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.
Solution:
public class Solution { public boolean isPalindrome(String s) { s=s.toLowerCase(); for(int i=0,j=s.length()-1;i<j;++i,--j){ while(i<j&&!isValid(s.charAt(i))) i++; while(i<j&&!isValid(s.charAt(j))) j--; if(s.charAt(i)!=s.charAt(j)) return false; } return true; } private boolean isValid(char c) { // TODO Auto-generated method stub if(c>=‘a‘&&c<=‘z‘) return true; if(c>=‘0‘&&c<=‘9‘) return true; return false; } }
原文：http://www.cnblogs.com/Phoebe815/p/4034172.html