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. That’s about where I am today!

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

Nested Primes

2012-12-22

Yesterday’s post from Programming Praxis poses an interesting problem: find the largest prime n such that the result of repeatedly removing each digit of n from left to right is also always prime.

For example, 6317 would be such a number, as not only is it prime, but so are 317, 17, and 7.

Ludum Dare 25 - First favorites

2012-12-18

This past weekend was Ludum Dare 25, the newest in a competition that has been running for more than 10 years where the entire goal is to go from nothing to a complete video game in 48 hours or less. I didn’t manage to participate this time around, but I’m looking forward to trying it out next April (they run every four months in April, August, and December).

Narcissistic Numbers

2012-12-14

Today’s post from Programming Praxis posits an interesting problem: how can we (efficiently) find all of the narcissistic numbers (in base 10)?

Generating non-repeating strings

2012-12-12

Based on this post from Programming Praxis, today’s goal is to write an algorithm that, given a number N and an alphabet A, will generate all strings of length N made of letters from A with no adjacent substrings that repeat.

So for example, given N = 5 and A = {a, b, c} the string abcba will be allowed, but none of abcbc, ababc, nor even aabcb will be allowed (the bc, ab, and a repeat).

It’s a little more general even than the version Programming Praxis specifies (they limit the alphabet to exactly *A = {1, 2, 3} *and more more general still than their original source which requires only one possible string, but I think it’s worth the extra complications.

Numbers of Wirth

2012-12-10

Niklaus Wirth gave the following problem back in 1973:

Develop a program that generates in ascending order the least 100 numbers of the set M, where M is defined as follows:

a) The number 1 is in M.

b) If x is in M, then y = 2 * x + 1 and z = 3 * x + 1 are also in M.

c) No other numbers are in M.

(via Programming Praxis)

It’s an interesting enough problem, so let’s work out a few different ways of doing it.

One Billion Primes - Segmented Sieve

2012-11-29

After a sum of the first billion primes post (originally from Programming Praxis), I decided to finally write a segmented version of the Sieve of Eratosthenes.

List algorithms and efficiency

2012-11-21

Programming Praxis’ new challenge(s) are to write three different list algorithms three times, each with a different runtime complexity. From their first post last week we have list intersection and union and from a newer post yesterday we have the difference of two lists. For each of those, we want to be able to write an algorithm that runs in O(n²) time, one that runs in O(n log n), and finally one that runs in O(n). It turns out that it’s more of an exercise in data structures than anything (although they’re all still technically ’list’ algorithms), but it’s still interesting to see how you can achieve the same goal in different ways that may be far more efficient.

Project Euler 9

2012-11-15

A Pythagorean triplet is a set of three natural numbers, a b c, for which,

a² + b² = c²

For example, 3² + 4² = 9 + 16 = 25 = 5².

There exists exactly one Pythagorean triplet for which a + b + c = 1000.

Find the product abc. – PROJECT EULER #9

Project Euler 8

2012-11-14

Find the greatest product of five consecutive digits in the 1000-digit number. – PROJECT EULER #8

Project Euler 7

2012-11-12

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10 001st prime number? – PROJECT EULER #7