class Solution {
public:
    vector<vector<int>> result;
    vector<int> path;

    void backtracking(vector<int>& candidates, int target, int sum) {
        if(target == sum) {
            result.push_back(path);
            return;
        } else if(sum > target) {
            return;
        }

        for(int i = 0; i < candidates.size(); i++) {
            if(path.size() == 0 || path[path.size()-1] <= candidates[i]) {
                path.push_back(candidates[i]);
                backtracking(candidates, target, sum + candidates[i]);
                path.pop_back();
            }
        }
    }

    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        backtracking(candidates, target, 0);
        return result;
    }
};

class Solution {
public:
    vector<vector<int>> result;
    vector<int> path;

    void backtracking(vector<int>& candidates, int target, int sum, int startIndex) {
        if(target == sum) {
            result.push_back(path);
            return;
        }

        // Don't need to backtracking if already above target
        for(int i = startIndex; i < candidates.size() && sum + candidates[i] <= target; i++) {
            path.push_back(candidates[i]);
            backtracking(candidates, target, sum + candidates[i], i);
            path.pop_back();
        }
    }

    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end()); // Need sort
        backtracking(candidates, target, 0, 0);
        return result;
    }
};