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.

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.

*/

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;

}

}