Valid Palindrome 2 ways.

#This is the cheesy way i came up with.
class Solution:
    def isPalindrome(self, s: str) -> bool:

        alphnm = ''.join(ch.lower() for ch in s if ch.isalnum())
        return alphnm == alphnm[::-1]

#This is the two pointer solution.
class Solution:
    def isPalindrome(self, s: str) -> bool:

        alphnm = ''.join(ch.lower() for ch in s if ch.isalnum())
        left = 0
        right = len(alphnm) - 1

        while left < right:
            if alphnm[left] != alphnm[right]:
                return False
            left += 1
            right -= 1

        return True