I went pretty naive with my solution: https://github.com/sb8244/advent-of-code-2019/blob/master/lib/two.ex
I’m going for speed to solve (124 pt 2), so end up with whatever popped in my head first. I am surprised with whatever I did that caused part 2 to solve in < 500ms though, given what I’ve heard about others taking 2s. The speed difference may have to do with my use of maps rather than lists. I learned last year that, essentially, I should always use Map for these problems.
I fully expect this solution to evolve significantly in future challenges—as the problem statement hinted at. In particular, I expect this to quickly evolve into an interpreter that supports loops and conditionals, which is where they’ll throw in performance doozies.
I got part 2 down to about 50ms on my machine after removing a stupid misstake where I was executing the “program” twice for every multiplication..
