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
Input: s = "A man, a plan, a canal: Panama"
Output: true
"amanaplanacanalpanama" is a palindrome.
Input: s = "race a car"
Output: false
"raceacar" is not a palindrome.
Input: s = " "
Output: true
s is an empty string "" after removing non-alphanumeric characters. Since an empty string reads the same forward and backward, it is a palindrome.