Ponder This: A Q&A with puzzle master Oded Margalit

The Ponder This puzzles began as a way for IBM researchers to increase productivity. Some employees found that when they got stuck on a problem, that immersing themselves in solving a completely different type of problem helped get them back on track. Researchers started sharing their most ambitious puzzles, and eventually this evolved into a published monthly challenge — Ponder This.

Oded Margalit, a Machine Learning researcher at the IBM Research — Haifa lab, took on the role of unofficial Ponder This puzzlemaster in February, 2009.

First and foremost, I love puzzles and have been doing them since I was a little kid. I think Ponder This is a great connection to IBM's "think" motto and a good way to extend IBM to the general public. I also like to imagine all the smart people who work on the puzzles as a potential think tank for future IBM challenges!

I generally make them up or use ideas that people submit. Occasionally, we have used puzzles from other sources, but we found that many of our users are already familiar with anything that's been published. The challenge is that our original puzzles haven't been tested.

As far as level, each puzzle is posted for a month before the solution is revealed. Twice, we left a puzzle posted for two months because it was too hard. Other times, the solutions start coming in so quickly that we know it's too easy. But I'm getting the hang of what works.

Every puzzle has a story. The most memorable one for me was a few years ago: one of our regular solvers was hospitalized. When his daughter would visit him, she brought along a Ponder This puzzle. The family used it to help pass the time. He sent in the solution from his bed in the ICU!

Another pair of solvers were inspired by one of our puzzles in their own research. Eventually, their ideas were published in the prestigious Physics Review Letter journal, along with a special citation for Ponder This.

The last research I did showed that we have about 2,500 solvers from around the world.

We plan to continue, and we welcome new solvers and suggestions. We are also happy to receive suggestions for a significant value — send us a meaningful number and we'll create a puzzle around it.

With a nod to IBM's centennial year, all of the 2011 puzzles are being connected to IBM. The solution to one puzzle, for example, was 77,147 — the number of dollars the computing system Watson won on Jeopardy! May's puzzle was based on bar codes, an IBM Research invention.

Oded adds that he considers the perfect puzzle as being easy to describe yet difficult to solve, and most importantly, that the solution is easy to understand.

"Just look around, anything in the world can be made into a puzzle."

There are 80 students in a school. Each of them eats fruit for dessert every day, and the available fruits are apples, bananas, and cherries.

Find a possible setting of desserts for 14 days, such that for every set of three students, there exists at least one day in which they all ate different desserts. Please supply your solution as a list of lines, in which each line is 80 characters long and contains the letters A, B, and C.

Labels: ibm research, ibm100, puzzle