216. Combination Sum III

public static List<List<Integer>> combinationSum3(int k, int n) {
int[] nums = {1,2,3,4,5,6,7,8,9};
Set<Set<Integer>> result = threeSum(nums, k, 0, n);
List<List<Integer>> list = new LinkedList<>();
for(Set<Integer> set : result) {
List<Integer> tlist = new LinkedList<>();
tlist.addAll(set);
list.add(tlist);
}
return list;

}

public static Set<Set<Integer>> threeSum(int[] nums, int k, int start, int target) {
Set<Set<Integer>> result = new HashSet<>();
if(nums[start] * k > target || nums[nums.length-1] * k < target) {
return result;
}
for(int i = start; i < nums.length; i++) {
if(k == 1) {
if(target < nums[i]) {
break;
}else if(target > nums[i]) {
continue;
}else {
Set<Integer> set = new HashSet<>();
set.add(nums[i]);
result.add(set);
break;
}
}
for(Set<Integer> tlist : threeSum(nums, k-1, start+1, target- nums[i])) {
if(!tlist.contains(nums[i])) {
tlist.add(nums[i]);
result.add(tlist);
}

}
}
return result;
}