Whether you will/have celebrate(d) Christmas, Hannukah, Kwanzaa, the southern solstice, HumanLight, Saturnalia, or something else entirely: have a peaceful and contented time.

One of my colleagues came into my office the other day, and said to me: If p is prime and greater than 3, prove that p² – 1 is divisible by 24. Interested readers might want to try this for themselves: it’s not particularly difficult. Of course I started in…

For the most part, forget about space complexity. Time complexity is the important one. You can often trade off time for space, though, so be aware of how much you’re using. O(1), or constant time, is the best option: if you know the array index, great! Unfortunately, hash tables usually…