计算C++算法运行时间

#include <iostream>
#include <ctime>
using namespace std;
int main()
{ 
     clock_t start,finish;
     //先行后列
    start=clock();
    //执行内容
    //.......
    finish=clock();
    //totaltime=(double)()/CLOCKS_PER_SEC;
    cout<<"先行后列遍历时间为："<<finish-start<<"ms"<<endl;
    return 0;
}