set < int > del_set ;
        int sz = to_delete.size();
        for (int i = 0 ; i < sz ; i++)
        {
            del_set.insert(to_delete[i]);
        }
        vector < TreeNode* > res;
        fun (root , del_set, res, true);
        return res;

    }
    TreeNode* fun (TreeNode* root, set<int>& to_delete, vector < TreeNode*>& res, bool r )
    {
        if (!root)
            return NULL;

        bool del = to_delete.find(root->val) != to_delete.end();

        if (r && !del)
        {
            res.push_back(root);
        }

        root->left = fun (root -> left , to_delete, res, del);
        root->right = fun (root -> right , to_delete, res, del);

        return del? NULL : root;