7: Rebuild the binary tree

Enter the results of the preorder traversal and midorder traversal of a binary tree, please reconstruct the binary tree. Suppose that the input pre-order traversal and mid-order traversal results do not contain duplicate numbers. For example, input the pre-order traversal sequence {1,2,4,7,3,5,6,8} and mid-order traversal sequence {4,7,2,1,5,3,8,6}, then reconstruct the binary tree return.

class TreeNode:
    def __init__(self,x):
        self.val = x
        self.right = None
        self.left = None

class solution:
    def ReConstructBinaryTree(self,pre,tin):
        lenth = len(pre)
        if lenth == 0:
            return None
        elif lenth== 1:
            return TreeNode(pre)
        else:
            root = TreeNode(pre[0])
            root.left = self.ReConstructBinaryTree(pre[1:tin.index(pre[0])+ 1],tin[:tin.index(pre[0])])
            root.right = self.ReConstructBinaryTree(pre[tin.index(pre[0])+ 1:],tin[tin.index(pre[0])+ 1:])
        return root

Use recursive thinking