高精度加法

#include<stdio.h>
#include<algorithm>
#include<iostream>
#include<string.h>
using namespace std;
int add(char a ,char b)
{
    return (a-'0')+(b-'0');
}
int d[1000];
int main(void)
{
    string c = "";
    string a , b;
    cin>>a>>b;
    int lena = a.length();
    int lenb = b.length();
    if(lena > lenb)
    {
        for(int i = 1 ; i <= lena-lenb ; i++)
            b = '0'+b;
    }
    else
    {
        for(int i = 1 ; i <= lenb-lena ; i++)
            a = '0'+a;
    }
    /*-------------------------------------------*/
    //cout<<a<<endl;
    //cout<<b<<endl;
    int cnt = 0;
    int jin = 0;
    for(int i = b.length()-1 ; i >= 0 ; i --)
    {
        if(add(a[i],b[i])+jin >= 10)
        {
            d[cnt++] = (add(a[i],b[i])+jin)%10;
            jin = (add(a[i],b[i])+jin)/10;
        }
        else
        {
            d[cnt++] = add(a[i],b[i])+jin;
            jin = 0;
        }
    }
    if(jin == 1)
        d[cnt ++] = 1;
    for(int i = cnt-1 ; i >=0  ; i --)
        cout<<d[i];
    cout<<endl;
}