Combination Sum

题目链接

思路： 简单回溯。

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