Valid Palindrome

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代码：

public class Solution {    public boolean isPalindrome(String s) {        int start =0;int end = s.length()-1;while(start < end){while((s.charAt(start)<'A' || s.charAt(start)>'z' || (s.charAt(start)>'Z' && s.charAt(start)<'a')) && start<s.length()-1 && (s.charAt(start)<'0' || s.charAt(start)>'9'))start++;while((s.charAt(end)<'A' || s.charAt(end)>'z' || (s.charAt(end)>'Z' && s.charAt(end)<'a')) && end>0  && (s.charAt(end)<'0' || s.charAt(end)>'9'))end--;if(start < end){if(s.charAt(start) == s.charAt(end) ||s.charAt(start)+32 == s.charAt(end) || s.charAt(start)-32 == s.charAt(end)){start++;end--;}else{return false;}}}return true;    }}