LeetCode 125. Valid Palindrome

最新推荐文章于 2025-09-10 15:24:29 发布

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最新推荐文章于 2025-09-10 15:24:29 发布

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文章标签：数据结构与算法 java runtime

原文链接：http://www.cnblogs.com/flowingfog/p/9913647.html

本文详细解析了LeetCode第125题“Valid Palindrome”的解决方案，介绍了如何通过忽略非字母数字字符并进行大小写转换来判断字符串是否为回文。代码实现使用Java语言，分享了一种高效且简洁的方法。

LeetCode 125. Valid Palindrome

分析

难度易

来源

https://leetcode.com/problems/valid-palindrome/

题目

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"

Output: true

Example 2:

Input: "race a car"

Output: false

解答

Runtime: 6 ms, faster than 72.53% of Java online submissions for Valid Palindrome.

 1 package LeetCode;
 2 
 3 public class L125_ValidPalindrome {
 4     public boolean isPalindrome(String s) {
 5         s=s.toLowerCase();
 6         if(s.length()<=1)
 7             return true;
 8         int head=0,tail=s.length()-1;
 9         while(head<=tail){
10             if(!Character.isLetterOrDigit(s.charAt(head)))
11             {
12                 head++;
13                 continue;
14             }
15             if(!Character.isLetterOrDigit(s.charAt(tail)))
16             {
17                 tail--;
18                 continue;
19             }
20             if(s.charAt(head)==s.charAt(tail))
21             {
22                 head++;
23                 tail--;
24             }else
25                 return false;
26         }
27         return true;
28     }
29     public static void main(String[] args){
30         L125_ValidPalindrome l125=new L125_ValidPalindrome();
31         String s="A man, a plan, a canal: Panama";
32         //String s="race a car";
33         System.out.println(l125.isPalindrome(s));
34     }
35 }