[Leetcode] (python): 103-binary Tree Zigzag level Order traversal

Source of the topic:

https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/

Test Instructions Analysis:

The z-word width traverses the tree.

Topic Ideas:

This problem can be compared with the Trickery method. First get the result of the width traversal, and then flip the second layer to be able.

Code (Python):

　　

#Definition for a binary tree node.#class TreeNode (object):#def __init__ (self, x):#self.val = x#self.left = None#self.right = Noneclasssolution (object):defZigzaglevelorder (self, root):""": Type Root:treenode:rtype:list[list[int]]"""ans= []        defBFS (root,level):ifRoot! =None:ifLen (ANS) < level + 1: Ans.append ([]) ans[level].append (root.val) BFS (Root.left,level + 1) BFS (Root.right,level+ 1) BFS (root,0) I= 1 whileI <len (ans): Ans[i].reverse () I+ = 2returnans

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[Leetcode] (python): 103-binary Tree Zigzag level Order traversal