LeetCode 103. Binary Tree Zigzag Level Order Traversal

题目

思路

层次遍历，记录层数，逆序输出即可。

代码

# 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]]
        """
        res_list = []
        queue = []
        tmp_list = []
        if root: queue.append(root)
        level = 0
        num_list = []
        while queue:
            node = queue[0]
            num_list.append(node.val)
            queue.pop(0)
            if node.left: tmp_list.append(node.left)
            if node.right: tmp_list.append(node.right)
            if not queue:
                if level % 2: res_list.append(num_list[::-1])
                else: res_list.append(num_list[:])
                num_list = []
                level += 1
                queue[:] = tmp_list[:]
                tmp_list = []
        return res_list