Valid Palindrome

Valid Palindrome

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: After removing non-alphanumeric characters and converting to lowercase,
"amanaplanacanalpanama" is a palindrome.

Example 2:

Input: s = "race a car"
Output: false
Explanation: After processing, "raceacar" is not a palindrome.

Example 3:

Input: s = " "
Output: true
Explanation: After removing non-alphanumeric characters, s is an empty string "".
An empty string reads the same forward and backward, so it is a palindrome.

Constraints

• 1 <= s.length <= 2 * 10^5
• s consists only of printable ASCII characters.

Expected Complexity

• Time: O(n)
• Space: O(1)