两个大整数相乘

#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#define N 550
using namespace std;
int ans[N];
string s1, s2;

int main()
{
    int i, j, n, ls1, ls2, len;
    while (cin>>s1>>s2)
    {
        ls1 = s1.length() - 1;
        ls2 = s2.length() - 1;
        len = ls1 + ls2;
        memset(ans, 0, sizeof(ans));
        for (i = ls1; i >= 0; i--)
            for (j = ls2; j >= 0; j--)
            {
                ans[len - (i + j)] += (s1[i] - ‘0‘) * (s2[j] - ‘0‘);//字符串最后一位对应的是个位数
            }
        len++;//结果的位数不超过ls1+ls2-1，从0开始数
         for (i = 0; i < len; i++)
         {
             ans[i + 1] += ans[i] / 10;
             ans[i] = ans[i] % 10;
         }
         while (!ans[len] && len > 0)//结果最少有ls1+ls2-2位数
            len--;
         for (; len >= 0; len--)
            cout<<ans[len];
         cout<<endl;
    }
    return 0;
}