题解 | #判断是不是完全二叉树#

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param root TreeNode类
# @return bool布尔型
#
from queue import deque

class Solution:
    def isCompleteTree(self, root: TreeNode) -> bool:
        # use level order travese to check
        if not root:
            return True
        nodes = deque()
        flag = False
        nodes.append(root)
        while nodes:
            node = nodes.popleft()
            if node:
                if flag:
                    return False
                nodes.append(node.left)
                nodes.append(node.right)
            else:
                flag = True
        return True