Is it correct to ask to solve an NP-complete problem on a job interview? [closed]

Answer 1

I don't see any problem with asking something like this. Also, programmers should NOT be expected to recognize NP-complete problems by rote. They should, however, be able to identify that their algorithm is potentially slow regardless of whether a given problem is NP-complete.

Answer 2

I don't see a problem with this, but I do somewhat question the usefulness of these sorts of questions in interviews in general.

The benefit of asking questions like this, as an interviewer, is see how the person approaches a problem, and how they think. If you tell them to talk it out, you can find out quite a bit about how they will approach a difficult problem.

That being said, during an interview, most people aren't at their best - so throwing something that's somewhat "tricky" like this is often overkill, IMO.

Answer 3

No, it's rude and a sign that the interviewer just likes being in a position of power. Haha, peon! I know the answer, and you don't! And boy, do I love to make you squirm trying to come up with it!

About the only way it could be even slightly valid as a useful interview question is if it were a well-known question or one that was somehow obviously NP-complete, and asked in a way that encouraged discussion of feasibility.

Answer 4

There is nothing wrong with giving an NP-complete problem as a programming challenge during an interview. I only see something wrong with expecting to find a polynomial-time solution to the problem during the interview.

An interviewer should want to see how a candidate deals with a variety of situations -- including situations that the candidate can't find an easy solution to. "Impossible" questions show how the candidate reacts when there's no simple solution. Does the candidate just give up? How many different attempts does the candidate search? How far-reaching are the solutions tried? When does the candidate ask for help -- and how? Does the candidate complain that the problem "isn't fair"?

In short, such an interview question isn't about solving P=NP... it's a psychological answer.

Answer 5

It's good to ask a question that is hard to answer, to see how a programmer reasons through a problem.

But it all depends on how the interviewer asks the question, and prompts the programmer towards a solution if they aren't a mathematical genius (i.e. to see how they reason, and how they react to questions like "that's a good start, but what if...") rather than to detect if they are autistic and can provide an optimal solution in 4.3 seconds).

It's worth remembering that interviews are highly stressful affairs in which many people find such questions very difficult to answer well - a much simpler question will usually suffice without putting the interviewee under undue stress/pressure.

If you do it to deliberately try to see how they deal with stress is just stupid - that isn't the sort of stress a programmer has to deal with in their job, so you're not testing anything worthwhile.

Answer 6

I think it's valid to ask a question you know the interviewee won't know the answer to.

Everyone encounters problems they don't know the answer to. This type of question will give you insight as to what the interviewee's internal process is. If they logically conclude things and start to formulate a correct answer, even if it's not the best dynamic programming algorithm for it, it shows that they can reason well and discover an answer.

Also, since they likely don't know everything about the problem, this sort of question lets you see how comfortable the interviewee is with asking for help or clarification.

I think the best way to answer this type of question is to ask for any clarifications if something is missing or not well known, and then postulate an answer, pointing out why you think it is correct, and why it likely isn't the best solution.