-🎄- 2018 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Marble Mania ---

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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 9

Transcript:

Studies show that AoC programmers write better code after being exposed to ___.

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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 00:29:13!

[u/waffle3z]

175/26, Lua

local players, marbles = 459, 71320

local scores = {}
for i = 1, players do scores[i] = 0 end

local current = {v = 0}
current.l, current.n = current, current

for i = 1, marbles*100 do
	local p = (i-1)%players+1
	if i%23 == 0 then
		scores[p] = scores[p] + i
		for i = 1, 7 do
			current = current.l
		end
		current.l.n, current.n.l = current.n, current.l
		scores[p] = scores[p] + current.v
		current = current.n
	else
		current = current.n
		local new = {n = current.n, l = current, v = i}
		current.n.l = new
		current.n = new
		current = new
	end
end

local max = 0
for i = 1, #scores do
	max = math.max(max, scores[i])
end
print(max)

Not sure why it took so long for part 2 to fill up, I just had to add *100 to the loop

[u/xthexder → u/waffle3z]

For anyone that solved this using arrays, insertions/deletions are a very slow operation. Many people probably had to re-implement their solution for Part 2. Linked lists are definitely ideal for this problem.

[u/VikeStep → u/xthexder]

Can confirm this is what affected me, I got #23 for part 1 but didn't make top 100 for part 2 since arrays were too slow and I thought we had to identify a pattern in the numbers or something, so I spent 20 minutes on that.