码迷,mamicode.com
首页 > 其他好文 > 详细

19.2.1 [LeetCode 32] Longest Valid Parentheses

时间:2019-02-01 19:50:13      阅读:125      评论:0      收藏:0      [点我收藏+]

标签:col   字符串   i++   output   char   lan   nbsp   show   左右   

Given a string containing just the characters ‘(‘ and ‘)‘, find the length of the longest valid (well-formed) parentheses substring.

Example 1:

Input: "(()"
Output: 2
Explanation: The longest valid parentheses substring is "()"

Example 2:

Input: ")()())"
Output: 4
Explanation: The longest valid parentheses substring is "()()"

题意

找最长的合法左右括号字符串

题解

这道题还蛮难的,一开始我的dp思路错误了(n3的复杂度真是不像话)

把dp数组设为以当前索引值为末尾的合法字符串的长度就可以做了

技术分享图片
 1 class Solution {
 2 public:
 3     int longestValidParentheses(string s) {
 4         int l = s.length();
 5         if (l < 2)return 0;
 6         int ans = 0;
 7         vector<int>dp;
 8         dp.resize(l);
 9         for (int i = 0; i < l; i++)
10             dp[i] = 0;
11         if (s[0] == (&&s[1] == )) {
12             ans = 2;
13             dp[1] = 2;
14         }
15         for (int i = 2; i < l; i++) {
16             if (s[i] == ()continue;
17             if (s[i - 1] == ()dp[i] = dp[i - 2] + 2;
18             else {
19                 int last = dp[i - 1];
20                 if (i - last - 1 >= 0 && s[i - last - 1] == () {
21                     dp[i] = last + 2;
22                     if (i - last - 2 >= 0)
23                         dp[i] += dp[i - last - 2];
24                 }
25             }
26             ans = max(ans, dp[i]);
27         }
28         return ans;
29     }
30 };
View Code

 

19.2.1 [LeetCode 32] Longest Valid Parentheses

标签:col   字符串   i++   output   char   lan   nbsp   show   左右   

原文地址:https://www.cnblogs.com/yalphait/p/10346751.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!