【leetcode刷题】32. Longest Valid Parentheses

原题链接
https://leetcode.com/problems/longest-valid-parentheses/
解题思路
利用动态规划。如果遍历过程中出现了一个)，则检查它的前面是否为(，如果是，就给这个后括号处对应的长度值加2,；继续遍历，如果接着还是)，则再往前检索一位，…
代码

class Solution(object):
    def longestValidParentheses(self, s):
        """
        :type s: str
        :rtype: int
        """
        
        if s == '':
            return 0

        result = [0 for i in range(0,len(s))]
        for right in range(1, len(s)):
            if s[right] == ')':
                left = right - 1 - result[right-1]
                if s[left] == '(' and left>=0:
                    result[right] = result[right-1] + 2
                    if left-1>=0:
                        result[right] += result[left-1]
        return max(result)

参考
https://blog.****.net/qqxx6661/article/details/77876647
https://shenjie1993.gitbooks.io/leetcode-python/032 Longest Valid Parentheses.html