递归求子集

#include<iostream>
#include<vector>
using namespace std;
void solution(int i,vector<int> &nums,vector<int> &item,vector<vector<int> > &result)   //传引用 
{
    if(i >= nums.size())
    return ;

    item.push_back(nums[i]);
    result.push_back(item);
    solution(i+1,nums,item,result);

    item.pop_back();
    solution(i+1,nums,item,result);
}
int main()
{
    vector<int> nums;
    nums.push_back(1);
    nums.push_back(2);
    nums.push_back(3);
    vector<int> item;
    vector<vector<int> >result;
    int i = 0;
    result.push_back(item);    //将空集push进result 
    solution(i,nums,item,result);
    for(int i = 0; i < (1<< nums.size()); i++)
    {
        if(result[i].size() == 0)
        {
            cout<<"[]";
        }
        for(int j = 0; j < result[i].size(); j++)
        {
            cout<<"["<<result[i][j]<<"]";
        }
        cout<<endl;
    }
}