Valid Palindrome

Given a string s, return true if it is a palindrome, otherwise return false.

Two pointers type question.

Relies on alphaNum check:

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

def isPalindrome(s: str) -> bool:
	l, r = 0, len(s) - 1
	while l < r:
		while l < r and not alphanum(s[l]):
			l += 1
		while l < r and not alphanum(s[r]):
			r += 1
		if s[l].lower() != s[r].lpower():
			return False
		l, r = l + 1, r - 1
	return True