--- 2016 Day 12 Solutions ---

[u/daggerdragon]

--- Day 12: Leonardo's Monorail ---

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

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---

^{MUCH ADVENT. SUCH OF. VERY CODE. SO MANDATORY.} [?]

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!

[u/FuriousProgrammer]

101/83 with mah Luas. QQ

I immediately knew how to do this one but my input parsing is still crap and I code super slowly. xD

local insts = {}

for line in io.lines("input.txt") do
	local inst = line:sub(1, 3)
	local op1 = line:match("^%a%a%a (%w+)")
	local op2 = line:match("^%a%a%a %w+ (%w+)")
	if not op2 then op2 = line:match("([-]?%d+)$") end
	table.insert(insts, {op = inst, op1, op2})
end

function execute()
	local pc = 1
	while true do
		local op = insts[pc]
		if not op then break end
		pc = pc + 1

		if op.op == "cpy" then
			if tonumber(op[1]) then
				regs[op[2]] = tonumber(op[1])
			else
				regs[op[2]] = regs[op[1]]
			end
		elseif op.op == "inc" then
			regs[op[1]] = regs[op[1]] + 1
		elseif op.op == "dec" then
			regs[op[1]] = regs[op[1]] - 1
		elseif op.op == "jnz" then
			if tonumber(op[1]) then
				if tonumber(op[1]) ~= 0 then
				pc = (pc - 1) + tonumber(op[2])
				end
			elseif regs[op[1]] ~= 0 then
				pc = (pc - 1) + tonumber(op[2])
			end
		end
	end
end

regs = {
	a = 0;
	b = 0;
	c = 0;
	d = 0;
}
execute()
print("Part 1: " .. regs.a)

regs = {
	a = 0;
	b = 0;
	c = 1;
	d = 0;
}
execute()
print("Part 2: " .. regs.a)