LeetCode题解：Longest Valid Parentheses

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.

思路：

首先扫描一遍，mark所有的成对括号。然后数一下最长的记号。

题解：

class Solution {public:    int longestValidParentheses(string s) {        stack<int> LP;        for(int i = 0; i < s.size(); ++i)        {            char ch  = s[i];            if (ch == '(')                LP.push(i);            else            {                if (!LP.empty())                {                    s[LP.top()] = ' ';                    s[i] = ' ';                                        LP.pop();                }            }        }                int longest = 0;        int curr_len = 0;        for(auto& ch : s)            if (ch == ' ')                curr_len++, longest = max(curr_len, longest);            else                curr_len = 0;                return longest;    }};