大数加法的字符串实现

#include<iostream>
#include <string.h>
#include <stdio.h>
using namespace std;

char s1[200],s2[200],sum[210];

void add()
{
    int lena=strlen(s1);
    int lenb=strlen(s2);
    int maxlen=(lena<lenb)?lenb:lena;

    int carry=0,k=0;
    while(lena-->0 && lenb-->0)
    {
        int left=s1[lena]-'0';
        int right=s2[lenb]-'0';
        int s=left+right+carry;
        carry=s/10;
        s%=10;
        sum[k++]=s+'0';
    }
    if(lena<=0)
    {
        while(lenb-->0)
        {
            int left=0;
            int right=s2[lenb]-'0';
            int s=left+right+carry;
            carry=s/10;
            s%=10;
            sum[k++]=s+'0';
        }
    }
    else if(lenb<=0)
    {
        while(lena-->0)
        {
            int left=s1[lena]-'0';
            int right=0;
            int s=left+right+carry;
            carry=s/10;
            s%=10;
            sum[k++]=s+'0';

        }
    }
    if(carry!=0)
        sum[k++]=carry+'0';
    sum[k]='';
    strrev(sum);
}

int main()
{
    cin>>s1>>s2;
    add();
    cout<<"result is "<<sum<<endl;
    return 0;
}