Optimal Palindrome Check | Dataford Interview Questions

Infineon Technologies Americas uses compact device identifiers and diagnostic strings in embedded tooling. Given an identifier, determine whether it is a palindrome after ignoring non-alphanumeric characters and treating uppercase and lowercase ASCII letters as equivalent.

Your solution must scan the string in linear time and use constant auxiliary space. Do not create a reversed string or a filtered copy of the input.

Formal Specification

Implement is_palindrome(text), where text is a string. Return True if the normalized sequence reads identically from left to right and right to left, otherwise return False. A character is retained only if it is an ASCII letter or digit. ASCII letters should be compared case-insensitively. The input string itself must not be modified.

Constraints

0 <= len(text) <= 10^6
text contains printable ASCII characters only
Ignore every character that is not an ASCII letter or digit
Compare ASCII letters without regard to case
Use O(1) auxiliary space

Function Signature

def is_palindrome(text):

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