题解 | #整数与IP地址间的转换#

#include <iostream>
#include <sstream>
using namespace std;

//IP地址类
class IPAddress {
  private:
    int a, b, c, d;

  public:
    //构造函数
    IPAddress(const string s);

    IPAddress(const unsigned long long int a);

    //析构函数
    ~IPAddress();

    //将IP地址转换成一个整数
    unsigned long long int transform(void)const;

    //将一个整数转换成IP地址
    void transform(const unsigned long long int n);

    //输出（<<运算符重载）
    friend ostream& operator<<(ostream& cout, IPAddress ip);
};

IPAddress::IPAddress(const string s) {
    //输入重定向到字符串s，从字符串流读取数据
    istringstream iss(s);
    char ch;
    iss >> this->a;
    iss >> ch;
    if (ch != '.') {
        cout << "输入格式有误！" << endl;
        return;
    }
    iss >> this->b;
    iss >> ch;
    if (ch != '.') {
        cout << "输入格式有误！" << endl;
        return;
    }
    iss >> this->c;
    iss >> ch;
    if (ch != '.') {
        cout << "输入格式有误！" << endl;
        return;
    }
    iss >> this->d;
    return;
}

IPAddress::IPAddress(const unsigned long long int a) {
    //先初始化，再赋值
    this->a = 0;
    this->b = 0;
    this->c = 0;
    this->d = 0;
    this->transform(a);
    return;
}

IPAddress::~IPAddress() {
}

unsigned long long int IPAddress::transform(void) const {
    //在二进制下正整数左移八位相当于乘以2的8次方，也就是256；
    return this->d + 256 * this->c + 256 * 256 * this->b + 256 * 256 * 256 *
           this->a;
}

void IPAddress::transform(const unsigned long long int n) {
    //将右移8位用除以256代替，并记录每一次的余数
    int m = n;
    this->d = n % 256;
    m = n / 256;
    if (m <= 0)
        return;
    this->c = m % 256;
    m = m / 256;
    if (m <= 0)
        return;
    this->b = m % 256;
    m = m / 256;
    if (m <= 0)
        return;
    this->a = m % 256;
    m = m / 256;
    if (m > 0)
        cout << "输入超出范围！" << endl;
    return;
}

int main() {
    //为避免数据溢出，用无符号长长整型代替整型
    unsigned long long int b = 0;
    string s;
    while (cin >> s >> b) { // 注意 while 处理多个 case
        IPAddress ip1(s), ip2(b);
        cout << ip1.transform() << endl;
        cout << ip2 << endl;
    }
}
// 64 位输出请用 printf("%lld")

ostream& operator<<(ostream& cout, IPAddress ip) {
    cout << ip.a << '.' << ip.b << '.' << ip.c << '.' << ip.d;
    // TODO: 在此处插入 return 语句
    return cout;
}