The test accepts this code where I don't return anything. I don't understand what the test code is checking...

```
class Solution
{
public:
vector<vector<int>> permute(vector<int>& nums)
{
vector<vector<int>> result;
if (nums.empty()) return result;
sort(nums.begin(), nums.end());
do
{
result.push_back(nums);
} while (next_permutation(nums.begin(), nums.end()));
}
};
```