Problem

In an OpenAI chat surface, some validation checks may need to determine whether a user-provided string reads the same forward and backward. Write a function that returns True if a string is a palindrome and False otherwise.

A palindrome is a string that is identical when reversed. For this problem, compare characters exactly as given: do not ignore spaces, punctuation, or letter casing.

Formal Specification

• Input: a string s
• Output: a boolean indicating whether s is a palindrome

Examples

Example 1

• Input: s = "racecar"
• Output: True
• Explanation: The string is the same from left to right and right to left.

Example 2

• Input: s = "openai"
• Output: False
• Explanation: Reversing the string produces a different value.

Example 3

• Input: s = "Aa"
• Output: False
• Explanation: Comparison is case-sensitive, so "A" != "a".

Constraints

• 0 <= len(s) <= 10^5
• s contains printable ASCII characters
• Use an algorithmic solution in Python

A solution with two pointers is expected and should run in linear time.