也许Haskell更优美？

main = print . product . map read . words =<< getContents

#include<iostream>
#include<cstring>
using namespace std;
const int Maxlen=10001;
int main()
{
char a1[Maxlen],b1[Maxlen];
int a[Maxlen],b[Maxlen],c[Maxlen],lena,lenb,lenc,x;
memset(a,0,sizeof(a));
memset(b,0,sizeof(b));
memset(c,0,sizeof(c));
gets(a1);
gets(b1);
lena=strlen(a1);
lenb=strlen(b1);
for(int i=0;i<=lena-1;i++) a[lena-i]=a1[i]-48;
for(int j=0;j<=lenb-1;j++) b[lenb-j]=b1[j]-48;

for(int i=1;i<=lena;i++)
{
x=0;
for(int j=1;j<=lenb;j++)
{
c[i+j-1]+=a[i]*b[j]+x;
x=c[i+j-1]/10;
c[i+j-1]%=10;
}
c[i+lenb]=x; // 进位
}

lenc=lena+lenb;
while(c[lenc]==0&&lenc>1)
lenc--;
for( int i=lenc;i>=1;i--)
cout<<c[i];
cout<<endl;
return 0;

}