Since in the past few years I've only been interviewing freelancers for temporary positions on the projects I've worked on, I kept going with this simpler task. Now even with that, some people struggle. And I see that as a very bad sign. But I'm always giving hints and helping. I always start by saying that if you have any questions or feel like discussing an idea, feel free. And if they keep thinking and don't tell anything I'll start the discussion. (But that's part of the test, because, you know, things like this happen during real work: you get stuck, you don't understand the requirements, etc. And then I will want you to reach out and ask/discuss.)
Another task I do during the interviews is code review. Even if you do badly on the first one. The piece of code (now actually two pieces) has a lot of room for improvement, while only about 20 lines long. That's a totally different kind of task, less about problem solving and I guess less prone to cause anyone to freeze.
Oh. We kind of talked past each other then. Sorry!
Just today I had ~15 minutes to craft a basic SQL update statement generator based on an (almost) arbitrary JSON input. Save for me misunderstanding the requirements initially, I aced it and the interviewer was impressed.
General problem-solving and chatting about real problems that the company has I found to be the best format of technical interviews. One experienced programmer can extremely easily call out BS if the candidate is faking their expertise.
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As for me freezing, yeah, it can happen but I accepted it. I can't have all the IT problem space in my head all the time. I expect the interviewer to be flexible in these cases. If not, oh well, life goes on.
I am fairly experienced and I can simulate stuff in my head quite quickly but this often has a detrimental effect -- I get a few ideas, see all their flaws and get an analysis paralysis. I flunked one otherwise promising interview by doing this.
Sometimes you just freeze, you know. I have confidence of having excellent problem-solving skills but they are not always summonable on demand right at this minute.
I have a fairly successful -- if very rich on employers -- career so I should probably view the above as a personal weakness and not as something inherently bad, but I am not sure.
How do you feel about such people?
(I usually prefer a take-home assignment even if it's more work. It gives me a chance to show excellent craftsmanship and attention to detail, which I really want to demonstrate during the interview process.)