Is Palindrome

class Solution {
    public boolean isPalindrome(String s) {
        int left = 0, right = s.length() - 1;

        while (left <= right) {
            char leftChar = Character.toLowerCase(s.charAt(left));
            char rightChar = Character.toLowerCase(s.charAt(right));

            if (!Character.isLetterOrDigit(leftChar)){
                left++;
                continue;
            }
            if (!Character.isLetterOrDigit(rightChar)){
                right--;
                continue;
            }
            if (leftChar != rightChar) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }
}

class Solution:
    def isPalindrome(self, s: str) -> bool:

        left, right = 0, len(s) - 1

        while left < right:
            leftChar = s[left]
            rightChar = s[right]

            while left < right and not self.isAlphNum(leftChar):
                left += 1
                leftChar = s[left]

            while left < right and not self.isAlphNum(rightChar):
                right -= 1
                rightChar = s[right]

            leftChar = leftChar.lower()
            rightChar = rightChar.lower()

            if leftChar != rightChar:
                return False

            left += 1
            right -= 1

        return True

    def isAlphNum(self, c: str) -> bool:
        return (
            ('a' <= c <= 'z') or
            ('A' <= c <= 'Z') or
            ('0' <= c <= '9')
        )