大整数乘法

int a[101], b[101], c[202];
int mul(int l1, int l2, int a1[101], int a2[101], int c[202])
{
        int i, j;
        int y;//进位

        int x;//乘积

        int z;//余数

        int w;//乘积结果保存位置

        memset((void *)&c[0], 0, sizeof(int));
        for(i = 0; i < 101; i++){
                for(j = 0; j < 101; j++){
                        x = a1[i] * a2[j];
                        z = x % 10;
                        y = x/10;
                        w = i + j;
                        c[w] += z;
                        c[w+1] += y + c[w]/10;
                        c[w] %= 10;
                }
        }

        w = l1 + l2;
        if(c[w-1] == 0){
                w--;
        }

        return w;
}