# 实现二叉树先序、中序、后序遍历

![last modify](https://img.shields.io/static/v1?label=last%20modify\&message=2022-10-14%2014%3A59%3A33\&color=yellowgreen\&style=flat-square) [![](https://img.shields.io/static/v1?label=\&message=%E4%B8%AD%E7%AD%89\&color=yellow\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/..#中等) [![](https://img.shields.io/static/v1?label=\&message=%E7%89%9B%E5%AE%A2\&color=green\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/..#牛客) [![](https://img.shields.io/static/v1?label=\&message=%E6%B7%B1%E5%BA%A6%E4%BC%98%E5%85%88%E6%90%9C%E7%B4%A2\&color=blue\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/..#深度优先搜索)

> [实现二叉树先序，中序和后序遍历\_牛客题霸\_牛客网](https://www.nowcoder.com/practice/a9fec6c46a684ad5a3abd4e365a9d362)

**问题简述**

```
给定一棵二叉树，分别按照二叉树先序，中序和后序打印所有的节点。
```

**思路：DFS**

<details>

<summary><strong>Python</strong></summary>

```python
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
# 
# @param root TreeNode类 the root of binary tree
# @return int整型二维数组
#
class Solution:
    def threeOrders(self , root: TreeNode) -> List[List[int]]:
        # write code here
        
        p, i, s = [], [], []
        
        def dfs(x):
            if x is None:
                return 
            
            p.append(x.val)
            dfs(x.left)
            i.append(x.val)
            dfs(x.right)
            s.append(x.val)
        
        dfs(root)
        return [p, i, s]
```

</details>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://imhuay.gitbook.io/studies/algorithms/problems/2022/03/niu-ke-0045-zhong-deng-shi-xian-er-cha-shu-xian-xu-zhong-xu-hou-xu-bian-li.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.