I am a fan of using puzzles in interviews, especially for developers. But it is important to do it right and to draw the right conclusions. Here are some things that I have learned over the years.
1. Puzzles should be just one of many different parts of the interview.
2. Try to find a set of puzzles that works for you and use the same puzzles with many candidates to get better comparability.
3. Focus primarily on approach and behavior and only secondarily on outcome.
4. Unless the position specifically calls for ability to think under stress (e.g. certain ops positions), try to put the candidate at ease. Being in an interview is stressful for many folks.
5. Ask for a vocalization or visualization of the thought process.
So what are some of the things that I believe can be learned from puzzles?
- Is someone naturally curious?
- Do they think before talking?
- Can they explain how they are thinking about a problem? Verbally? Visually?
- Does someone get easily frustrated?
- Do they ask for help if they get stuck?
- How does someone react to getting an answer wrong? Give up or persist?
If applied right, I believe puzzles can provide a lot of insight along these lines into how candidates will approach problems they encounter. I was reminded of all of this by the Amazon booth at OSCON. Every day they provided a new code puzzle. I enjoyed solving them, but possibly even more enjoyed observing the reactions and approaches of others!
