Given a set of candidate numbers (C) and a target number (T), find all unique
combinations in C where the candidate numbers sums to T.
The same repeated
number may be chosen from C unlimited number of times.
Note:
All numbers
(including target) will be positive integers.
Elements in a combination (a1,
a2, .. , ak) must be in non-descending order. (ie, a1 <= a2 <= ... <=
ak).
The solution set must not contain duplicate combinations.
For
example, given candidate set 2,3,6,7 and target 7,
A solution set
is:
[7]
[2, 2, 3]
Solution: Sort & Recursion.
1 class Solution {
2 public:
3 vector<vector<int> > res;
4 void combinationSum(vector<int> &candidates, int target, vector<int> &com, int start)
5 {
6 if(target == 0) {
7 res.push_back(com);
8 return;
9 }
10 for(int i = start; i < candidates.size() && target >= candidates[i]; i++) {
11 com.push_back(candidates[i]);
12 combinationSum(candidates, target-candidates[i], com, i); // start = i;
13 com.pop_back();
14 }
15 }
16
17 vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
18 sort(candidates.begin(), candidates.end());
19 vector<int> com;
20 combinationSum(candidates, target, com, 0);
21 return res;
22 }
23 };
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原文：http://www.cnblogs.com/zhengjiankang/p/3646346.html