15 1!+2!+…+k!=?

 

#include <stdio.h>    //暂定
main ()
{
    unsigned long long sum,Sum=0;
    int k,i, j;
    scanf("%d",&k);
    for(i=1;i<=k;i++)
    {
        sum=1;
        for(j=1;j<=i;j++)
        {
            sum =sum*j;
        }
        Sum=Sum+sum;
    }
    printf("%d",Sum);
    return 0;
}


#include <stdio.h>       //正确
main()
{
    unsigned k,i,sum=0,old_fact=1,fact=1;
    scanf("%d",&k);
    for (i=1;i<=k;i++)
      {
        old_fact=fact;
        fact*=i;
        sum+=fact;
        if(fact/old_fact!=i)
          {
            printf("overflow");
            return;
          }
      }
      printf("%d",sum);
}