Reduce the time complexity of solution from O(n^2) to O(n)

[NITIN23329]

Problem link : https://leetcode.com/problems/reverse-substrings-between-each-pair-of-parentheses/ O(n^2) solution : https://github.com/NITIN23329/LeetCode/blob/c6b42b50f0692df6ad329fbacb0c7e8dd7e191f1/Stack/ReverseSubstringBtwEachParentheses.java#L1