Being able to put together a sort from compares and swaps (or inserts, or whatever you have available) is at least evidence that you won't either panic or storm off when the tools you have are something less than ideal.
> [...] is at least evidence that you won't either panic or storm off when the tools you have are something less than ideal.
Maybe. Maybe not? Most of the time our tools are far from ideal anyway. Most of the time the important factors are a direct consequence of management/leadership/team. (Deadlines, feature creep, crazy engineering practices - eg. hand rolling sort, crazy interview practices - 8 hours of hardcore interview or whatnot, and so on.)
* I always have access to a decent stdlib and would not need to implement sort itself
* But I do need to design and implement bespoke algorithms
The algorithms are nothing groundbreaking - they're things like how to grow and shrink a buffer when reading from a socket. But I'd struggle if I didn't know a few examples of different algorithms and how to think about their trade offs, and basic sorting algorithms (not like this article!) are ideal for that. Maybe I'm doing unusual work but it doesn't really feel like it.
Edit: To put it another way: in a past job, we had some unfortunate examples of people being hired whose ability to work with algorithms was sadly not up to scratch, and it had a serious practical impact on their ability to do their job. If they had been asked a few questions about sorting algorithms in their interview then that could have been avoided.
Of course, knowing about specific algorithms is handy, and adjusting the question to find an appropriate spec to implement for a given problem could be a nice touch.
I think that either approach above is strictly better than implementing algorithms from memory and would produce a far better signal.
The project was written in SmallTalk, running on a very old implementation (last updated in 1999 I think) and we had a problem where clicking on column headers in the UI to sort would be very slow if most of the values were equal. The problem was that the standard library array sort was quicksort (which also meant that sorting on several columns broke since quicksort isn't stable), but since SmallTalk makes these things possible when you need to replacing the stdlib quicksort with mergesort was actually a fairly simple operation.