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 Queue
class Solution:
    def isCompleteTree(self , root: TreeNode) -> bool:
        if root is None:
            return None
        q = Queue()
        q.put(root)
        flag = 'node'
        while not q.empty():
            n = q.qsize()
            for i in range(n):
                cur = q.get()
                if not cur: #出现了空结点但后续还有结点说明不是完全二叉树
                    flag = 'leaf'
                else:
                    if flag == 'leaf':
                        return False
                    q.put(cur.left)
                    q.put(cur.right)
        return True