AoC19/d07.lua

function get_arg(mem, pos, arg)
    local param_mode = mem[pos] // (10 ^ (arg + 1)) % 10
    if #mem < pos + arg then
        print(string.format("Error: Opcode too short at end of memory: %d", pos))
        os.exit(false)
    end
    local arg = mem[pos + arg]
    if param_mode == 0 then
        arg = arg + 1
        if #mem < arg then
            print(string.format("Error: Memory offset out of bounds: %d", arg))
            os.exit(false)
        end
    end
    return arg
end

function get_param(mem, pos, arg)
    local param_mode = mem[pos] // (10 ^ (arg + 1)) % 10
    local arg = get_arg(mem, pos, arg)
    if param_mode == 0 then
        return mem[arg]
    end
    return arg
end

function interpret(mem, state, input_func, output_func)
    if not state.pos then
        state.pos = 1
    end

    local pos = state.pos
    while true do
        if #mem < pos then
            print(string.format("Instruction pointer ran off of memory"))
            os.exit(false)
        end

        local opcode = mem[pos] % 100

        if opcode == 1 then
            mem[get_arg(mem, pos, 3)] = get_param(mem, pos, 1) + get_param(mem, pos, 2)
            pos = pos + 4
        elseif opcode == 2 then
            mem[get_arg(mem, pos, 3)] = get_param(mem, pos, 1) * get_param(mem, pos, 2)
            pos = pos + 4
        elseif opcode == 3 then
            local val = input_func()
            if not val then
                state.pos = pos
                return true
            end
            mem[get_arg(mem, pos, 1)] = val
            pos = pos + 2
        elseif opcode == 4 then
            output_func(get_param(mem, pos, 1))
            pos = pos + 2
        elseif opcode == 5 then
            if get_param(mem, pos, 1) ~= 0 then
                pos = get_param(mem, pos, 2) + 1
            else
                pos = pos + 3
            end
        elseif opcode == 6 then
            if get_param(mem, pos, 1) == 0 then
                pos = get_param(mem, pos, 2) + 1
            else
                pos = pos + 3
            end
        elseif opcode == 7 then
            mem[get_arg(mem, pos, 3)] = get_param(mem, pos, 1) < get_param(mem, pos, 2) and 1 or 0
            pos = pos + 4
        elseif opcode == 8 then
            mem[get_arg(mem, pos, 3)] = get_param(mem, pos, 1) == get_param(mem, pos, 2) and 1 or 0
            pos = pos + 4
        elseif opcode == 99 then
            state.pos = pos
            return false
        else
            print(string.format("Error: Invalid opcode %d at %d", opcode, pos - 1))
            os.exit(false)
        end
    end
end

function input_stdin()
    io.stdout:write("> ")
    return io.stdin:read("n")
end

function output_stdout(val)
    io.stdout:write(val)
    io.stdout:write("\n")
end

function input_array(array)
    function inner()
        return table.remove(array, 1)
    end
    return inner
end

function output_array(array)
    function inner(val)
        table.insert(array, val)
    end
    return inner
end

file = io.open(arg[1])
program = {}
for num in string.gmatch(file:read(), "(-?%d+),?") do
    table.insert(program, tonumber(num))
end
file:close()

function get_signal(phase)
    signal = 0
    for i = 1, 5 do
        memory = {table.unpack(program)}
        output = {}
        interpret(memory, {}, input_array({phase[i], signal}), output_array(output))
        signal = output[1]
    end
    return signal
end

function get_signal_p2(phase)
    machines = {}
    for i = 1, 5 do
        if i == 1 then
            input = {}
        else
            input = machines[i - 1].output
        end
        table.insert(input, phase[i] + 5)
        machines[i] = {mem={table.unpack(program)}, input=input, output={}}
    end
    machines[5].output = machines[1].input
    table.insert(machines[1].input, 0)

    while true do
        done = true
        for i = 1, 5 do
            if interpret(machines[i].mem, machines[i], input_array(machines[i].input), output_array(machines[i].output)) then
                done = false
            end
        end
        if done then
            break
        end
    end
    return machines[5].output[1]
end

biggest = 0
biggest_p2 = 0
for i = 0, (5 ^ 5) - 1 do
    phase = {
        i // (5 ^ 4) % 5,
        i // (5 ^ 3) % 5,
        i // (5 ^ 2) % 5,
        i // (5 ^ 1) % 5,
        i // (5 ^ 0) % 5
    }
    count = {}
    for _, x in ipairs(phase) do
        if not count[x] then
            count[x] = 0
        end
        count[x] = count[x] + 1
    end
    double = false
    for _, x in pairs(count) do
        if x > 1 then
            double = true
        end
    end

    if not double then
        signal = get_signal(phase)
        if signal > biggest then
            biggest = signal
        end
        signal = get_signal_p2(phase)
        if signal > biggest_p2 then
            biggest_p2 = signal
        end
    end
end

print("Part 1:", biggest)
print("Part 2:", biggest_p2)