双向链表的结构与基本操作（初始化，头插，尾插，删除，输出，清空，销毁等）

本文介绍: 双向链表的结构与基本操作（初始化，头插，尾插，删除 p os 位置的值，删除第一个 val值，获取节点个数，判空，输出，清空，销毁）

typedef struct DNode

{
    int data;

    struct DNode* next;//后继指针

    struct DNode* prio;//前驱指针

}DNode ,*DList;

//初始化
void InitList(DList plist)
{
	assert(plist != NULL);
	if (plist == NULL)
		return;
	//plist-&gt;data不使用
	plist-&gt;next = NULL;
	plist-&gt;prio = NULL;
}

//考试重点
//头插
bool Insert_head(DList plist, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	//创建新节点
	DNode* p = (DNode*)malloc(sizeof(DNode));
	assert(p != NULL);
	p-&gt;data = val;
	//插入新节点

	p-&gt;next = plist-&gt;next;//绑线
	plist-&gt;next = p;
	p-&gt;prio = plist;
	if(p-&gt;next!=NULL)//判断很重要
	{
		p-&gt;next->prio = p;
	}
	return true;
}

//考试重点
//尾插 
bool Insert_tail(DList plist, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	//创建新节点
	DNode* p = (DNode*)malloc(sizeof(DNode));
	assert(p != NULL);
	p->data = val;
	
	//找尾巴
	DNode* q;
	for (q = plist; q->next != NULL; q = q->next)
	{
		;
	}
	//插入数据
	//将p插入到q的后面
	p->next = q->next;//p->next=NULL;
	p->prio = q;
	q->next = p;

	return true;


}

//插入数据，在plist链表的pos位置插入val;
bool Insert(DList plist, int pos, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	if (pos<0 || pos>GetLength(plist))
	{
		return false;
	}
	//申请节点
	DNode* p = (DNode*)malloc(sizeof(DNode));
	assert(p != NULL);
	p->data = val;
	//找位置
	DNode* q;
	int i = 0;
	for (q = plist; i < pos; i++, q = q->next)
	{
		;
	}
	//插入数据
	//将p插入到q的后面
	p->next = q->next;
	q->next = p;
	p->prio = q;
	if (p->next != NULL)//判断很重要
	{
		p->next->prio = p;
	}
	return true;
}

//判空
bool IsEmpty(DList plist)
{
	return plist->next == NULL;
}

//获取数据节点的个数
int GetLength(DList plist)
{
	int count = 0;
	for (DNode* p = plist->next; p != NULL; p = p->next)
	{
		count++;
	}
	return count;
}

//在plist中查找第一个key值，找到返回节点地址，没有找到返回NULL；
DNode* Search(DList plist, int key)
{
	for (DNode* p = plist->next; p != NULL; p = p->next)
	{
		if (p->data == key)
		{
			return p;
		}
	}
	return NULL;
}

//删除pos位置的值
bool DelPos(DList plist, int pos)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;

	if (pos < 0 || pos >= GetLength(plist))
	{
		return false;
	}
	//找位置
	DNode* p;
	int i;
	for (p = plist, i = 0; i < pos; i++, p = p->next)
	{
		;
	}
	DNode* q = p->next;//q是要删除的点,注意,q可能是最后一个点
	//删除
	p->next = q->next;
	if (q->next != NULL)
	{
		q->next->prio = q->prio;//OK
	  //q->next->prio=p;//OK  q->prio就是p
	}
	//释放
	free(q);
	return true;
}

//考试重点
//删除第一个val的值
bool DelVal(DList plist, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;

	DNode* p = Search(plist, val);
	if (p == NULL)
		return false;

	p->prio->next = p->next;
	if (p->next != NULL)//判断很重要
	{
		p->next->prio = p->prio;
	}
	free(p);
	return true;
}

//返回key的前驱地址，如果不存在返回NULL；
DNode* GetPrio(DList plist, int key)
{
	DNode* p = Search(plist, key);

	return p == NULL ? NULL : p->prio;
}

//返回key的后继地址，如果不存在返回NULL；
DNode* GetNext(DList plist, int key)
{
	DNode* p = Search(plist, key);

	return p == NULL ? NULL : p->next;
}

//输出
void Show(DList plist)
{
	for (DNode *p = plist->next; p != NULL; p = p->next)
	{
		printf("%d  ", p->data);
	}	
	printf("n");
}

//清空数据
void Clear(DList plist)
{
	Destroy(plist);
}

//销毁整个内存
void Destroy(DList plist)
{
	assert(plist != NULL);
	if (plist == NULL)
		return;
	//总是删除第一个节点
	DNode* p;
	while (plist->next != NULL)
	{
		p = plist->next;
		plist->next = p->next;
		//可以不用处理
		/*if (p->next != NULL)
		{
			p->next->prio = plist;
		}*/
		free(p);
	}
}