# 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]) -> Optional[TreeNode]:
if len(preorder) == 0:
return None
root = TreeNode(val=preorder[0])
mid = inorder.index(root.val)
root.left = self.buildTree(preorder[1:mid + 1], inorder[:mid])
root.right = self.buildTree(preorder[1+mid:], inorder[mid+1:])
return root