String Data Structure

  • Last Updated : 18 Jun, 2022

Practice Problems on String

Strings are defined as an array of characters. The difference between a character array and a string is the string is terminated with a special character ‘\0’.

Declaring a string is as simple as declaring a one dimensional array. Below is the basic syntax for declaring a string in C programming language.

char str_name[size];

‘Recent Articles’ on Strings

Topics :

 

DSA-Self-Paced

Basics :

  1. Function to copy string
  2. Pangram Checking
  3. Missing characters to make a string Pangram
  4. Check if a string is Pangrammatic Lipogram
  5. Removing punctuations from a given string
  6. Rearrange characters in a string such that no two adjacent are same
  7. Program to check if input is an integer or a string
  8. Quick way to check if all the characters of a string are same
  9. Program to find the initials of a name
  10. Check Whether a number is Duck Number or not
  11. Round the given number to nearest multiple of 10
  12. Change string to a new character set
  13. Find one extra character in a string

Strings in C & C++ :

  1. Array of Strings in C++ (3 Different Ways to Create)
  2. Strings in C
  3. Storage for Strings in C
  4. sprintf() in C
  5. C program to find second most frequent character
  6. C Program to Sort an array of names or strings
  7. C++ Program to remove spaces from a string
  8. String Class in C++
  9. C++ program to concatenate a string given number of times
  10. std::string::append vs std::string::push_back() vs Operator += in C++
  11. Comparing two strings in C++
  12. Convert string to char array in C++
  13. Extract all integers from string in C++
  14. std::regex_match, std::regex_replace() | Regex (Regular Expression) In C++
  15. C program to Replace a word in a text by another given word
  16. stringstream in C++ and its applications
  17. C++ string class and its applications

Strings in Java :

  1. String Class in Java
  2. String in Switch Case in Java
  3. Java program to swap first and last characters of words in a sentence
  4. Java program to expand a String if range is given?
  5. Check if a given string is a valid number (Integer or Floating Point) in Java | SET 2 (Regular Expression approach)
  6. Get the first letter of each word in a string using regex in Java
  7. Reverse words in a given String in Java
  8. Reverse a string in Java (5 Different Ways)
  9. Compare two strings lexicographically in Java
  10. Searching characters and substring in a String in Java
  11. Possible Words using given characters in Python
  12. Using Set() in Python Pangram Checking
  13. Using OrderedDict() in Python to check order of characters in string
  14. Print anagrams together in Python using List and Dictionary
  15. K’th Non-repeating Character in Python using List Comprehension and OrderedDict
  16. Prefix matching in Python using pytrie module
  17. Print number with commas as 1000 separators in Python
  18. Pattern Occurrences : Stack Implementation Java

Strings in Python :

  1. String Methods in Python : Set 1 , Set 2 , Set 3
  2. Dictionary and counter in Python to find winner of election
  3. Maximum length of consecutive 1’s in a binary string in Python using Map function
  4. Python code to print common characters of two Strings in alphabetical order
  5. Using Counter() in Python to find minimum character removal to make two strings anagram
  6. Reverse string in Python
  7. Python groupby method to remove all consecutive duplicates
  8. Generate two output strings depending upon occurrence of character in input string in Python
  9. Python Dictionary to find mirror characters in a string
  10. Python | Convert a list of characters into a string
  11. Map function and Lambda expression in Python to replace characters
  12. Zip function in Python to change to a new character set
  13. SequenceMatcher in Python for Longest Common Substring
  14. Python | Print the initials of a name with last name in full
  15. Python counter and dictionary intersection example (Make a string using deletion and rearrangement)
  16. Python program to count number of vowels using sets in given string
  17. Python set to check if string is panagram
  18. Python | Check if a Substring is Present in a Given String
  19. Python sorted() to check if two strings are anagram or not
  20. Python | Remove leading zeros from an IP address
  21. Python | Count all prefixes in given string with greatest frequency
  22. Check if both halves of the string have same set of characters in Python
  23. Concatenated string with uncommon characters in Python
  24. Second most repeated word in a sequence in Python
  25. Regex in Python to put spaces between words starting with capital letters
  26. Python code to move spaces to front of string in single traversal
  27. String slicing in Python to rotate a string
  28. String slicing in Python to check if a string can become empty by recursive deletion
  29. Reverse words in a given String in Python
  30. Run Length Encoding in Python
  31. Anagram checking in Python using collections.Counter()
  32. Remove all duplicates from a given string in Python
  33. Remove all consecutive duplicates from the string
  34. Python program to check if a string is palindrome or not

Arthimetic Operation in String :

  1. Smallest number with sum of digits as N and divisible by 10^N
  2. Minimum sum of squares of character counts in a given string after removing k characters
  3. Maximum and minimum sums from two numbers with digit replacements
  4. Check if a given string is sum-string
  5. Sum of two large numbers
  6. Calculate sum of all numbers present in a string
  7. Extract maximum numeric value from a given string
  8. Calculate maximum value using ‘+’ or ‘*’ sign between two numbers in a string
  9. Maximum segment value after putting k breakpoints in a number
  10. Difference of two large numbers
  11. Check if a large number is divisible by 4 or not
  12. Check if a large number is divisible by 11 or not
  13. Number of substrings divisible by 6 in a string of integers
  14. Decimal representation of given binary string is divisible by 5 or not
  15. Number of substrings divisible by 8 but not by 3
  16. To check divisibility of any large number by 999
  17. Multiply Large Numbers represented as Strings
  18. Divide large number represented as string
  19. Remainder with 7 for large numbers
  20. Given two numbers as strings, find if one is a power of other
  21. Check whether a given number is even or odd
  22. Product of nodes at k-th level in a tree represented as string
  23. Program to find remainder when large number is divided by 11
  24. Ways to remove one element from a binary string so that XOR becomes zero
  25. Find the maximum subarray XOR in a given array
  26. Calculate the difficulty of a sentence
  27. Minimum Index Sum for Common Elements of Two Lists

Character Counting Based Problems :

  1. Count Uppercase, Lowercase, special character and numeric values
  2. Find the smallest window in a string containing all characters of another string
  3. Smallest window that contains all characters of string itself
  4. Count number of substrings with exactly k distinct characters
  5. Number of substrings with count of each character as k
  6. String with k distinct characters and no same characters adjacent
  7. Number of substrings of a string
  8. Distinct strings with odd and even changes allowed
  9. Find k’th character of decrypted string
  10. Count characters at same position as in English alphabets
  11. Count words in a given string
  12. Count words present in a string
  13. Count of words whose i-th letter is either (i-1)-th, i-th, or (i+1)-th letter of given word
  14. Program to find Smallest and Largest Word in a String
  15. Count substrings with same first and last characters
  16. Recursive solution to count substrings with same first and last characters
  17. Count of distinct substrings of a string using Suffix Array
  18. Count of distinct substrings of a string using Suffix Trie
  19. Count number of strings (made of R, G and B) using given combination
  20. Count of strings that can be formed using a, b and c under given constraints
  21. Count of substrings of a binary string containing K ones
  22. Group words with same set of characters
  23. Print all distinct characters of a string in order (3 Methods)
  24. Print common characters of two Strings in alphabetical order
  25. Common characters in n strings
  26. Find uncommon characters of the two strings
  27. Concatenated string with uncommon characters of two strings
  28. Program to remove vowels from a String
  29. Remove consecutive vowels from string
  30. Program to count vowels in a string (Iterative and Recursive)
  31. Count consonants in a string (Iterative and recursive methods)
  32. Alternate vowel and consonant string
  33. Given a binary string, count number of substrings that start and end with 1
  34. Number of distinct permutation a String can have
  35. Time complexity of all permutations of a string
  36. Permutations of a given string using STL
  37. Check if both halves of the string have same set of characters
  38. Count words that appear exactly two times in an array of words
  39. Check if frequency of all characters can become same by one removal
  40. Check if a string has all characters with same frequency with one variation allowed
  41. Count ways to increase LCS length of two strings by one
  42. Find the character in first string that is present at minimum index in second string
  43. Remove characters from the first string which are present in the second string
  44. Length of Longest sub-string that can be removed
  45. Count of character pairs at same distance as in English alphabets
  46. Count number of equal pairs in a string
  47. Count of strings where adjacent characters are of difference one
  48. Print number of words, vowels and frequency of each character

Subsequence & Substring :

  1. Longest subsequence where every character appears at-least k times
  2. Given two strings, find if first string is a subsequence of second
  3. Number of subsequences of the form a^i b^j c^k
  4. Number of subsequences in a string divisible by n
  5. Find number of times a string occurs as a subsequence in given string
  6. Number of subsequences as “ab” in a string repeated K times
  7. Count of ‘GFG’ Subsequences in the given string
  8. Count Distinct Subsequences
  9. Count distinct occurrences as a subsequence
  10. Longest common subsequence with permutations allowed
  11. Repeated subsequence of length 2 or more
  12. Print all longest common sub-sequences in lexicographical order
  13. Printing Longest Common Subsequence | Set 2
  14. Given number as string, find number of contiguous subsequences which recursively add up to 9 | Set 2
  15. Shortest Uncommon Subsequence
  16. Shortest Superstring Problem
  17. Printing Shortest Common Supersequence
  18. Shortest possible combination of two strings
  19. A Space Optimized Solution of LCS
  20. Sort a string according to the order defined by another string
  21. Shortest Common Supersequence
  22. Longest Repeating Subsequence
  23. Find largest word in dictionary by deleting some characters of given string
  24. Dynamic Programming | Set 12 (Longest Palindromic Subsequence)

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Reverse & Rotation :

  1. Perfect reversible string
  2. Reversing an Equation
  3. Left Rotation and Right Rotation of a String
  4. Generate all rotations of a given string
  5. Minimum rotations required to get the same string
  6. Check if strings are rotations of each other or not
  7. Check if a string can be obtained by rotating another string 2 places
  8. Count rotations divisible by 4
  9. Check if all rows of a matrix are circular rotations of each other
  10. Print reverse of a string using recursion
  11. Print words of a string in reverse order
  12. Program to reverse a string (Iterative and Recursive)
  13. Write a program to reverse an array or string
  14. Reverse an array without affecting special characters
  15. Reverse words in a given string
  16. Reverse individual words
  17. Reverse a string preserving space positions
  18. Reverse string without using any temporary variable
  19. Print reverse string after removing vowels
  20. Reverse vowels in a given string
  21. Reverse String according to the number of words
  22. Reverse each word in a linked list node
  23. Find if an array of strings can be chained to form a circle

Sorting & Searching :

  1. Sort an array of strings according to string lengths
  2. Sorting array of strings (or words) using Trie
  3. Sort string of characters
  4. Alternate Lower Upper String Sort
  5. Program to sort string in descending order
  6. Print array of strings in sorted order without copying one string into another
  7. Sort the given string using character search
  8. Given a sorted dictionary of an alien language, find order of characters
  9. Rearrange a string in sorted order followed by the integer sum
  10. Print distinct sorted permutations with duplicates allowed in input
  11. Minimum cost to sort strings using reversal operations of different costs
  12. Print number in ascending order which contains 1, 2 and 3 in their digits.
  13. Search in an array of strings where non-empty strings are sorted
  14. Sparse Search

Case Sensitive String :

  1. Lower case to upper case – An interesting fact
  2. isupper() and islower() and their application in C++
  3. Case conversion (Lower to Upper and Vice Versa) of a string using BitWise operators in C/C++
  4. Maximum distinct lowercase alphabets between two uppercase
  5. First uppercase letter in a string (Iterative and Recursive)
  6. Convert characters of a string to opposite case
  7. gOOGLE cASE of a given sentence
  8. Print all words matching a pattern in CamelCase Notation Dictonary
  9. Camel case of a given sentence
  10. Permute a string by changing case
  11. Toggle case of a string using Bitwise Operators
  12. How to design a tiny URL or URL shortener?

Occurrence Based String :

  1. Given a string, find its first non-repeating character
  2. Print all permutations with repetition of characters
  3. Find the first non-repeating character from a stream of characters
  4. Convert to a string that is repetition of a substring of k length
  5. Smallest length string with repeated replacement of two distinct adjacent
  6. Distributing all balls without repetition
  7. Maximum consecutive repeating character in string
  8. Minimum number of deletions so that no two consecutive are same
  9. K’th Non-repeating Character
  10. Find repeated character present first in a string
  11. Find the first repeated word in a string
  12. Find the first repeated character in a string
  13. Second most repeated word in a sequence
  14. Most frequent word in an array of strings
  15. Efficiently find first repeated character in a string without using any additional data structure in one traversal
  16. Queries for characters in a repeated string
  17. Return maximum occurring character in an input string
  18. Generate two output strings depending upon occurrence of character in input string.
  19. Print characters and their frequencies in order of occurrence
  20. Program to count occurrence of a given character in a string
  21. Check if all occurrences of a character appear together
  22. Group all occurrences of characters according to first appearance
  23. Print the string by ignoring alternate occurrences of any character
  24. Print the string after the specified character has occurred given no. of times
  25. Find all occurrences of a given word in a matrix
  26. Replace all occurrences of string AB with C without using extra space
  27. Rearrange a binary string as alternate x and y occurrences
  28. Remove recurring digits in a given number
  29. Find the most frequent digit without using array/string

Spacing :

  1. Remove spaces from a given string
  2. Move spaces to front of string in single traversal
  3. Put spaces between words starting with capital letters
  4. Removing spaces from a string using Stringstream
  5. Remove extra spaces from a string
  6. URLify a given string (Replace spaces is %20)
  7. String containing first letter of every word in a given string with spaces
  8. Print all possible strings that can be made by placing spaces
  9. Print all possible strings that can be made by placing spaces

Anagram :

  1. Check whether two strings are anagram of each other
  2. Given a sequence of words, print all anagrams together | Set 2
  3. Anagram Substring Search
  4. Print all pairs of anagrams in a given array of strings
  5. Remove minimum number of characters so that two strings become anagram
  6. Check if two strings are k-anagrams or not
  7. Check if binary representations of two numbers are anagram
  8. Given a sequence of words, print all anagrams together using STL
  9. Check if all levels of two trees are anagrams or not
  10. Count of total anagram substrings
  11. Minimum Number of Manipulations required to make two Strings Anagram Without Deletion of Character

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Palindrome :

  1. C Program to Check if a Given String is Palindrome
  2. Check if a given string is a rotation of a palindrome
  3. C++ Program to print all palindromes in a given range
  4. Check if characters of a given string can be rearranged to form a palindrome
  5. Dynamic Programming | Set 28 (Minimum insertions to form a palindrome)
  6. Longest Palindromic Substring | Set 2
  7. Find all palindromic sub-strings of a given string
  8. Online algorithm for checking palindrome in a stream
  9. Given a string, print all possible palindromic partitions
  10. Print all palindromic partitions of a string
  11. Dynamic Programming | Set 17 (Palindrome Partitioning)
  12. Count All Palindromic Subsequence in a given String
  13. Minimum characters to be added at front to make string palindrome
  14. Palindrome Substring Queries
  15. Suffix Tree Application 6 – Longest Palindromic Substring
  16. Palindrome pair in an array of words (or strings)
  17. Make largest palindrome by changing at most K-digits
  18. Lexicographically first palindromic string
  19. Recursive function to check if a string is palindrome
  20. Minimum number of Appends needed to make a string palindrome
  21. Longest Non-palindromic substring
  22. Minimum number of deletions to make a string palindrome
  23. Minimum steps to delete a string after repeated deletion of palindrome substrings
  24. Count of Palindromic substrings in an Index range
  25. Minimum insertions to form a palindrome with permutations allowed
  26. Nth Even length Palindrome

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Binary String :

  1. Count of operations to make a binary string”ab” free
  2. Change if all bits can be made same by single flip
  3. Length of Longest sub-string that can be removed
  4. Number of flips to make binary string alternate
  5. 1’s and 2’s complement of a Binary Number
  6. Efficient method for 2’s complement of a binary string
  7. Count binary strings with k times appearing adjacent two set bits
  8. Count strings with consecutive 1’s
  9. Generate all binary strings from given pattern
  10. Add two bit strings
  11. Count number of binary strings without consecutive 1’s
  12. Generate all binary permutations such that there are more or equal 1’s than 0’s before every point in all permutations
  13. Check if a string follows a^nb^n pattern or not
  14. Binary representation of next number
  15. Binary representation of next greater number with same number of 1’s and 0’s
  16. Maximum difference of zeros and ones in binary string
  17. Check if a binary string has a 0 between 1s or not | Set 2
  18. Min flips of continuous characters to make all characters same in a string
  19. Concatenation of two strings in PHP
  20. Program to add two binary strings
  21. Convert String into Binary Sequence
  22. Generate all binary strings without consecutive 1’s
  23. Minimum number of characters to be removed to make a binary string alternate
  24. Check divisibility of binary string by 2^k
  25. Removing elements between the two zeros
  26. Find i’th Index character in a binary string obtained after n iterations
  27. Number of substrings with odd decimal value in a binary string
  28. Generate n-bit Gray Codes
  29. Print N-bit binary numbers having more 1’s than 0’s in all prefixes
  30. Add n binary strings

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Lexicographic pattern :

  1. Powet Set in Lexicographic order
  2. Lexicographically n-th permutation of string
  3. Lexicographic rank of string using stl
  4. Lexicographically minimum string rotation | Set 1
  5. Generating distinct subsequences of a given string in lexicographic order
  6. Lexicographically smallest string obtained after concatenating array
  7. Lexicographical Maximum substring of string
  8. Lexicographical concatenation of all substrings of a string
  9. Construct lexicographically smallest palindrome
  10. Lexicographically smallest string whose hamming distance from given string is exactly K
  11. Lexicographically next string
  12. Lexicographically largest subsequence such that every character occurs at least k times
  13. Lexicographically first alternate vowel and consonant string
  14. Find a string in lexicographic order which is in between given two strings
  15. Print all permutations in sorted (lexicographic) order
  16. How to find Lexicographically previous permutation?
  17. Find n-th lexicographically permutation of a string | Set 2
  18. Lexicographic rank of a string

Pattern Searching :

  1. Searching for Patterns | Set 5 (Finite Automata)
  2. Pattern Searching | Set 7 (Boyer Moore Algorithm – Bad Character Heuristic)
  3. Manacher’s Algorithm – Linear Time Longest Palindromic Substring – Part 4
  4. Z algorithm
  5. Search a Word in a 2D Grid of characters
  6. Printing string in plus ‘+’ pattern in the matrix
  7. Wildcard Pattern Matching
  8. Dynamic Programming | Wildcard Pattern Matching | Linear Time and Constant Space
  9. Replace a character c1 with c2 and c2 with c1 in a string S
  10. Aho-Corasick Algorithm
  11. Count of occurrences of a “1(0+)1” pattern in a string
  12. Find all the patterns of “1(0+)1” in a given string | SET 2
  13. In-place replace multiple occurrences of a pattern
  14. Find all strings that match specific pattern in a dictionary
  15. Check if string follows order of characters defined by a pattern or not
  16. Find nth term of the Dragon Curve Sequence
  17. Count of number of given string in 2D character array

More >>

Split String :

  1. Tokenizing a string in C++
  2. Split a sentence into words in C++
  3. How to split a string in C/C++, Python and Java?
  4. Check if given string can be split into four distinct strings
  5. Split numeric, alphabetic and special symbols from a String
  6. Splitting a Numeric String
  7. Ways to split string such that each partition starts with distinct character
  8. Partition a number into two divisble parts
  9. Partition given string in such manner that i’th substring is sum of (i-1)’th and (i-2)’th substring
  10. Breaking a number such that first part is integral division of second by a power of 10
  11. Divide a string in N equal parts
  12. Minimum Word Break
  13. Word Break Problem
  14. Word Break Problem using Backtracking

Balance Parentheses & Bracket Evaluation :

  1. Identify and mark unmatched parenthesis in an expression
  2. Cost to Balance the parentheses
  3. Check for balanced parentheses in an expression | O(1) space
  4. Check for balanced parentheses in an expression
  5. Length of Longest Balanced Subsequence
  6. Balanced expression with replacement
  7. Evaluate a boolean expression represented as string
  8. Find maximum depth of nested parenthesis in a string
  9. Print all ways to break a string in bracket form
  10. Find an equal point in a string of brackets
  11. Minimum Swaps for Bracket Balancing
  12. Check if two expressions with brackets are same
  13. Expression contains redundant bracket or not
  14. Range Queries for Longest Correct Bracket Subsequence
  15. Evaluate an array expression with numbers, + and –
  16. Print Bracket Number
  17. Find index of closing bracket for a given opening bracket in an expression
  18. Binary tree to string with brackets
  19. Construct Binary Tree from String with bracket representation
  20. Minimum number of bracket reversals needed to make an expression balanced

Conversion :

  1. Convert all substrings of length ‘k’ from base ‘b’ to decimal
  2. Convert Binary fraction to Decimal
  3. Convert decimal fraction to binary number
  4. Convert a sentence into its equivalent mobile numeric keypad sequence
  5. Check if it is possible to convert one string into another with given constraints
  6. Converting one string to other using append and delete last operations
  7. Converting Decimal Number lying between 1 to 3999 to Roman Numerals
  8. Converting Roman Numerals to Decimal lying between 1 to 3999
  9. Inverting the Move to Front Transform
  10. Burrows – Wheeler Data Transform Algorithm
  11. Check if it is possible to transform one string to another
  12. Transform the string
  13. An in-place algorithm for String Transformation
  14. Ways of transforming one string to other by removing 0 or more characters
  15. Transform One String to Another using Minimum Number of Given Operation
  16. Convert Ternary Expression to a Binary Tree
  17. Prefix to Infix Conversion
  18. Prefix to Postfix Conversion
  19. Postfix to Prefix Conversion
  20. Postfix to Infix

Misc :

  1. Word Wrap problem ( Space optimized solution )
  2. Form minimum number from given sequence
  3. Maximum number of characters between any two same character in a string
  4. Print shortest path to print a string on screen
  5. Minimum number of stops from given path
  6. Check whether second string can be formed from characters of first string
  7. Mirror characters of a string
  8. Find words which are greater than given length k
  9. Find last index of a character in a string
  10. Find position of the given number among the numbers made of 4 and 7
  11. Find winner of an election where votes are represented as candidate names
  12. Compare Version Numbers with large inputs allowed
  13. Possibility of moving out of maze
  14. Possibility of a word from a given set of characters
  15. Find the arrangement of queue at given time
  16. Program to generate all possible valid IP addresses from given string
  17. Program to validate an IP address
  18. Program to check for a Valid IMEI Number
  19. Decode a median string to the original string
  20. Decode a string recursively encoded as count followed by substring
  21. Minimal operations to make a number magical
  22. Program to check for ISBN
  23. Program for credit card number validation
  24. Maximize a number considering permutations with values smaller than limit
  25. Find if a string starts and ends with another given string

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