3Sum.cpp

/*
Given an integer array nums, return all the triplets 
[nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, 
and nums[i] + nums[j] + nums[k] == 0.

Notice that the solution set must not contain duplicate triplets.
Constraints:

3 <= nums.length <= 3000
-105 <= nums[i] <= 105
*/
class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        int target = 0;
        sort(nums.begin(), nums.end());
        set<vector<int>> s;
        vector<vector<int>> output;
        for (int i = 0; i < nums.size(); i++){
            int j = i + 1;
            int k = nums.size() - 1;
            while (j < k) {
                int sum = nums[i] + nums[j] + nums[k];
                if (sum == target) {
                    s.insert({nums[i], nums[j], nums[k]});
                    j++;
                    k--;
                } else if (sum < target) {
                    j++;
                } else {
                    k--;
                }
            }
        }
        for(auto triplets : s)
            output.push_back(triplets);
        return output;
    }
};