大数加法

#include<iostream>
#include<string>
using namespace std;
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;
}
int main()
{int t;
 cin>>t;
 for(int m=1;m<=t;m++)
 {
    string s1,s2,ans;
    cin>>s1>>s2;
    ans=sum(s1,s2);
    cout<<"Case "<<m<<":"<<endl;
    cout<<s1<<" + "<<s2<<" = "<<ans<<endl;
    if(m!=t)
    cout<<endl;
 }

    return 0;
}

这个模板感觉挺简单