、
void push(std::vector<std::vector<int>> &a,std::vector<int> &v,std::vector<int> &nums,int n,int s){
if(v.size()==n){
a.push_back(v);
return;
}
for(int i=s;i<nums.size();i++){
v.push_back(nums[i]);
push(a,v,nums,n,i+1);
v.pop_back();
}
}
std::vector<std::vector<int>> subsets(std::vector<int>& nums) {
int n=0;
std::vector<int> v;
std::vector<std::vector<int>> a;
std::vector<int> flag;
for(int i=0;i< nums.size();i++){
flag.push_back(0);
}
while(n!=nums.size()+1){
v.clear();
if(n==0)
a.push_back(v);
else{
push(a,v,nums,n,0);
}
n++;
}
return a;
}