双向循环链表

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

typedef struct node
{
	int data;
	struct node *next;
	struct node *pre;
}Node;

Node *pHead=NULL;

void insert(Node *pNode)
{
	if(NULL == pHead)
	{
		pHead = pNode;
		pHead->next = pNode;
		pHead->pre = pNode;
		return;
	}
	/*插头法*/
	pNode->next = pHead;
	pNode->pre = pHead->pre;
	pHead->pre->next = pNode;
	pHead->pre = pNode;
	pHead = pNode;
}

void del(int data)
{
	Node *p;
	if(NULL == pHead)
		return;
	p = pHead;	
	if(data == pHead->data)/*刚好为head*/
	{
		if(pHead == p->next)/*只有一个node*/
		{
			free(pHead);
			pHead = NULL;
		}
		else
		{
			pHead = p->next;
			p->next->pre = p->pre;
			p->pre->next = p->next;
			free(p);
		}
		return;
	}
	p = pHead->pre;
	do
	{
		if(data == p->data)
		{
			break;
		}
		p = p->pre;	
	}
	while(pHead->pre != p);
	
	p->next->pre = p->pre;
	p->pre->next = p->next;
	free(p);
	
	return ;
}

void display(void )
{
	Node *p;
	p = pHead->pre;
	do
	{
		printf("%d  ", p->data);
		p = p->pre;	
	}
	while(pHead->pre != p);
	
	printf("\n\r");
}

int main(void )
{
	int i;
	Node *p;
	for(i=0; i<100; i++)
	{
		p = (Node *)malloc(sizeof(Node));
		p->data = i;
		insert(p);
	}
	display();
	for(i=30; i<90; i++)
	{
		del(i);
	}
	del(99);
	display();
	return 0;
}