[Sync Iteration] elixir/binary-search-tree/1

solutions/elixir/binary-search-tree/1/lib/binary_search_tree.ex

@@ -0,0 +1,38 @@
+defmodule BinarySearchTree do
+  @type bst_node :: %{data: any, left: bst_node | nil, right: bst_node | nil}
+
+  @doc """
+  Create a new Binary Search Tree with root's value as the given 'data'
+  """
+  @spec new(any) :: bst_node
+  def new(data), do: %{data: data, left: nil, right: nil}
+
+  @doc """
+  Creates and inserts a node with its value as 'data' into the tree.
+  """
+  @spec insert(bst_node, any) :: bst_node
+  def insert(tree, data) when data > tree.data do
+    case tree.right do
+      nil -> %{tree | right: new(data)}
+      node -> %{tree | right: insert(node, data)}
+    end
+  end
+
+  def insert(tree, data) do
+    case tree.left do
+      nil -> %{tree | left: new(data)}
+      node -> %{tree | left: insert(node, data)}
+    end
+  end
+
+  @doc """
+  Traverses the Binary Search Tree in order and returns a list of each node's data.
+  """
+  @spec in_order(bst_node) :: [any]
+  def in_order(tree), do: tree |> flatten_tree() |> List.flatten()
+
+  defp flatten_tree(tree) when tree.left == nil and tree.right == nil, do: [tree.data]
+  defp flatten_tree(tree) when tree.left == nil, do: [tree.data, flatten_tree(tree.right)]
+  defp flatten_tree(tree) when tree.right == nil, do: [flatten_tree(tree.left), tree.data]
+  defp flatten_tree(tree), do: [flatten_tree(tree.left), tree.data, flatten_tree(tree.right)]
+end