
ListGiven n names, count for each length x the pairs whose length-x prefixes and length-x suffixes are both equal.	Medium7	TrieString+1	No attempts yet	2s	1024 MB	Judgeable
MelmanFind every length-n substring of s that differs from t only at two positions exactly k apart, and print the count and start indices.	Medium7	String matchingString	No attempts yet	2s	1024 MB	Judgeable
BetGiven two strings of letters and digits, decide whether both could come from one original string by replacing some Roman numeral substrings with Arabic numbers.	Medium7	Dynamic programmingString matching+1	No attempts yet	2s	1024 MB	Judgeable
Pizza MarathonAnswer sums of prices over pizzas whose names start with pizza i's name and have length at least k, with point price updates.	Medium7	TrieTree+2	No attempts yet	5s	1024 MB	Judgeable
GameGiven n, the length of a hidden palindrome, and m logged appends, decide whether the word is unique, ambiguous, or impossible.	Medium7	StringUnion-find+1	No attempts yet	2s	1024 MB	Judgeable
CardsGiven word t and cards where no card is a suffix of another, find the fewest cards, copies allowed, whose row contains t, and print that row.	Medium7	Dynamic programmingString matching+1	No attempts yet	2s	1024 MB	Judgeable
Ancient CalendarGiven N up to 10^18, count the adjacent zero pairs in the concatenated Zeckendorf representations of 1, 2, 3, ... within the first N characters.	Medium7	Dynamic programmingMath+1	No attempts yet	2s	1024 MB	Judgeable
MadnessGiven apartment ids and lit windows on a grid, find the fewest apartments to change so a target lit/dark pattern appears as a sub-rectangle.	Medium7	MatrixString matching+1	No attempts yet	2s	1024 MB	Judgeable
Strange DigitsGiven a base b, an allowed digit set, and a decimal n up to 10^100, decide whether n has no representation, exactly one, or more than one.	Medium7	Dynamic programmingMath+1	No attempts yet	2s	1024 MB	Judgeable
String CoveringFor each prefix of a string w, find the length of the shortest string whose occurrences together cover every position of that prefix.	Medium7	String matchingDynamic programming	No attempts yet	2s	1024 MB	Judgeable
LabyrinthGiven a directed graph whose edges carry words of up to 10 letters, find the lexicographically smallest shortest path label from s to t.	Medium7	Shortest pathGraph+1	No attempts yet	2s	1024 MB	Judgeable
ClotheslineGiven a string of three shirt colors, answer per-color counts on ranges while moving segments to the front or back and reversing segments.	Medium7	TreeString+1	No attempts yet	2s	1024 MB	Judgeable
Balanced bracket stringsGiven a bracket string and queries (L, R), decide whether some split point k inside (L, R) divides A[L..R] into two balanced bracket strings.	Medium7	Prefix sumString+1	No attempts yet	2s	1024 MB	Judgeable
Swapping BracketsCount the nonempty position sets S where rearranging the brackets inside S can turn the sequence into a proper bracket sequence, modulo 998244353.	Medium7	Dynamic programmingCombinatorics+1	No attempts yet	1.5s	1024 MB	Judgeable
LCP QueriesGiven strings s_i and t_j, each query concatenates the listed t_j and asks for the sum of its LCP with every s_i.	Medium7	TrieString matching+1	No attempts yet	2.5s	1024 MB	Judgeable
Edit distance on tableGiven a grid of letters and a string T, find the smallest edit distance between T and any string spelled by a walk on the grid.	Medium7	Dynamic programmingGraph+1	No attempts yet	3s	1024 MB	Judgeable
StringFor each query (i, r), count the lengths l from 1 to r where s[i:i+l-1] is lexicographically smaller than R(s[i+l:i+2l-1]).	Medium7	String matchingBinary search+1	No attempts yet	2s	1024 MB	Judgeable
Thwack!Given a 1D board of black stones, white stones, and empty cells, list every first move that wins for the first player under optimal play.	Medium7	Game theoryString	No attempts yet	5s	1024 MB	Judgeable
Beautiful NumberGiven two huge decimal numbers l and r (up to 10^5 digits), find x in [l, r] that maximizes the product of its digits.	Medium7	GreedyString+1	No attempts yet	2s	1024 MB	Judgeable
Binary GameTwo players append bits to a binary string, and whoever creates a forbidden substring loses. Decide the winner or whether the game is a draw.	Medium7	Game theoryTrie+2	No attempts yet	2s	1024 MB	Judgeable
Open Olympiad in DesignGiven n required lengths, find the fewest letters needed to write n distinct strings of those lengths in strictly increasing lexicographic order.	Medium7	Binary searchGreedy+2	No attempts yet	1s	1024 MB	Judgeable
Maggie's HomeworkRange-assign updates overwrite digits, and each query asks for the sum of all substring values in a range that do not start with 0, modulo 1e9+7.	Medium7	Segment treeMath+1	No attempts yet	4s	1024 MB	Judgeable
Gold Stimulation Also Needs a Meal FirstCount the starting levels F_1 where the sums of exactly M ingredients inside the window [F_1, F_1 + D_K] match the plan exactly, shifted by F_1.	Medium7	Dynamic programmingString matching+2	No attempts yet	2s	512 MB	Judgeable
Cycle CorrespondenceGiven two cycles of K barn labels, find the largest number of barns that can receive the same label in both assignments.	Medium7	ArrayString matching+1	No attempts yet	2s	1024 MB	Judgeable
StringologyFor each i from 0 to n-1, find the longest prefix of s, shorter than n, that is a suffix of pre(s, i) + t.	Medium7	StringString matching	No attempts yet	1s	1024 MB	Judgeable
Occupy the CitiesGiven a row of cities with some occupied, find the fewest rounds needed for every occupied city to take one adjacent empty city until all are occupied.	Medium7	StringBinary search+1	No attempts yet	1s	1024 MB	Judgeable
Interesting NumbersGiven n integers and k, find the longest subsequence in which the XOR of every pair of elements is at most k.	Medium7	Bit manipulationTrie+1	No attempts yet	3s	1024 MB	Judgeable
LRGiven string A, find the K-th smallest string among all 2^N strings built by repeatedly taking a character from the front or back of A.	Medium7	GreedyString+1	No attempts yet	2s	1024 MB	Judgeable
Digit TranslationGiven a lowercase string, replace written digit words with digits to find the shortest reachable string length and count the distinct strings of that length modulo 9302023.	Medium7	StringDynamic programming+1	No attempts yet	1s	2048 MB	Judgeable
StringGiven a string A that is a prefix of the infinite string built by repeating a block k times and inserting symbols between copies, find the minimal k.	Medium7	String matchingMath+1	No attempts yet	1s	1024 MB	Judgeable
Dispersed parenthesesCount the disperse parentheses sequences of length n whose depth is exactly k, modulo 10^9+9.	Medium7	Dynamic programmingString+1	No attempts yet	1s	1024 MB	Judgeable
Set Expression TranspilerGiven an Aniya expression over sets A to T using ~, &, and \|, print an equivalent Hayaku expression using &, \|, and \ within the length limit, or NO if none exists.	Medium7	RecursionString+1	No attempts yet	1s	1024 MB	Judgeable
Pancake FlippingDecide whether a target W/B pancake pattern is reachable by prefix or suffix flips at equal adjacent pairs, and print one valid sequence of operations.	Medium7	SimulationString+1	No attempts yet	2s	1024 MB	Judgeable
Multiplication in Base N (HUGE)Multiply two integers written in base N, where N may be negative, each up to 3,000,000 digits, and print the product in base N.	Medium7	StringMath+1	No attempts yet	10s	1024 MB	Judgeable
White Light 2Given a row of N red, green, or blue lights, find the minimum cost to turn off lights from either end or recolor lights so the lit colors repeat RGB.	Medium7	Dynamic programmingString+1	No attempts yet	1s	1024 MB	Judgeable
NameFind the length of the shortest name that contains both S and T as subsequences, with equal letters at least K characters apart.	Medium7	Dynamic programmingString	No attempts yet	1s	1024 MB	Judgeable
Central StringGiven N strings of equal length L and a bound D, the task is to find a string within Hamming distance D of every input string, or report that none exists.	Medium7	StringBrute force+2	No attempts yet	3s	1024 MB	Judgeable
Harmonic OperationsCount the contiguous sublists of K operations (reverse, rotate left, rotate right) that map the string S back to itself.	Medium7	MathString+1	No attempts yet	1s	1024 MB	Judgeable
CowreographyGiven two binary strings with equal counts of ones, find the fewest swaps of positions at most K apart that turn the first string into the last.	Medium7	GreedyString+1	No attempts yet	2s	1024 MB	Judgeable
Logical MoosGiven a boolean and/or statement, each query asks whether replacing keywords l through r with one true or false can make the whole statement equal a target value.	Medium7	Segment treeString+1	No attempts yet	2s	1024 MB	Judgeable
Do You Know Palindrome?Given a string S of up to 10^6 lowercase letters, count the palindromic substrings that contain the x-th character for each query.	Medium7	StringString matching+1	No attempts yet	1s	1024 MB	Judgeable
A Duel of Two Proud GeniusesGiven A in base u and B in base v, each with up to 3,000,000 digits of equal length, decide whether A is larger, B is larger, or they are equal.	Medium7	MathString+1	No attempts yet	0.5s	1024 MB	Judgeable
밤양갱Find the fewest seconds to type 'daldidalgo' N times then 'daldidan', using single-letter appends or pasting a substring already typed.	Medium7	StringString matching+1	No attempts yet	1s	1024 MB	Judgeable
Minimum String ExtractionGiven an N by M grid of lowercase letters, hide exactly K columns and read the remaining cells row by row to find the lexicographically smallest string.	Medium7	GreedyString+1	No attempts yet	1s	1024 MB	Judgeable
DoublingGiven pairs (s, c) where typing c after s doubles the message, find the fewest appends and deletes needed to build string T from empty.	Medium7	StringDynamic programming+1	No attempts yet	3s	1024 MB	Judgeable
XOR MaximumGiven a binary string, find the largest XOR of the binary values of two of its substrings, which may overlap or be equal.	Medium7	StringBit manipulation+1	No attempts yet	2s	1024 MB	Judgeable
Slime SynthesisGiven a row of slimes with digit levels, merge adjacent pairs of equal level into one slime of level plus one, and find the maximum number of merges possible.	Medium7	Dynamic programmingIntervals+1	No attempts yet	8s	1024 MB	Judgeable
Tour CourseGiven which tourists on a circular route end with affection at least 1, build a snowfield or desert pattern for the N segments, or report NO if none exists.	Medium7	Prefix sumString+1	No attempts yet	2s	1024 MB	Judgeable
Reducing BoredomGiven a string of N zeros and N ones, find the fewest adjacent swaps so that every segment's count difference between 0s and 1s is at most K.	Medium7	Prefix sumGreedy+1	No attempts yet	1s	1024 MB	Judgeable
Broken CalculatorInsert parentheses into an expression so that a calculator with equal-priority + and * gives the intended value modulo P in every evaluation order.	Medium7	Dynamic programmingString+1	No attempts yet	1s	1024 MB	Judgeable
VirusGiven a bit string under range updates that map 0 and 1 to chosen bits, check after each update whether the string matches the regex (1(10)+1*\|0+10)+.	Medium7	Segment treeString matching	No attempts yet	2s	1024 MB	Judgeable
Trainee's LetterGiven N letter pages with M pages lost, the task is to find which of K names appear in the letter no matter which M pages are missing.	Medium7	String matchingDynamic programming	No attempts yet	3s	1024 MB	Judgeable
BipBop 커플Given N moves, find the expected number of verses two random starts dance in sync before diverging or reaching the end, as a reduced fraction.	Medium7	StringString matching+2	No attempts yet	1s	1024 MB	Judgeable
HotfixGiven a string of up to 10^6 ASCII letters, count how many times each letter appears in the output that lists every distinct substring with its occurrence count.	Medium7	StringString matching	No attempts yet	8s	1024 MB	Judgeable
Reptile EggsFind the longest subsequence of the egg line that matches a regular expression with ?, *, brackets, and parentheses, or report -1 if none matches.	Medium7	Dynamic programmingString matching+1	No attempts yet	1s	1024 MB	Judgeable
Disgruntled DinerGiven the order log and partly hidden pinned tickets, decide whether all tickets for table t are item m, or find the fewest tickets to flip to check it.	Medium7	GraphString+1	No attempts yet	2s	1024 MB	Judgeable
CoversFind the minimum cost to build string T from an empty string using appends of P (free), single characters (cost 1), or deleting a suffix and then appending P.	Medium7	Dynamic programmingString matching+1	No attempts yet	1s	2048 MB	Judgeable
Palindromic LengthGiven a lowercase string of up to 100,000 letters, find the fewest palindromic substrings it can be split into with no overlaps.	Medium7	Dynamic programmingString+1	No attempts yet	0.5s	2048 MB	Judgeable
Finding KeysFor each key on a circular keychain, find the smallest k whose k-pattern of up and down comparisons with the next k keys no other key shares.	Medium7	StringString matching+1	No attempts yet	2s	2048 MB	Judgeable
Longest Common SubstringCount the pairs of binary strings s (length n) and t (length m) that have w as one of their longest common substrings, modulo 998244353.	Medium7	Dynamic programmingString matching+1	No attempts yet	5s	2048 MB	Judgeable
Parenthesis String EditorSimulate cursor edits on a parenthesis string and XOR each step index into C whenever the text is balanced.	Medium7	Segment treeLinked list+1	No attempts yet	3s	2048 MB	Judgeable
Knowns and UnknownsGiven two professor orders and their partial visit lists, decide for each student whether they attended, skipped, or cannot be determined.	Medium7	ArrayString matching+1	No attempts yet	3s	2048 MB	Judgeable
It's Mooin' TimeGiven an M/O string with per-position flip costs, find the minimum cost to contain at least k moos of length L, for every k.	Medium7	GreedyString+1	No attempts yet	3s	2048 MB	Judgeable
Reverse SevererGiven a string S and several queries T, decide whether each T can be formed by splitting S into pieces and concatenating them in reverse piece order.	Medium7	StringDynamic programming+1	No attempts yet	1s	2048 MB	Judgeable
The Journey of the KingGiven a dictionary, match Anda's cards with yours whenever a concatenation of the two words in either order is a dictionary word, maximizing the matches.	Medium7	String matchingGraph	No attempts yet	1s	2048 MB	Judgeable
Krasan CodeGiven 26 code words, one per letter, decide whether two different original words can translate to the same string (Ruzan) or never do (Krasan).	Medium7	StringString matching+1	No attempts yet	2s	2048 MB	Judgeable
Difficult PasswordCount passwords of length L to R that contain a digit and a letter, have no A equal characters in a row, and have no B-long ascending or descending run, modulo 1e9+7.	Medium7	Dynamic programmingMatrix+1	No attempts yet	3s	2048 MB	Judgeable
Counting Is Not Fun (Easy Version)After each clue fixing a good pair, count the balanced bracket sequences with n good pairs that contain all clues so far, modulo 998244353.	Medium7	Dynamic programmingCombinatorics+1	No attempts yet	3s	2048 MB	Judgeable
BitsetsCount the columns where the bits in rows l through r are all equal, with each query's l and r generated online from the previous answers.	Medium7	Bit manipulationPrefix sum+1	No attempts yet	3s	2048 MB	Judgeable
What is the most tedious part of running a contest?Build S by typing single characters or pasting one copied prefix of S, minimizing typed characters first and total actions second.	Medium7	Dynamic programmingString matching+1	No attempts yet	1s	1024 MB	Judgeable
SteganographyGiven point-coloring updates and queries, check whether two equal-sized rectangles on the lattice have identical color patterns.	Medium7	String matchingPrefix sum+1	No attempts yet	4s	1024 MB	Judgeable
KSA String 2Given a string of K, S, and A, find the minimum number of remove or move-to-front operations that turn it into the longest string repeating KSA.	Medium7	StringDynamic programming+1	No attempts yet	1s	1024 MB	Judgeable
Palindrome SentencesGiven up to 13 distinct words, count ordered arrangements of a subset of them whose concatenation without spaces forms a palindrome.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	2s	128 MB	Judgeable
Zero Run PatternGiven two binary strings repeated in a growing pattern, find the first position within the first 10^16 characters where C consecutive zeros occur.	Hard8	StringBinary search+2	No attempts yet	2s	128 MB	Judgeable
Non-Repeating WordFind the lexicographically smallest length-N string over the first A letters that never contains K consecutive copies of any nonempty block.	Hard8	BacktrackingString+2	No attempts yet	2s	128 MB	Judgeable
Increasing ListReplace every '?' in a string with a digit or comma to form the lexicographically smallest strictly increasing list of positive integers with no leading zeros, or print -1 if impossible.	Hard8	BacktrackingGreedy+2	No attempts yet	2s	128 MB	Judgeable
Count Palindromic Word SequencesCount ordered sequences of given words, space-joined, whose concatenation (ignoring spaces) is a palindrome of length at most K, modulo a prime.	Hard8	Dynamic programmingString matching+2	No attempts yet	2s	128 MB	Judgeable
Magic StoneGiven n, k, and i, find the i-th lexicographically smallest length-n I/X string with at most k differing adjacent pairs, treating a string and its reverse as identical.	Hard8	CombinatoricsDynamic programming+2	No attempts yet	2s	128 MB	Judgeable
Increasing SequenceSplit a digit string into pieces forming a strictly increasing sequence of numbers, minimizing the last value with tie-breaks favoring larger earlier numbers.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
Merge WordsGiven up to 12 uppercase words, find the shortest string containing all of them as substrings, breaking ties by lexicographic order.	Hard8	Dynamic programmingBit manipulation+2	No attempts yet	5s	128 MB	Judgeable
Increasing SequenceSplit a huge digit string into pieces forming a strictly increasing sequence of numbers, breaking ties by minimizing the last piece then maximizing earlier pieces, and output the product mod 1,000,000,003.	Hard8	Dynamic programmingGreedy+2	No attempts yet	2s	128 MB	Judgeable
Nested Reversal SequenceGiven two binary strings, find the minimum number of substring reversals, each interval nested inside the previous one, needed to turn the first string into the second, or report impossibility.	Hard8	StringGreedy+2	No attempts yet	2s	128 MB	Judgeable
Number ConcatenationGiven a subsequence left after deleting digits from the concatenation of 1,2,...,N, find the smallest N that could produce it.	Hard8	String matchingBinary search+2	No attempts yet	2s	128 MB	Judgeable
LaserCount primitive direction vectors (a,b) with max(a,b) <= K whose periodic grid-wraparound character string contains each given word as a substring.	Hard8	Number theoryMath+2	No attempts yet	5s	128 MB	Judgeable
DuelTwo players alternately mark empty cells on a strip, winning instantly by forming three consecutive marks, and the task is to decide if the first player can force a win and list all winning first moves.	Hard8	Game theoryCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Palindrome EncodingGiven a binary string, repeatedly delete the second half of any even-length palindromic substring and find the minimum length achievable.	Hard8	Dynamic programmingString+2	No attempts yet	2s	128 MB	Judgeable
Partial DNA SubstringsGiven a DNA string, count distinct substrings occurring at least m times and find the K-th one under length-then-lex order.	Hard8	String matchingBinary search+1	No attempts yet	2s	16 MB	Judgeable
Number of TreesCount the number of rooted ordered trees whose DFS-with-repeated-parent-writes traversal string equals a given string, modulo 1e9.	Hard8	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable
Compressing a StringFind the minimum length of a string obtained by optimally applying nested k(S) run-length style compression to a given lowercase string of length up to 200.	Hard8	Dynamic programmingString+1	No attempts yet	2s	128 MB	Judgeable