题解 | #按之字形顺序打印二叉树#

在层序遍历的基础上添加列表的倒置逻辑，基础还是层序遍历。

import queue
class Solution:
    def Print(self , pRoot: TreeNode) -> List[List[int]]:
        # write code here
        if not pRoot:
            return []
        q = queue.Queue()
        q.put(pRoot)
        res = []
        reversal_count = 0
        while not q.empty():
            q_len = q.qsize()
            q_res = []
            for _ in range(q_len):
                temp = q.get()
                if temp.left:
                    q.put(temp.left)
                if temp.right:
                    q.put(temp.right)
                q_res.append(temp.val)
            if reversal_count % 2:
                q_res = self.list_reversal(q_res)
                print(q_res)
            res.append(q_res)
            reversal_count += 1 
        return res
                
                
    def list_reversal(self, res: List[int]) -> list[int]:
        temp = []
        len_res = len(res)
        for i in range(len_res):
            temp.append(res[len_res - 1 - i])
        return temp