*foj 1453 Bignum Arithmetic

Problem Description
In this problem,you will be concerned with integers with very large numbers of digits. You must write code which will repeatedly accept (until end of file) two lines each containing an unsigned integer,and output the product of the two input unsigned integers. The output must not contain any leading zeros.

You can assume that each integer will contain at most 80 digits. The input ends with an end of file.

Sample Input
0342
1298
12
3
Sample Output
443916
36

代码:

#include<stdio.h>
#include<string.h>
char s1[1005],s2[1005];
int a[1005],b[1005],c[1500];
void mul(char s1[],char s2[])
{
    int l1,l2;
    l1=strlen(s1),l2=strlen(s2);
    int l=l1+l2;
    int i,j,k=0;
    for(i=l1-1,j=0;i>=0;i--,j++)a[j]=s1[i]-'0';
    for(i=l2-1,j++)b[j]=s2[i]-'0';
    memset(c,0,sizeof(c));//对数组c初始化
    for(i=0;i<l1;i++)
        for(j=0;j<l2;j++)
            c[i+j]+=a[i]*b[j];
    for(i=0;i<l;i++)
        if(c[i]>9)
            c[i+1]+=c[i]/10,c[i]%=10;
    while(c[l]==0&&l>0)//*去掉前导0，但保证最后有一个0！！否则结果为0不能输出
        l--;
    for(i=l;i>=0;i--)
        printf("%d",c[i]);
    printf("\n");
}
int main()
{
    while(scanf("%s",s1)!=EOF)
    {
        getchar();//吞掉回车
        gets(s2);
    mul(s1,s2);
    }
    return 0;
}