leetcode

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.

class Solution {
public:
    int longestValidParentheses(std::string s) {
        int dp[1000005], i, max = 0;
		memset(dp, 0, sizeof(dp));
		for(i = 1; i < s.size(); i++) 
		{
			if(s[i] != ')' || s[i-dp[i]-1] != '(') continue;
			dp[i+1] = 2 + dp[i] + dp[i-dp[i]-1];
			if(dp[i+1] > max) max = dp[i+1];
		}
		return max;
    }
};