Valid Palindrome

Here is the link to the problem: Valid Palindrome.

Problem Statement:

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.

Examples:

Example 1:

Input: s = “A man, a plan, a canal: Panama”

Output: true

Explanation: “amanaplanacanalpanama” is a palindrome.

Example 2:

Input: s = “race a car”

Output: false

Explanation: “raceacar” is not a palindrome.

Example 3:

Input: s = " "

Output: true

Explanation: s is an empty string "" after removing non-alphanumeric characters.

Since an empty string reads the same forward and backward, it is a palindrome.

My Solution

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        s = ''.join(char.lower() for char in s if char.isalnum())
        if s == s[::-1]:
            return True
        else:
            return False

This is quite simple one. I just used join to remove all characters besides Alphanumeric characters. NOTE: if it was to only check for alphabets, we would have used isalpha() instead of isalnum().

Later, we check if the string and its reverse is the same.