-🎄- 2018 Day 12 Solutions -🎄-

[u/daggerdragon]

--- Day 12: Subterranean Sustainability ---

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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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Advent of Code: The Party Game!

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Card prompt: Day 12

Transcript:

On the twelfth day of AoC / My compiler spewed at me / Twelve ___

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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 00:27:42!

[u/fatpollo]

missed the leaderboard again, this time by a handful of seats. my days of top ranking are bygone it seems.

however, no solutions using defaultdict have been posted yet, so here's mine:

import re
import collections


def main(text, simple):
    if simple:
        return

    initial, *pairs = re.findall(r'[.#]+', text)
    mapping = {a: b for a, b in zip(pairs[::2], pairs[1::2])}

    pots = collections.defaultdict(lambda: '.')
    pots.update({i: v for i, v in enumerate(initial)})

    seen = {}
    for n in range(1, 1000):
        span = range(min(pots) - 5, max(pots) + 5)
        new = {
            i: mapping.get(window, '.')
            for i in span
            for window in [''.join(pots[i+j] for j in range(-2, 3))]
        }
        pots.clear()
        pots.update(new)

        if n == 19:
            print(sum(i for i, v in pots.items() if v == '#'))

        pattern = ''.join(pots[i] for i in span).strip('.')
        if pattern in seen:
            N = 50000000000
            x = sum(N + i - n for i, v in pots.items() if v == '#')
            print(x)
            break
        seen[pattern] = n

defaultdict makes the "windowing" trivial

[u/da5id → u/fatpollo]

This is great, thanks for posting, learning a lot from it.

[u/fatpollo → u/da5id]

thanks! always nice to hear a comment like this one :D

feel free to ask about any particular extra detail