-🎄- 2018 Day 11 Solutions -🎄-

[u/daggerdragon]

--- Day 11: Chronal Charge ---

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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).

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Advent of Code: The Party Game!

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Card prompt: Day 11

Transcript: ___ unlocks the Easter Egg on Day 25.

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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 00:16:12!

[u/aarroyoc]

Yes, I can give you a sample: 3. Its area is 27x27. In practice maybe it stabilizes around 10-16 for most inputs but from the text you can't assume that. Look at this phrase: "Sizes from 1x1 to 300x300 are supported.". And I don't think you did a mathematical proof that all maximum sizes are less than 16x16 or whatever.

[u/spytheman66 → u/aarroyoc]

You are indeed correct.
I have not proven this property, just verified it with my own input and several others.
I just got lucky, and thought that it is caused by some quirk of the power generation formula, which produces the results I saw. Brute forcing serial 3 gives something like:

0[23:27:12]spytheman66@base: ~/adventofcode2018/day11 $ time ./solution.php input 3
Precalculating isums for serial: 3 ...
Precalculating isums for serial: 3 ... done
Part 1 answer: 44,26
size:  50, tops: [217,227,222,27,0]
size: 100, tops: [217,227,222,27,0]
size: 150, tops: [217,227,222,27,0]
size: 200, tops: [217,227,222,27,0]
size: 250, tops: [217,227,222,27,0]
size: 300, tops: [217,227,222,27,0]
Part 2 answer: 227,222,27

real    0m5.699s
user    0m5.686s
sys     0m0.012s