【leetcode】Combination Sum

 1 class Solution {
 2 
 3 public:
 4 
 5     vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
 6 
 7         
 8 
 9         sort(candidates.begin(),candidates.end());
10 
11         vector<vector<int> > result;
12 
13         vector<int> tmp;
14 
15  
16 
17         backtracking(result,candidates,target,tmp,0,0);
18 
19         
20 
21         return result;
22 
23     }
24 
25     
26 
27     void backtracking(vector<vector<int> > &result,vector<int> &candidates, int &target,vector<int> tmp, int sum,int index)
28 
29     {
30 
31  
32 
33         if(sum==target)
34 
35         {
36 
37             result.push_back(tmp);
38 
39             return;
40 
41         }
42 
43         else
44 
45         {
46 
47             int sum0=sum;
48 
49             //注意index
50 
51             for(int i=index;i<candidates.size();i++)
52 
53             {
54 
55                 tmp.push_back(candidates[i]);
56 
57                 sum=sum0+candidates[i];
58 
59                 if(sum>target)
60 
61                 {
62 
63                     break;
64 
65                 }
66 
67                 backtracking(result,candidates,target,tmp,sum,i);
68 
69                 tmp.pop_back();
70 
71             }            
72 
73         }        
74 
75     }
76 
77 };