class Solution {
public List> fourSum(int[] nums, int target) {
Arrays.sort(nums);
Set
> s = new HashSet<>();
List
> output = new ArrayList<>();
for (int i = 0; i < nums.length; i++) {
for (int j = i + 1; j < nums.length; j++) {
int k = j + 1;
int l = nums.length - 1;
while (k < l) {
long sum = nums[i];
sum += nums[j];
sum += nums[k];
sum += nums[l];
if (sum == target) {
s.add(Arrays.asList(nums[i], nums[j], nums[k], nums[l]));
k++;
l--;
} else if (sum < target) {
k++;
} else {
l--;
}
}
}
}
output.addAll(s);
return output;
}
}