Factoring factorials

2014-01-27

There was a new post on Programming Praxis a few days ago that seemed pretty neat:

Given a positive integer n, compute the prime factorization, including multiplicities, of n! = 1 · 2 · … · n. You should be able to handle very large n, which means that you should not compute the factorial before computing the factors, as the intermediate result will be extremely large.

Graph coloring

2014-01-15

Here’s another one from /r/dailyprogrammer:

… Your goal is to color a map of these regions with two requirements: 1) make sure that each adjacent department do not share a color, so you can clearly distinguish each department, and 2) minimize these numbers of colors.

Essentially, graph coloring.

Graph radius

2014-01-14

Here’s a quick problem from the DailyProgrammer subreddit. Basically, we want to calculate the radius of a graph:

radius(g) = \min\limits_{n_0 \in g} \max\limits_{n_1 \in g} d_g(n_0, n_1)

Overlapping circles

2014-01-03

Here’s a quick little programming task that I came to via a post on L2Program (who in turn seems to have found it on Reddit). The basic idea is to take a given list of circles and to determine the area enclosed (while correctly accounting for overlap).

Edges to adjacency

2013-12-23

Another quick one, this time from /r/dailyprogrammer:

Your goal is to write a program that takes in a list of edge-node relationships, and print a directed adjacency matrix for it. Our convention will follow that rows point to columns. Follow the examples for clarification of this convention.

Rock-paper-scissors

2013-12-21

Quick and to the point: let’s write a program to play rock-paper-scissors¹².

Twitter puddle

2013-11-30

This one has been sitting in my backlog for a while and its been a while since I’ve gotten to write a programming post¹, but now seems as good time as ever: Twitter puzzle

Making music, part 3: Making noise

2013-11-12

Last week we parsed some music. That post was in a bit of a hurry, so we had to leave off a fair few important pieces (like ties and slurs for one; chords for a rather bigger one). We’ll get to them soon, but for now we want to actually get something playing back.

Making music, part 2: Taking shape

2013-11-07

It’s been a bit, but as you may have noticed life is a bit mad at the moment. But I’ve still made some progress.

When we left off last time, we’d finished the first step towards making some lovely music with Racket: tokenization. Now we want to take those songs and form them into something actually approaching music.

Making music, part 1: Reading ABC notation

2013-10-29

It’s been a bit since I’ve had time to post¹, but I’ve got an interesting new project that I’ve been working on. It’s a bit more complicated, ergo spread out over a few posts, but those tend to be the more interesting posts anyway, eh?

The basic idea is that I want to be able to write and play music in Racket. One end goal would be to make a library available for the C211 class to give them something else to work with (in addition to <a href="//blog.jverkamp.com"/wombat-ide/c211-image-api/">images and <a href="//blog.jverkamp.com"/wombat-ide/c211-turtle-api/">turtles). To that end, here’s my current plan of attack²:

Write a lexer for ABC notation to turn raw text into a list of tokens
Write a parser to turn those tokens into a song (for example dealing with the interactions between key signature/accidentals and meter/note duration)
Use the rsound library on Planet2 / pkg to play back individuals notes and chords
Tie it all together to play a parsed song in ABC notation using the rsound library
(maybe): Use the rsound library to save ABC files as WAV audio
(maybe): Figure out the format and save ABC files as MIDI
(maybe): Render songs as music sheets/li>

Sounds like fun! Let’s get started.