c++ 双向链表

#include <iostream>
using std::cout;
using std::endl;
struct Node
{
	int data;
	struct Node * next;
	struct Node * pre;
};

一、创建双向链表

Node * createList()
{
	Node * head = new Node;
	if (NULL == head)
		exit(-1);
	head->next = head;
	head->pre = head;
	return head;
}

二、插入元素(头插法)
让新来的节点先有所指

void insertList(Node * head,int n)
{
	Node * cur = new Node;
	if (NULL == cur)
		exit(-1);
	cur->next = head->next;
	cur->pre = head;
	head->next = cur;
	cur->next->pre = cur;
	
	cur->data = n;
}

三、链表长度

int lenList(Node * head)
{
	int i = 0;
	Node * t = head->next;
	while (t != head)
	{
		i++;
		t = t->next;
	}
	return i;
}

四、查找遍历

Node * findList(Node * head,int fn)
{
	Node * forward = head->next;
	Node * back = head->pre;
	while (forward != back->next)
	{
		if (forward->data == fn)
			return forward;
		if (back->data == fn)
			return back;
		if (forward == back)
			break;
		forward = forward->next;
		back = back->pre;
	}
	return NULL;
}

五、删除其中元素

void deleteList(Node * pFind)
{
	pFind->pre->next = pFind->next;
	pFind->next->pre = pFind->pre;
	delete pFind;
}

六、排序
（类似于先删除 再插入）

void sortDlist(Node * head)
{
	int len = lenList(head);
	Node *prep = NULL;
	Node *p = NULL;
	Node *q = NULL;
	Node *t = NULL;
	for (int i = 0;i < len - 1;i++)
	{
		p = head->next;
		q = p->next;
		for (int j = 0;j < len - 1 - i;j++)
		{
			if ((p->data)<(q->data))
			{
				p->pre->next = q;
				q->pre = p->pre;

				p->next = q->next;
				p->pre = q;

				q->next = p;
				p->next->pre = p;

				t = p;
				p = q;
				q = t;
			}
			p = p->next;
			q = q->next;
		}
	}
}

七、销毁链表

void desList(Node * head)
{
	head->pre->next = NULL;
	Node *t = NULL;
	while (head != NULL)
	{
		t = head;
		head = head->next;
		delete t;
	}
}