Counting leaves

Author: Ben Schmeckpeper

CountLeaves.exs

@@ -0,0 +1,25 @@
+defmodule CountLeaves do
+  def of([]), do: 0
+  def of([head | tail]), do: of(head) + of(tail)
+  def of(_), do: 1
+end
+
+ExUnit.start
+
+defmodule CountLeavesTest do
+  use ExUnit.Case, async: true
+
+  test "it counts leaves in an empty list" do
+    assert CountLeaves.of([]) == 0
+  end
+
+  test "it count leaves in a flat list" do
+    assert CountLeaves.of([1,2,3]) == 3
+  end
+
+  test "it count leaves in nested lists" do
+    assert CountLeaves.of([[1, 2], 3]) == 3
+    assert CountLeaves.of([1, [2, 3]]) == 3
+    assert CountLeaves.of([[1, 2], [3, 4]]) == 4
+  end
+end