链表(1)C语言实现 单链表 无头结点 基本操作 无头结点单链表的基本操作 详解 链表的概念及结构 数据结构

3.链表

3.1 链表的概念及结构

概念：链表是一种物理存储结构上非连续、非顺序的存储结构，数据元素的逻辑顺序是通过链表

中的指针链接次序实现的

注意：

1.从上图可看出，链式结构在逻辑上是连续的，但是在物理上不一定连续

2.现实中的结点一般都是从堆上申请出来的

3.从堆上申请的空间是按照一定的策略来分配的，两次申请的空间可能连续也可能不连续

3.2 链表的分类

1. 单向或者双向

2. 带头或者不带头  

 

3. 循环或者非循环 

 3.3 单链表的实现

#include
#include
#include
typedef int SLDataType;//元素类型

1.结点 

typedef struct ListNode
{
	SLDataType data;
	struct ListNode* next;
}ListNode;

2.动态申请一个结点

ListNode* BuySListNode(SLDataType x)
{
	ListNode* newnode = (ListNode*)malloc(sizeof(ListNode));
	assert(newnode!=NULL);
	newnode->data = x;
	newnode->next = NULL;
	return newnode;
}

3.单链表打印

void SListPrint(ListNode* plist)
{
	ListNode* cur = plist;
	while (cur != NULL)
	{
		printf("%d ", cur->data);
		cur = cur->next;
	}
	printf("\n");
}

4.单链表尾插

void SListPushBack(ListNode** pplist, SLDataType x)
{
    assert(pplist!=NULL);
	ListNode* newnode = BuySListNode(x);
	if (*pplist == NULL)//没有结点
	{
		*pplist = newnode;
	}
	else
	{
		ListNode* tail = *pplist;
		while (tail->next != NULL)
		{
			tail = tail->next;
		}
		tail->next = newnode;
	}
}

5.单链表的头插

void SListPushFront(ListNode** pplist, SLDataType x)
{
    assert(pplist!=NULL);
	ListNode* newnode = BuySListNode(x);
	newnode->next = *pplist;
	*pplist = newnode;
}

6.单链表的尾删

void SListPopBack(ListNode** pplist)
{
    assert(pplist!=NULL);
	assert(*pplist!=NULL);
	if ((*pplist)->next == NULL)
	{
		free(*pplist);
		*pplist = NULL;
	}
	else
	{
		ListNode* tailPrev = NULL;
		ListNode* tail = *pplist;
		while (tail->next != NULL)
		{
			tailPrev = tail;
			tail = tail->next;
		}
		free(tail);
		tailPrev->next = NULL;
	}
}

7.单链表的头删

void SListPopFront(ListNode** pplist)
{
    assert(pplist!=NULL);
	assert(*pplist!=NULL);
	ListNode* cur = (*pplist)->next;
	free(*pplist);
	*pplist = cur;
}

8.单链表查找

ListNode* SListFind(ListNode* plist, SLDataType x)
{
	ListNode* p = plist;
	while (p != NULL)
	{
		if (p->data == x)return p;
		p = p->next;
	}
	return NULL;
}

9.把x插入到pos处

void SListInsert(ListNode** pplist, ListNode* pos, SLDataType x)
{
	assert(pplist!=NULL);
	assert(pos!=NULL);
	// 头插
	if (pos == *pplist)
	{
		SListPushFront(pplist, x);
	}
	else
	{
		ListNode* prev = *pplist;
		while (prev->next != pos)
		{
			prev = prev->next;
		}
		ListNode* newnode = BuySListNode(x);
		prev->next = newnode;
		newnode->next = pos;
	}
}

10.删除pos位置的值

void SListErase(ListNode** pplist,ListNode* pos)
{
	assert(pplist != NULL);
	assert(pos != NULL);
	if (*pplist== pos)
	{
		SListPopFront(pplist);
	}
	else
	{
		ListNode* prev = *pplist;
		while (prev->next != pos)
		{
			prev = prev->next;
		}
		prev->next = pos->next;
		free(pos);
		pos = NULL;
	}
}

11.单链表在pos位置之后插入x

void SListInsertAfter(ListNode* pos, SLDataType x)
{
	assert(pos != NULL);
	ListNode* newnode = BuySListNode(x);
	newnode->next = pos->next;
	pos->next = newnode;
}

 12.删除pos位置之后的值

void SListEraseAfter(ListNode* pos)
{
	assert(pos != NULL);
	if (pos->next == NULL)
		return;
	ListNode* q = pos->next;
	pos->next = q->next;
	free(q);
	q = NULL;
}

13.单链表销毁

void SListDestory(ListNode* plist)
{
	assert(plist != NULL);
	while (plist->next!= NULL)
	{
		ListNode* q = plist->next;
		plist->next = q->next;
		free(q);
		q = NULL;
	}
	free(plist);
}