大数相乘

在论坛看到的，巨巨Or2

# include<stdio.h>
# include<string.h>
# include<malloc.h>
char a[100],b[100],c[100];
void multiply(char* a,char* b,char* c)
{
    int i,j,ca,cb,* s;
    ca=strlen(a);
    cb=strlen(b);
    s=(int*)malloc(sizeof(int)*(ca+cb));
    for (i=0;i<ca+cb;i++)
    	s[i]=0;
    for (i=0;i<ca;i++)
    	for (j=0;j<cb;j++)
    		s[i+j+1]+=(a[i]-'0')*(b[j]-'0');
    for (i=ca+cb-1;i>=0;i--)
    	if (s[i]>=10)
    	{
    	    s[i-1]+=s[i]/10;
    	    s[i]%=10;
        }
    i=0;
    while (s[i]==0)
    	i++;
   	for (j=0;i<ca+cb;i++,j++)
   		c[j]=s[i]+'0';
    c[j]='';
    free(s);
}
int main()
{
    while(~scanf("%s%s",a,b))
    {
        multiply(a,b,c);
        printf("%sn",c);
    }
    return 0;
}