[LeetCode] Combination Sum I

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:
    void calc(vector<vector<int> >&res, vector<int>&one,
            vector<int> &candidates,
            int s, int target)
    {
        if(0 == target) res.push_back(one);
        for(int i=s;i<candidates.size() && candidates[i] <= target;i++)
        {
            one.push_back(candidates[i]);
            calc(res, one, candidates, i, target-candidates[i]);
            one.pop_back();
        }
    }
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) 
    {
        sort(candidates.begin(), candidates.end());
        vector<vector<int> > res;
        vector<int> one;
        calc(res, one, candidates, 0, target);
        return res;
    }
};