程序2-4

1 #include
     
       2 #include
      
        3 int main() 4 { 5     int n, count = 0; 6     scanf("%d",&n); 7     while(n>1) 8     { 9         if(n % 2 ==1) n = 3*n +1;10         else n/=2;11         count++;12     }13     printf("%d\n",count);14     return 0;15 }
      
     

程序2-5

1 #include
     
       2 #include
      
        3 int main() 4 { 5     int i, j, n, S = 0; 6     scanf("%d",&n); 7     for(i = 1;i<=n;i++) 8     { 9         int factorial = 1;10         for(j = 1;j <=i;j++)11         {12             factorial *= j;13         }14         S +=factorial;15     }16     printf("%d\n",S % 1000000);17     return 0;18 }
      
     

 程序2-6

1 #include
     
       2 #include
      
        3 int main() 4 { 5     const int MOD = 1000000; 6     int i, j, n, S = 0; 7     scanf("%d",&n); 8     for(i = 1;i<=n;i++) 9     {10         int factorial = 1;11         for(j = 1;j <=i;j++)12         {13             factorial = (factorial*j%MOD);14         }15         S = (S+factorial)%MOD;16     }17     printf("%d\n",S);18     printf("Time used = %0.2lf\n",(double)clock() /CLOCKS_PER_SEC);19     return 0;20 }