尝试在 python 中构建二叉搜索树时出现类型错误

Question

我正在尝试构建 BST，但是当我尝试运行程序时出现以下错误：

TypeError: 'method' object is not iterable

我不确定为什么会发生这种情况，因为我假设 in_order_traversal 方法将是 BST class 的一个属性。 下面是我的代码。

class BST:
    def __init__(self,data):
        self.data = data
        self.left = None
        self.right = None
    #

    def add_child(self,data):
        if data == self.data: #check if value already exists in tree
            return

        if data <self.data: #should go on the left side then

            if self.left: #check if left tree has a value
                self.left.add_child(data) #if it has a value, use add_child method to add another child to the left
            else: #if it does not have a value
                self.left = BST(data)


        else:
            if self.right:
                self.right.add_child()
            else:
                self.right = BST(data) #if there is no right tree, init a new right tree with data

    #visit left, root then right
    def in_order_traversal(self):
        elements = []

        if self.left:
            elements += self.left.in_order_traversal()

        elements.append(self.data) #append the root

        if self.right:
            elements += self.right.in_order_traversal


        return elements



def build_tree(data):
    root = BST(data[0])

    for i in range(1,len(data)):
        root.add_child(data[i])
    return root

if __name__ == '__main__':
    numbers = [12,3,1,20]
    numbers_tree = build_tree(numbers)
    print(numbers_tree.in_order_traversal())

Answer 1

def in_order_traversal(self):
    elements = []

    if self.left:
        elements += self.left.in_order_traversal()

    elements.append(self.data) 

    if self.right:
        elements += self.right.in_order_traversal()        #CHANGE

    return elements

您实际上忘记在in_order_traversal方法之后写括号，这导致了错误。