大数运算c++

string add(string s1,string s2)
{
    if(s1.length()<s2.length()){
        string temp=s1;
        s1=s2;
        s2=temp;
    }
    int i,j;
    for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--){
        s1[i]=s1[i]+(j>=0?s2[j]-'0':0);
        if(s1[i]-'0'>=10){
            s1[i]=(s1[i]-'0')%10+'0';
            if(i) s1[i-1]++;
            else s1='1'+s1;
        }
    }
    return s1;
}

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=100000000;
char a[maxn],b[maxn];
string add(string s1,string s2)
{
    if(s1.length()<s2.length()){
        string temp=s1;
        s1=s2;
        s2=temp;
    }
    int i,j;
    for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--){
        s1[i]=s1[i]+(j>=0?s2[j]-'0':0);
        if(s1[i]-'0'>=10){
            s1[i]=(s1[i]-'0')%10+'0';
            if(i) s1[i-1]++;
            else s1='1'+s1;
        }
    }
    return s1;
}
int main()
{
    while(scanf("%s%s",&a,&b)){
        cout<<add(a,b)<<endl;
    }
}