class Solution {
public List> fourSum(int[] nums, int target) {
Arrays.sort(nums);
Set> set = new HashSet<>();
for (int i = 0; i < nums.length; i++) {
for (int j = i + 1; j < nums.length; j++) {
int newTarget = target - nums[i] - nums[j];
int start = j + 1;
int end = nums.length - 1;
while (start < end) {
if ((nums[start] + nums[end]) == newTarget) {
set.add(Arrays.asList(nums[i], nums[j], nums[start++], nums[end--]));
}
else if ((nums[start] + nums[end]) < newTarget) {
start++;
}
else {
end--;
}
}
}
}
return new ArrayList<>(set);
}
}