125. Valid Palindrome

Leetcode

Neetcode

Code

class Solution:
    def isPalindrome(self, s: str) -> bool:
        i = 0
        j = len(s)-1
        
        while i < j:
            while i < j and not self.is_alpha_num(s[i]):
                i += 1
            while j>i and not self.is_alpha_num(s[j]):
                j -= 1
 
            if s[i].lower() != s[j].lower():
                return False
 
            i += 1
            j -= 1
 
        return True
 
    def is_alpha_num(self, c):
        return (
            (ord('A') <= ord(c) <= ord('Z')) or \
            (ord('a') <= ord(c) <= ord('z')) or \
            (ord('0') <= ord(c) <= ord('9'))
        )