The earliest memory I have of ‘programming’ is in the early/mid 90s when my father brought home a computer from work. We could play games on it … so of course I took the spreadsheet program he used (LOTUS 123, did I date myself with that?) and tried to modify it to print out a helpful message for him. It … halfway worked? At least I could undo it so he could get back to work…

After that, I picked up programming for real in QBASIC (I still have a few of those programs lying around), got my own (junky) Linux desktop from my cousin, tried to learn VBasic (without a Windows machine), and eventually made it to high school… In college, I studied computer science and mathematics, mostly programming in Java/.NET, although with a bit of everything in the mix. A few of my oldest programming posts on this blog are from that time.

After that, on to grad school! Originally, I was going to study computational linguistics, but that fell through. Then programming languages (the school’s specialty). And finally I ended up studying censorship and computer security… before taking a hard turn into the private sector to follow my PhD advisor.

Since then, I’ve worked in the computer security space at a couple of different companies. Some don’t exist any more, some you’ve probably heard of. I still program for fun too, and not just in security.

But really, I still have a habit of doing a little bit of everything. Whatever seems interesting at the time!

Project Euler 3

2012-11-05

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143? – PROJECT EULER #3

Project Euler 2

2012-11-04

Each new term in the Fibonacci sequence is generated by adding the previous two terms.

By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms. – Project Euler #2

Project Euler 1

2012-11-03

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000. – Project Euler #1

Project Euler

2012-11-03

I’m going to start posting a series working out the solutions to Project Euler’s problems. Mostly I’ll be working in Racket (at least for now), although if another language has a particularly interesting / efficient solution that Racket cannot match, I’ll post that as well.

The Sum Of The First Billion Primes

2012-11-01

This problem from Programming Praxis came about in the comments to my last post and intrigued me. So today, we are trying to sum the first one billion primes. Summing the first hundred, thousand, even million primes isn’t actually that bad. But it takes a bit more effort when you scale it up to a billion. And why’s that?

Pandigital Sums

2012-10-31

Yesterday’s new post from Programming Praxis asked us to find all triples (a, b, a+b) such that a and b are three digits and a+b is four and concatenating the numbers results in a pandigital number (one with all 10 digits). After that, find the smallest individual number in any of these triples.

Bitvectors in Racket

2012-10-29

A bit shorter on time today, so I’ve just got a quick library that I worked out to solve another problem (I’ll post it later this week when it’s actually working). Basically, when you need to store a heck of a lot of binary flags and don’t want to waste space, the best way to do it would be as one long list of bits. It’s really easy to do in a language like C, but how can you do it in Racket?

Pythagorean Triples

2012-10-27

When Programming Praxis mentioned that the newest challenge sounded like a Project Euler problem, they were’t wrong. Basically, the idea is to count the number of Pythagorean Triples with perimeters (sum of the three numbers) under a given value. The necessary code to brute force the problem is really straight forward, but then they asked for the count up to one million. With the brute force O(n^2) algorithm (and a relatively high constant), that’s not really feasible. So that’s when we have to get a bit more creative.

Determining country by latitude/longitude

2012-10-25

Yesterday I talked about how I used censorship research) where the API will report longitude and latitude but not always country.

Determining country by IP

2012-10-24

In my line of research, it’s often useful to be able to identify where a country is using just it’s IP address. I’ve done it a few different ways over the years, but the simplest I’ve found is using the MaxMind GeoLite Country database directly. To speed such lookups, I’ve written a simple Python script that can run a whole series of such queries for you.