#include <algorithm>
#include <string>
#include <iostream>
#include <vector>

std::vector<std::vector<int>> threeSum(std::vector<int>& nums) {
    std::sort(nums.begin(), nums.end());
    
    std::vector<std::vector<int>> res;
    for (auto it = nums.begin(); it != nums.end(); ++it) {
        auto left = it + 1;
        auto right = nums.rbegin();
        while (left < right.base()) {
            auto sum = *it + *left + *right;
            if (sum < 0) {
                ++left;   
            } else if (sum > 0) {
                ++right;   
            } else {
                res.push_back({*it, *left, *right});
                std::cout << *it << " " <<  *left << " " << *right << std::endl;
                ++left;
                ++right;
            }
        }
    }
    return res;
}

int main()
{
    std::vector<int> v {4, 2, -6, 42, -42, 0, 21, 21};
    threeSum(v);
}