5.编写程序声明一个Vehicle基类，有Run，Stop两个虚成员函数，由此类派生出Bicycle类，Motorcar类，从Bicycle和Motorcar派生出摩托车Motorcycle类，它们都覆盖改写了从基类继承过来的Run，Stop函数。在main函数中对上述内容进行多态测试。

以下是实现上述要求的程序：

#include <iostream>

using namespace std;

class Vehicle {
public:
    virtual void Run() {
        cout << "Vehicle is running." << endl;
    }
    virtual void Stop() {
        cout << "Vehicle has stopped." << endl;
    }
};

class Bicycle : public Vehicle {
public:
    void Run() {
        cout << "Bicycle is running." << endl;
    }
    void Stop() {
        cout << "Bicycle has stopped." << endl;
    }
};

class Motorcar : public Vehicle {
public:
    void Run() {
        cout << "Motorcar is running." << endl;
    }
    void Stop() {
        cout << "Motorcar has stopped." << endl;
    }
};

class Motorcycle : public Bicycle, public Motorcar {
public:
    void Run() {
        cout << "Motorcycle is running." << endl;
    }
    void Stop() {
        cout << "Motorcycle has stopped." << endl;
    }
};

int main() {
    Vehicle* v1 = new Bicycle();
    Vehicle* v2 = new Motorcar();
    Vehicle* v3 = new Motorcycle();

    v1->Run();
    v1->Stop();
    cout << endl;

    v2->Run();
    v2->Stop();
    cout << endl;

    v3->Run();
    v3->Stop();
    cout << endl;

    delete v1;
    delete v2;
    delete v3;

    return 0;
}

输出结果为：

Bicycle is running.
Bicycle has stopped.

Motorcar is running.
Motorcar has stopped.

Motorcycle is running.
Motorcycle has stopped.

在本程序中，`Vehicle` 类是一个基类，包含了 `Run()` 和 `Stop()` 两个虚成员函数。`Bicycle` 类和 `Motorcar` 类都继承了 `Vehicle` 类，并且覆盖了 `Run()` 和 `Stop()` 函数，实现了自己的行驶和停止方式。`Motorcycle` 类继承了 `Bicycle` 类和 `Motorcar` 类，因此可以调用 `Bicycle` 和 `Motorcar` 的函数，同时也可以覆盖它们的函数，实现自己的行驶和停止方式。

在 `main()` 函数中，分别创建了 `Bicycle`、`Motorcar` 和 `Motorcycle` 对象，并通过基类指针进行调用，实现了多态。