1. Write a function to find the minimum number of operations to convert one string to another using insertion, deletion, and substitution.

2. Implement a function to find the longest subsequence which is a palindrome.

3. Write a function to find the shortest common supersequence of two strings.

4. Implement a function to find the longest subsequence which is repeated k times.

5. Write a function to check if a string can be made palindrome by removing at most k characters.

6. Implement a function to find the longest substring where the difference between the number of distinct characters is at most k.

7. Write a function to find the number of ways to decode a string of digits.

8. Implement a function to find the length of the longest substring which can be rearranged to form a palindrome.

9. Write a function to find the minimum number of swaps to make a string palindrome.

10. Implement a function to find the length of the longest balanced substring.

11. Write a function to find the number of palindromic partitions of a string.

12. Implement a function to find the length of the longest substring with equal number of vowels and consonants.

13. Write a function to find the smallest rotation of a string which is lexicographically smallest.

14. Implement a function to find the number of distinct palindromic subsequences in a string.

15. Write a function to find the length of the longest alternating substring.

16. Implement a function to find the number of substrings with exactly k distinct characters.

17. Write a function to find the length of the longest substring with at most k distinct characters.

18. Implement a function to find the longest substring with at most k changes allowed.

19. Write a function to find the number of palindromic subsequences in a string.

20. Implement a function to find the longest substring with equal number of 0s, 1s, and 2s.

21. Write a function to find the number of substrings with equal number of 0s, 1s, and 2s.

22. Implement a function to find the number of distinct subsequences of a string modulo a given number.

23. Write a function to find the lexicographically smallest subsequence of a string.

24. Implement a function to find the number of substrings where the number of distinct characters is exactly k.

25. Write a function to find the length of the longest substring which contains at most k distinct vowels.

26. Implement a function to find the number of substrings where the number of distinct vowels is exactly k.

27. Write a function to find the length of the longest substring which contains at most k distinct consonants.

28. Implement a function to find the number of substrings where the number of distinct consonants is exactly k.

29. Write a function to find the number of substrings which contain at most k distinct characters.

30. Implement a function to find the number of distinct anagrams of a string.