Okay -- backup. I pulled out my HTC smart phone. At least I could review the photos I'd taken of my cousin's wedding.
Sorry -- battery dead.
So I was stuck reading the copy of Technology Review in my backpack. Nothing wrong with Technology Review, it's an excellent magazine. But it's nice to get away from thinking about technology too often. I think this is one reason engineers are so attracted to cycling. Bikes are so amazingly elegant in their simplicity.
Technology's review theme was the top 10 emerging technologies of the year. There among those listed was solid state batteries. Obviously there's a lot of room for improvement there.
So I switched between Technology Review, making notes on my maze program on a pad of engineering paper I had in my backpack, and just thinking. Thinking is good, too. In an earlier age we used to do it more than we have time for now as each year an ever greater fraction of our awake hours are filled with external stimulation. Another advantage to cycling, or even better running, is it provides time to think... that is if it is done without an iPod, a gadget I've so far avoided.
Anyway, here's another boat puzzle.... this one my previous algorithm can't solve, but is solveable with two seats on the boat. It resulted from another conversation I had on the train. Those "animals" connected with line segments cannot be left unsupervised on the same shore. I've indicated animals with numbers, with or without prime marks, where I used the prime marks to reflect the clear symmetry of this puzzle. The circled animals are the maximal independent set, and must be left behind on the first trip across to avoid immediate failure.