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【leetcode】Combination Sum II

Combination Sum II

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

Each number in C may only be used once in the combination.

Note:

All numbers (including target) will be positive integers.
Elements in a combination (a₁, a₂, … , a_k) must be in non-descending order. (ie, a₁ ≤ a₂ ≤ … ≤ a_k).
The solution set must not contain duplicate combinations.

For example, given candidate set 10,1,2,7,6,1,5 and target 8,
A solution set is:
[1, 7]
[1, 2, 5]
[2, 6]
[1, 1, 6]

要考虑去重

每次都从当前位置选取元素，遇到重复的直接跳过就可以了

 1 class Solution {
 2 
 3 public:
 4 
 5    
 6 
 7     vector<vector<int> > combinationSum2(vector<int> &candidates, int target)
 8 
 9     {
10 
11        
12 
13         sort(candidates.begin(),candidates.end());
14 
15         vector<vector<int> > result;
16 
17         vector<int> tmp;
18 
19  
20 
21         backtracking(result,candidates,target,tmp,0,0);
22 
23        
24 
25         return result;
26 
27     }
28 
29    
30 
31     void backtracking(vector<vector<int> > &result,vector<int> &candidates, int &target,vector<int> tmp, int sum,int index)
32 
33     {
34 
35  
36 
37         if(sum==target)
38 
39         {
40 
41             result.push_back(tmp);
42 
43             return;
44 
45         }
46 
47         else
48 
49         {
50 
51             int sum0=sum;
52 
53            
54 
55             for(int i=index;i<candidates.size();i++)
56 
57             {
58 
59                 if(i>index&&candidates[i]==candidates[i-1])
60 
61                 {
62 
63                     continue;
64 
65                 }
66 
67                
68 
69                 tmp.push_back(candidates[i]);
70 
71                
72 
73                
74 
75                 sum=sum0+candidates[i];
76 
77                 if(sum>target)
78 
79                 {
80 
81                     break;
82 
83                 }            
84                 backtracking(result,candidates,target,tmp,sum,i+1);
85 
86                 tmp.pop_back();
87 
88             }            
89 
90         }        
91 
92     }

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原文地址：https://www.cnblogs.com/reachteam/p/4192432.html