Archive for February, 2007

Choosing up sides

Tuesday, February 20th, 2007

A while ago I wrote about the playground ritual of choosing teams for a ball game. The simplest algorithm has two captains, A and B, who take turns choosing players until everyone is assigned to one team or the other. Call this the ABAB algorithm. Donald B. Aulenbach suggested a very easy modification that produces […]

Working on the railroad

Saturday, February 10th, 2007

The March-April issue of American Scientist is now available on the Web; paper copies should be on their way soon. My column is about hump yards and turnouts and wyes—in other words, about algorithms for railroad workers. “Computing with locomotives and box cars takes a one-track mind.” There’s a small puzzle near the end of […]

Postage due

Thursday, February 8th, 2007

There was a line at the Post Office window, so I went to the self-service counter, plopped my letter on the scale, and found that it weighed a whisker under two ounces. I bought stamps from the machine and stuck on a 39-cent and a 24-cent. I was just about to drop the letter in […]

The stepchild

Tuesday, February 6th, 2007

A new jeremiad foretelling the doom of computer science as an academic discipline has just been published by the British Computer Society. It’s by Neil McBride, principal lecturer in the School of Computing, De Montfort University, Leicester.
Some of what McBride says strikes me as breathtakingly wrong-headed:

Now vastly complex applications for businesses, for science and for […]

The land surveyor’s algorithm

Friday, February 2nd, 2007

Here’s an algorithm for finding the area of any simple polygon. First, assign an orientation to every edge by drawing an arrowhead pointing in the counterclockwise direction around the cycle of edges. After this labeling, each vertex of the polygon becomes the “tail” endpoint of one edge and the “head” endpoint of another. Now, for […]