def reConstructBinaryTree(self, pre, tin):
    if not pre:
        return None
    cur_val = pre.pop(0)
    root = TreeNode(cur_val)
    index = tin.index(cur_val)
    root.left = self.reConstructBinaryTree(pre[:index], tin[:index])
    root.right = self.reConstructBinaryTree(pre[index:], tin[index+1:])
    return root

就是···递归吧。