C语言双链表

C语言双链表

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

typedef struct node
{
	int data;
	struct node *prev;
	struct node *next;
}st,*pt;

pt node_init(void);					//初始化节点
void add_head(pt head,int data);	//头插
void add_tail(pt head,int data);	//尾插
void del_node(pt head,int data);	//删除
void show(pt head);					//显示


int main(int argc, char const *argv[])
{
	int data;
	pt head = node_init();
	while(1)
	{
		printf("请输入:");
		scanf("%d",&data);
		if(data > 0)
		{
			add_head(head,data);
		}
		else if(data < 0)
		{
			del_node(head,-data);
		}
		else
			break;

		show(head);
	}
	return 0;
}


pt node_init(void)
{
	pt head = (pt)malloc(sizeof(st));
	if(head == NULL)
	{
		perror("init failed");
		return NULL;
	}
	head->prev = NULL;
	head->next = NULL;
	return head;
}

//头插
void add_head(pt head,int data)
{
	pt new_node = node_init();
	new_node->data = data;			//赋值
	if(new_node == NULL)
	{
		perror("new_node failed");
		return;
	}

	if(head->next == NULL)			//假如不判断，则头节点下一个为空时，78行无法执行
	{
		//直接插入 
		head->next = new_node;
		new_node->prev =  head;
		return ;
	}

	new_node->prev = head;			//新节点上一个指向头，下一个指向头原来的下一个
	new_node->next = head->next;	//新节点指向头的下一个
	head->next = new_node;			//头节点下一个指向新节点
	new_node->next->prev = new_node;//新节点下一个节点指向自己

	printf("插入成功\n");

} 

//尾插
void add_tail(pt head,int data)
{
	pt new_node = node_init();
	if(new_node == NULL)
	{
		perror("new_node failed");
		return;
	}
	pt pos = head;
	while(pos->next != NULL)
	{
		pos = pos->next;
	}
	new_node->data = data;		//赋值
	new_node->next = NULL;		//新节点下一个指向空
	new_node->prev = pos;		//新节点上一个指向原末尾节点
	pos->next = new_node;		//原末尾节点指向新节点
	printf("插入成功\n");
	

}

//删除
void del_node(pt head,int data)
{
	pt pos = head->next;
	pt tmp;
	int flag = 0;
	while(pos->next != NULL)
	{

		if(pos->data == data)
		{
			flag++;
			tmp = pos;					//代替pos的指向
			pos = pos->prev;			//回到上一个地方

			tmp->prev->next = tmp->next;//牵线
			tmp->next->prev = tmp->prev;
			tmp->next = NULL;			//指向空再释放
			tmp->prev = NULL;
			free(tmp);
			
		}
		pos = pos->next;
	}

	if(pos->data == data)			//假如最后一个数据符合
	{
		pos->prev->next = NULL; 	//指向空再释放
		pos->prev = NULL;
		flag++;
		free(pos);
	}

	printf("删除%d个\n",flag);
}

//显示
void show(pt head)
{
	pt pos = head->next;
	printf("****\n");
	while(pos != NULL)
	{
		printf("%d\n", pos->data);
		pos = pos->next;
	}

}