#include <iostream>
#include <thread>
#include <vector>
#include <mutex>
#include <chrono>
#include <algorithm>
//#define PARAL
//#define SEQ

std::mutex mut;

void worker(std::vector<int>& vct, int q, int pos, char thr_num)
{
        for (int i = pos; i < pos + q; ++i)
        {
                if (vct[i] % 2 != 0)
                        vct[i] = 0;
        }
}

int main(int argc, char* argv[])
{
        const auto TEST_SIZE = 100000000;
        std::vector<int> result(TEST_SIZE);
        std::generate(result.begin(),result.end(),std::rand);
        auto beg = std::chrono::steady_clock::now();

#ifdef PARAL
        int quart = result.size() / std::thread::hardware_concurrency();
        std::vector<std::thread> threads;
        for (size_t i = 0; i < std::thread::hardware_concurrency();++i) {
            threads.emplace_back(worker,std::ref(result),quart,quart*i,i);
        }
        for (auto && it : threads)
            it.join();
#elif defined (SEQ)
        worker(result,result.size(),0,0);
#endif
        std::cout << std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - beg).count();
        return 0;
}