125-valid-palindrome

Question

https://leetcode.com/problems/valid-palindrome/description/

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Example:

"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Thought Process

1. Two Pointers
   1. Having two pointer at the ends of the string, we can compare character by character
   2. Time complexity O(n)
   3. Space complexity O(1)

Solution

class Solution {
    public boolean isPalindrome(String s) {
        int i = 0, j = s.length() - 1;
        while (i < j){
            if (!Character.isLetterOrDigit(s.charAt(i))){
                i++;
            } else if (!Character.isLetterOrDigit(s.charAt(j))){
                j--;
            } else {
                if (Character.toLowerCase(s.charAt(i)) 
                    != Character.toLowerCase(s.charAt(j))) return false;
                i++;
                j--;
            }
        }
        return true;
    }
}

Additional