Saved from https://leetcode.com/problems/valid-palindrome/

lc125

class Solution:
    def isPalindrome(self, s: str) -> bool:
        l, r = 0, len(s)-1
        while l < r:
            if not s[l].isalnum():
                l += 1
            elif not s[r].isalnum():
                r -= 1
            else:
                if s[r].lower() != s[l].lower():
                    return False
                l += 1
                r -= 1
        return True