euler_1.ex

# If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

# Find the sum of all the multiples of 3 or 5 below 1000.


defmodule Multiples do
  def get(n), do: sum(n, 0)

  defp sum(0, accum), do: accum
  defp sum(n, accum) when rem(n, 3) == 0, do: sum(n-1, accum + n)
  defp sum(n, accum) when rem(n, 5) == 0, do: sum(n-1, accum + n)
  defp sum(n, accum), do: sum(n-1, accum)
end

IO.puts "The sum is #{Multiples.get(999)}"