Day 10: Cathode-Ray Tube

Mix.install([:kino])

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

Part 1

https://adventofcode.com/2022/day/10

signals =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn
    "noop" -> :noop
    "addx " <> value -> {:add, String.to_integer(value)}
  end)

normalized_signals =
  signals
  |> Enum.flat_map(fn
    :noop -> [0]
    {:add, value} -> [0, value]
  end)

registers =
  [0 | normalized_signals |> Enum.drop(-1)]
  |> Enum.scan(1, &amp;(&amp;1 + &amp;2))

registers
|> Enum.with_index(1)
|> Enum.reduce([], fn {value, cycle}, signal_strength ->
  case rem(cycle - 20, 40) do
    0 -> [{cycle, value} | signal_strength]
    _ -> signal_strength
  end
end)
|> Enum.map(fn {cycle, register} -> cycle * register end)
|> Enum.sum()

Part 2

https://adventofcode.com/2022/day/10#part2

pixels =
  registers
  |> Enum.with_index(1)
  |> Enum.reduce([], fn {register, cycle}, pixels ->
    position = rem(cycle - 1, 40)

    pixel =
      case abs(register - position) <= 1 do
        true -> "#"
        false -> "."
      end

    case position do
      39 -> ["\n", pixel | pixels]
      _ -> [pixel | pixels]
    end
  end)
  |> Enum.reverse()

pixels
|> IO.iodata_to_binary()
|> IO.puts()