Problem¶

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

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

Example 1:

**Input:** s = "A man, a plan, a canal: Panama"
**Output:** true
**Explanation:** "amanaplanacanalpanama" is a palindrome.

Solve¶

Do as the problem ask, without any optimization:

1. Lower key all character,
2. Keep all alphabet and numbers character only, storing in a new variable call alphabel_only
3. Check if alphabel_only backward and forward is the same

class Solution:
    def isPalindrome(self, s: str) -> bool:
        s = s.lower()
        alphabel_only = ""
        for c in s:
            if ord("a") <= ord(c) <= ord("z") or ord("0") <= ord(c) <= ord("9") :
                alphabel_only += c

        for i, c in enumerate(alphabel_only):
            if alphabel_only[len(alphabel_only) - 1 - i] != c:
                return False
        return True