未完待续的C++大数类BigInteger Anti

看着JAVA诱人的大数类在ACM中很好用，可是我不会JAVA，感觉为了大数类去学习JAVA太麻烦了，不如写个C++的大数类，目前还未完善，只有部分功能的雏形，因为现在知识有限，即使拿着C++ Primer Plus和刘汝佳的白书各种翻，也才写了这一点，不过目测除了前导零没有什么bug了，刚才拿这个代码A了个题。。然后我打算慢慢完善它。。。

#include <iostream>
#include <cstring>
using namespace std;
const int MAXLENTH = 10000;
class BigInteger
{
    private:
    char s[MAXLENTH+10];
    int len;
    public:
    void init(){memset(s, 0, sizeof(s)); len = 1;}
    BigInteger(){init();}
    friend istream& operator>> (istream &in, BigInteger &x);
    friend ostream& operator<< (ostream &out, BigInteger &x);
    BigInteger operator= (char *num);
    BigInteger operator+ (BigInteger &y);
    BigInteger operator+= (BigInteger &y);
};

istream& operator>> (istream &in, BigInteger &x)
{
    x.init();
    char str[MAXLENTH];
    in >> str;
    x = str;
    return in;
}

ostream& operator<< (ostream &out, BigInteger &x)
{
    char ans[MAXLENTH];
    for(int i = 0; i < x.len; i++)
        ans[i] = x.s[x.len-i-1] + '0';
    ans[x.len] = '\0';
    out << ans;
    return out;
}

BigInteger BigInteger::operator= (char *num)
{
    len = strlen(num);
    for(int i = 0; i < len; i++)
        s[i] = num[len-i-1] - '0';
    return *this;
}

BigInteger BigInteger::operator+ (BigInteger &y)
{
    BigInteger z;
    for(int i = 0, c = 0; i <= MAXLENTH; i++)
    {
        int sum = s[i] + y.s[i] + c;
        z.s[i] = sum % 10;
        c = sum / 10;
    }
    int j = MAXLENTH;
    for( ; j > 0; j--)
        if(z.s[j])break;
    z.len = j+1;
    return z;
}

BigInteger BigInteger::operator+= (BigInteger &y)
{
    *this = *this + y;
    return *this;
}

int main()
{
    BigInteger a, b, c;
    while(cin >> a >> b)
    {
        c = a + b;
        cout << c << endl;
    }
    return 0;
}