1. Write a function to check if two strings are rotations of each other.

2. Implement a function to find the longest common prefix of an array of strings.

3. Write a function to find the longest common suffix of an array of strings.

4. Implement a function to check if a string is a valid shuffle of two other strings.

5. Write a function to generate all substrings of a string.

6. Implement a function to find the longest palindromic substring.

7. Write a function to find the longest repeating substring.

8. Implement a function to find the length of the longest substring without repeating characters.

9. Write a function to count the number of palindromic substrings in a string.

10. Implement a function to find the longest substring with at most k distinct characters.

11. Write a function to find the longest substring with all distinct characters.

12. Implement a function to find the length of the shortest substring containing all unique characters of another string.

13. Write a function to find the smallest window in a string containing all characters of another string.

14. Implement a function to check if a string is a subsequence of another string.

15. Write a function to find the minimum window substring.

16. Implement a function to find the edit distance between two strings.

17. Write a function to find the longest common subsequence of two strings.

18. Implement a function to find the longest common substring of two strings.

19. Write a function to check if two strings are isomorphic.

20. Implement a function to find the number of distinct subsequences of a string.

21. Write a function to generate all permutations of a string.

22. Implement a function to generate all combinations of characters in a string.

23. Write a function to find all anagrams of a string in another string.

24. Implement a function to check if a string contains another string as a subsequence.

25. Write a function to find the longest prefix which is also a suffix.

26. Implement a function to find the lexicographic rank of a string.

27. Write a function to find the longest substring with at most k changes allowed.

28. Implement a function to find the minimum number of insertions to form a palindrome.

29. Write a function to find the minimum number of deletions to form a palindrome.

30. Implement a function to find the longest repeating character replacement.