C++实现 3.7猫狗队列

2019年11月8日 83次阅读

猫狗队列还是挺经典的一道题，思路是对不同类型的对象进行“包裹”，包裹后成为相同的类进行统一处理，不借助编译器的话，手写代码还是很容易出错的，果然简单的题也不是看起来那么简单。
直接上代码：

#include <iostream>
#include <string>
#include <queue>
#include <stdexcept>
using namespace std;

class Animal
{
private:
    int order;
    string type;

public:

    Animal() {}
    Animal(string s) : type(s) {}

    void setOrder(int d) { order = d; }
    int  getOrder() { return order; }
    void setType(string t) { type = t;}
    string  getType() { return type; }

    bool isOrderThan(Animal a) { return this->order < a.order; }
};

class Dog : public Animal
{
public:
    Dog() : Animal("Dog") {}
    Dog(Animal& a) : Dog() {}
};

class Cat : public Animal
{
public:
    Cat() : Animal("Cat") {}
    Cat(Animal& a) : Cat() {}
};

class AnimalQueue : public Animal
{
    queue<Dog> dogs;
    queue<Cat> cats;
    int order = 0;

public:
    void enqueue(Animal& a)
    {
        // 为a设置顺序，该顺序统计每个动物的整体入队顺序
        a.setOrder(order);
        ++order;
        if("Dog" == a.getType()) dogs.push(Dog(a));
        else if("Cat" == a.getType()) cats.push(Cat(a));
    }

    void enqueue(Dog a)
    {
        a.setOrder(order);
        ++order;
        dogs.push(a);
    }
    void enqueue(Cat a)
    {
        a.setOrder(order);
        ++order;
        cats.push(a);
    }

    Dog dequeueDog()
    {
        if(dogs.empty()){ throw runtime_error("队列已空!"); }

        Dog a = dogs.front();
        dogs.pop();
        return a;
    }

    Cat dequeueCat()
    {
        if(cats.empty()) { throw runtime_error("队列已空!"); }

        Cat a = cats.front();
        cats.pop();
        return a;
    }

    Animal dequeueAny()
    {
        // 查看猫狗队列的首部，弹出旧的值
        if(dogs.empty()){
            return dequeueCat();
        }
        else if(cats.empty()){
            return dequeueDog();
        }

        Dog dog = dogs.front();
        Cat cat = cats.front();
        if(dog.isOrderThan(cat))
        {
            return dequeueDog();
        } else {
            return dequeueCat();
        }
    }

};

ostream& operator << (ostream& output, Animal& animal)
{
    output << animal.getType();
    return output;
}


void Test1()
{
    AnimalQueue aq;
    Animal temp;
    aq.enqueue(Dog());
    aq.enqueue(Cat());
    aq.enqueue(Cat());
    for(int i = 0; i < 3; ++i)
    {
        temp = aq.dequeueAny();
        cout << "This is a " <<  temp << endl;
    }

}

int main()
{
    Test1();
    return 0;
}
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