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class Solution {
public:
    vector<vector<int>> res;
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        vector<int> path;
        sort(candidates.rbegin(), candidates.rend());
        backtrack(candidates, target, 0, path);
        return res;
    }

    void backtrack(vector<int> &cand, int sum, int idx, vector<int> &path){
        if(sum == 0){
            res.push_back(path);
            return;
        }
        for(int i=idx; i<cand.size(); i++){
            if(sum-cand[i] >= 0){
                path.push_back(cand[i]);
                sum-=cand[i];
                backtrack(cand, sum, i, path);
                path.pop_back();
                sum+=cand[i];
            }
        }
    }

};