C++之时间统计

1.最精确

QueryPerformanceFrequency(&nFreq);
cout <<nFreq.QuadPart<<endl;//获得计数频率
QueryPerformanceCounter(&s);//获取当前计数次数
  QueryPerformanceCounter(&e);//获取当前计数次数
  float tt = e.QuadPart - s.QuadPart;      

2.

<windows.h>的DWORD GetTickCount(void);返回（retrieve）从操作系统启动所经过（elapsed）的毫秒数
int TimeStart=GetTickCount();
int TimeEnd=GetTickCount();      

3.

time_t stime , etime ;//time_t = long
time( &stime ); 
time( &etime );      

4.

double begin=(double)clock();
double end=(double)clock();