求阶乘+估计运行时间

#include<stdio.h>//#include<stdlib.h>//如果用system pause的话,其实iostream也是可以的。#include<iostream>#include<time.h>int main(){const int MOD = 1000000;//因为题目只要求末6位int i,j,n,S = 0;scanf("%d",&n);int factorial = 1;for (i = 1;i <= n; i++){//int factorial = 1;/*for (j=1; j<=i;j++){factorial = (factorial * j %MOD);}*/factorial = factorial *i%MOD;//感觉是改进了呢~S = (S+factorial ) % MOD;}printf("%d\n",S);printf("Time used = %.21f\n",(double)clock() / CLOCKS_PER_SEC);        //测算程序时间，但是包含了数据键盘输入的时间，至于用命令行控制以求得完整的程序运行时间有待研究。。//Windows和Linux的命令行：echo 20|时间测算（W）echo |./时间测算（没能成功T-T。。）system("pause");return 0;}