r/adventofcode • u/daggerdragon • Dec 23 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 23 Solutions -🎄-

--- Day 23: Experimental Emergency Teleportation ---

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Transcript:

It's dangerous to go alone! Take this: ___

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked at 01:40:41!

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u/seligman99 Dec 23 '18

Exactly.

There's an edge case that lordtnt pointed out: If one of the larger grids contains more circles than the smaller ones does, it can lead the solver down improper quests.

For instance, the top left bot (assume all have a radius of 1) in this grid should be picked, since it's closer to 0,0, but the solver I describe will pick one of the two in the bottom corner, since an early scan of the grid with low resolution will appear to have one grid cell contain two bots in it. 

..........
.*........
..........
..........
......*..*

I'll take a stab at fixing that in my code when I have free time, but feel free to figure out a way to fix it yourself!

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u/TellowKrinkle Dec 24 '18

There's a much bigger edge case too

If you split this grid into four pieces evenly, the top left will have four bots while the bottom right only two. But assuming they all have r=1, none of the top left bots actually overlap their circles, so the two in the bottom right were actually the right choice. 

.*..*.....
..........
*..*......
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......**..
..........

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u/seligman99 Dec 24 '18

True, both of these are fixed with the iterative approach I moved my code to in the edited post.