// 友元类
#include <iostream>
#include <cstring>
#include <cstdlib>

using namespace std;

class B;

class C
{
public:
    void showB(B &b);
};

class B
{
    friend class C;

private:
    int x;

public:
    B(int x) : x(x) {}
    void show()
    {
        cout << "成员函数 x = " << x << endl;
    }
};

void C::showB(B &b)
{
    cout << "友元类 b.x = " << b.x << endl;
}

int main()
{
    B b(100);
    b.show();
    C c;
    c.showB(b);
    return 0;
}