8.15 실행시간 측정

#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
#include <chrono>

using namespace std;

class Timer
{
    using clock_t = std::chrono::high_resolution_clock;
    using second_t = std::chrono::duration<double, std::ratio<1>>;
    
    std::chrono::time_point<clock_t> start_time = clock_t::now();
public:
    void elapsed()
    {
        std::chrono::time_point<clock_t> end_time = clock_t::now();
        
        cout << std::chrono::duration_cast<second_t>(end_time - start_time).count() << "\n";
    }
}

int main()
{
    random_device rnd_device; // 
    mt19937 mersenne_engine{ rnd_device() }; // random generator
    
    vector<int> vec(10);
    for (unsigned int i=0; i<vec.size(); ++i)
        vec[i] = i;
    
    std::shuffle(begin(vec), end(vec), mersenne_engine); // shuffle
    
    for (auto &e : vec) cout << e << " ";
    cout << "\n";
    
    Timer timer; // 생성자에서 start time 생김
    
    std::sort(vec.begin(),vec.end());
    
    timer.elapsed(); // 걸린 시간 반환
    
    for (auto &e : vec) cout << e << " ";
    cout << "\n";
    
    return 0;
}