day 16

day16/part1.lua

@@ -0,0 +1,84 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local hex = io.open(arg[3]):read("*a")
+--local hex = "8A004A801A8002F478"
+local hexmap = {
+	["0"] = "0000", ["1"] = "0001", ["2"] = "0010", ["3"] = "0011",
+	["4"] = "0100", ["5"] = "0101", ["6"] = "0110", ["7"] = "0111",
+	["8"] = "1000", ["9"] = "1001", ["A"] = "1010", ["B"] = "1011",
+	["C"] = "1100", ["D"] = "1101", ["E"] = "1110", ["F"] = "1111",
+}
+
+local bytes = {}
+for char in chars(hex) do
+	if hexmap[char] then table.insert(bytes, hexmap[char]) end
+end
+
+local bitstring = table.concat(bytes)
+
+local function literal(bitstring)
+	local v = 0
+	while char(bitstring, 1) == "1" do
+		v = v * 16 + bin2dec(bitstring:sub(2, 5))
+		bitstring = bitstring:sub(6)
+	end
+	v = v * 16 + bin2dec(bitstring:sub(2, 5))
+	return v, bitstring:sub(6)
+end
+
+local function countoperator(bitstring)
+	local count = bin2dec(bitstring:sub(1, 11))
+	bitstring = bitstring:sub(12)
+	local p, packets = nil, {}
+	for i = 1, count do
+		p, bitstring = packet(bitstring)
+		table.insert(packets, p)
+	end
+	return packets, bitstring
+end
+
+local function lengthoperator(bitstring)
+	local length = bin2dec(bitstring:sub(1, 15))
+	bitstring = bitstring:sub(16)
+	local target = #bitstring - length
+	local p, packets = nil, {}
+	while #bitstring > target do
+		p, bitstring = packet(bitstring)
+		table.insert(packets, p)
+	end
+	return packets, bitstring
+end
+
+local function operator(bitstring)
+	if char(bitstring, 1) == "1" then
+		return countoperator(bitstring:sub(2))
+	else
+		return lengthoperator(bitstring:sub(2))
+	end
+end
+
+function packet(bitstring)
+	local version = bin2dec(bitstring:sub(1, 3))
+	local pactype = bin2dec(bitstring:sub(4, 6))
+	local content
+	if pactype == 4
+	then content, bitstring = literal(bitstring:sub(7))
+	else content, bitstring = operator(bitstring:sub(7))
+	end
+	return { version = version, pactype = pactype, content = content }, bitstring
+end
+
+function sumversions(packet)
+	if packet.pactype == 4 then
+		return packet.version
+	else
+		local sum = packet.version
+		for i, p in pairs(packet.content) do
+			sum = sum + sumversions(p)
+		end
+		return sum
+	end
+end
+
+print(sumversions(packet(bitstring)))

day16/part2.lua

@@ -0,0 +1,119 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local hex = io.open(arg[3]):read("*a")
+--local hex = "8A004A801A8002F478"
+local hexmap = {
+	["0"] = "0000", ["1"] = "0001", ["2"] = "0010", ["3"] = "0011",
+	["4"] = "0100", ["5"] = "0101", ["6"] = "0110", ["7"] = "0111",
+	["8"] = "1000", ["9"] = "1001", ["A"] = "1010", ["B"] = "1011",
+	["C"] = "1100", ["D"] = "1101", ["E"] = "1110", ["F"] = "1111",
+}
+
+local bytes = {}
+for char in chars(hex) do
+	if hexmap[char] then table.insert(bytes, hexmap[char]) end
+end
+
+local bitstring = table.concat(bytes)
+
+local function literal(bitstring)
+	local v = 0
+	while char(bitstring, 1) == "1" do
+		v = v * 16 + bin2dec(bitstring:sub(2, 5))
+		bitstring = bitstring:sub(6)
+	end
+	v = v * 16 + bin2dec(bitstring:sub(2, 5))
+	return v, bitstring:sub(6)
+end
+
+local function countoperator(bitstring)
+	local count = bin2dec(bitstring:sub(1, 11))
+	bitstring = bitstring:sub(12)
+	local p, packets = nil, {}
+	for i = 1, count do
+		p, bitstring = packet(bitstring)
+		table.insert(packets, p)
+	end
+	return packets, bitstring
+end
+
+local function lengthoperator(bitstring)
+	local length = bin2dec(bitstring:sub(1, 15))
+	bitstring = bitstring:sub(16)
+	local target = #bitstring - length
+	local p, packets = nil, {}
+	while #bitstring > target do
+		p, bitstring = packet(bitstring)
+		table.insert(packets, p)
+	end
+	return packets, bitstring
+end
+
+local function operator(bitstring)
+	if char(bitstring, 1) == "1" then
+		return countoperator(bitstring:sub(2))
+	else
+		return lengthoperator(bitstring:sub(2))
+	end
+end
+
+function packet(bitstring)
+	local version = bin2dec(bitstring:sub(1, 3))
+	local pactype = bin2dec(bitstring:sub(4, 6))
+	local content
+	if pactype == 4 then
+		content, bitstring = literal(bitstring:sub(7))
+	else
+		content, bitstring = operator(bitstring:sub(7))
+	end
+	return { version = version, pactype = pactype, content = content }, bitstring
+end
+
+local function intop(p, binop)
+	local acc = evaluate(p.content[1])
+	for i = 2, #p.content do
+		acc = binop(acc, evaluate(p.content[i]))
+	end
+	return acc
+end
+
+local function boolop(p, binop)
+	if binop(evaluate(p.content[1]), evaluate(p.content[2]))
+	then return 1
+	else return 0
+	end
+end
+
+local typemap = {
+	[0] = function(p)
+		return intop(p, function(a, b) return a + b end)
+	end,
+	[1] = function(p)
+		return intop(p, function(a, b) return a * b end)
+	end,
+	[2] = function(p)
+		return intop(p, math.min)
+	end,
+	[3] = function(p)
+		return intop(p, math.max)
+	end,
+	[4] = function(p)
+		return p.content
+	end,
+	[5] = function(p)
+		return boolop(p, function(a, b) return a > b end)
+	end,
+	[6] = function(p)
+		return boolop(p, function(a, b) return a < b end)
+	end,
+	[7] = function(p)
+		return boolop(p, function(a, b) return a == b end)
+	end,
+}
+
+function evaluate(packet)
+	return typemap[packet.pactype](packet)
+end
+
+print(evaluate(packet(bitstring)))

utils.lua

@@ -74,3 +74,13 @@ function chars(s)
 		end
 	end
 end
+
+function bin2dec(str)
+	local v = 0
+	for c in chars(str) do
+		v = v * 2
+		if c == "1" then v = v + 1 end
+	end
+	return v
+end
+