Binary tree BFS traversal - AttributeError: 'list' object has no attribute 'value'

Question

class BinaryTreeNode:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None    

def level_order_traversal(root):
        q = []
        result = []
        if not root:
            return result
        q.append(root)
        while q:
            temp_q = []
            res_q = []
            node = q.pop(0)
            res_q.append(node.value)
            if node.left:
                temp_q.append(node.left)
            if node.right:
                temp_q.append(node.right)
            q = temp_q
            result.append(res_q)
        return result

if __name__ == "__main__":
    result = level_order_traversal([0, 1, None, None, 2, 4, None, None, 3])
    print(result)

Answer 1

代码挑战站点通常会将 JSON 输入转换为给定 class 的实例——在本例中为 BinaryTreeNode 和相同的嵌套实例。

一旦您决定在代码挑战框架之外测试您的代码，您就必须自己做好准备。如果您希望它使用列表作为输入，请将此辅助函数添加到您的工具集中：

def to_binary_tree(items):
    if not items:
        return None

    it = iter(items)
    root = BinaryTreeNode(next(it))
    q = [root]
    for node in q:
        val = next(it, None)
        if val is not None:
            node.left = BinaryTreeNode(val)
            q.append(node.left)
        val = next(it, None)
        if val is not None:
            node.right = BinaryTreeNode(val)
            q.append(node.right)
    return root

现在您可以：

if __name__ == "__main__":
    result = level_order_traversal(to_binary_tree([0, 1, None, None, 2, 4, None, None, 3]))
    print(result)

Binary tree BFS traversal - AttributeError: 'list' object has no attribute 'value'

Binary tree BFS traversal - AttributeError: 'list' object has no attribute 'value'

python-3.x

algorithm

data-structures

attributeerror