用c++类写的大数加法模板

#include<iostream>
#include<string>
using namespace std;
class Large_number
{
public:
Large_number(string a,string b):s1(a),s2(b){};
string Sum(string,string);
void Display();
private:
string s1;
string s2;
};
string Large_number::Sum(string a,string b)
{
if(a.length()<b.length())
{
string temp=a; a=b; b=temp;
}
int i,j;
for(i=a.length()-1,j=b.length()-1;i>=0;i--,j--)
{
a[i]=char(a[i]+(j>=0?b[j]-'0':0));
if(a[i]-'0'>=10)
{
a[i]=char((a[i]-'0')%10+'0');
if(i) a[i-1]++;
else a='1'+a;
}
}
return a;
}
void Large_number::Display()
{
cout<<s1<<"+"<<s2<<"="<<Sum(s1,s2)<<endl;
}
int main()
{
string a,b;
while(cin>>a>>b)
{
Large_number object(a,b);
object.Display();
}
return 0;
}