Data commit

Task/Perfect-shuffle/Elixir/perfect-shuffle.elixir

@@ -0,0 +1,24 @@
+defmodule Perfect do
+  def shuffle(n) do
+    start = Enum.to_list(1..n)
+    m = div(n, 2)
+    shuffle(start, magic_shuffle(start, m), m, 1)
+  end
+
+  defp shuffle(start, start, _, step), do: step
+  defp shuffle(start, deck, m, step) do
+    shuffle(start, magic_shuffle(deck, m), m, step+1)
+  end
+
+  defp magic_shuffle(deck, len) do
+    {left, right} = Enum.split(deck, len)
+    Enum.zip(left, right)
+    |> Enum.map(&Tuple.to_list/1)
+    |> List.flatten
+  end
+end
+
+Enum.each([8, 24, 52, 100, 1020, 1024, 10000], fn n ->
+  step = Perfect.shuffle(n)
+  IO.puts "#{n} : #{step}"
+end)