/**

* time: O(n^2)

* space: O(n)

*

* - time: becasue of two nested loop and inner loop having a linear time complexity.

* - space: because of a HashSet to store the triplets.

*/

class Solution {

public List<List<Integer>> threeSum(int[] nums) {

Arrays.sort(nums);

int i = 0, j, k;

int ni = 0, nj, nk;

Set<List<Integer>> res = new HashSet<>();

while (i < nums.length && ni <= 0) {

ni = nums[i];

j = i + 1;

k = nums.length - 1;

while (j < k) {

nj = nums[j];

nk = nums[k];

int sum = ni + nj + nk;

if (sum < 0) {

j++;

} else if (sum > 0) {

k--;

} else {

res.add(List.of(ni, nj, nk));

j++;

}

}

i++;

}

return res.stream()

.toList();

}

}