String Unique Characters | Dataford Interview Questions

J.B. Hunt 360 may receive shipment reference strings from multiple operational workflows. Implement a function that determines whether a string contains only unique characters.

Treat characters as distinct based on their exact values. The comparison is case-sensitive, so A and a are different characters. Spaces, punctuation, digits, and other characters must also be checked. Return True when no character appears more than once, and return False as soon as a duplicate is found.

Formal Specification

Given one string s, return a boolean:

True if every character in s occurs exactly once or the string is empty.
False if any character occurs more than once.

Do not modify the input string.

Constraints

0 <= len(s) <= 10^5
The input may contain letters, digits, whitespace, punctuation, and Unicode characters
Character comparison is case-sensitive

Function Signature

def has_unique_characters(s):

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