Day 2

Mix.install([
  {:kino, "~> 0.11.0"}
])

Inputs

input_box = Kino.Input.textarea("input")

input = Kino.Input.read(input_box)
input_lines = String.split(input, "\n")

Part 1

defmodule Safety1 do
  def is_safe([first, second | _] = list) do
    kind = if first < second, do: :asc, else: :desc
    is_safe(list, kind)
  end

  defp is_safe([_head | []], _kind), do: true
  
  defp is_safe([first, second | _] = [_head | tail], :asc) do
    cond do
      second - first > 3 || second - first < 1 -> false
      true -> is_safe(tail, :asc)
    end
  end

  defp is_safe([first, second | _] = [_head | tail], :desc) do
    cond do
      first - second > 3 || first - second < 1 -> false
      true -> is_safe(tail, :desc)
    end
  end
end

input_lines
|> Enum.map(fn line -> line |> String.split(" ") |> Enum.map(&amp;String.to_integer/1) end)
|> Enum.count(&amp;Safety1.is_safe/1)

Part 2 (Probably broken but works for me lol)

defmodule Safety2 do
  def is_safe([first, second | _] = list) do
    kind = if first < second, do: :asc, else: :desc
    is_safe(list, kind, true)
  end

  defp is_safe([_head | []], _kind, _elves_can_get_away_with_reactor_going_wild), do: true
  
  defp is_safe([first, second | _] = [_head | tail], :asc, elves_can_get_away_with_reactor_going_wild) do
    cond do
      second - first > 3 || second - first < 1 ->
        if elves_can_get_away_with_reactor_going_wild,
          do: is_safe(tail, :asc, false),
          else: false

      true -> is_safe(tail, :asc, elves_can_get_away_with_reactor_going_wild)
    end
  end

  defp is_safe([first, second | _] = [_head | tail], :desc, elves_can_get_away_with_reactor_going_wild) do
    cond do
      first - second > 3 || first - second < 1 -> 
        if elves_can_get_away_with_reactor_going_wild,
          do: is_safe(tail, :desc, false),
          else: false

      true -> is_safe(tail, :desc, elves_can_get_away_with_reactor_going_wild)
    end
  end
end

input_lines
|> Enum.map(fn line -> line |> String.split(" ") |> Enum.map(&amp;String.to_integer/1) end)
|> Enum.count(&amp;Safety2.is_safe/1)