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

List<List<Integer>> result = new ArrayList<>();

if (nums.length < 3) return result;

Arrays.sort(nums);

final int target = 0;

for (int i = 0; i < nums.length - 2; ++i) {

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

int j = i+1;

int k = nums.length-1;

while (j < k) {

if (nums[i] + nums[j] + nums[k] < target) {

++j;

while(nums[j] == nums[j-1] && j < k) ++j;

} else if(nums[i] + nums[j] + nums[k] > target) {

--k;

while(nums[k] == nums[k+1] && j < k) --k;

} else {

result.add(Arrays.asList(nums[i], nums[j], nums[k]));

++j;

--k;

while(nums[j] == nums[j-1] && j < k) ++j;

while(nums[k] == nums[k+1] && j < k) --k;

}

}

}

return result;

}