Longest valid bracket

Give you one that only contains ‘(’ and ‘)’ String , Find the longest effective （ The format is correct and continuous ） The length of the bracket substring .
Enhanced bracket matching , So we all want to use stack to do , In fact, it can also be used dp To do it
Method 1 ：
Utilization stack ：

class Solution {
    
    public int longestValidParentheses(String s) {
    
        Stack<Integer> q = new Stack<Integer>();
        int len = s.length();
        int ans=0;
        q.push(-1);
        for(int i=0;i<len;i++){
    
            if(s.charAt(i)=='(')
                q.push(i);
            else{
    
                q.pop();
                if(q.isEmpty())
                    q.push(i);
                else
                    ans = Math.max(ans,i-q.peek());
            }
        }
        return ans;
    }
}

Method 2 ：
dp

class Solution {
    
    public int longestValidParentheses(String s) {
    
        int len = s.length();
        int dp[] = new int [len+5];
        int ans=0;
        for(int i=1;i<len;i++){
    
            if(s.charAt(i)==')'){
    
                if(s.charAt(i-1)=='('){
    
                    dp[i] = (i>=2?dp[i-2]:0)+2;
                }
                else if (i - dp[i - 1] > 0 && s.charAt(i - dp[i - 1] - 1) == '('){
    
                    dp[i]=dp[i-1]+(i-dp[i-1]>=2?dp[i-dp[i-1]-2]:0)+2;
                }
                     ans = Math.max(ans,dp[i]);
            }
        }
        return ans;
    }
}

still dp fast