题解 | #最长的括号子串#

import java.util.*;

public class Solution {
    /**
     *
     * @param s string字符串
     * @return int整型
     */
    public int longestValidParentheses (String s) {
        // write code here
        if (s.length() <= 1) return 0;
        int res = 0;
        int[] dp = new int[s.length()];
        for (int i = 1; i < s.length(); i++) {
            if (s.charAt(i) == ')') {
                if (s.charAt(i - 1) == '(') {
                    dp[i] = 2 + (i > 2 ? dp[i - 2] : 0);
                } else if (i - dp[i - 1] - 1 >= 0 && s.charAt(i - dp[i - 1] - 1) == '(') {
                    dp[i] = 2 + dp[i - 1] + (i - dp[i - 1] - 2 > 0 ? dp[i - dp[i - 1] - 2] : 0);
                }
            }
            res = Math.max(res, dp[i]);
        }
        return res;
    }
}