day10.livemd

Day10

Mix.install([
  {:kino, "~> 0.8.0"}
])

Input

input = Kino.Input.textarea("Your puzzle input")

Parse input

instructions =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    case String.split(line, " ") do
      [instruction] ->
        instruction

      [instruction, count] ->
        {instruction, String.to_integer(count)}
    end
  end)

{cycles, _} =
  Enum.reduce(instructions, {[1], 1}, fn instruction, {cycles, x} ->
    case instruction do
      "noop" ->
        {cycles ++ [x], x}

      {"addx", count} ->
        new_x = x + count
        {cycles ++ [x, new_x], new_x}
    end
  end)

Part 1

selected_cycles = [20, 60, 100, 140, 180, 220]

Enum.reduce(selected_cycles, 0, fn i, acc ->
  acc + Enum.at(cycles, i - 1) * i
end)

Part 2

Enum.each(0..(Enum.count(cycles) - 1), fn i ->
  x = Enum.at(cycles, i)

  col = Integer.mod(i, 40)

  if col == 0 do
    IO.puts("")
  end

  if col in [x - 1, x, x + 1] do
    IO.write(" #")
  else
    IO.write("  ")
  end
end)