难度中等772收藏分享切换为英文接收动态反馈
给你一个二叉树,请你返回其按 层序遍历 得到的节点值。 (即逐层地,从左到右访问所有节点)。
示例:
二叉树:[3,9,20,null,null,15,7]
,
3 / \ 9 20 / \ 15 7
返回其层序遍历结果:
[ [3], [9,20], [15,7] ]
广度优先遍历:
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def levelOrder(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
if root is None:
return []
que = []
que.append(root)
res_all = []
while que:
res_level = []
for _ in range(len(que)):
cur_node = que.pop(0)
if cur_node:
res_level.append(cur_node.val)
if cur_node.left:
que.append(cur_node.left)
if cur_node.right:
que.append(cur_node.right)
if res_level:
res_all.append(res_level)
return res_all