Longest valid parentheses

class Solution {
public:
    int longestValidParentheses(string s)
    {
        int maximum=0;
        int i;
        int open=0,close=0;
        int n=s.size();
        for(i=0;i<n;i++)
        {
            if(s[i]=='(')
            {
                open++;
            }
            else
            {
                close++;
            }
            if(open==close)
            {
                maximum=max(maximum,close*2);
            }
            else if(close>open)
            {
                open=0;
                close=0;
            }
        }
        
        open=0;
        close=0;
        for(i=n-1;i>=0;i--)
        {
            if(s[i]=='(')
            {
                open++;
            }
            else
            {
                close++;
            }
            if(open==close)
            {
                maximum=max(maximum,close*2);
            }
            else if(close<open)
            {
                open=0;
                close=0;
            }
        }
        return maximum;
    }
};