I was solving [AoC Day 21](http://adventofcode.com/2017/day/21), which for part B asks you to run 18 iterations.
First I've made Python/numpy solution (runs in 0.40 sec), which scales nicely even to 24 iterations (runs in ~16 sec). My [Nim solution](https://gist.github.com/anonymous/bc528ced2cb4faeede915f1f8d0211ee) runs 18 iterations in 0.14 sec, but 24 iterations take ~8 sec. Here is the [input](https://gist.github.com/anonymous/795715d5f5263565b83733993bb1002f). \--- I'm Nim beginner so I'm think I could get speedup and better scaling if I maybe use some other data structure (perhaps arrays? I couldn't have proc's return type to be openArray, so I decided to use seqs). Do you have any ideas how to speed this up?
