Score of Parentheses

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

 

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

Solution:

class Solution {
    public int scoreOfParentheses(String S) {
        int result = 0;
        int mul = 0;
        char[] arr = S.toCharArray();
        for (int i = 0; i < arr.length; i ++) {
            char c = arr[i];
            if (c == '(') {
                mul ++;
            } else {
                mul --;
            }
            if (c == ')' && arr[i - 1] == '(') {
                result += 1 << mul;
            }
        }
        return result;
    }
}