KCombinationSum

public static void main(String[] args) {
        int[] data = {1,2,3,4,5};
        int target = 6;
        int k = 3;
        System.out.println("combinations are " + kcombinationSum(data, target, k));
    }
    public static List<List<Integer>> kcombinationSum(int[] data, int target, int k){
        Arrays.sort(data);
        List<List<Integer>> res = new ArrayList<>();
        List<Integer> temp = new ArrayList<>();
        kcombinationSumUtil(data, res, temp, target, 0, k);
        return res;
    }

    public static void kcombinationSumUtil(int[] data, List<List<Integer>> res, List<Integer> temp, int target, int start, int k){
        if(target == 0 && temp.size() == k){
            res.add(new ArrayList<>(temp));
        }
        else {
            for(int i=start; i<data.length && target-data[i] >=0 ; i++){
                temp.add(data[i]);
                kcombinationSumUtil(data, res, temp, target - data[i], i+1, k); // i+1, because same number cannot be used twice
                temp.remove(temp.size()-1);
            }
        }
    }