1 void backTrace(int sum, int target, int a[], int index, int t, vector<int>& candidates)
 2 {
 3     if (sum == target)
 4     {
 5         vector<int> b;
 6         for (int i = 0; i < t; i++)
 7         {
 8             b.push_back(a[i]);
 9         }
10         sort(b.begin(),b.end());
11         result.push_back(b);
12     }
13     if (sum>target)
14     {
15         return;
16     }
17     for (int i = index; i < candidates.size(); i++)
18     {
19         a[t] = candidates[i];
20         backTrace(sum + candidates[i], target, a, i, t + 1, candidates);
21     }
22 }

 1 #include<iostream>
 2 #include<vector>
 3 #include<algorithm>
 4
 5 using namespace std;
 6
 7
 8 vector<vector<int>> result;
 9 int a[100];
10
11 void backTrace(int sum, int target, int a[], int index, int t, vector<int>& candidates)
12 {
13     if (sum == target)
14     {
15         vector<int> b;
16         for (int i = 0; i < t; i++)
17         {
18             b.push_back(a[i]);
19         }
20         result.push_back(b);
21     }
22     if (sum>target)
23     {
24         return;
25     }
26     for (int i = index; i < candidates.size(); i++)
27     {
28         a[t] = candidates[i];
29         backTrace(sum + candidates[i], target, a, i, t + 1, candidates);
30         if (candidates[i] + sum > target)
31             return;
32     }
33 }
34
35 vector<vector<int>> combinationSum(vector<int>& candidates, int target)
36 {
37     sort(candidates.begin(), candidates.end());
38     backTrace(0, target, a, 0, 0, candidates);
39     return result;
40 }
41
42 int main()
43 {
44     vector<int> can = { 2, 3, 6, 7 };
45     combinationSum(can, 7);
46     for (int i = 0; i < result.size(); i++)
47     {
48         for (int j = 0; j < result[i].size(); j++)
49         {
50             cout << result[i][j] << "    ";
51         }
52         cout << endl;
53     }
54 }