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题目描述：Longest Valid Parentheses
Given a string containing just the characters ‘(‘ and ‘)‘, find the length of the longest valid (well-formed) parentheses substring.
For "(()", the longest valid parentheses substring is "()", which has length = 2.
Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.
代码如下：
class Solution { public: int longestValidParentheses(string s) { int max_len = 0, last = -1; //last是上一次的‘)‘的位置 stack<int> lefts; for(int i = 0; i < s.size(); i++){ //s[i]为‘(‘，则将i入栈 if(s[i] == ‘(‘) lefts.push(i); //s[i]为‘)‘ else{ if(lefts.empty()) last = i; else{ lefts.pop(); //若栈为空，则 if(lefts.empty()) max_len = max(max_len, i - last); else max_len = max(max_len, i - lefts.top()); } } } return max_len; } };
LeetCode 032 Longest Valid Parentheses
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原文地址：http://www.cnblogs.com/510602159-Yano/p/4279074.html
