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Design a C++ universal linked list: realize polymorphic two-way function

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Release： 2018-07-24 17:58:51

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之前用c实现的通用链表，将链表的data域从具体类型转变为 void*指针，用c实现时费力气的是指针的赋值和也要做到通用的打印

链接：c实现的通用的双向链表现在用c++重新实现，思想大都一致：

不采用模板类，而采用虚函数实现多态性，达到通用的目的，data域不存储任何跟类型有关的信息，而是指针，将数据放于抽象类中，由指针与之建立联系。

Design a C++ universal linked list: realize polymorphic two-way function

链表有头指针尾指针，以及之后的一系列插入删除打印操作，这些函数都写在链表类中。

链表指针类型为链表结点类，结点的指针域和 data域，都是指针类型，data域指向一个抽象类 object对象。

object类是一个抽象类，当需要链表存放整型数据，就具体实现一个存放整型的子类去继承这个类，必须实现抽象类中的虚函数，以打印函数为例，每一个不同数据类型的子类都得有自己的打印函数，而object 不关心如何打印。

class intobject :public Object
{
public:
	intobject(int d = 0) :data(d)
	{}
	~intobject()
	{}
	void Print()const
	{
		cout << data << "-->";
	}
private:
	int data;
};
////////////////////////////////////////////////////////////
class strobject :public Object
{
public:
	strobject(char *str) 
	{
		if (str == NULL)
		{
			data = new char[1];
			data[0] = &#39;\0&#39;;
		}
		else
		{
			data = new char[strlen(str) + 1];
			strcpy(data, str);
		}
	}
	~strobject()
	{}
	void Print()const
	{
		cout << "\"" << data << "\"" << "-->";
	}
private:
	char * data;
};

////////////////////////////////////////////////////////////
class floatobject :public Object
{
public:
	floatobject(float d = 0) :data(d)
	{}
	~floatobject()
	{}
	void Print()const
	{
		cout << data << "-->";
	}
private:
	float data;
};
////////////////////////////////////////////////////////////

void main()
{
	list mylist;
	for (int i = 0; i < 5; ++i)
	{
		intobject *pi = new intobject(i);
		mylist.push_back(pi);
	}
	mylist.printlist();

	char* arr[5] = { "affd", "fdas", "fdfss", "ere", "qret" };
	for (int i = 0; i < 5; i++)
	{
		strobject*ps = new strobject(arr[i]);
		mylist.push_back(ps);
	}
	mylist.printlist();

	float brr[5] = { 0.34, 54.32, 0.53, 43.2, 5.878 };
	for (int i = 0; i < 5; i++)
	{
		floatobject*ps = new floatobject(brr[i]);
		mylist.push_back(ps);
	}
	mylist.printlist();
}

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Design a C++ universal linked list: realize polymorphic two-way function

链表的释放：

Design a C++ universal linked list: realize polymorphic two-way function

class Object
{
public:
	Object()
	{}
	virtual ~Object()//因为是虚函数，调动父类析构的 同时 调动子类的析构
	{}
	////定义接口   通用的打印
	virtual void Print()const = 0;//纯虚函数  子类继承了之后必须实现打印函数
};
class list;

class listnode
{
	friend class list;
public:
	listnode()
	{
		data = NULL;
		next = NULL;
	}
	listnode(Object *pobj)
	{
		data = pobj;
		next = NULL;
	}
	~listnode()
	{
		delete data;
		next = NULL;
	}

private:
	Object *data;
	listnode *next;
};

class list
{
public:
	list()
	{
		head = tail = new listnode;
	}
	~list()
	{
		listnode *delp = head->next;
		while (delp!= tail)
		{
			head->next = delp->next;
			delete delp;
			delp = head->next;
		}
		delete head;
		head = tail = NULL;
	}
	void push_back(Object *pb)//尾插
	{
		listnode *s = new listnode(pb);
		assert(s != NULL);
		tail->next = s;
		tail = s;		
	}
	void printlist()const
	{
		listnode *p = head->next;
		while (p != NULL)
		{
			p->data->Print();
			p = p->next;
		}
		cout << "NULL" << endl;
	}
private:
	listnode *head;
	listnode *tail;
};


////////////////////////////////////////////////////////////
class intobject :public Object
{
public:
	intobject(int d = 0) :data(d)
	{}
	~intobject()
	{
		cout << "delete int" << endl;
	}
	void Print()const
	{
		cout << data << "-->";
	}
private:
	int data;
};
////////////////////////////////////////////////////////////
class strobject :public Object
{
public:
	strobject(char *str) 
	{
		if (str == NULL)
		{
			data = new char[1];
			data[0] = &#39;\0&#39;;
		}
		else
		{
			data = new char[strlen(str) + 1];
			strcpy(data, str);
		}
	}
	~strobject()
	{
		cout << "delete string" << endl;
		delete []data;
		data = NULL;
	}
	void Print()const
	{
		cout << "\"" << data << "\"" << "-->";
	}
private:
	char * data;
};

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