Palindrome Check Without Reverse | Dataford Interview Questions

An ING mobile banking workflow receives reference strings that may need a basic format check. Implement a function that determines whether the given string is a palindrome without using built-in reverse operations such as reversed(), str.reverse(), or slicing with [::-1].

A palindrome reads identically from left to right and right to left. Treat uppercase and lowercase characters as different, and treat spaces and punctuation as ordinary characters. The function must return True when the complete string is a palindrome and False otherwise.

Formal Specification

Implement is_palindrome(s).

Input: s, a string containing zero or more characters.
Output: A Boolean value indicating whether s is a palindrome.
You may use len() and character indexing, but you must not construct a reversed copy of the string or call a built-in reverse method.

Constraints

0 <= len(s) <= 10^5
The string may contain Unicode characters
Matching is case-sensitive
Whitespace and punctuation are significant
Do not use built-in reverse operations
Use O(1) auxiliary space

Function Signature

def is_palindrome(s):

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