longest_common_prefix.ex

defmodule LongestCommonPrefix do
  @spec run([String.t()]) :: String.t()
  def run(strings) do
    strings
    |> Stream.map(&String.graphemes/1)
    |> Stream.zip_with(&Function.identity/1)
    |> Stream.take_while(&all_same?/1)
    |> Stream.map(&hd/1)
    |> Enum.join()
  end    

  @spec all_same?([String.t()]) :: boolean()
  def all_same?([char | chars]) do
    Enum.all?(chars, &(&1 == char))
  end
end