[nradov]

We use some simple coding problems during interviews. Subjectively they seem to work, but I have no objective way to quantify how well they work.

My favorite question to ask involves walking through a tree structure and summing up a particular property of all the leaf nodes. It can be done recursively or (preferably) iteratively. About half the candidates can't really do it. I often see answers that only process two levels of the tree, or aren't thread safe, or include lots of duplicate code, or simply don't work at all.

Joel Spolsky has some good suggestions on the subject. http://www.joelonsoftware.com/articles/GuerrillaInterviewing...