Authorship attribution: Part 2

Last time, we used word rank to try to figure out who could possibly have written Cuckoo’s calling. It didn’t work out so well, but we at least have a nice framework in place. So perhaps we can try a few more ways of turning entire novels into a few numbers.

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A programming puzzle: f(f(n)) = -n

Two Programming Praxis puzzles in a week? Madness! Let’s do it!

This time, the puzzle at first seems rather minimal:

Write a function f so that f(f(n)) = -n for all integers n.

If you haven’t seen this problem before, take a moment to think though it. It’s a neat little problem–a close cousin to a lateral thinking puzzle.

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Approximating Pi with Buffon's Needle

I’m a bit late for Pi Day, but Programming Praxis had a neat problem on Friday that I wanted to check out:

Suppose we have a floor made of parallel strips of wood, each the same width, and we drop a needle onto the floor. What is the probability that the needle will lie across a line between two strips?

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Triangle Trilemma

Four points, a square?) and comes originally from a Google Code Jam problem. The problem is stated simply enough

Accept three points as input, determine if they form a triangle, and, if they do, classify it at equilateral (all three sides the same), isoceles (two sides the same, the other different), or scalene (all three sides different), and also classify it as acute (all three angles less than 90 degrees), obtuse (one angle greater than 90 degrees) or right (one angle equal 90 degrees).

But once you start implementing it, that’s when things get more interesting. 😄

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Four points, a square?

Another post from Programming Praxis. This one was originally intended for Friday but they posted it early, so I figured I would go ahead and do the same. The problem is actually deceptively straight forward:

Given four points, do they form a square?

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