返回某集合的所有子集

#include<iostream>
#include<vector>
using namespace std;
vector<vector<int>> getSubsets(vector<int>& set, int index){
vector<vector<int>> allsubsets;
if ((int)set.size() == index){
vector<int> s;
allsubsets.push_back(s);
}
else{
allsubsets = getSubsets(set, index + 1);
int item = set[index];
vector<vector<int>> moreSubsets;
for (int i=0; i < (int)allsubsets.size(); i++){
vector<int> newsubset;
for (int j = 0; j < (int)allsubsets[i].size(); j++)
newsubset.push_back(allsubsets[i][j]);
newsubset.push_back(item);
moreSubsets.push_back(newsubset);
}
for (int j = 0; j < (int)moreSubsets.size(); j++)
allsubsets.push_back(moreSubsets[j]);
}
return allsubsets;
}

int main(){
vector<int> set;
set.push_back(1); set.push_back(2); set.push_back(3); set.push_back(4);
vector<vector<int>> subset = getSubsets(set, 0);
for (int i = 0; i < (int)subset.size(); i++){
for (int j = 0; j < (int)subset[i].size(); ++j){
cout << subset[i][j] << " ";
}
cout << endl;
}

cin.get();
return 0;
}