题目描述

blablabla

样例

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
from collections import deque

class Solution(object):
    def printFromTopToBottom(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if not root:
            return []
        q = deque()
        rtn = list()
        q.append(root)
        pre_l = 1
        while q:
            cnt = 0
            t = list()
            for i in range(pre_l):
                item = q.popleft()
                t.append(item.val)
                if item.left:
                    cnt += 1
                    q.append(item.left)
                if item.right:
                    cnt += 1
                    q.append(item.right)
            pre_l = cnt
            rtn.append(t)
        return rtn

算法1

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

blablabla

算法2

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

blablabla