def simple_bst():
#build a binary tree of three nodes in two levels
sbst = BinarySearchTree()
curr_root = TreeNode(3)
root_left = TreeNode(1)
root_right = TreeNode(7)
curr_root.left_child = root_left
curr_root.right_child = root_right
sbst.root_node = curr_root
return sbst
def unbalanced_bst():
#build a binary search tree of seven nodes in four levels
ubst = BinarySearchTree()
curr_root = TreeNode(6)
root_left = TreeNode(4)
root_left_left = TreeNode(2)
root_right = TreeNode(16)
root_right_left = TreeNode(10)
root_right_right = TreeNode(26)
root_right_right_right = TreeNode(42)
ubst.root_node = curr_root
curr_root.left_child = root_left
curr_root.left_child.left_child = root_left_left
curr_root.right_child = root_right
curr_root.right_child.left_child = root_right_left
curr_root.right_child.right_child = root_right_right
curr_root.right_child.right_child.right_child = root_right_right_right
return ubst
def balanced_tree():
#build a binary tree of seven nodes in three levels
bt = BinaryTree()
curr_root = TreeNode(7)
root_left = TreeNode(3)
root_left_left = TreeNode(1)
root_left_right = TreeNode(5)
root_right = TreeNode(11)
root_right_left = TreeNode(9)
root_right_right = TreeNode(13)
bt.root_node = curr_root
curr_root.left_child = root_left
curr_root.left_child.left_child = root_left_left
curr_root.left_child.right_child = root_left_right
curr_root.right_child = root_right
curr_root.right_child.left_child = root_right_left
curr_root.right_child.right_child = root_right_right
return bt