POJ 2389

 #include <iostream>
 #include <algorithm>
 #include <string>
 #define MAXN 300
 using namespace std;

 int tem[MAXN];

 void big_int_mul(string a,string b,string & ans);

 int main()
 {
     //freopen("acm.acm","r",stdin);
     string a;
     string b;
     string ans;
     cin>>a>>b;
     big_int_mul(a,b,ans);
     cout<<ans<<endl;
 }

 void big_int_mul(string a,string b,string & ans)
 {
     int len_1 = a.length();
     int len_2 = b.length();
     int len = a.length() + b.length();
     int i;
     int j;
     for(i = ; i < len_1; ++ i)
     {
         for(j = ; j < len_2; ++ j)
         {
             tem[i+j+] += (a[i]-'')*(b[j] - '');
         }
     }
     for(i = len - ; i > ; -- i)
     {
         if(tem[i] >= )
         {
             tem[i-] += tem[i]/;
             tem[i] %= ;
         }
     }
     j = ;
     while(tem[j] == )
     {
         ++ j;
     }

     for(; j < len; ++ j)
     {
         ans += char(tem[j]+'');
     }
 }