LongestValidParentheses_DP.cpp

class Solution {
public:
    int longestValidParentheses(string s) {
        int len_s = s.size();
        int dp[len_s+1]{0};
        int maxLen = 0;
        for(int i = 1; i < len_s; i++){
            if(s[i] == ')'){
                if(s[i - 1] == '('){
                    dp[i] = (i-2>=0 ? dp[i - 2] : 0) + 2;
                }
                else{
                    if(i - dp[i-1] - 1 >= 0 && s[i - dp[i-1] - 1] == '(')
                        dp[i] = dp[i-1] + 2 + (i-dp[i-1]-2 >=0 ? dp[i - dp[i-1] - 2] : 0);
                }
            }
            maxLen = max(maxLen, dp[i]);
        }
        return maxLen;
    }
};