leetcode32 最长有效括号

た入场券 2023-06-18 05:54 13阅读 0赞

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给定一个只包含 '(' 和 ')' 的字符串，找出最长的包含有效括号的子串的长度。

示例 1:

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

输入: ")()())"  
输出: 4  
解释: 最长有效括号子串为 "()()"

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public class Solution {
        public int longestValidParentheses(String s) {
            int maxans = 0;
            int dp[] = new int[s.length()];
            for (int i = 1; i < s.length(); ++i) {
                if (s.charAt(i) == '(')continue;
                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;
                }
                if(maxans<dp[i])maxans = dp[i];
            }
            return maxans;
        }
    }

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