leetcode--Valid Palindrome

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

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

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

[java] view plain copy

1. public class Solution {  
2.     public boolean isPalindrome(String s) {  
3.         int low = 0;  
4.         int high = s.length()-1;  
5.         while(low<high){  
6.             if(!check(s.charAt(low))){  
7.                 low++;continue;  
8.             }else if(!check(s.charAt(high))){  
9.                 high--;continue;  
10.             }else{  
11.                 if(s.charAt(low)!=s.charAt(high)&&s.charAt(low)-s.charAt(high)!=32  
12.                         && s.charAt(high)-s.charAt(low)!=32){  
13.                     return false;  
14.                 }else{  
15.                     low++;high--;  
16.                 }  
17.             }  
18.         }  
19.         return true;  
20.     }  
21.       
22.     public boolean check(char c){  
23.         if(c>='a'&&c<='z' || c>='A'&&c<='Z' || c>='0'&&c<='9')  
24.             return true;  
25.         return false;  
26.     }  
27. }  

原文链接http://blog.csdn.net/crazy__chen/article/details/46383581