I don't think that you need to go beyond about 200...

# advent-of-code

[andyb]

I don't think that you need to go beyond about 200 iterations as the resulting pattern settles to a Steady State even through it drifts rightward 1 character per iteration. After this all this does is add a score of 1 per alive plant per iteration & so you can shortcut the calculation for 50,000,000,000

[littlelightcz]

To be honest, I had no clue how to make it so fast to run over all those iterations, so you've saved my part B day, sir 🙂 thanks a lot, really good idea.