Raindrops

Challenge Overview

Convert a number into its corresponding raindrop sounds - Pling, Plang and Plong.

Introduction

Raindrops is a slightly more complex version of the FizzBuzz challenge, a classic interview question.

Instructions

Your task is to convert a number into its corresponding raindrop sounds.

If a given number:

is divisible by 3, add “Pling” to the result.
is divisible by 5, add “Plang” to the result.
is divisible by 7, add “Plong” to the result.
is not divisible by 3, 5, or 7, the result should be the number as a string.

Examples

28 is divisible by 7, but not 3 or 5, so the result would be "Plong".
30 is divisible by 3 and 5, but not 7, so the result would be "PlingPlang".
34 is not divisible by 3, 5, or 7, so the result would be "34".

A common way to test if one number is evenly divisible by another is to compare the [remainder][remainder] or [modulus][modulo] to zero.
Most languages provide operators or functions for one (or both) of these.

[remainder]: https://exercism.org/docs/programming/operators/remainder
[modulo]: https://en.wikipedia.org/wiki/Modulo_operation

Source: Exercism elixir/raindrops

💡 View Solution

defmodule Raindrops do
  def convert(number) do
    result =
      [{3, "Pling"}, {5, "Plang"}, {7, "Plong"}]
      |> Enum.filter(fn {d, _} -> rem(number, d) == 0 end)
      |> Enum.map_join(&elem(&1, 1))
    if result == "", do: Integer.to_string(number), else: result
  end
end