Valid a string is palindrome or not.

Valid_Palindrome.java

package wcy.leetcode.gist;

/**
 * Created by ChauyanWang on 12/20/14.
 */
public class Valid_Palindrome {
    public boolean Solution (String s) {
        if( s == null || s.length() == 0) return true;
        s = s.toLowerCase();
        int start = 0;
        int end = s.length() -1;
        while(start < end) {
            if((s.charAt(start) < '0' || s.charAt(start) > '9') &&
                    (s.charAt(start) < 'a' || s.charAt(start) > 'z')) {
                start ++;
                continue;
            }

            if((s.charAt(end) < '0' || s.charAt(end) > '9') &&
                    (s.charAt(end) < 'a' || s.charAt(end) > 'z')) {
                end --;
                continue;
            }

            if(s.charAt(end) != s.charAt(start)) return false;
            start++;
            end --;
        }
        return true;
    }
}