Combination Sum

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]

 

class Solution {
public:
vector<vector<int> > res;
vector<vector<int> > combinationSum(vector<int> &candidates, int target)
{
res.clear();
vector<int> path;
sort(candidates.begin(), candidates.end());
execute(candidates, target, 0, path);
return res;
}
void execute(vector<int> &candidates, int target, int pos, vector<int>& path)
{
for (int i = pos; i < candidates.size(); i++)
{
if(candidates[i] > target)
return;
path.push_back(candidates[i]);
if(candidates[i] == target)
{
res.push_back(path);
path.pop_back();
return;
}
else
execute(candidates, target - candidates[i], i, path);
path.pop_back();
}
}
};