time.h 头文件定义了四个变量类型、两个宏和各种操作日期和时间的函数.
https://www.runoob.com/cprogramming/c-standard-library-time-h.html
使用time.h中的clock函数获取时间间隔:
clock_t start, finish;
double Total_time;
start = clock();
//...
finish = clock();
Total_time = (double)(finish - start) / CLOCKS_PER_SEC;//s