# [Solved] 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.

## Question

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:

```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 Solution

```# 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 buildTree(self, preorder: List[int], inorder: List[int]) -> TreeNode:
if inorder:
x = preorder.pop(0)
ind = inorder.index(x)
root = TreeNode(x)
root.left = self.buildTree(preorder,inorder[:ind])
root.right = self.buildTree(preorder,inorder[ind+1:])
return root```