79.Combination Sum

class Solution {
public:
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        vector<vector<int> > res;
        vector<int> out;
        sort(candidates.begin(), candidates.end());
        combinationSumDFS(candidates, target, 0, out, res);
        return res;
    }
    void combinationSumDFS(vector<int> &candidates, int target, int start, vector<int> &out, vector<vector<int> > &res) {
        if (target < 0) return;
        else if (target == 0) res.push_back(out);
        else {
            for (int i = start; i < candidates.size(); ++i) {
                out.push_back(candidates[i]);
                combinationSumDFS(candidates, target - candidates[i], i, out, res);
/*Note 这里用的是i是因为当前元素可以重复出现。如果用pos的话，又从头开始了会有重复的，用i＋1的话直接dfs到当前位置之后的元素
*/
                out.pop_back();
            }
        }
    }
};

• http://www.cnblogs.com/grandyang/p/4419259.html