Q:
给定一个二叉树,返回其节点值的锯齿形层次遍历。(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行)。
例如:
给定二叉树 [3,9,20,null,null,15,7]
,
3 / \ 9 20 / \ 15 7
返回锯齿形层次遍历如下:
[ [3], [20,9], [15,7] ]
链接:https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/description/
思路:正常的二叉树层次遍历+对输出进行处理
代码:
# 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 zigzagLevelOrder(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
res = []
que = [root]
if root == None:
return res
while que:
tempList = []
for i in range(len(que)):
node = que.pop(0)
tempList.append(node.val)
if node.left:
que.append(node.left)
if node.right:
que.append(node.right)
res.append(tempList)
temp = []
for i in range(len(res)):
if i%2 == 0:
temp.append(res[i])
else:
temp.append(res[i][::-1])
return (temp)