阶乘之和(防止int类型溢出的小技巧&计时函数)

printf("%f",(double)clock()/CLOCKS_PER_SEC);

#include"iostream"
#include"ctime"
using namespace std; 

int main()
{
    const int MOD = 1e6;
    int n,s=0;
    scanf("%d",&n);
    for(int i=1;i<=n;++i){
        int fa=1;
        for(int j=1;j<=i;++j)
        fa=(fa*j%MOD);
        s=(s+fa)%MOD;
    }
    printf("%d\n",s);
    printf("Time used = %.2f\n",(double)clock()/CLOCKS_PER_SEC);
    return 0;
}