day 24 part 1 but too slow

day24/part1.lua

@@ -0,0 +1,120 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local function trunc(a)
+	if a < 0 then
+		return math.ceil(a)
+	else
+		return math.floor(a)
+	end
+end
+
+local map = { w=1, x=2, y=3, z=4 }
+local instructions = {}
+for line in io.lines(arg[3]) do
+	local inst, a1, a2 = unpack(split(line, " "))
+	if inst == "inp" then
+		table.insert(instructions, function(memory, input)
+			local i, o = 9, memory[a1]
+			return function()
+				if i > 1 then
+					i = i - 1
+					memory[a1] = i
+					return input * 10 + i
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	elseif inst == "add" then
+		table.insert(instructions, function(memory, input)
+			local done, o = false, memory[a1]
+			return function()
+				if not done then
+					memory[a1] = memory[a1] + (memory[a2] or tonumber(a2))
+					done = true
+					return input
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	elseif inst == "mul" then
+		table.insert(instructions, function(memory, input)
+			local done, o = false, memory[a1]
+			return function()
+				if not done then
+					memory[a1] = memory[a1] * (memory[a2] or tonumber(a2))
+					done = true
+					return input
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	elseif inst == "div" then
+		table.insert(instructions, function(memory, input)
+			local done, o = false, memory[a1]
+			return function()
+				if not done and (memory[a2] or tonumber(a2)) ~= 0 then
+					memory[a1] = trunc(memory[a1] / (memory[a2] or tonumber(a2)))
+					done = true
+					return input
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	elseif inst == "mod" then
+		table.insert(instructions, function(memory, input)
+			local done, o = false, memory[a1]
+			return function()
+				local v = memory[a2] or tonumber(a2)
+				if not done and memory[a1] >= 0 and v > 0 then
+					memory[a1] = memory[a1] % v
+					done = true
+					return input
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	elseif inst == "eql" then
+		table.insert(instructions, function(memory, input)
+			local done, o = false, memory[a1]
+			return function()
+				if not done then
+					if memory[a1] == (memory[a2] or tonumber(a2)) then
+						memory[a1] = 1
+					else
+						memory[a1] = 0
+					end
+					done = true
+					return input
+				else
+					memory[a1] = o
+				end
+			end
+		end)
+	end
+end
+
+local maximum = 0
+local function backtrack(i, memory, input)
+	if i == #instructions then
+		if memory.z == 0 and input > maximum then
+			print(input)
+			print(os.date())
+			maximum = input
+		end
+	else
+		-- io.write("i "..tostring(i).." ")
+		-- printtable(memory)
+		for newinput in instructions[i](memory, input) do
+			backtrack(i + 1, memory, newinput)
+		end
+	end
+end
+
+backtrack(1, { w=0, x=0, y=0, z=0 }, 0)
+print(maximum)