Score of Parentheses

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

Solution:

class Solution {
    public int scoreOfParentheses(String S) {
        int ans=0,bal=0;
        for(int i=0;i<S.length();i++)
        {
            if(S.charAt(i)=='(')
            {
                bal++;
            }
            else
            {
                bal--;
                if(S.charAt(i-1)=='(')
                ans+=Math.pow(2,bal);
            }

        }
        return ans;
    }
}