adventofcode-2021/day19/part2.lua

#!/usr/bin/env luajit
require("utils")
require("pqueue")

local scanners = {}
local scanner = {}
for line in io.lines(arg[3]) do
	if #line == 0 then
		table.insert(scanners, scanner)
		scanner = {}
	elseif char(line, 2) == "-" then
	else
		local x, y, z = unpack(split(line, ","))
		local beacon = { x = tonumber(x)
		               , y = tonumber(y)
		               , z = tonumber(z) }
		               -- , q = pqueue() }
		table.insert(scanner, beacon)
	end
end
table.insert(scanners, scanner)

for _, scanner in pairs(scanners) do
	for i = 1, #scanner do
		for j = i + 1, #scanner do
			local d = (scanner[i].x - scanner[j].x) ^ 2
			        + (scanner[i].y - scanner[j].y) ^ 2
			        + (scanner[i].z - scanner[j].z) ^ 2
			-- scanner[i].q:add(d)
			-- if #scanner[i].q.items > 4 then scanner[i].q:pop() end
			-- scanner[j].q:add(d); scanner[j].q:pop()
			-- if #scanner[j].q.items > 4 then scanner[j].q:pop() end
		end
	end
end

local function minp(a, b)
	return { x = a.x - b.x, y = a.y - b.y, z = a.z - b.z }
end

local function addp(a, b)
	return { x = a.x + b.x, y = a.y + b.y, z = a.z + b.z }
end

local rotations = { function(p) return { x =  p.x, y =  p.y, z =  p.z } end
                  , function(p) return { x =  p.x, y =  p.z, z = -p.y } end
                  , function(p) return { x =  p.x, y = -p.y, z = -p.z } end
                  , function(p) return { x =  p.x, y = -p.z, z =  p.y } end
                  , function(p) return { x =  p.y, y = -p.x, z =  p.z } end
                  , function(p) return { x =  p.y, y =  p.z, z =  p.x } end
                  , function(p) return { x =  p.y, y =  p.x, z = -p.z } end
                  , function(p) return { x =  p.y, y = -p.z, z = -p.x } end
                  , function(p) return { x = -p.x, y = -p.y, z =  p.z } end
                  , function(p) return { x = -p.x, y = -p.z, z = -p.y } end
                  , function(p) return { x = -p.x, y =  p.y, z = -p.z } end
                  , function(p) return { x = -p.x, y =  p.z, z =  p.y } end
                  , function(p) return { x = -p.y, y =  p.x, z =  p.z } end
                  , function(p) return { x = -p.y, y = -p.z, z =  p.x } end
                  , function(p) return { x = -p.y, y = -p.x, z = -p.z } end
                  , function(p) return { x = -p.y, y =  p.z, z = -p.x } end
                  , function(p) return { x =  p.z, y =  p.y, z = -p.x } end
                  , function(p) return { x =  p.z, y =  p.x, z =  p.y } end
                  , function(p) return { x =  p.z, y = -p.y, z =  p.x } end
                  , function(p) return { x =  p.z, y = -p.x, z = -p.y } end
                  , function(p) return { x = -p.z, y = -p.y, z = -p.x } end
                  , function(p) return { x = -p.z, y = -p.x, z =  p.y } end
                  , function(p) return { x = -p.z, y =  p.y, z =  p.x } end
                  , function(p) return { x = -p.z, y =  p.x, z = -p.y } end
                  }

local function eqp(a, b)
	return a.x == b.x and a.y == b.y and a.z == b.z
end

local function rotate(a, r)
	local b = {}
	for _, p in pairs(a) do
		table.insert(b, r(p))
	end
	return b
end

local function move(a, d)
	local b = {}
	for _, p in pairs(a) do
		table.insert(b, { x = p.x + d.x
		                , y = p.y + d.y
		                , z = p.z + d.z })
	end
	return b
end

local function similar(a, b)
	local counter = 0
	for i, pa in pairs(a) do
		for j, pb in pairs(b) do
			if eqp(pa, pb) then
				counter = counter + 1
				break
			end
		end
		if counter >= 12 then
			return counter
		end
	end
	return 0
end

function compare(a, b)
	for _, r in pairs(rotations) do
		local br = rotate(b, r)
		for _, pa1 in pairs(a) do
			for _, pb1 in pairs(br) do
				local d = minp(pa1, pb1)
				local b_ = move(br, d)
				if similar(a, b_) >= 12 then
					return b_, d
				end
			end
		end
	end
	return nil
end

local beacons = {}
local counter = 0
local function countbeacons(scanner)
	for _, b in pairs(scanner) do
		local xs = beacons[b.x] or {}
		local ys = xs[b.y] or {}
		if ys[b.z] == nil then
			ys[b.z] = true
			counter = counter + 1
		end
		xs[b.y] = ys
		beacons[b.x] = xs
	end
end

local compareWiths = { scanners[1] }
local todos = { unpack(scanners, 2) }
local locations = { { x=0, y=0, z=0 } }
while #todos > 0 do
	print(#todos)
	local newCompareWiths = {}
	local newtodos = {}
	for _, todo in pairs(todos) do
		local found, d = nil
		for _, compareWith in pairs(compareWiths) do
			found, d = compare(compareWith, todo)
			if found then break end
		end
		if found then
			table.insert(newCompareWiths, found)
			table.insert(locations, d)
		else
			table.insert(newtodos, todo)
		end
	end
	todos = newtodos
	compareWiths = newCompareWiths
end

local max = 0
for i = 1, #locations do
	for j = i + 1, #locations do
		local d = math.abs(locations[i].x - locations[j].x)
		        + math.abs(locations[i].y - locations[j].y)
		        + math.abs(locations[i].z - locations[j].z)
		if d > max then max = d end
	end
end
print(max)