Finding Prime Factors

I have been working in my spare time on the Euler project problems. Now, for most languages, these problems aren’t too big of a deal, because most modern languages do much of the work for you (at least on the early problems). I’m working on learning c++ though, and it doesn’t do a lot of the work for you, which is great in my opnion. One thing it’s really helping me with is number theory (or whatever it would actually be called). I never went to school for computer science, so I lack much of the math that many developers have. That said, nealry every problem that Euler has, is a really great test, not only of programming ability, but of number knowledge.

My most recent problem I’ve been working on is refactoring my code to solve problem 3. Now, this problem isn’t that difficult. Where the difficulty lies is in the calculation speed. My original program solved this one in about ten minutes I think (again, if you’re sporting something like ruby, php, perl, etc, you have probably solved this faster because they built good calculation methods into the language). In going bad to refactor though, I’ve been focusing more on wasy to more efficiently calculate these things via brute force (I’m sure there’s an equation for this out there, but I’m using a for loop). Here is the list of things that I found to speed up the calculation process.