题解 | #从上往下打印二叉树#

稍加尝试即可发现，打印顺序即为BFS队列入队顺序。

# 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 int整型一维数组
#
class Solution:
    def PrintFromTopToBottom(self , root: TreeNode) -> List[int]:
        # write code here
        #BFS
        if root is None:
            return None
        Queue = [root]
        lRes = []
        while len(Queue) >= 1:
            nNodeTemp = Queue.pop(0)
            lRes.append(nNodeTemp.val)
            if nNodeTemp.left:
                Queue.append(nNodeTemp.left)
            if nNodeTemp.right:
                Queue.append(nNodeTemp.right)
                
        return lRes