Another update from ingydotnet^djgoku

Task/Average-loop-length/Elixir/average-loop-length.elixir

@@ -0,0 +1,28 @@
+defmodule RC do
+  def factorial(0), do: 1
+  def factorial(n), do: Enum.reduce(1..n, 1, &(&1 * &2))
+
+  def loop_length(n), do: loop_length(n, HashSet.new)
+
+  defp loop_length(n, set) do
+    r = :random.uniform(n)
+    if Set.member?(set, r), do: Set.size(set),
+                            else: loop_length(n, Set.put(set, r))
+  end
+
+  def task(runs) do
+    IO.puts " N    average   analytical   (error) "
+    IO.puts "===  =========  ==========  ========="
+    Enum.each(1..20, fn n ->
+      sum_of_runs = Enum.reduce(1..runs, 0, fn _,sum -> sum + loop_length(n) end)
+      avg = sum_of_runs / runs
+      analytical = Enum.reduce(1..n, 0, fn i,sum ->
+        sum + (factorial(n) / :math.pow(n, i) / factorial(n-i))
+      end)
+      :io.format "~3w  ~9.4f   ~9.4f  (~6.2f%)~n", [n, avg, analytical, abs(avg/analytical - 1)*100]
+    end)
+  end
+end
+
+runs = 100_000
+RC.task(runs)