[matho]

Here's my problem with using quicksort at interview:

A developer who writes an implementation of the quicksort algorithm as part of their job should usually be removed from their post for incompetence.

The interview process should be a two-way procedure which also allows the candidate to understand what is expected of them in a role (and make their decision about the job accordingly). If regurgitating quicksort is expected, then this is a fair test: otherwise, this is not how you should be presenting the job.