leetcode 最长有效括号_leetcode 三数之和

输入：s = "(()"
输出：2
解释：最长有效括号子串是 "()"
示例 2：

输入：s = ")()())"
输出：4
解释：最长有效括号子串是 "()()"
示例 3：

输入：s = ""
输出：0

class Solution { 
   
public:
    const int INF = 0x3f3f3f3f;
    int work(string x){ 
   
        int res = 0;
        for(int i = 0,j = 0,cnt = 0;j < x.size();j ++){ 
   
            if(x[j] == '(')cnt ++;
            else cnt --;
            if(cnt == 0)res = max(res,j - i + 1);
            if(cnt < 0)i = j + 1,cnt = 0;
        }
        return res;
    }
    int longestValidParentheses(string s) { 
   
        int res = 0;
        res = work(s);
        reverse(s.begin(),s.end());
        for(auto &c : s){ 
   
            if(c == '(')c = ')';
            else c = '(';
        }
            
        res = max(res,work(s));
        return res;
    }
};