Archives for November 2011

November 2011 (4)
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PCPlus 299: Answering difficult questions

I’d just read a book called Introduction to the Theory of Computation by Michael Sipser and found it fascinating enough that I tried to encapsulate what NP-complete means in a 2000-word essay for October 2010’s issue. Was I successful? You’ll have to read it to find out. […]


Blog issues. Or GraffitiCMS issues. Or GoDaddy issues.

Apologies to all if you saw a whole bunch of posts appearing and disappearing in the past hour. I’m having – all of a sudden – extreme problems with publishing a blog post from Windows Live Writer to this blog, which is hosted on GoDaddy. This first happened on November 5, but I thought it was a transient issue and ignored it. And then over the weekend I wrote the “adding parentheses” post but it would not publish, no matter what. I finally published it just now with Graffiti’s admin app, which is not nice. […]


Postfix to infix, part 2: adding the parentheses

Once upon a time (all right, it was in May 2010), I wrote an article for PCPlus about generating all possible arithmetic operations with the standard four operators. You can read the article here. After I’d written it, I wrote a blog post about how easy it was to convert the RPN form (Reverse Polish Notation) of the expressions I was generating into the standard algebraic or infix form. You can read that post here. (Note that this post will make more sense if you read these two articles first to get some background.) […]


PCPlus 298: Solving Rubik’s Cube

Ah, memories, memories. For September 2010’s issue I wrote about how to solve Rubik’s Cube, and it allowed me to revisit my days at Kings’, London, when I first came across the puzzle. Back in those days (and probably even now), the Maths Society at Kings had a fun weekend away in Windsor Great Park where we’d have talks about recreational mathematics. (Yes, I know, many people don’t think “recreational” and “mathematics” can be in the same sentence, but bear with me here.) Of course, it was an occasion for too much drinking and smoking and playing 3-card brag and staying up all night, but in 1979 we discovered a puzzle that pushed all that aside: Rubik’s Cube. […]