class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>> res = new ArrayList<>();
        HashSet<String> set = new HashSet<>();
        for (int i = 0; i < nums.length; i++) {

            if (nums[i] > 0) {
                break;
            }

            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }

            int left = i + 1;
            int right = nums.length - 1;
            while (left < right) {
                if (left < 0) {
                    return res;
                }
                int t = nums[left] + nums[right];
                if (t + nums[i] > 0) {
                    right -= 1;
                } else if (t + nums[i] < 0) {
                    left += 1;
                } else {
                    String key = "" + nums[i] + nums[left] + nums[right];
                    if (!set.contains(key)) {
                        res.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    }
                    set.add(key);

                    while (left < right && nums[left] == nums[left + 1]) {
                        left++;
                    }

                    left += 1;
                }
            }
        }
        return res;
    }
}