双向链表

				 
/*
 *不带头的链表
 **/

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

struct node
{
	int var;
	struct node* prev;
	struct node* next;
};

//头插法
void Add(int v,struct node**head){
	struct node*pnew=(struct node*)malloc(sizeof(struct node));
	pnew->var=v;

	//如果链表头为空
	if (!(*head))
	{
		//新结点就是头
		(*head) = pnew;
		pnew->prev=pnew->next=NULL;
	}
	else
	{
		//新结点的前驱指针置空
		pnew->prev=NULL;
		//新结点的后继指针指向链表头
		pnew->next=(*head);
		//链表头的前驱指针指向新结点
		(*head)->prev=pnew;
		//链表头指针指向新结点
		(*head)=pnew;
	}
}
//删除值为v的链表结点
void Del(int v,struct node**head){
	if (!head)
	{
		return;
	}
	struct node*p=*head,*p1=*head;
	while (p)
	{
		if (p->var == v)
		{
			if (p == *head)
			{
				(*head)=p->next;
				(*head)->prev=NULL;
				//free(p);
				printf("已删除(头)\n");
				return;
			}
			else
			{
				//printf("%d %d\n",p1->var,p->var);
				p1->next=p->next;
				if (p->next)
				{
					p->next->prev=p1;
					printf("不是最后\n");
				}
				//free(p);
				//printf("%d %d\n",p1->var,p->var);
				
				printf("已删除\n");
				return;
			}
		}
		p1=p;
		p=p->next;
	}
	printf("不存在\n");
}
//从头打印链表
void Print1(struct node*head){
	struct node*p=head;
	while (p)
	{
		printf("%d ",p->var);
		p=p->next;
	}
	printf("\n");
}
//从尾打印
void Print2(struct node*head){
	struct node*p=head;
	while (p->next)
		p=p->next;

	while (p)
	{
		printf("%d ",p->var);
		p=p->prev;
	}
	printf("\n");
}
int main(){
	int a[]={1,2,3,4,5};
	int i;
	struct node*head=NULL;
	for (i=0;i<5;i++)
	{
		Add(a[i],&head);
	}
	Print1(head);
	Print2(head);

	Del(5,&head);
	Print1(head);

	Del(1,&head);
	Print1(head);

	Del(3,&head);
	Print1(head);
	getchar() ;
}

宏定义法，非常巧妙
参考GitHub王博靖

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

struct node
{
	int var;
	struct node* prev;
	struct node* next;
	node(int v):var(v),prev(NULL),next(NULL){}
};


#define LL_ADD(item, list) do { 	\
	item->prev = NULL;				\
	item->next = list;				\
	list = item;					\
} while(0)

#define LL_REMOVE(item, list) do {						\
	if (item->prev != NULL) item->prev->next = item->next;	\
	if (item->next != NULL) item->next->prev = item->prev;	\
	if (list == item) list = item->next;					\
	item->prev = item->next = NULL;							\
} while(0)

//从头打印链表
void Print1(struct node*head){
	struct node*p=head;
	while (p)
	{
		printf("%d ",p->var);
		p=p->next;
	}
	printf("\n");
}

int main(){
	node*list=NULL;

	int a[]={1,2,3,4,5};
	for (int i=0;i<5;i++){
		node*p=new node(a[i]);
		LL_ADD(p,list);
	}

	Print1(list);

	getchar();
}