//f will take the input array, the index or the position of the element on which we need to take the decision and the result vector of vectors

void helper(vector<int>&nums, int startIndex, vector<vector<int>>& res){

int n= nums.size();

//base case

if (startIndex==n){

res.push_back({});

return;

}

//f(ar,startIndex)= f(ar,startIndex+1) U {nums[startIndex] U f(ar.startIndex+1)}

vector<vector<int>> subSol;

helper(nums, startIndex+1, res);

//exclude the startIndex

subSol= res;

//include the startIndex

vector<int> temp;

for (int i=0;i<subSol.size();i++){

temp= subSol[i];

temp.push_back(nums[startIndex]);

res.push_back(temp);

}

}

vector<vector<int>> subsets(vector<int>& nums) {

vector<vector<int>> res;

helper(nums,0,res);

return res;

}