逆FizzBuzz

逆FizzBuzzをElixirで。

defmodule ReverseFizzBuzz do
  def fb do
    Stream.iterate(1,&(&1+1))
    |> Stream.map(fn(n) -> {n,"#{if rem(n,3)==0, do: 'Fizz'}#{if rem(n,5)==0, do: 'Buzz'}"} end)
    |> Stream.filter(fn {_,b} -> b != "" end)
  end

  def find(input) do
    count = Enum.count(input)
    list = fb |> Enum.take(15*(1+trunc(Float.ceil(count/7,0))))
    case (0..Enum.count(list)-1
      |> Enum.map(fn(i) -> Enum.slice(list, i, count) end)
      |> Enum.filter(fn(i) -> Enum.map(i,&(elem(&1,1))) == input end)) do
        [] -> 'NotFound'
        res ->
          Enum.min_by(res,fn(i) -> elem(List.last(i),0)-elem(List.first(i),0) end)
          |> Enum.map(&(elem(&1,0)))
          |> Enum.reduce(fn(x,acc) -> "#{acc},#{x}" end)
    end
  end
end

IO.puts ReverseFizzBuzz.find(String.split(List.first(System.argv),","))