vector<vector<int>> threeSum(vector<int>& nums) {

vector<vector<int>> result;

int n = nums.size();

if (n < 3) {

return result;

}

sort(nums.begin(), nums.end());

for (int i = 0; i < n - 2; i++) {

if (nums[i] > 0) {

break;

}

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

continue;

}

int j = i + 1;

int k = n - 1;

while (j < k) {

int sum = nums[i] + nums[j] + nums[k];

if (sum < 0) {

j++;

} else if (sum > 0) {

k--;

} else {

result.push_back({nums[i], nums[j], nums[k]});

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

j++;

}

j++;

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

k--;

}

k--;

}

}

}

return result;

}