Code

class Solution {
public:
    vector<vector<int>> result;
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<int> cur;
        vector<bool> visited(nums.size(), 0);
        result.push_back(cur);
        dfs(cur, visited, nums, 0);
        return result;
    }

    void dfs(vector<int> cur, vector<bool> visited, vector<int> nums, int base) {
        for (int i=base; i<nums.size(); i++) {
            if (!visited[i]) {
                visited[i] = true;
                cur.push_back(nums[i]);
                result.push_back(cur);
                dfs(cur, visited, nums, i+1);
                cur.pop_back();
                visited[i] = false;
            }
        }
    }
};