# 105. Construct Binary Tree from Preorder and Inorder Traversal

#### Medium

***

Given two integer arrays `preorder` and `inorder` where `preorder` is the preorder traversal of a binary tree and `inorder` is the inorder traversal of the same tree, construct and return *the binary tree*.

 

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/02/19/tree.jpg)

```
Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
Output: [3,9,20,null,null,15,7]
```

**Example 2:**

```
Input: preorder = [-1], inorder = [-1]
Output: [-1]
```

 

**Constraints:**

* `1 <= preorder.length <= 3000`
* `inorder.length == preorder.length`
* `-3000 <= preorder[i], inorder[i] <= 3000`
* `preorder` and `inorder` consist of **unique** values.
* Each value of `inorder` also appears in `preorder`.
* `preorder` is **guaranteed** to be the preorder traversal of the tree.
* `inorder` is **guaranteed** to be the inorder traversal of the tree.

```python
class Solution:
    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
        if inorder:
            index = inorder.index(preorder.pop(0))
            root = TreeNode(inorder[index])
            root.left = self.buildTree(preorder, inorder[:index])
            root.right = self.buildTree(preorder, inorder[index+1:])
            return root
```