Given a balanced parentheses string S, compute the score of the string based on the following rule:

• () has score 1
• AB has score A + B, where A and B are balanced parentheses strings.
• (A) has score 2 * A, where A is a balanced parentheses string.

 

Example 1:

Input: "()"
Output: 1

Example 2:

Input: "(())"
Output: 2

Example 3:

Input: "()()"
Output: 2

Example 4:

Input: "(()(()))"
Output: 6

 

Note:

1. S is a balanced parentheses string, containing only ( and ).
2. 2 <= S.length <= 50

class Solution {
    public int scoreOfParentheses(String S) {
        Stack<Integer> stack = new Stack();
        int cur = 0;
        for(char c : S.toCharArray()) {
            if(c == '(') {
                stack.push(cur);
                cur = 0;
            }
            else {
                cur = stack.pop() + Math.max(1, 2 * cur);
            }
        }
        return cur;
    }
}

https://leetcode.com/problems/score-of-parentheses/discuss/141777/C%2B%2BJavaPython-O(1)-Space