Ask HN: coding challenges as part of interviews: yes or no?

I also worked for a company once who had several enthousiastic , seemingly bright people with somewhat limited experience come in for interviews, but they didn't make the cut because they didn't pass some coding challenges. The guy who did get hired went to a good school and was a good coder, but was way too arrogant, difficult to work with and repeatedly refused to do what his manager asked him to work on. And how did that guy interview other candidates? He screened them by their education, and when they would come in he would give them one programming challenge without asking any other questions. Nobody seemed to realize that there were big problems with the company's hiring strategies and that developers themselves were largely to blame for that.

I use a simple coding challenge as a weeder question. It requires basic use of recursion (without explicitly saying so) -- no math, no big-O, no gotchas, just writing a simple recursive function to process a small tree. It takes decent coders a few minutes to complete. Less-than-decent coders really struggle with it.

This is only a wheat/chaff separator, though. If possible, I like to see code from actual projects they've worked on to get a feel for the bigger picture (tip: open source your personal projects and obsess a bit over the code, so you have something to show off). Plus there's all the other non-code aspects to the interview.

This reminds me of a group of main frame programmers I knew who had been forced to become Perl web developers. About a month later they were asked to hire another Perl programmer and one of their interview questions was what's the difference between 'chomp' and 'chop' (chomp removes the final character of a string if it's a newline, chop does it regardless).

They were shocked that the interviewee didn't know the answer because they considered it basic knowledge, "it's in the first chapter for gosh sake." The first chapter in this case covered differences between Perl 4 and Perl 5.

In Perl 5, nobody uses 'chop', they all use 'chomp.' Many experienced Perl programmers might even have forgotten that 'chop' existed.

And that's my major problem with gotcha questions, they tend to be pretty far from measuring if a person can actually write productive code.

Haha yep. I like that movie no matter how ridiculous it is. Some of the motivational techniques in that movie would work wonders.

They're a necessity. For the simple reason that too many people lie on their CV, no matter how good their CV looks you have no-idea how much of it is accurate.

Obviously there are cases where you wouldn't use it, but generally they only apply when you know someone's capable of coding anyway (i.e. due to an indisputable reputation, experience working with them, etc.).

However as a predictive measure it's fairly limited in that it's a binary indicator. If someone fails then there's a fair chance they're a terrible developer, if someone passes there's a fair chance they're not a terrible developer.