大数相加 模板

#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; 
} 

原文地址：http://blog.youkuaiyun.com/hengjie2009/article/details/7442605