leetcode讲解--856. Score of Parentheses

题目

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

题目地址

讲解

这道题分类都有点难，可以算在智力题里面。主要是要理解一个套路：

"(()(()))" -> "(())" + "((()))" = 2 + 4

这样就会发现，可以维护一个层数变量，然后遍历的时候，遇到'('就加一，遇到")"就减一，遇到"()"这一对，就相当于找到了一组。然后把找到的所有组相加就行了。

java代码

class Solution {
    public int scoreOfParentheses(String S) {
        int d = -1;
        int result = 0;
        for(int i=0;i<S.length();i++){
            d += S.charAt(i)=='('?1:-1;
            if(S.charAt(i)=='(' && S.charAt(i+1)==')'){
                result += 1 << d;
            }
        }
        return result;
    }
}