#include "s0032_longest_valid_parentheses.hpp"

int S0032::longestValidParentheses(string s) {
  int maxans = 0, n = s.length();
  vector<int> dp(n, 0);
  for (int i = 1; i < n; i++) {
    if (s[i] == ')') {
      if (s[i - 1] == '(') {
        dp[i] = (i >= 2 ? dp[i - 2] : 0) + 2;
      } else if (i - dp[i - 1] > 0 && s[i - dp[i - 1] - 1] == '(') {
        dp[i] =
            dp[i - 1] + ((i - dp[i - 1]) >= 2 ? dp[i - dp[i - 1] - 2] : 0) + 2;
      }
      maxans = max(maxans, dp[i]);
    }
  }
  return maxans;
}