Day 03: Binary Diagnostic

Mix.install([
  {:kino, "~> 0.9.2"}
])

:ok

Input

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

test_input = Kino.Input.textarea("Test Input")

Part 01

gamma_fn = fn comp, v -> if comp == 1, do: v + 1, else: v - 1 end

epsilon_fn = fn comp, v -> if comp == 0, do: v + 1, else: v - 1 end

list_to_bin = fn l ->
  l
  |> Enum.reverse()
  |> Enum.with_index(fn bit, index -> {index, bit} end)
  |> Enum.reduce(0, fn {index, bit}, acc ->
    if bit == 1, do: acc + :math.pow(2, index), else: acc
  end)
end

numbers =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(&(&1 |> String.graphemes()))
  |> Enum.map(&(&1 |> Enum.map(fn b_s -> String.to_integer(b_s) end)))

numbers_len =
  numbers
  |> Enum.at(0)
  |> length()
  |> (&(&1 - 1)).()

gamma_map =
  0..numbers_len
  |> Enum.to_list()
  |> Enum.with_index(fn el, _i -> {el, 0} end)
  |> Map.new()

epsilon_map =
  0..numbers_len
  |> Enum.to_list()
  |> Enum.with_index(fn el, _i -> {el, 0} end)
  |> Map.new()

gamma_rate =
  numbers
  |> Enum.reduce(gamma_map, fn gamma, acc ->
    gamma =
      Enum.with_index(gamma, fn b, i ->
        {b, i}
      end)

    Enum.reduce(gamma, acc, fn {b, i}, acc2 ->
      Map.update(acc2, i, 0, fn v ->
        gamma_fn.(b, v)
      end)
    end)
  end)
  |> Enum.map(fn {_k, count} ->
    if(count > 0, do: 1, else: 0)
  end)

epsilon_rate =
  numbers
  |> Enum.reduce(epsilon_map, fn epsilon, acc ->
    epsilon =
      Enum.with_index(epsilon, fn b, i ->
        {b, i}
      end)

    Enum.reduce(epsilon, acc, fn {b, i}, acc2 ->
      Map.update(acc2, i, 0, fn v ->
        epsilon_fn.(b, v)
      end)
    end)
  end)
  |> Enum.map(fn {_k, count} -> if count > 0, do: 1, else: 0 end)

solution = (list_to_bin.(gamma_rate) * list_to_bin.(epsilon_rate)) |> round()
IO.puts("Power consumption of the submarine: #{solution}")

Power consumption of the submarine: 2003336

:ok

Part 02