Bit Manipulation - Subsets

// Runtime: 8 ms
class Solution {
public:
vector<vector<int>> subsets(vector<int>& nums) {
sort(nums.begin(), nums.end());
int num_subset = pow(2, nums.size());
vector<vector<int> > res(num_subset, vector<int>());
for (int i = 0; i < nums.size(); i++)
for (int j = 0; j < num_subset; j++)
if ((j >> i) & 1)
res[j].push_back(nums[i]);
return res;
}
};