3Sum2.cpp

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
// Two pinter approach

vector<vector<int>> threeSum(vector<int> &nums)
{
    int n = nums.size();
    vector<vector<int>> ans;

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

    for (int i = 0; i < n; i++)
    {
        if (i > 0 && nums[i] == nums[i - 1])
        {
            continue;
        }

        int j = i + 1, k = n - 1;

        while (j < k)
        {
            int sum = nums[i] + nums[j] + nums[k];
            if (sum < 0)
            {
                j++;
            }
            else if (sum > 0)
            {
                k--;
            }
            else
            {
                ans.push_back({nums[i], nums[j], nums[k]});
                j++;
                k--;

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

    return ans;
}

int main()
{
    vector<int> nums = {-1, 0, 1, 2, -1, 4};

    vector<vector<int>> result = threeSum(nums);

    for (const auto &triplet : result)
    {
        cout << "[";
        for (size_t i = 0; i < triplet.size(); ++i)
        {
            cout << triplet[i];
            if (i < triplet.size() - 1)
                cout << ", ";
        }
        cout << "]" << endl;
    }

    return 0;
}