C++小练习

1.定义Boat与Car两个类，二者都有weight属性，
定义两者的一个友原函数getTotalWeight（），
计算二者的重量和。

class Car;
class Boat
{
public:
int weight;
friend int getTotalWeight(Boat &boat, Car &car);
Boat(int a):weight(a){}
};


class Car
{
public:
int weight;
friend int getTotalWeight(Boat &boat, Car &Car);
Car(int a):weight(a){}
};


int getTotalWeight(Boat &boat, Car &Car)
{
return boat.weight + Car.weight;
}

void main()
{
Boat A(100);
Car B(20);
cout<<"两者的重量总和："<<endl;
cout<<getTotalWeight(A,B)<<endl;
}

　　

2.声明一个Cat类，拥有静态成员catnum，记录Cat的个体数目；
声明静态成员函数GetHowMany()，存取catnum。
设计程序测试这个类，体会静态数据成员和静态成员函数的用法。

class Cat
{
public:
Cat(){++catnum;}
Cat(const Cat& cat){++catnum;}
virtual ~Cat(){--catnum;}
static int GetHowMany(){return catnum;}
private:
static int catnum;
};

int Cat::catnum=0;

int main()
{
Cat a;
Cat b;
cout<<"catnum:"<<Cat::GetHowMany()<<endl;
Cat c(a);
Cat* p=new Cat();
cout<<"catnum:"<<Cat::GetHowMany()<<endl;
delete p;
cout<<"catnum:"<<Cat::GetHowMany()<<endl;
return 0;
}