Parenthesis problem:-

1.https://leetcode.com/problems/generate-parentheses
2.https://leetcode.com/problems/score-of-parentheses
3.https://leetcode.com/problems/valid-parentheses
4.https://leetcode.com/problems/valid-parentheses Easy
5.https://leetcode.com/problems/remove-outermost-parentheses Easy
6.https://leetcode.com/problems/different-ways-to-add-parentheses/ Medium
7.https://leetcode.com/problems/remove-invalid-parentheses Hard
8.https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses Medium
9.https://leetcode.com/problems/maximum-nesting-depth-of-the-parentheses Easy
10.https://leetcode.com/problems/longest-valid-parentheses/ Hard

Counting of substring based on some condition:-

1.https://leetcode.com/problems/number-of-wonderful-substrings Medium
2.https://leetcode.com/problems/sum-of-beauty-of-all-substrings/ Medium
3.https://leetcode.com/problems/maximum-number-of-occurrences-of-a-substring Medium
4.https://leetcode.com/problems/number-of-wonderful-substrings Medium

Check types of string:-

1.https://leetcode.com/problems/isomorphic-strings Easy
2.https://leetcode.com/problems/valid-anagram Easy

3. https://leetcode.com/problems/additive-number Medium
   4.https://leetcode.com/problems/buddy-strings Easy
   5.https://leetcode.com/problems/longest-happy-prefix Hard
   6.https://leetcode.com/problems/increasing-decreasing-string Easy
   7.https://leetcode.com/problems/check-if-a-string-can-break-another-string Medium
   8.https://leetcode.com/problems/determine-if-two-strings-are-close Medium
   9.https://leetcode.com/problems/check-if-two-string-arrays-are-equivalent Easy
   10.https://leetcode.com/problems/check-if-word-equals-summation-of-two-words Easy
   11.https://leetcode.com/problems/check-if-one-string-swap-can-make-strings-equal Easy

Palindromic string:-

1.https://leetcode.com/problems/palindrome-partitioning Medium
2.https://leetcode.com/problems/palindrome-partitioning-ii Hard
3.https://leetcode.com/problems/valid-palindrome Easy
4.https://leetcode.com/problems/shortest-palindrome Hard
5.https://leetcode.com/problems/palindrome-pairs Hard
6.https://leetcode.com/problems/longest-palindrome Easy
7.https://leetcode.com/problems/longest-palindromic-subsequence Medium
8.https://leetcode.com/problems/find-the-closest-palindrome Hard
9.https://leetcode.com/problems/palindromic-substrings Medium
10.https://leetcode.com/problems/valid-palindrome-ii Easy
11.https://leetcode.com/problems/longest-chunked-palindrome-decomposition Hard 12.https://leetcode.com/problems/break-a-palindrome Medium

13. https://leetcode.com/problems/can-make-palindrome-from-substring Medium
    14.https://leetcode.com/problems/palindrome-partitioning-iii Hard
    15.https://leetcode.com/problems/minimum-insertion-steps-to-make-a-string-palindrome Hard
    16.https://leetcode.com/problems/remove-palindromic-subsequences Easy
    16.https://leetcode.com/problems/construct-k-palindrome-strings Medium
    17.https://leetcode.com/problems/split-two-strings-to-make-palindrome Medium

Sorting on String:-
1.https://leetcode.com/problems/sort-characters-by-frequency Medium
2.https://leetcode.com/problems/custom-sort-string

Longest and shortest kind of String Problem :-

https://leetcode.com/problems/longest-duplicate-substring Hard
2.https://leetcode.com/problems/longest-string-chain Medium
3.https://leetcode.com/problems/longest-common-subsequence Medium
4.https://leetcode.com/problems/longest-happy-string Medium
5.https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters Medium
6.https://leetcode.com/problems/find-longest-awesome-substring Hard
7.https://leetcode.com/problems/largest-substring-between-two-equal-characters Easy
8.https://leetcode.com/problems/largest-odd-number-in-string Easy

Longest Substring Without Repeating Characters:
Find the length of the longest substring without repeating characters in a given string.
https://leetcode.com/problems/longest-substring-without-repeating-characters/

Minimum Window Substring:
Given a string S and a string T, find the minimum window in S that contains all the characters of T.
https://leetcode.com/problems/minimum-window-substring/

Regular Expression Matching:
Implement regular expression matching with support for '.' and '*'.
https://leetcode.com/problems/regular-expression-matching/

Edit Distance:
Determine the minimum number of operations required to convert one string into another, where operations include insert, delete, and replace.
https://leetcode.com/problems/edit-distance/

String to Integer (atoi):
Implement the atoi function which converts a string to an integer.
https://leetcode.com/problems/string-to-integer-atoi/

Group Anagrams:
Given an array of strings, group anagrams together.
https://leetcode.com/problems/group-anagrams/

Longest Palindromic Substring:
Find the longest palindromic substring in a given string.
https://leetcode.com/problems/longest-palindromic-substring/

ZigZag Conversion:
Convert a given string into a zigzag pattern with a specified number of rows.
https://leetcode.com/problems/zigzag-conversion/

Valid Parentheses:
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
https://leetcode.com/problems/valid-parentheses/

String Compression:
Implement a method to perform basic string compression using the counts of repeated characters. For example, the string "aabcccccaaa" would become "a2b1c5a3".
https://leetcode.com/problems/string-compression/

Please give suggestions if you want to make any.