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The coding interview that I failed
I’m talking a lot about candidates and the hiring process we go through right now. I thought it would only be fair to share a story about an interview task that I failed.
That was close to 20 years ago, and I was looking for my first job. Absolutely no professional experience and painfully aware of that. I did have a few years of working on Open Source projects, so I was confident that I had a good way to show my abilities.
The question was simple, write the code to turn the contents of this table into a hierarchical XML file:
In other words, they wanted:
To answer the question, I was given pen and paper, by the way. That made my implementation choices quite hard, since I had to write it all in long hand. I tried to reproduce this from memory, and it looks like this:
This is notepad code, and I wrote it using modern API. At the time, I was using ADO.Net and the XmlDocument. The idea is the same, however, and it will spare you going through a mass of really uninteresting details.
I got so many challenges to this answer,though. I relied on null being sorted first on SQL Server and then on the fact that a parent must exist before its children. Aside from these assumptions, which I feel are fairly safe to make, I couldn’t figure out what the big deal was.
Eventually it turned out that the interviewers were trying to guide me toward a recursive solution. It never even occurred to me, since I was doing that with a single query and a recursive solution would need many such queries.
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