51nod 1057 N的阶乘

#include <bits/stdc++.h>
using namespace std;

int a[10010];

int main()
{
int n,i,siz,j;
while(cin>>n)
{
memset(a,0,sizeof(a));
a[0]=1;
siz=1;
for(i=2;i<=n;i++)
{
for(j=0;j<siz;j++)
{
a[j]*=i;
}
for(j=0;j<siz;j++)
{
a[j+1]+=a[j]/10000;
a[j]%=10000;
}
for(;;siz++)
{
if(a[siz]==0)
break;
a[siz+1]+=a[siz]/10000;
a[siz]%=10000;
}
}
printf("%d",a[siz-1]);
for(i=siz-2;i>=0;i--)
{
printf("%04d",a[i]);
}
printf("\n");
}
}