题目链接

# 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 not preorder or not inorder:return Noneroot=TreeNode(preorder[0])root_index=inorder.index(preorder[0])root.left=self.buildTree(preorder[1:1+root_index],inorder[:root_index])root.right=self.buildTree(preorder[1+root_index:],inorder[root_index+1:])return root