solution added

binary_search_trees/array_to_bst.py

@@ -10,4 +10,21 @@ def arr_to_bst(arr):
         Balanced Binary Search Tree using the elements in the array.
         Return the root of the Binary Search Tree.
     """
-    pass
+    if arr == []:
+        return None
+
+    left = 0
+    right = len(arr) -1
+    return binary_search_in_arr(arr, left, right)
+
+
+def binary_search_in_arr(arr, left, right):
+    if arr == []:
+        return None
+    if right >= left:
+        mid = left + (right - left) // 2
+        node = TreeNode(arr[mid])
+        node.right = binary_search_in_arr(arr, mid+1, right)
+        node.left = binary_search_in_arr(arr, left , mid - 1)
+        return node
+    return None

tests/test_array_to_bst.py

@@ -20,7 +20,7 @@ def test_will_return_balanced_bst_for_even_lengthed_list():
     answer = arr_to_bst(arr)
 
     # Assert
-    assert is_bst(answer) and is_balanced_tree(answer)
+    assert is_bst(answer) and is_balanced_tree(answer) 
 
 def test_will_return_balanced_bst_for_long_list():
     # Arrange