Posted by: elenadbutler | January 14, 2009

## Bus-wait and Rubik’s Cubes

Two recent items of note in the NYT:

Recently, a group of Harvard students were featured for their work on the Bus-Wait problem. The problem is this: you’re waiting for the bus, and start to get bored. You wonder if you should just walk. Scott Kominers and friends found that you should almost always wait. If you start walking and catch the bus on your way, you’re just getting on the bus you would have caught by waiting, so that won’t save you time. And if you start walking and you miss the bus, then you’re totally screwed.

Interestingly, if you have a very short journey, and the buses tend come at long intervals (say, half an hour), you should walk. But, since most buses come often and move faster than you can walk, waiting is usually the best option. So go ahead, be lazy.

Another cool article is about Dr. Jessica Fridrich, who invented the most popular method for solving a Rubik’s Cube as quickly as possible. To use her method, the speedcuber (speedcubist? haha) must know and be able to deploy no fewer than 53 algorithms. When using her method, the cuber first solves the top two layers, using the face with the white square in the middle as the top. Then, to solve the bottom layer, the cuber has to get all the yellow squares on the bottom, a process called “orientation,” which has potential 40 algorithms  to use. The last step is called permutation (yay!) and requires the use of one of 13 algorithms to finish off the cube.

As cool as this sounds, to tell the truth, Rubik’s cubes kind of scare me. A friend of mine from high school did Rubik’s cube speedsolving competitions, and watching him was pretty impressive. Have any of you learned to solve a Rubik’s cube? How long did it take? Maybe once this final is over I’ll finally learn!

## Responses

1. Nice Blog

2. Just dropping by.Btw, you website have great content!

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3. I learned to solve it when I was in tenth grade, 25 years ago! I got inspired by a fourth grader in the school who would sit next to me on the bus on our way back home. He once solved it in 42 seconds. I recently solved it in 52 seconds. I love this blog. Good luck, Mario.