public static void main(String[] args) {

int n = 9, k = 3;

L216 l = new L216();

System.out.println(l.combinationSum3(k, n));

}

/**

public List<List<Integer>> combinationSum3(int k, int n) {

List<List<Integer>> resultList = new ArrayList<>();

List<Integer> list = new ArrayList<>();

loop(k, n, 0, list, resultList, 0);

return resultList;

}

public void loop(int k, int n, int sum, List<Integer> list, List<List<Integer>> resultList, int lastValue) {

if (list.size() == k) {

return;

}

for (int i = 1; i <= 9; i++) {

if (!list.contains(i)) {

if (i < lastValue) {

continue;

}

if (sum + i < n && list.size() < k) {

list.add(i);

loop(k, n, sum + i, list, resultList, i);

list.remove(list.size() - 1);

} else if (sum + i == n && list.size() == k - 1) {

list.add(i);

resultList.add(new ArrayList<>(list));

list.remove(list.size() - 1);

}

}

}

}