# 【c++版数据结构】之双链表的实现（领头结点以及尾节点）

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【c++版数据结构】之双链表的实现（带头结点以及尾节点）

```#ifndef DLIST_H_
#define DLIST_H_

typedef enum{FALSE,TRUE}Status;
#include<iostream>
#include<cassert>
using namespace std;

template<class Type>
class List;

template<class Type>
class ListNode
{
friend class List<Type>;
private:
Type data;
ListNode<Type> *next;
ListNode<Type> *prio;
public:
ListNode() :data(Type()), next(NULL), prio(NULL){}
ListNode(Type d, ListNode<Type> *p = NULL, ListNode<Type> *n = NULL) :data(d), prio(p), next(n){}
Type getData()const{ return data; }
};

template<class Type>
class List
{
private:
ListNode<Type> *first;
ListNode<Type> *last;
size_t          size;
public:
ListNode<Type>* _BuyNode(const Type &x,ListNode<Type> *p = NULL,ListNode<Type> *n = NULL)
{
ListNode<Type> *s = new ListNode<Type>(x,p,n);
assert(s != NULL);
return s;
}
List()
{
ListNode<Type> *s = _BuyNode(0);
first = last = s;
size = 0;
}
~List()
{
destory();
}
Status push_back(const Type &x)
{
ListNode<Type> *s = _BuyNode(x, last, NULL);
last->next = s;
last = s;
size++;
return TRUE;
}
void show_list()
{
ListNode<Type> *s = first->next;
while (s != NULL)
{
cout << s->data << "->";
s = s->next;
}
cout << "Nul." << endl;
}
Status push_front(const Type &x)//-------------------->>注意插入的节点是第一个节点的情况（单独考虑）
{
ListNode<Type> *s = _BuyNode(x, first, first->next);
if (size == 0)
{
last->next = s;
last = s;
}
else
{
first->next->prio = s;
first->next = s;
}
size++;
return TRUE;
}
Status pop_back()
{
if (size == 0)
{
cout << "双链表已空，无法尾删" << endl;
return FALSE;
}
ListNode<Type> *s = last->prio;
delete last;
last = s;
last->next = NULL;
size--;
return TRUE;
}
Status pop_front()//-------------------->>注意删除的节点是最后一个节点的情况（单独考虑）
{
if (size == 0)
{
cout << "双链表已空，无法头删" << endl;
return FALSE;
}
ListNode<Type> *s = first->next;
if (size == 1)
{
last = first;
last->next = NULL;
}
else
{
first->next = s->next;
s->next->prio = first;
}
delete s;
size--;
return TRUE;
}
//Status pop_front()
//{
//	if (size == 0)
//	{
//		cout << "双链表已空，无法头删" << endl;
//		return FALSE;
//	}
//	ListNode<Type> *s = first->next;
//	if (size == 1)
//	{
//		last = first;
//	//	last->next = NULL;---------->1
//	}
//	else
//	{
//	//	first->next = s->next;---------->2  1，2作用相同合并为3
//		s->next->prio = first;
//	}
//	first->next = s->next; -------->3
//	delete s;
//	size--;
//}
Status insert_val(const Type &x)
{
ListNode<Type> *s = first;
while (s->next != NULL && s->next->data < x)//找到所插入元素的前一个节点，然后在它的后面插入
{
s = s->next;
}
if (s->next == NULL)
push_back(x);
else
{
ListNode<Type> *p = _BuyNode(x, s, s->next);
s->next->prio = p;
s->next = p;
size++;
}
return TRUE;
}
size_t lenth()
{
return size;
}
ListNode<Type>* find(const Type &x)
{
ListNode<Type> *s = first->next;
while (s != NULL && s->data != x)
{
s = s->next;
}
return s;
}
Status delete_val(const Type &x)
{
ListNode<Type> *s = find(x);
if (s == NULL)
{
cout << "该元素不存在，无法删除" << endl;
return FALSE;
}
if (s == last)
{
pop_back();       //最后一个节点的next为NULL，NULL没有前驱，所以s->next->prio = s->prio; 此句不成立
}
else
{
s->next->prio = s->prio;
s->prio->next = s->next;
delete s;
size--;
}
return TRUE;
}
void sort()
{
if (size == 0 || size == 1)
return;
ListNode<Type> *s = first->next;
ListNode<Type> *p = s->next;
s->next = NULL;
//s->next->prio = NULL
last = s;
while (p != NULL)
{
s = p;
p = p->next;//将s按值插入到链表

ListNode<Type> *q = first;
while (q->next != NULL && q->next->data < s->data)//寻找前一个节点的位置，在该节点的后面插入该节点
{
q = q->next;
}
if (q->next == NULL)//没有比插入节点大得节点，进行尾插即可
{
last->next = s;
s->prio = last;
last = s;
last->next = NULL;
}
else//寻找到前一个节点的位置，在该节点的后面插入该节点
{
s->prio = q;
s->next = q->next;
q->next->prio = s;
q->next = s;
}

}

}
void reserve()
{
if (size == 0 || size == 1)
return;
ListNode<Type> *s = first->next;
ListNode<Type> *p = s->next;
s->next = NULL;
//s->next->prio = NULL
last = s;
while (p != NULL)
{
s = p;
p = p->next;//将s头插到链表

s->next = first->next;
first->next->prio = s;
s->prio = first;
first->next = s;
}
}
void clear()
{
if (size == 0)
return;
ListNode<Type> *s = first->next;
while (s != NULL)
{
if (size == 1)
{
last = first;
last->next = NULL;

}
else
{
first->next = s->next;
s->next->prio = first;
}
delete s;
size--;
s = first->next;
}
}
void destory()
{
clear();
delete[] first;
first = last = NULL;
}
ListNode<Type>* next(ListNode<Type> *s)
{
return s->next;
}
ListNode<Type>* prio(ListNode<Type> *s)
{
if (s == first->next) //-------------->第一个节点没有前驱，返回NULL
return NULL;
else
return s->prio;
}
};
#endif```

```#include"DList.h"
#include<cstdlib>

int main()
{
List<int> mylist;
int item;
int n;
int select = 1;
//ListNode<int> *p;
while (select)
{
cout << "*************************************** *" << endl;
cout << "*[1] push_back           [2] push_front *" << endl;
cout << "*[3] show_list           [4] pop_back   *" << endl;
cout << "*[5] pop_front           [6] insert_val *" << endl;
cout << "*[7] lenth               [8] find       *" << endl;
cout << "*[9] merge               [10] delete_val*" << endl;
cout << "*[11] sort               [12] reserve   *" << endl;
cout << "*[13] next               [14] clear     *" << endl;
cout << "*[15] prio               [0] quit_system*" << endl;
cout << "请选择：>";
cin >> select;
switch (select)
{
case 1:
cout << "请输入要插入的元素（-1结束):>";
while (cin >> item, item != -1)
{
mylist.push_back(item);
}
break;
case 2:
cout << "请输入要插入的元素（-1结束）:>";
while (cin >> item, item != -1)
{
mylist.push_front(item);
}
break;
case 3:
mylist.show_list();
break;
case 4:
mylist.pop_back();
break;
case 5:
mylist.pop_front();
break;
case 6:
cout << "请输入要插入的元素：";
cin >> item;
mylist.insert_val(item);
break;
case 7:
cout << "长度为：" << mylist.lenth() << endl;
break;
case 8:
cout << "请输入要查找的元素：";
cin >> item;
if (mylist.find(item))
cout << "it's found" << endl;
else
cout << "it's not exist" << endl;
break;
case 9:
cout << "请输入要删除的位置：";
cin >> n;
//mylist.delete_pos(n,item);
break;
case 10:
cout << "请输入要删除的元素：";
cin >> item;
mylist.delete_val(item);
break;
case 11:
mylist.sort();
break;
case 12:
mylist.reserve();
break;
case 14:
mylist.clear();
break;
default:
break;
}
}
system("pause");
return 0;
}```