題目描述

請實現一個函式按照之字形列印二叉樹，即第一行按照從左到右的順序列印，第二層按照從右至左的順序列印，第三行按照從左到右的順序列印，其他行以此類推。

題目地址

https://www.nowcoder.com/practice/91b69814117f4e8097390d107d2efbe0?tpId=13&tqId=11212&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

思路

層次遍歷儲存結點，最後奇數層翻轉

Python

# -*- coding:utf-8 -*-
class
 
 TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node5 = TreeNode(5)
node1.left = node2
node1.right = node3
node2.left = node4
node3.right = node5
class Solution:
    
 
def Print(self, pRoot):
        # write code here
        # 層次遍歷儲存結點，最後奇數層翻轉
        ans = []
        if not pRoot:
            return ans
        queue = []
        queue.append(pRoot)
        while queue:
            temp = []
            for i in range(len(queue)):
                r = queue.pop(0)
                temp.append(r.val)
                
 
if r.left:
                    queue.append(r.left)
                if r.right:
                    queue.append(r.right)
            ans.append(temp)
        for i in range(1,len(ans),2):
            ans[i] = ans[i][::-1]
        return ans

if __name__ == '__main__':
    # [[1] [3 2] [4 5]]
    result = Solution().Print(node1)
    print(result)