doukaku_3rd_elixir.exs

defmodule CalculaMachine do

  def calculate(encoded_string) do
    _size, encoded_value = String.split(encoded_string, ":")

    to_bit(encoded_string)
    |> to_numerical_fomula()
    |> calculate_formula()
    |> encode()
  end

  defp to_bit(byte) do
    :io.format("~.2B~n", [String.to_integer(byte, 16)])
  end

  defp to_numerical_fomula(bit) do
    decode(bit, "")
  end

  defp decode("00" <> bits, acc), do: decode(bits, "0" <> acc)
  defp decode("01" <> bits, acc), do: decode(bits, "1" <> acc)
  defp decode("100" <> bits, acc), do: decode(bits, "2" <> acc)
  defp decode("1010" <> bits, acc), do: decode(bits, "3" <> acc)
  defp decode("1011" <> bits, acc), do: decode(bits, "4" <> acc)
  defp decode("1100" <> bits, acc), do: decode(bits, "5" <> acc)
  defp decode("11010" <> bits, acc), do: decode(bits, "6" <> acc)
  defp decode("11011" <> bits, acc), do: decode(bits, "7" <> acc)
  defp decode("111000" <> bits, acc), do: decode(bits, "8" <> acc)
  defp decode("111001" <> bits, acc), do: decode(bits, "9" <> acc)
  defp decode("1110100" <> bits, acc), do: decode(bits, "+" <> acc)
  defp decode("1110101" <> bits, acc), do: decode(bits, "-" <> acc)
  defp decode("1110110" <> bits, acc), do: decode(bits, "*" <> acc)
  defp decode("1110111" <> bits, acc), do: decode(bits, "/" <> acc)
  defp decode(_, acc), do: String.reverse(acc)

  defp calculate_formula(formula) do
    Tree.build_tree(formula)
    |> Tree.calculate
  end

  defp encode(calculate_result) do

  end
 end

defmodule Tree do
  defstruct [:left, :right, :value]

  def build_tree(formula) do

  end
end