大整数模拟加(字符串)

string add1(string s1,string s2)
{
if(s1==""&&s2=="")return "0";
else if(s1=="")return s2;
else if(s2=="")return s1;

string maxs=s1,mins=s2;
if(s1.length()<s2.length()){
maxs=s2;
mins=s1;
}
int a=maxs.length()-1,b=mins.length()-1;
for(int i=b;i>=0;i--)
maxs[a--]+=mins[i]-'0';
for(int i=maxs.length()-1;i>0;i--)
if(maxs[i]>'9')
{
maxs[i]-=10;
maxs[i-1]++;
}
if(maxs[0]>'9')
{
maxs[0]-=10;
maxs='1'+maxs;
}
return maxs;
}