15.3Sum.cpp

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        sort(nums.begin(), nums.end());
        for (int i = 0; i < nums.size(); ++i) {
            // Skip duplicate elements to avoid duplicate triplets
            if (i > 0 && nums[i] == nums[i - 1])
                continue;
            int target = -nums[i];
            int left = i + 1;
            int right = nums.size() - 1;
            while (left < right) {
                int sum = nums[left] + nums[right];
                if (sum == target) {
                    res.push_back({nums[i], nums[left], nums[right]});
                    // Skip duplicate elements
                    while (left < right && nums[left] == nums[left + 1])
                        ++left;
                    while (left < right && nums[right] == nums[right - 1])
                        --right;
                    ++left;
                    --right;
                } else if (sum < target) {
                    ++left;
                } else {
                    --right;
                }
            }
        }
        return res;
    }
};