C++实现带头节点的单链表

用友元函数
友元函数会破坏封装性，C++能不用就尽量不用

#include <iostream>

class CLink;
class Node
{
public:
	Node(int val)
	{
		mdata=val;
		pnext=NULL;
	}
	//不用写析构函数 因为头结点是在栈上开辟的 
	//不需要手动去释放 所以不写析构函数
private:
	int mdata;
	Node* pnext;
	friend class CLink;//友元关系//单向性
};

/*
构造函数的初始化列表
*/
class CLink
{
public:
	CLink() :head(0){}
	void InsertHead(int val)
	{
		Node* pnewnode=new Node(val);
		pnewnode->pnext=head.pnext;
		head.pnext=pnewnode;
	}
	void Show()
	{
		Node* pCur=head.pnext;
		while(pCur!=NULL)
		{
			std::cout<<pCur->mdata<<" ";
			pCur=pCur->pnext;
		}
		std::cout<<std::endl;
	}
	~CLink()
	{
		Node* pCur=head.pnext;
		Node* pBack=pCur;
		while(pCur!=NULL)
		{
			pBack=pCur->pnext;
			delete pCur;
			pCur=pBack;
		}
		head.pnext=NULL;
	}
	
	Node* Find(int val)
	{
		Node* pCur=head.pnext;
		while(pCur->pnext!=NULL)
		{
			if(pCur->mdata==val)
			{
				break;
			}
			pCur=pCur->pnext;
		}
		return pCur;
	}
	typedef Node MyNode;

private:
	Node head;
};

int main()
{
	CLink c1;
	for(int i=0;i<10;i++)
	{
		c1.InsertHead(i+1);
	}
	c1.Show();
	CLink::MyNode* pf=c1.Find(5);
	std::cout<<pf<<std::endl;
	return 0;
}

不用友元函数，不会破坏函数的封装性

#include <iostream>

class CLink
{
public:
	CLink() :head(0){};
	void InsertHead(int val)
	{
		Node* pnewnode=new Node(val);
		pnewnode->pnext=head.pnext;
		head.pnext=pnewnode;
	}
	void Show()
	{
		Node* pCur=head.pnext;
		while(pCur!=NULL)
		{
			std::cout<<pCur->mdata<<" ";
			pCur=pCur->pnext;
		}
		std::cout<<std::endl;
	}
	~CLink()
	{
		Node* pCur=head.pnext;
		Node* pBack=pCur;
		while(pCur!=NULL)
		{
			pBack=pCur->pnext;
			delete pCur;
			pCur=pBack;
		}
		head.pnext=NULL;
	}
	class Node;
	Node* Find(int val)
	{
		Node* pCur=head.pnext;
		while(pCur->pnext!=NULL)
		{
			if(pCur->mdata==val)
			{
				break;
			}
			pCur=pCur->pnext;
		}
		return pCur;
	}
	typedef Node MyNode;

private:
	class Node
	{
	public:
		Node(int val):mdata(val),pnext(NULL){}
	public:
		int mdata;
		Node* pnext;
	};
	Node head;
};

int main()
{
	CLink c1;
	for(int i=0;i<10;i++)
	{
		c1.InsertHead(i+1);
	}
	c1.Show();
	CLink::MyNode* pf=c1.Find(5);
	std::cout<<pf<<std::endl;
	return 0;
}