大数加法 模版

 c++ 代码，写的不错，留下来当模版

#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 n,count=1;string s1,s2;cin>>n;while(n--){cin>>s1>>s2;cout<<"Case "<<count++<<':'<<endl;cout<<s1<<" + " <<s2<<" = "<<sum(s1,s2)<<endl;if(n>0) cout<<endl;}return 0;}