clone_tree.py

class TreeNode:
  def __init__(self, value, left=None, right=None):
    self.value = value
    self.left = left
    self.right = right
  
def build_a_tree():
  root = TreeNode(10)
  a = TreeNode(20)
  b = TreeNode(30)
  c = TreeNode(40)
  d = TreeNode(50)
  
  root.left = a
  root.right = b
  a.right = c
  b.left = d

  return root

def clone_tree(root):
  """clone a tree"""
  if root is None:
    return None
  
  new_root = TreeNode(root.value)
  new_root.left = clone_tree(root.left)
  new_root.right = clone_tree(root.right)
  return new_root

"""driver program"""

root = build_a_tree()

new_root = clone_tree(root)

print(new_root.value)
print(new_root.left.value)
print(new_root.right.value)
print(new_root.left.right.value)
print(new_root.right.left.value)