Improved doctests for some functions (TheAlgorithms#11334)

Author: MrBubb1es

data_structures/binary_tree/binary_tree_traversals.py

@@ -97,6 +97,8 @@ def level_order(root: Node | None) -> Generator[int, None, None]:
  """
  Returns a list of nodes value from a whole binary tree in Level Order Traverse.
  Level Order traverse: Visit nodes of the tree level-by-level.
+ >>> list(level_order(make_tree()))
+ [1, 2, 3, 4, 5]
  """
 
  if root is None:
@@ -120,6 +122,10 @@ def get_nodes_from_left_to_right(
  """
  Returns a list of nodes value from a particular level:
  Left to right direction of the binary tree.
+ >>> list(get_nodes_from_left_to_right(make_tree(), 1))
+ [1]
+ >>> list(get_nodes_from_left_to_right(make_tree(), 2))
+ [2, 3]
  """
 
  def populate_output(root: Node | None, level: int) -> Generator[int, None, None]:
@@ -140,10 +146,14 @@ def get_nodes_from_right_to_left(
  """
  Returns a list of nodes value from a particular level:
  Right to left direction of the binary tree.
+ >>> list(get_nodes_from_right_to_left(make_tree(), 1))
+ [1]
+ >>> list(get_nodes_from_right_to_left(make_tree(), 2))
+ [3, 2]
  """
 
  def populate_output(root: Node | None, level: int) -> Generator[int, None, None]:
- if root is None:
+ if not root:
  return
  if level == 1:
  yield root.data
@@ -158,6 +168,8 @@ def zigzag(root: Node | None) -> Generator[int, None, None]:
  """
  ZigZag traverse:
  Returns a list of nodes value from left to right and right to left, alternatively.
+ >>> list(zigzag(make_tree()))
+ [1, 3, 2, 4, 5]
  """
  if root is None:
  return