class Solution {
public:
vector<vector<int>> threeSum(vector<int>& nums) {
vector<vector<int>> result;
sort(nums.begin(), nums.end());
for(int i = 0; i < nums.size(); i++) {
int target = -nums[i];
int front = i + 1;
int back = nums.size() - 1;
while(front < back) {
int sum = nums[front] + nums[back];
if (sum < target) {
front++;
} else if (sum > target) {
back--;
} else {
vector<int> triplet(3, 0);
triplet[0] = nums[i];
triplet[1] = nums[front];
triplet[2] = nums[back];
result.push_back(triplet);
while(front < back && nums[front] == triplet[1]) front++;
while(front < back && nums[back] == triplet[2]) back--;
}
}
while (i + 1 < nums.size() && nums[i + 1] == nums[i]) {
i++;
}
}
return result;
}
};