Advent 2022 - Day 10

Mix.install([
  {:kino, github: "livebook-dev/kino"}
])

:ok

Setup

input = Kino.Input.textarea("Please paste your input file:")

instructs =
  input
  |> Kino.Input.read()
  |> String.split("\n")
  |> Enum.map(&String.split(&1, " "))
  |> Enum.map(fn list ->
    case list do
      ["noop"] -> {:noop}
      ["addx", val] -> {:addx, String.to_integer(val)}
    end
  end)

[
  {:noop},
  {:noop},
  {:noop},
  {:addx, 3},
  {:addx, 7},
  {:noop},
  {:noop},
  {:noop},
  {:noop},
  {:addx, 6},
  {:noop},
  {:addx, -1},
  {:noop},
  {:addx, 5},
  {:addx, 1},
  {:noop},
  {:addx, 4},
  {:noop},
  {:noop},
  {:noop},
  {:noop},
  {:addx, 6},
  {:addx, -1},
  {:noop},
  {:addx, 3},
  {:addx, -13},
  {:addx, -22},
  {:noop},
  {:noop},
  {:addx, 3},
  {:addx, 2},
  {:addx, 11},
  {:addx, -4},
  {:addx, 11},
  {:addx, -10},
  {:addx, 2},
  {:addx, 5},
  {:addx, 2},
  {:addx, -2},
  {:noop},
  {:addx, 7},
  {:addx, 3},
  {:addx, -2},
  {:addx, 2},
  {:addx, 5},
  {:addx, 2},
  {:addx, -2},
  {:addx, -8},
  {:addx, ...},
  {...},
  ...
]

defmodule CPU do
  def cycle({:addx, val}, x, history) do
    eventual_x = x + val
    history = [x, x] ++ history
    {eventual_x, history}
  end

  def cycle({:noop}, x, history), do: {x, [x | history]}

  def cycle(:instruct, [instruct | instructs], x, history) do
    {x, history} = cycle(instruct, x, history)
    cycle(:instruct, instructs, x, history)
  end

  def cycle(:instruct, [], _x, history), do: history

  def run(instructs), do: cycle(:instruct, instructs, 1, [])
end

{:module, CPU, <<70, 79, 82, 49, 0, 0, 8, ...>>, {:run, 1}}

defmodule CRT do
  def display(cycles) do
    bars = Enum.chunk_every(cycles, 40)

    for bar <- bars do
      for {x, pixel} <- Enum.with_index(bar) do
        after_start = pixel >= x - 1
        before_end = pixel <= x + 1
        if after_start and before_end, do: "#", else: "."
      end
    end
    |> Enum.join("\n")
  end
end

{:module, CRT, <<70, 79, 82, 49, 0, 0, 9, ...>>, {:display, 1}}

Part 1

history = CPU.run(instructs) |> Enum.reverse()

[1, 1, 1, 1, 1, 4, 4, 11, 11, 11, 11, 11, 11, 17, 17, 17, 16, 16, 16, 21, 21, 22, 22, 22, 26, 26,
 26, 26, 26, 26, 32, 32, 31, 31, 31, 34, 34, 21, 21, -1, -1, -1, -1, 2, 2, 4, 4, 15, 15, 11, ...]

20..220//40
|> Enum.map(&(Enum.at(history, &1 - 1) * &1))
|> Enum.sum()

12560

Part 2

CRT.display(history) |> IO.write()

###..#....###...##..####.###...##..#....
#..#.#....#..#.#..#.#....#..#.#..#.#....
#..#.#....#..#.#..#.###..###..#....#....
###..#....###..####.#....#..#.#....#....
#....#....#....#..#.#....#..#.#..#.#....
#....####.#....#..#.#....###...##..####.

:ok