import java.util.Stack;

class Solution {
    public String reverseParentheses(String s) {
        char[] cs = s.toCharArray();
        Stack<Integer> stk = new Stack<>();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == '(') {
                stk.add(i);
            } else if (s.charAt(i) == ')') {
                int j = stk.pop();
                reverse(cs, j, i);
            }
        }
        StringBuilder sb = new StringBuilder();
        for (char c : cs) {
            if (c != '(' && c != ')') {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    public void reverse(char[] cs, int l, int r) {
        while (l < r) {
            char c = cs[l];
            cs[l] = cs[r];
            cs[r] = c;
            l++;
            r--;
        }
    }
}

import java.util.Stack;

class Solution {
    public String reverseParentheses(String s) {
        int n = s.length();
        int[] ps = new int[n];
        Stack<Integer> stk = new Stack<>();
        for (int i = 0; i < n; i++) {
            if (s.charAt(i) == '(') {
                stk.add(i);
            } else if (s.charAt(i) == ')') {
                int j = stk.pop();
                ps[i] = j;
                ps[j] = i;
            }
        }
        StringBuilder sb = new StringBuilder();
        int d = 1;
        for (int i = 0; i < n; i += d) {
            if (s.charAt(i) == '(' || s.charAt(i) == ')') {
                i = ps[i];
                d = -d;
            } else {
                sb.append(s.charAt(i));
            }
        }
        return sb.toString();
    }
}