class Node: # 这是一个带有构造函数的类节点，其中包含类型数据的数据变量和左右指针。
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

def display(tree): #按顺序遍历树

    if tree is None: 
        return

    if tree.left is not None:
        display(tree.left)

    print(tree.data)

    if tree.right is not None:
        display(tree.right)

    return

def depth_of_tree(tree): #这是查找二叉树深度的递归函数。
    if tree is None:
        return 0
    else:
        depth_l_tree = depth_of_tree(tree.left)
        depth_r_tree = depth_of_tree(tree.right)
        if depth_l_tree > depth_r_tree:
            return 1 + depth_l_tree
        else:
            return 1 + depth_r_tree


def is_full_binary_tree(tree): # 这个函数返回的是完整的二叉树吗？
    if tree is None:
        return True
    if (tree.left is None) and (tree.right is None):
        return True
    if (tree.left is not None) and (tree.right is not None):
        return (is_full_binary_tree(tree.left) and is_full_binary_tree(tree.right))
    else:
        return False


def main(): # 用于测试的主要功能。
    tree = Node(1)
    tree.left = Node(2)
    tree.right = Node(3)
    tree.left.left = Node(4)
    tree.left.right = Node(5)
    tree.left.right.left = Node(6)
    tree.right.left = Node(7)
    tree.right.left.left = Node(8)
    tree.right.left.left.right = Node(9)

    print(is_full_binary_tree(tree))
    print(depth_of_tree(tree))
    print("Tree is: ")
    display(tree)


if __name__ == '__main__':
    main()

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