3sum

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Set<List<Integer>> res = new HashSet<>();
        if (nums.length == 0)
            return new ArrayList<>(res);
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {
            int j = i + 1;
            int k = nums.length - 1;
            while (j < k) {
                int sum = nums[j] + nums[k];
                if (sum == -nums[i]) {
                    res.add(Arrays.asList(nums[i], nums[j++], nums[k--]));
                } else if (sum > -nums[i]) {
                    k--;
                } else if (sum < -nums[i]) {
                    j++;
                }

            }

        }
        return new ArrayList<>(res);

    }
}