Included four questions to be solved in 120 minutes on Hackerrank.

1. Plus One (https://leetcode.com/problems/plus-one/)
2. Make Parenthesis Valid (https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/)
3. A variation of https://leetcode.com/problems/merge-intervals/
4. A variation of https://leetcode.com/problems/palindrome-partitioning/

All the best!