帶表頭的單循環鏈表的實現

通常在循環鏈表的第一個節點前附加一個特殊的節點來作爲標記，這個節點稱爲循環鏈表的頭結點，頭結點的數據域爲空域，或者按照需要設定。

在這裏，我們將a1節點的地址設爲first，頭結點僅當作特殊標記。如果不想增加頭結點，也可以實現單循環鏈表。

本篇的單循環鏈表是根據上篇《單鏈表的實現》上稍作修改而來，有什麼好的建議請指點我！

1.頭文件

#ifndef CHAIN_H
#define CHAIN_H

#include<iostream>
//帶頭節點的循環鏈表，頭結點是空表
template<class T>
class chainnode
{
  template<class T>
  friend class chain;
public:
	chainnode()   //循環鏈表設置默認構造函數對數據域不作初始化
	{
		next = nullptr;//初始化節點時，將該節點指向自己
	}
	~chainnode()
	{

	}
	void setdata(const T& dat)
	{
		data = dat;
	}
public:
	T getdata()
	{
		return data;
	}
	chainnode<T>* getnext()
	{
		return next;
	}
private:
	T data;
	chainnode<T>* next;
};

template<class T>
class chain
{

public:
	chain()
	{
		head= new chainnode < T > ; //單獨開闢一個節點當作循環鏈表的頭節點,且頭結點不存儲數據
		length = 0;
		head->next = head;
		first = nullptr;
	}
	~chain()       
	{
		chainnode<T>* temp=head->next;
		while (temp!=head)
		{
			chainnode<T>* curr = temp;
			temp = temp->next;
			delete curr;
		}
		delete head;
	}

public:
	bool isempty()   //當循環鏈表中只存在表頭的時候，爲空
	{
		return first == nullptr;
	}
	chainnode<T>* getfirst()
	{
		return first;
	}

	chainnode<T>* gethead()
	{
		return head;
	}

	void deletenode(int pos);
	int  getlength();
	void insertbefore(T dat, int pos);
	void insertafter(T dat, int pos);
	T find(int pos);
private:
	chainnode<T>* first; //指向第一個有意義的節點
	chainnode<T>* head; //頭結點，特殊標記
	int length;
};


template<class T>
void chain<T>::insertbefore(T dat, int pos)  //在pos位置前面插入一個元素
{
	if (pos< 0 || pos>length)
	{
		std::cout << "輸入的位置數錯誤" << endl;
		exit(1);
	}

	chainnode<T>* now = new chainnode < T >;
	now->data = dat;
	if (first == nullptr)  //如果循環鏈表只有表頭，爲空表
	{
		first = now;
		head->next = first;
		first->next = head;
		++length;
	}
	else
	{
		chainnode<T>* pp = first;
		for (int i = 1; i < pos - 1 && pp; ++i)
			pp = pp->next;
		if (pp)
		{
			if (pos == 1)
			{
				now->next = first;
				head->next = now;
				first = now;
			}
			else
			{
				now->next = pp->next;
				pp->next = now;
			}
			++length;
		}
	}
}

template<class T>
void chain<T>::insertafter(T dat, int pos)
{
	if (pos < 0 || pos>length)
	{
		std::cout << "輸入的位置數錯誤" << endl;
		exit(1);
	}

	chainnode<T>* now = new chainnode < T >;
	now->data = dat;
	if (first == nullptr)
	{
		first = now;
		head->next = now;
		first->next = head;
		++length;
	}
	else
	{
		chainnode<T>* pp = first;
		for (int i = 1; i < pos && pp; ++i)
			pp = pp->next;
		if (pp)
		{
			if (pos == length)
			{
				now->next = head;
				pp->next = now;
				
			}
			else
			{
				now->next = pp->next;
				pp->next = now;
			}
			++length;
		}
	}
}
template<class T>
T chain<T>::find(int pos)
{
	if (first)
	{
		if (pos<0 || pos>length)
		{
			std::cout << "輸入的位置數錯誤" << endl;
			exit(1);
		}
		chainnode<T>* curr=first;
		for (int i = 1; i < pos; ++i)
			curr = curr->next;
		return curr->data;
	}
}
template<class T>
int chain<T>::getlength()
{
	if (first == nullptr)
		return  0;
	chainnode<T>* current = first;
	int len = 0;
	while (current!=head)
	{
		++len;
		current = current->next;
	}
	length = len;
	return len;
}

template<class T>
void chain<T>::deletenode(int pos)
{
	if (first)
	{
		if (pos<0 || pos>length)
		{
			std::cout << "輸入的位置數錯誤" << endl;
			exit(1);
		}
		if (pos == 1)
		{
			chainnode<T>* temp = first;
			head->next = first->next;
			first = first->next;
			delete temp;
			--length;
		}
		else
		{
			chainnode<T>* tem = first;
			for (int i = 1; i < pos - 1 && tem; ++i) //獲得pos前一個元素的地址
				tem = tem->next;
			if (tem &&tem->next)   //確保第pos個元素存在
			{
				chainnode<T>* curr = tem->next; //curr是pos位置元素的地址
				tem->next = curr->next;
				delete curr;
				--length;
			}
		}
	}
}

template<class T>
std::ostream& operator <<(std::ostream& out, chain<T>& list) 
{
	chainnode<T>* cc = list.getfirst();
	for (int i = 1; i <= list.getlength(); ++i)
	{
		out <<cc->getdata() << " ";
		cc = cc->getnext();
	}
	std::cout << std::endl;
	return out;
}
#endif

2.main文件

#include<iostream>
#include"chain.h"
using namespace std;

int main()
{
	chain<char> liner;
	liner.insertafter('A', 0);
	liner.insertafter('B', 1);
	liner.insertafter('C', 2);
	liner.insertafter('D', 3);
	liner.insertbefore('E',1);
	//*********測試循環鏈表是否完成********
	(liner.gethead())->setdata('H');//用H表示頭結點數據，頭結點數據默認爲空
	chainnode<char>* xx = liner.getfirst();
	for (int i = 1; i < 10; ++i)
	{
		cout << xx->getdata() << " ";
		xx = xx->getnext();
	}
	cout << endl;
	//*********這段代碼目的只爲測試********
	auto dd = liner.find(3);
	cout << dd << endl;
	cout<< liner << endl;
	system("pause");
	return 0;
}