#include <iostream>
#include <future>
#include <mutex>
#include <vector>
#include <cmath>
#include <algorithm>
#include <numeric>


class RangeTimer
{
    decltype(std::chrono::system_clock::now()) start;
public:
    RangeTimer()
    {
        start = std::chrono::system_clock::now();
    }
    ~RangeTimer()
    {
        auto end = std::chrono::system_clock::now();
        std::chrono::duration<double> elapsedTime = end - start;
        std::cout << "range timer " << elapsedTime.count()<< " s\n";
    }
};

long long int f1()
{
    RangeTimer tim;
    long long int tmp = 0;
    for(int i = 0; i < 2e8; i++)
        tmp += i;
    return tmp;
   /* std::vector<int> v;
    for(int i = 0; i < 2e8; i++)
        v.push_back(i);
    return std::accumulate(v.begin(), v.end(), 0.);*/
}

long long int f2()
{
    RangeTimer tim;
    long long int wynik = 0;
    std::mutex m;
    std::future watek1 = std::async(std::launch::async, [&wynik, &m]()
    {
        long long int tmp = 0;
        for(int i = 0; i < 1e8; i++)
            tmp += i;
        {
            std::lock_guard _(m);
            wynik += tmp;
        }
    });
    {
        long long int tmp = 0;
        for(int i = 1e8; i < 2e8; i++)
            tmp += i;
        //m.lock();
        wynik += tmp;
        //m.unlock();
    }
    watek1.wait();
    return wynik;
}

long long int f4()
{
    RangeTimer tim;
    long long int wynik = 0;
    std::mutex m;
    std::future watek1 = std::async(std::launch::async, [&wynik, &m]()
    {
        long long int tmp = 0;
        for(int i = 0; i < 0.5e8; i++)
            tmp += i;
        {
            //std::lock_guard _(m);
            wynik += tmp;
        }
    });
    std::future watek2 = std::async(std::launch::async, [&wynik, &m]()
    {
        long long int tmp = 0;
        for(int i = 0.5e8; i < 1e8; i++)
            tmp += i;
        {
            //std::lock_guard _(m);
            wynik += tmp;
        }
    });
    std::future watek3 = std::async(std::launch::async, [&wynik, &m]()
    {
        long long int tmp = 0;
        for(int i = 1e8; i < 1.5e8; i++)
            tmp += i;
        {
            //std::lock_guard _(m);
            wynik += tmp;
        }
    });
    {
        long long int tmp = 0;
        for(int i = 1.5e8; i < 2e8; i++)
            tmp += i;
        //m.lock();
        wynik += tmp;
        //m.unlock();
    }
    watek1.wait();
    watek2.wait();
    watek3.wait();
    return wynik;
}
int main()
{
    long long int wynik = f1();
    std::cout << wynik << "\n\n";

    long long int wynik2 = f2();
    std::cout << wynik2 << "\n\n";

    long long int wynik4 = f4();
    std::cout << wynik4 << std::endl;

    return 0;
}