C/C++ 计时函数

time()

可精确到秒.
time(NULL);获取当前的系统时间，返回的结果是一个整数，其值表示从1970年1月1日00:00:00到当前时刻的秒数.
需要的头文件:

#include <time.h>

示例代码:

    time_t tmStartTime;
    time_t tmEndTime;

    tmStartTime = time(NULL);

    // do something...
    for (int i = 0; i < 10000; i++)
    {
        printf("%d\n", i);
    }

    tmEndTime = time(NULL);

    printf("Use Time: %ld", tmEndTime - tmStartTime);

QueryPerformanceCounter()

头文件:

#include <windows.h>

用法举例:

    LARGE_INTEGER timeStartCount;
    LARGE_INTEGER timeEndCount;
    LARGE_INTEGER timeFreq;
    QueryPerformanceFrequency(&timeFreq);
    QueryPerformanceCounter(&timeStartCount);
    int nSleepCount = 1234;
    Sleep(nSleepCount);
    QueryPerformanceCounter(&timeEndCount);
    double elapsed = (((double)(timeEndCount.QuadPart - timeStartCount.QuadPart) * 1000/ timeFreq.QuadPart));

    cout << "nSleepCount: "<< nSleepCount<<"; 实际用时 : " << elapsed <<"ms"<<endl;

运行结果:

运行结果