BCG X may process text from reports and client communications where punctuation, spaces, and capitalization should not affect comparisons. Given a string, determine whether it is a palindrome after ignoring every non-alphanumeric character and treating uppercase and lowercase letters as equal.
Implement is_palindrome(s), where s is a string. Return True if the filtered string reads identically from left to right and right to left; otherwise, return False. The filtered string contains only letters and digits. An empty filtered string is considered a palindrome.
Use a two-pointer approach that compares characters from both ends without creating a separate filtered string.
def is_palindrome(s):