package string;

/**
 * Created by gouthamvidyapradhan on 13/07/2017.
 * Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
 * <p>
 * For example,
 * "A man, a plan, a canal: Panama" is a palindrome.
 * "race a car" is not a palindrome.
 * <p>
 * Note:
 * Have you consider that the string might be empty? This is a good question to ask during an interview.
 * <p>
 * For the purpose of this problem, we define empty string as valid palindrome.
 */
public class ValidPalindrome {
    public static void main(String[] args) throws Exception {
        System.out.println(new ValidPalindrome().isPalindrome("989 "));
    }

    public boolean isPalindrome(String s) {
        if (s == null || s.isEmpty()) return true;
        s = s.toLowerCase();
        for (int i = 0, j = s.length() - 1; i < j; ) {
            char f = s.charAt(i);
            char l = s.charAt(j);
            if (!(f >= 'a' && f <= 'z') && !(f >= '0' && f <= '9')) {
                i++;
                continue;
            }
            if (!(l >= 'a' && l <= 'z') && !(l >= '0' && l <= '9')) {
                j--;
                continue;
            }
            if (f != l)
                return false;
            i++;
            j--;
        }
        return true;
    }

}