应用题  
    请打开考生文件夹下的解决方案文件proj2,其中定义了vehicle类,并派生出motorcar类和bicycle类。然后以motorcar和bicycle作为基类,再派生出motorcycle类。要求将vehicle作为虚基类,避免二义性问题。请在程序中的横线处填写适当的代码并删除横线,以实现上述类定义。此程序的正确输出结果应为:
    80
    150
    100
    1
    注意:只能在横线处填写适当的代码,不要改动程序中的其他内容,也不要删除或移动“//****found****”。
    #include<iostream.h>
    class vehicle
    {
    private:
    int MaxSpeed;
    int Weight;
    public:
    //**********found**********
    vehicle(int maxspeed,int weight):______
    ~vehicle(){};
    int getMaxSpeed(){return MaxSpeed;}
    int getWeight(){return Weight;}
    };
    //**********found**********
    class bicycle:______ public vehicle
    {
    private:
    int Height;
    public:
    bicycle(int maxspeed,int weight,int height):vehicle(maxspeed,weight),Height(height){}
    int getHeight(){return Height;};
    };
    //**********found**********
    class motorcar:______public vehicle
    {
    private:
    int SeatNum;
    public:
    motorcar(int maxspeed,int weight,int seatnum):vehicle(maxspeed,weight),SeatNum(seatnum){}
    int getSeatNum(){return SeatNum;};
    };
    //**********found**********
    class motorcycle:______
    {
    public:
    motorcycle(int maxspeed,int weight,int height):vehicle(maxspeed,weight),bicycle(maxspeed,weight,height),motorcar(maxspeed,weight,1){}
    };
    void main()
    {
    motorcycle a(80,150,100);
    cout<<a.getMaxSpeed()<<endl;
    cout<<a.getWeight()<<endl;
    cout<<a.getHeight()<<endl;
    cout<<a.getSeatNum()<<endl;
    }
 
【正确答案】(1)MaxSpeed(maxspeed),Weight(weight){}; (2)virreal (3)virtual (4)public bicycle,public motorcar 答案考生文件夹
【答案解析】[考点] 本题考查vehicle类及其派生类motorcar和bicycle,再由这两类派生出motoreycle类,其中涉及构造函数、成员函数和析构函数。构造函数采用成员初始化列表来完成对私有成员的初始化,派生类的书写要注意关键字。 (1)主要考查考生对构造函数的掌握,构造函数使用初始化列表来对私有成员MaxSpeed和Weight初始化。 (2)主要考查考生对派生类的掌握,题目要求将vehicle作为虚基类,避免二义性问题。因此在这里添加virtual使vehicle成为虚基类。 (3)主要考查考生对派生类的掌握,题目要求以motorcar和bicycle作为基类,再派生出motomycle类。在主函数中可以看到motorcycle类的实例a调用getHeight函数和getSeatNum函数,由此可知这两个基类都是公有继承,因此得出语句:public bicycle,public motorcar。 虚基类继承时要添加关键字virtual,以避免二义性。