Efficient Palindrome Check | Dataford Interview Questions

JPMorgan Chase QA systems may receive reference strings containing inconsistent capitalization, spaces, or punctuation. Given a reference string, determine whether it is a palindrome after converting letters to lowercase and ignoring every non-alphanumeric character.

Use an efficient two-pointer algorithm that compares valid characters from the beginning and end without creating a second normalized string.

Formal Specification

Implement is_palindrome(text), where text is a string containing ASCII letters, digits, spaces, and punctuation. Return True if the normalized string reads identically forward and backward. Return False otherwise. An empty string, or a string containing no alphanumeric characters, is considered a palindrome.

Constraints

0 <= len(text) <= 2 * 10^5
text contains ASCII letters, digits, spaces, and punctuation
Comparisons are case-insensitive
Non-alphanumeric characters must be ignored

Function Signature

def is_palindrome(text):

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