Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

题目大意:给一个字符串S,存在唯一的最长的回文子串,求这个回文子串。

解题思路:首先这个题有O(n)的解,是在http://articles.leetcode.com/2011/11/longest-palindromic-substring-part-ii.html这里有详细的解释,本文的算法是O(n^2)的,中规中矩的做法。回文有两种,abba和aba,本文分别对子串以i为中心进行检查偶数和奇数哪个长,同时记录长度,下标,奇偶等信息。

Talk is cheap>>

  public String longestPalindrome(String s) {
if (s == null || s.length() <= 1) {
return s;
}
int max_len = 0, pos = 0;
boolean odd = false;
for (int i = 0; i < s.length(); i++) {
int forward = i - 1;
int backward = i + 1;
int len = 0;
while (forward >= 0 && backward < s.length() && s.charAt(forward) == s.charAt(backward)) {
forward--;
backward++;
len++;
}
if (max_len < (len * 2 + 1)) {
max_len = len * 2 + 1;
odd = true;
pos = i;
}
len = 0;
forward = i;
backward = i + 1;
while (forward >= 0 && backward < s.length() && s.charAt(forward) == s.charAt(backward)) {
forward--;
backward++;
len++;
}
if (max_len < len * 2) {
max_len = len * 2;
odd = false;
pos = i;
}
}
if (odd) {
return s.substring(pos - (max_len - 1) / 2, pos + (max_len - 1) / 2 + 1);
}
return s.substring(pos - max_len / 2 + 1, pos + max_len / 2 + 1);
}

Longest Palindromic Substring——LeetCode的更多相关文章

  1. Longest Palindromic Substring -LeetCode

    题目 Given a string s,find the longest palindromic substring in S.You may assume  that the maximum len ...

  2. Longest Palindromic Substring leetcode java

    题目: Given a string S, find the longest palindromic substring in S. You may assume that the maximum l ...

  3. [LeetCode] Longest Palindromic Substring 最长回文串

    Given a string S, find the longest palindromic substring in S. You may assume that the maximum lengt ...

  4. Leetcode Longest Palindromic Substring

    Given a string S, find the longest palindromic substring in S. You may assume that the maximum lengt ...

  5. 求最长回文子串 - leetcode 5. Longest Palindromic Substring

    写在前面:忍不住吐槽几句今天上海的天气,次奥,鞋子里都能养鱼了...裤子也全湿了,衣服也全湿了,关键是这天气还打空调,只能瑟瑟发抖祈祷不要感冒了.... 前后切了一百零几道leetcode的题(sol ...

  6. LeetCode 5 Longest Palindromic Substring(最长子序列)

    题目来源:https://leetcode.com/problems/longest-palindromic-substring/ Given a string S, find the longest ...

  7. 【JAVA、C++】LeetCode 005 Longest Palindromic Substring

    Given a string S, find the longest palindromic substring in S. You may assume that the maximum lengt ...

  8. [LeetCode] Longest Palindromic Substring(manacher algorithm)

    Given a string S, find the longest palindromic substring in S. You may assume that the maximum lengt ...

  9. leetcode:Longest Palindromic Substring(求最大的回文字符串)

    Question:Given a string S, find the longest palindromic substring in S. You may assume that the maxi ...

随机推荐

  1. masonry使用介绍

    Masonry使用介绍 下面是Masonry的代码地址:https://github.com/Masonry/Masonry 介绍一个简单使用: <pre><code>[vie ...

  2. 如何设置jsp默认的编码为utf-8

    方法一: 文件里写: <%@ page contentType="text/html; charset=UTF-8"  %> 方法二: 选择window –> P ...

  3. [转] Are You Making a Big Mistake in This Volatile Market?

    Stock market volatility continues unabated. It may be too early to tell, but I’m marking the top of ...

  4. GDB调试技巧

    1. 查看内存分布 (gdb) info proc mappings 2. 对于类的调试,先通过行号来设断点, 比如:(gdb) b TcpConnection.cc:63 3. 打印数组的内容 (g ...

  5. iOS 独立开发记录(上)

    个月前,完成了个人App的2.0版本,也在普天同庆的六一儿童节这天上架了.因为是个人开发,很多实现都是边探索边做.现在完成之后再回顾,发现自己走了些弯路.所以写了这篇总结,概览了从想法.设计.开发到最 ...

  6. spring定时器任务多任务串行执行问题排查

    最近发现个生产问题,定时器任务某些任务没有及时执行.经过研究排查发现spring 定时器任务scheduled-tasks默认配置是单线程串行执行的,这就造成了若某个任务执行时间过长,其他任务一直在排 ...

  7. Linux shell入门基础(四)

    四.进程优先级前台后台 01.进程控制 #find /name aaa & #ps aux | grep find #updatedb &  #ps aux | grep update ...

  8. 什么是mimeType?

    因特网多媒体邮件扩展标示内容是什么格式.告诉浏览器或者server如何解析该数据http的请求和相应都含有一个mimeType字段 =>content-type(通用首部)

  9. Java并发编程之CAS

    CAS(Compare and swap)比较和替换是设计并发算法时用到的一种技术.简单来说,比较和替换是使用一个期望值和一个变量的当前值进行比较,如果当前变量的值与我们期望的值相等,就使用一个新值替 ...

  10. 给出2n+1个数,其中有2n个数出现过两次,如何用最简便的方法找出里面只出现了一次的那个数(转载)

    有2n+1个数,其中有2n个数出现过两次,找出其中只出现一次的数 例如这样一组数3,3,1,2,4,2,5,5,4,其中只有1出现了1次,其他都是出现了2次,如何找出其中的1? 最简便的方法是使用异或 ...