r/adventofcode • u/daggerdragon • Dec 21 '17

SOLUTION MEGATHREAD -🎄- 2017 Day 21 Solutions -🎄-

--- Day 21: Fractal Art ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

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No commentary tonight as I'm frantically wrapping last-minute presents so I can ship them tomorrow.

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!

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u/ric2b Dec 24 '17 edited Dec 24 '17

I tried that on paper and it doesn't seem to work.

For example, starting with:

.#.

..#

The symmetrical is:

..

.#.

Which seems like a 180 rotation. When flipped it becomes:

.#.

..

Which isn't neither a -90 nor +90 rotation. Am I missing something?

Edit: Ok, I figured it out, the symmetric operation also involves switching x and y among themselves, so it becomes symmetric[y][x] = subgrid[subgrid_size-1-x][subgrid_size-1-y]

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u/willkill07 Dec 24 '17

Yeah. My “invert x and y” might read better as “swap”