3-1.cpp

计算N！的程序（可计算到1000）

#include<stdio.h>
#define MAX 1000
main()
{
  int a[MAX],b[MAX];
  int n;
  int i,j,k,r;
  printf("Enter your number:");
  scanf("%d",&n);
  for(i=1;i<MAX;i++)a[i]=0;
   a[0]=1;
   for(j=2;j<=n;j++)
    {
     for(i=0;i<MAX;i++)
       b[i]=a[i];
       for(k=1;k<j;k++)
	  for(i=0;i<MAX;i++)
           {
           r=a[i]+b[i];
	   if(r>9)a[i+1]++;
	   a[i]=r%10;
	   }
     }
    k=MAX-1;
    while(a[k]==0)k--;
    printf("%d!=",n);
    for(i=k;i>=0;i--)
      printf("%d",a[i]);
}