C++ 大数加法之字符串实现

#include<iostream>
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 cin=0,k=0;
    while(lena-->0 && lenb-->0)
    {
        int left=s1[lena]-'0';
        int right=s2[lenb]-'0';
        int s=left+right+cin;
        cin=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+cin;
            cin=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+cin;
            cin=s/10;
            s%=10;
            sum[k++]=s+'0';
 
        }
    }
    if(cin!=0)
        sum[k++]=cin+'0';
    sum[k]='\0';
    strrev(sum);
}
 
int main()
{
    gets(s1);
    gets(s2);
    add();
    cout<<"result is "<<sum<<endl;
    system("pause");
    return 0;
}