leetcode 树的锯齿形状遍历

二叉树的锯齿形层次遍历

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],

返回锯齿形层次遍历如下：

[

  [3],

  [20,9],

  [15,7]

]

leetcode 树的锯齿形状遍历

我的想法是把树的每一层存起来，然后技术层次的结点顺序翻转一下

 # Definition for a binary tree node.

 # class TreeNode:

 #     def __init__(self, x):

 #         self.val = x

 #         self.left = None

 #         self.right = None

 class Solution:

     def zigzagLevelOrder(self, root):

         """

         :type root: TreeNode

         :rtype: List[List[int]]

         """

         if root is None:

             return []

         res = [[root]]

         res_int = [[root.val]]

         i = 0

         while i < len(res):

             cur = res[i]

             nLayer = []

             nLyayer_int = []

             for n in cur:

                 if n.left is not None:

                     nLayer.append(n.left)

                     nLyayer_int.append(n.left.val)

                 if n.right is not None:

                     nLayer.append(n.right)

                     nLyayer_int.append(n.right.val)

             if nLayer:

                 res.append(nLayer)

                 if i % 2 == 0:

                     nLyayer_int.reverse()

                 res_int.append(nLyayer_int)

             i += 1

         return res_int

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leetcode 树的锯齿形状遍历

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