3sum.cpp

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        int n = nums.size();
        sort(nums.begin(), nums.end());
        
        for (int i = 0; i < n - 2; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) continue;
            int target = -nums[i];  
            int j = i + 1, k = n - 1;
            
            while (j < k) {
                int sum = nums[j] + nums[k];
                
                if (sum == target) {
                    res.push_back({nums[i], nums[j], nums[k]});
                    j++;
                    k--;
                    while (j < k && nums[j] == nums[j - 1]) j++;
                    while (j < k && nums[k] == nums[k + 1]) k--;
                    
                } 
                else if (sum < target) {
                    j++;
                } 
                else {
                    k--;
                }
            }
        }
        
        return res;
    }
};