https://leetcode-cn.com/problems/remove-outermost-parentheses/

 

Java Solution

 1 class Solution {
 2     public String removeOuterParentheses(String S) {
 3         char[] chars = S.toCharArray();
 4         int flag = 0;
 5         StringBuilder result = new StringBuilder();
 6         
 7         for (char c : chars) {
 8             if (c == '(') {
 9                 if (flag == 0) {
10                     flag ++;
11                     continue;
12                 }
13                 flag ++;
14             } else if (c == ')') {
15                 flag --;
16                 if (flag == 0) {
17                     continue;
18                 }
19             }
20             result.append(c);
21         }
22         return result.toString();
23     }
24 }