代码如下：
#include<iostream>
#include<string>
using namespace std;
int main()
{
        string sum(string s1,string s2);
  string s1,s2;
  cin>>s1>>s2;
        cout<<sum(s1,s2)<<endl;
  return 0;
}
string sum(string s1,string s2)    
{    
         if(s1.length()<s2.length())    
         {    
                    string temp=s1;    
                    s1=s2;    
                    s2=temp;    
         }    
         for(int i=s1.length()-1,j=s2.length ()-1;i>=0;i–,j–)    
         {    
                    s1[i]=char(s1[i]+(j>=0?s2[j]-‘0’:0));    
                    if(s1[i]-‘0’>=10)    
                    {    
                            s1[i]=char((s1[i]-‘0′)%10+’0’);    
                            if(i)    
                                     s1[i-1]++;    
                            else    
                                     s1=’1’+s1;    
                    }    
         }    
         return s1;    
}