class Tree_structure:
   def __init__(self, data=None):
      self.key = data
      self.children = []

   def set_root_node(self, data):
      self.key = data

   def add_vals(self, node):
      self.children.append(node)

   def search_val(self, key):
      if self.key == key:
         return self
      for child in self.children:
         temp = child.search(key)
         if temp is not None:
            return temp
      return None

   def count_leaf_node(self):
      leaf_nodes = []
      self.count_leaf_node_helper_fun(leaf_nodes)
      return len(leaf_nodes)

   def count_leaf_node_helper_fun(self, leaf_nodes):
      if self.children == []:
         leaf_nodes.append(self)
      else:
         for child in self.children:
            child.count_leaf_node_helper_fun(leaf_nodes)

tree = None

print('菜单（假定没有重复的键）')
print('在根处添加')
print('在下面添加')
print('计数')
print('退出')

while True:
   my_input = input('您想执行哪个操作？').split()

   operation = my_input[0].strip().lower()
   if operation == 'add':
      data = int(my_input[1])
      newNode = Tree_structure(data)
      sub_op = my_input[2].strip().lower()
      if sub_op == 'at':
         tree = newNode
      elif sub_op == 'below':
         my_pos = my_input[3].strip().lower()
         key = int(my_pos)
         ref_node = None
         if tree is not None:
            ref_node = tree.search_val(key)
         if ref_node is None:
            print('没有这样的键。')
            continue
         ref_node.add_vals(newNode)

   elif operation == 'count':
      if tree is None:
         print('树为空')
      else:
         count = tree.count_leaf_node()
         print('叶节点数为：{}'.format(count))

   elif operation == 'quit':
      break

菜单（假定没有重复的键）
在根处添加
在下面添加
计数
退出
您想执行哪个操作？添加78个根
您想执行哪个操作？在78下面添加90
您想执行哪个操作？在78下面添加8
您想执行哪个操作？计数
叶节点数为：2
您想执行哪个操作？退出