Elixir Coding Dojo at UTFPR - 24/October/2018

look_and_say.ex

defmodule LookAndSay do
  def lookandsay(numero) do
    numero
    |> Integer.digits()
    |> lookandsay_inicia()
    |> Integer.undigits()
  end

  defp lookandsay_inicia([cabeca | cauda]) do
    lookandsayauxaux(cabeca, cauda, 1)
  end

  defp lookandsayauxaux(estado, [], i) do
    [i, estado]
  end

  defp lookandsayauxaux(estado, [estado | cauda], i) do
    lookandsayauxaux(estado, cauda, i + 1)
  end

  defp lookandsayauxaux(estado, [novoestado | cauda], i) do
    [i, estado] ++ lookandsayauxaux(novoestado, cauda, 1)
  end
end

look_and_say_test.exs

defmodule LookAndSayTest do
  use ExUnit.Case

  test "Look and Say de 1 é 11" do
    assert LookAndSay.lookandsay(1) == 11
  end

  test "Look and Say de 555 é 35" do
    assert LookAndSay.lookandsay(555) == 35
  end

  test "Look and Say de 55 é 25" do
    assert LookAndSay.lookandsay(55) == 25
  end

  test "Look and Say de 11 é 21" do
    assert LookAndSay.lookandsay(11) == 21
  end

  test "Look and Say de 5 é 15" do
    assert LookAndSay.lookandsay(5) == 15
  end

  test "Look and Say de 123 é 111213" do
    assert LookAndSay.lookandsay(123) == 111_213
  end

  test "Look and Say de 551 é 2511" do
    assert LookAndSay.lookandsay(551) == 2511
  end

  test "Look and Say de 555555 é 65" do
    assert LookAndSay.lookandsay(555_555) == 65
  end
end