计算程序运行时间！！！

#include<iostream>
#include<time.h>
int main()
{
    clock_t start_time=clock();
    {
        //被测试代码
    }
    clock_t end_time=clock();
    cout<< "Running time is: "<<static_cast<double>(end_time-start_time)/CLOCKS_PER_SEC*1000<<"ms"<<endl;//输出运行时间
    return 0;
}