C++ 计时

#include 
#include 

using namespace std;

int main()
{
	int a = 0;
	clock_t start = clock();
	a = a + 1;
	clock_t end = clock();
	double time;
	time = (double)(end - start) / (double)CLOCKS_PER_SEC;
	std::cout << "所用时间为: " << time << " s" << std::endl;
	std::system("pause");
	return (0);
}