# 树

树是一种典型的非结构化数据，常用于迭代计算。

## 二叉树的遍历

#### [94. 二叉树的中序遍历](https://leetcode-cn.com/problems/binary-tree-inorder-traversal/)

```python

# Definition for a binary tree node.

# class TreeNode:

# def __init__(self, val=0, left=None, right=None):

# self.val = val

# self.left = left

# self.right = right

class Solution:

def __init__(self)

self.list1 = [] ## 空列表

def inorderTraversal(self, root: TreeNode) -> List[int]:

self.mid(root)

return self.list1

def mid(self,root: TreeNode):

if root is None:

return None

self.inorderTraversal(root.left)

#print(root.val)

self.list1.append(root.val)

self.inorderTraversal(root.right)

```