数据结构--单链表(c语言实现)

一.单链表的设计

1.单链表的结构定义:

typedef struct Node{
   int data;//数据域
   struct Node* next;//后继指针
}Node,*List;

2.单链表的设计示意图:

3.注意,单链表的最后一个节点的next域为NULL;

4.为什么要有一个头节点?(简单方便,不用传二级指针);

二.单链表的实现

//初始化
void InitList(List plist)
{
	assert(plist != NULL);
	if (plist == NULL)
		return;
	//plist->data;//头节点的数据域不使用
	plist->next = NULL;
}

//考试重点
//头插
bool Insert_head(List plist, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	//动态申请一个节点
	Node* p = (Node *)malloc(sizeof(Node));
	assert(p != NULL);

	//将数据val放入到新节点
	p->data = val;

	//插入新节点
	p->next = plist->next;
	plist->next = p;

	return true;
}

//考试重点
//尾插
bool Insert_tail(List plist, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	//申请节点
	Node* p = (Node*)malloc(sizeof(Node));
	assert(p != NULL);
	//将数据val放入到新节点
	p->data = val;
	//找尾巴
	Node* q;
	for(q=plist;q->next!=NULL;q=q->next)
   {
		;
	}
	//插入新节点
	p->next = q->next;//p->next=NULL;
	q->next = p;
	return true;
}

//插入数据，在plist链表的pos位置插入val;
bool Insert(List plist, int pos, int val)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;

	if (pos<0 || pos>GetLength(plist))
	{
		return false;
	}
	Node* p = (Node*)malloc(sizeof(Node));
	assert(p != NULL);
	p->data = val;
	//找到位置
	Node* q;
	int i;
	for (q = plist, i = 0; i < pos; i++, q = q->next)
	{
		;
	}
	// 插入
	p->next = q->next;
	q->next = p;

	return true;
}

//判空
bool IsEmpty(List plist)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;

	return plist->next == NULL;
}

//获取数据节点的个数
int GetLength(List plist)
{
	assert(plist != NULL);
	if (plist == NULL)
		return 0;
	int count = 0;
	for (Node* 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；
Node* Search(List plist, int key)
{
	assert(plist != NULL);
	if (plist == NULL)
		return NULL;
	
	for (Node* 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(List plist, int pos)
{
	assert(plist != NULL);
	if (plist == NULL)
		return false;
	if (pos < 0 || pos >= GetLength(plist))
	{
		return false;
	}
	Node* p;
	int i;
	for (p = plist, i = 0; i < pos; i++, p = p->next)
	{
		;
	}
	//删除p后面的节点
	Node* q = p->next;
	p->next = q->next;
	free(q);

	return true;
}


//考试重点
//删除第一个val的值
bool DelVal(List plist, int val)
{
	Node* p = GetPrio(plist, val);
	if (p == NULL)
		return false;
	Node* q = p->next;
	//删除q
	p->next = q->next;//p->next=p->next->next;
	//释放q
	free(q);

	return true;
}

//返回key的前驱地址，如果不存在返回NULL；
Node* GetPrio(List plist, int key)
{
	for (Node* p = plist; p->next != NULL; p = p->next)
	{
		if (p->next->data == key)
			return p;
	}
	return NULL;
}

//返回key的后继地址，如果不存在返回NULL；
Node* GetNext(List plist, int key)
{
	assert(plist != NULL);
	if (plist == NULL)
		return NULL;

	Node* p = Search(plist, key);
	if (p == NULL)
		return NULL;

	return p->next;
}

//输出
void Show(List plist)
{
	//注意，头节点不能访问data
	for (Node* p = plist->next; p != NULL; p = p->next)
	{
		printf("%d ", p->data);
	}
	printf("\n");
}

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

void Destroy(List plist)
{
	//总是删除第一个数据节点
	Node* p;
	while (plist->next != NULL)
	{
		p = plist->next;
		plist->next = p->next;
		free(p);

		//error
		//plist->next = plist->next->next;
		//free(plist->next);
	}
}