程序设计与算法（三）第06周测验

001：看上去像多态

#include <iostream>
using namespace std;
class B {
private:
    int nBVal;
public:
    void Print()
    {
        cout << "nBVal=" << nBVal << endl;
    }
    void Fun()
    {
        cout << "B::Fun" << endl;
    }
    B(int n) { nBVal = n; }
};
// 在此处补充你的代码
class D:public B
{
private:
    int nDVal;
public:
    D(int nDval_) :nDVal(nDval_),B(3*nDval_){};
    
    void Fun()
    {
        cout << "D::Fun" << endl;
    }
 
    void Print()
    {
        B::Print();
        cout << "nDVal=" << nDVal << endl;
    }
 
};
int main() {
    B * pb; D * pd;
    D d(4); d.Fun();
    pb = new B(2); pd = new D(8);
    pb->Fun(); pd->Fun();
    pb->Print(); pd->Print();
    pb = &d; pb->Fun();
    pb->Print();
    return 0;}

002:Fun和Do

#include <iostream> 
using namespace std;
class A {
private:
    int nVal;
public:
    void Fun()
    {
        cout << "A::Fun" << endl;
    };
    void Do()
    {
        cout << "A::Do" << endl;
    }
};
class B :public A {
public:
    virtual void Do()
    {
        cout << "B::Do" << endl;
    }
};
class C :public B {
public:
    void Do()
    {
        cout << "C::Do" << endl;
    }
    void Fun()
    {
        cout << "C::Fun" << endl;
    }
};
void Call(B &p
    // 在此处补充你的代码
) {
    p.Fun(); p.Do();
}
int main() {
    C c;
    Call(c);
    system("pause");
    return 0;
}

003:这是什么鬼delete

#include <iostream> 
using namespace std;
class A 
{ 
public:
    A() { }
virtual ~A(){cout << "destructor A" << endl;} 
}; 
class B:public A { 
    public: 
    ~B() { cout << "destructor B" << endl; } 
}; 
int main() 
{ 
    A * pa; 
    pa = new B; 
    delete pa; 
    return 0;
}

 

 

004:怎么又是Fun和Do

#include <iostream>
using namespace std;
classA {
	private:
	int nVal;
	public:
	void Fun()
	{ cout << "A::Fun" << endl; };
	virtual void Do()
	{ cout << "A::Do" << endl; }
};
classB:public A {
	public:
	virtual void Do()
	{ cout << "B::Do" << endl;}
};
classC:public B {
	public:
	void Do( )
	{ cout <<"C::Do"<<endl; }
	void Fun()
	{ cout << "C::Fun" << endl; }
};
void Call(
A *p
) {
	p->Fun(); p->Do();
}
int main() {
	Call( new A());
	Call( new C());
	return 0;
}

#include <iostream> 
using namespace std;
classA 
{ 
public:
	A() { }
virtual ~A(){cout << "destructor A" << endl;} 
}; 
classB:public A { 
	public: 
	~B() { cout << "destructor B" << endl; } 
}; 
int main() 
{ 
	A * pa; 
	pa = new B; 
	delete pa; 
	return 0;
}