public boolean isPalindrome(String s) {
        int start = 0;
        int end = s.length() - 1;
        while (start < end) {
            if (!isAlphaNum(s.charAt(start))) {
                start++;
            } else if (!isAlphaNum(s.charAt(end))) {
                end--;
            } else {
                if (Character.toLowerCase(s.charAt(start++)) != Character.toLowerCase(s.charAt(end--))) {
                    return false;
                }
            }
        }
        return true;
    }
Date 04/09/2016
@author Tushar Roy

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.

https://leetcode.com/problems/valid-palindrome/
src/com/interview/string/ValidPalindrome.java