Second, it's a covert test for culture fit. Are you young (and thus still OK with grinding for tests)? Are you following industry trends? Are you in tune with the Silicon Valley culture? For the most part, a terrible thing to test, but also something that a lot of "young and dynamic" companies want to select for without saying so publicly. An AI startup doesn't want people who have family life and want to take 6 weeks off in the summer. You can't put that in a job req, but you can come up with a test regime that drives such people away.

It has very little to do with testing the skills you need for the job, because quite frankly, probably fewer than 1% of the SWE workforce is solving theoretical CS problems for a living. Even if that's you, that task is more about knowing where to look for answers or what experiments to try, rather than being able to rattle off some obscure algorithm.

It's interesting how powerful contraint solvers are (Ive never used one).

But actually all of these problems are fairly simple if we allow brute force solutions. They just become stacked loops.

It's about signaling. That's all it is. At least it's not finance where it's all dictated by if you were born into the right family that got you into the elite boarding schools for high school, etc. I would've never made it into finance unless I did a math phd and became a quant.

Really? This kind of interview needs to go away.

However, coding interviews are useful. It's just that "knowing the trick" shouldn't be the point. The point is whether the candidate knows how to code (without AI), can explain themselves and walk through the problem, explain their thought processes, etc. If they do a good enough reasoning job but fail to solve the problem (they run out of time, or they go on an interesting tangent that ultimately proves fruitless) it's still a "passed the test" situation for me.

Failure would mean: "cannot code anything at all, not even a suboptimal solution. Cannot reason about the problem at all. Cannot describe a single pitfall. When told about a pitfall, doesn't understand it nor its implications. Cannot communicate their thoughts."

An interview shouldn't be an university exam.

They aren't testing if you can write a solver. They are testing if you can use bricks that solvers are built out of because other software when it gets interesting is built out of the same stuff.

That's a bad algorithm, then, not a greedy algorithm. Wouldn't a properly-implemented greedy algorithm use as many coins as possible of a given large denomination before dropping back to the next-lower denomination?

If a candidate's only options are to either use a constraint solver or to implement a naïver-than-usual greedy algorithm, well, sorry, but that's a no-hire.