• if every iteration has unique state => iterative
• if results can be reused => recursive + @cache
• maybe try going recursive first next time...
• go for the dumbest approach first
  • even if it fails for part2, it's a helpful first step
• thinking about theoretical complexity for a minute might be a good idea
  • e.g. I tried running a search for day 16, when e.g. Dijkstra is a better idea