动物要吃饭

Description

定义Animal类，只有一个纯虚函数eat。

定义Dog、Cat、Sheep、Chicken四个类，它们都是Animal的子类。

每个类重载eat方法，每个方法输出的内容见样例。
Input

一系列0~3之内的整数。
Output

每个输入对应一行输出，0、1、2、3分别代表Dog、Cat、Sheep、Chicken。
Sample Input
0
1
2
3
2
3
1
0
Sample Output
Dog eats bone.
Cat eats fish.
Sheep eats grass.
Chicken eats worm.
Sheep eats grass.
Chicken eats worm.
Cat eats fish.
Dog eats bone.
HINT

Append Code
append.cc,

int main()
{
    int c;
    vector<Animal*> animals;
    vector<Animal*>::iterator itr;
    while(cin>>c)
    {
        switch(c)
        {
        case 0 :
            animals.push_back(new Dog());
            break;
        case 1:
            animals.push_back(new Cat());
            break;
        case 2:
            animals.push_back(new Sheep());
            break;
        case 3:
            animals.push_back(new Chicken());
        }
    }
    for (itr = animals.begin(); itr != animals.end(); itr++)
        (*itr)->eat();
    return 0;
}

---

AC代码

#include <iostream>
#include <vector>
using namespace std;
class Animal
{
public:
    virtual void eat()=0;
    virtual ~Animal(){}
};
class Dog:public Animal
{
public:
    void eat(){cout<<"Dog eats bone."<<endl;}
};
class Cat:public Animal
{
public:
    void eat(){cout<<"Cat eats fish."<<endl;}
};
class Sheep:public Animal
{
public:
    void eat(){cout<<"Sheep eats grass."<<endl;}
};
class Chicken:public Animal
{
public:
    void eat(){cout<<"Chicken eats worm."<<endl;}
};
int main()
{
    int c;
    vector<Animal*> animals;
    vector<Animal*>::iterator itr;
    while(cin>>c)
    {
        switch(c)
        {
        case 0 :
            animals.push_back(new Dog());
            break;
        case 1:
            animals.push_back(new Cat());
            break;
        case 2:
            animals.push_back(new Sheep());
            break;
        case 3:
            animals.push_back(new Chicken());
        }
    }
    for (itr = animals.begin(); itr != animals.end(); itr++)
        (*itr)->eat();
    return 0;
}