The 1999 U.S./Canada WPC Qualifying Exam
I remember about a year ago talking via email with Wei-Hwa Huang about strategies for finding solutions for puzzles. (The discussion was later placed on the Fathom It! website at http://www.mountainvistasoft.com/t-uniq.htm .) One thing that stuck in my mind is that puzzle magazines tend to give solutions for their puzzles without proving that the solutions were unique or showing how one would go about reaching that solution. It seems to me that, if you can't solve a problem, the very least you can do is to learn how to solve it, so that perhaps you can apply the same strategies to future problems.
With that in mind, here are complete solutions to the 1999 World Puzzle Championship qualifying exam for the U.S. and Canadian teams, along with my personal comments. (If anyone who took the test has any comments of their own, feel free to email them to me and I'll add them in as I find the time.)
I will not even try to pretend that I was able to solve all of these problems in 90 minutes, but after another two hours, I did have most of them solved. I'm trying to avoid looking at the solutions for problems that I haven't solved yet, and some of them are hard to describe, so maybe not everything is up here yet.
(In fact, I broke down and looked up the answers to #15 and #26, and I can't think of a single useful thing to say about them. If someone else wants to comment on the solutions to those, I'd be happy to put them here.)
General Comments: To qualify for the US team, you had to average 13 points every ten minutes throughout the test. I've got a lot of respect for anyone who can do that. I only picked up about one point per minute and I made a few mistakes along the way.
My thanks to World Puzzle Championship/Team USA, both for putting on a marvelous event and allowing me to set up this fan site of sorts.