class Solution:
    def isPalindrome(self, s: 'str') -> 'bool':
        i = 0
        j = len(s) - 1

        while i < j:
            if s[i].isalnum() and s[j].isalnum() and s[i].lower() == s[j].lower():
                i += 1
                j -= 1
            elif not s[i].isalnum():
                i += 1
            elif not s[j].isalnum():
                j -= 1
            else:
                return False
        return True