問題：

給定一個int陣列A，陣列中元素互不重複，給定一個數x，求所有求和能得到x的數字組合，組合中的元素來自A，可重複使用。

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

void getSet(vector<int>& nums, vector<vector<int> >& res, vector<int> &tem, int target, int index);
vector
 
<vector<int> > getSetOfSum(vector<int>& nums, int target)
{
    vector<vector<int> > res;
    if (nums.size() == 0)
        return {};
    sort(nums.begin(), nums.end());
    vector<int> tem;
    getSet(nums, res, tem, target, 0);
    return res;
}



void getSet(vector<int
 
>& nums, vector<vector<int> >& res, vector<int> &tem, int target, int index)
{
    if (target == 0)
        res.push_back(tem);

    for (int i = index; i < int(nums.size()); i++)
    {
        if (target - nums[i] < 0)
            return;
        tem.push_back(nums[i]);
        getSet(nums, res, tem, target 
 
- nums[i], i);
        tem.pop_back();
    }
}

int main()
{
    vector<vector<int> >ans;

    vector<int>nums = { 3,2,6,7 };
    int target = 7;
    ans = getSetOfSum(nums, target);
    int i = ans.size();
    for (int j = 0; j < i; j++)
    {
        for (auto v : ans[j])
        {
            cout << v << " ";
        }
        cout << endl;
    }
    system("pause");
    return 0;
}