At the appointed time of 6:30 pm, the Amazon recruiter called and went over the plan again - she would mail me the programming problem, and I would need to mail back my solution within 90 minutes. The problem had two parts; the first part was specific, and the second part asked for a more general solution. Only the first part was required.
When I got the mail, I read through carefully, noting the original and extension problems. Then... I smiled as I knew how to solve the general case. It took me about half the alloted time for me to write a program to solve the problem including the general case, document, and test. So I mailed back early and included more explanation, and felt pretty good about it.
I can't explain the exact question (the mail said it was to be kept confidential), but I think it is OK to mention the problem was an instance of "circuit satisfiability", a well known problem in computer science.