本人c++新手，最近在自学高精度乘法，求大神指点我的代码错在哪，万分感谢

#include <iostream>
#include <cstring>
using namespace std;

int main()
{
    int t;
    cin >> t;

    for(int z = 0;z < t;z++)
    {   
        int c[205] = {0};
        int i,j,len;
        string m,n;
        cin >> m >> n;

        memset(c,0,sizeof(c));
        for(i = 1;i <= m.length();i++)
            for(j = 1;j <= n.length();j++)
                c[i+j-1] = c[i+j-1]+(m[i]-48)*(n[j]-48);

        len = m.length()+n.length();
        for(i = 1;i < len;i++)
        {
            c[i+1] = c[i+1]+c[i]/10;
            c[i] = c[i]%10;
        }

        while(c[len] == 0)
        {
            len--;
        }

     
        for(i = len;i >= 1;i--)
        {
            cout << c[i];
        }

        cout << endl;
    }
}