单循环链表

单循环链表：最后一个有效节点的next域指向头节点，当链表内有效节点数为0时，头节点的next域指向头节点本身。
结构体设计：

typedef int ELEMTYPE;
typedef struct CNode
{
	ELEMTYPE data;
	struct CNode* next;//保存下一个结点的地址
}CNode,*PNode;

单循环
1、当链表内有效节点数量为0时

2、当链表有多个有效节点

3、头文件

typedef int ELEMTYPE;
typedef struct CNode
{
	ELEMTYPE data;
	struct CNode* next;//保存下一个结点的地址
}CNode,*PNode;
//初始化
void Init_clist(PNode plist);
//头插
bool Insert_head(PNode plist,int val);
//尾插
bool Insert_tail(PNode plist,int val);
//按位置插
bool Insert_pos(PNode plist, int pos,int val);
//头删
bool Del_head(PNode plist);
//未删
bool Del_tail(PNode plist);
//按位置删
bool Del_pos(PNode plist,int pos);
//按值删
bool Del_(PNode plist,int val);
//查找
PNode Search(PNode plist,int val);
//找值为val值的前驱
PNode Get_pre(PNode plist,int val);
//找值为val的后继
PNode Get_next(PNode plist,int val);
//读取有效节点个数
int Get_length(PNode plist);
//判空
bool IsEmpty(PNode plist);
//清空
void Clear(PNode plist);
//销毁
void Destory(PNode plist);
//打印
void Print(PNode plist);

4、函数实现

#include"LinkList.h"
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
//带有头节点的链表，第一个节点不用带数据
//初始化
void Init_list(PNode plist)
{
	assert(plist != NULL);
	if (plist == NULL)
	{
		return;
	}
	plist->next = NULL;
	return;
}
//头插
bool Insert_head(PNode plist, int val)
{
	assert(plist != NULL);
	//先购买一个节点
	PNode s = (PNode)malloc(sizeof(Node) * 1);
	s->data = val;
	s->next = plist->next;
	plist->next = s;
	return true;
}
//尾插
bool Insert_back(PNode plist, int val)
{
	assert(plist != NULL);
	PNode s = (PNode)malloc(sizeof(Node));
	assert(s != NULL);
	PNode p = plist;
	while (p->next != NULL)
	{
		p = p->next;
	}
	s->next = p->next;
	p->next = s;
	s->data = val;
	return true;
}
//按位置插
bool Insert_pos(PNode plist, int pos, int val)
{
	assert(plist != NULL);
	if (pos<0 || pos>Get_length(plist))
	{
		return false;
	}
	PNode s = (PNode)malloc(sizeof(Node) * 1);
	assert(s != NULL);
		PNode p = plist;
	int i = 0;
	while (i < pos)
	{
		p = p->next;
		i++;
	}
	s->next = p->next;
	p->next = s;
	s->data = val;
	return true;
}
//头删
bool Del_head(PNode plist)
{
	assert(plist != NULL);
	if (IsEmpty(plist))
	{
		return false;
	}
	PNode p = plist->next;
	plist->next = p->next;
	free(p);
	p = NULL;
	return true;
}
//尾删
bool Del_back(PNode plist)
{
	assert(plist != NULL);
	if (IsEmpty(plist))
	{
		return false;
	}
	PNode p = plist;
	while (nullptr != p->next)
	{
		if (NULL == p->next->next)
		{
			break;
		}
		p = p->next;
	}
	free(p->next);
	p->next = NULL;
	return true;
}
//按位置删
bool Del_pos(PNode plist, int pos)
{
	assert(plist != NULL);
	if (IsEmpty(plist))
	{
		return false;
	}
	if (pos<0 || pos>Get_length(plist) - 1)
	{
		return false;
	}
	PNode p = plist;
	int i = 0;
	while (i < pos)
	{
		p = p->next;
		i++;
	}
	PNode q = p->next;
	p->next = p->next->next;
	free(q);
	q = NULL;
	return true;
}
//按值删
bool Del_val(PNode plist, int val)
{
	assert(plist != NULL);
	if (NULL==Search(plist, val))
	{
		return false;
	}
	PNode p = plist;
	while (p->next != NULL)
	{
		if (p->next->data == val)
		{
			PNode q = p->next;
			p->next = q->next;
			free(q);
			return true;
		}
		p = p->next;
	}
}
//判空
bool IsEmpty(PNode plist)
{
	assert(plist != NULL);
	if (plist->next == NULL)
	{
		return true;
	}
	return false;
}
//搜索
PNode Search(PNode plist, int val)
{
	assert(plist != NULL);
	if (IsEmpty(plist))
	{
		return NULL;
	}
	PNode p = plist->next;
	while (NULL != p)
	{
		if (p->data == val)
		{
			return p;
		}
		p = p->next;
	}
	return NULL;
}
//返回节点前趋
PNode Search_pre(PNode plist, int val)
{
	assert(plist != NULL);
	if (NULL==Search(plist, val))
	{
		return NULL;
	}
	PNode p = plist;
	while (p->next != NULL)
	{
		if (p->next->data == val)
		{
			return p;
		}
		p = p->next;
	}
}
//返回节点后继
PNode Search_back(PNode plist, int val)
{
	assert(plist != NULL);
	PNode p = Search(plist, val);
	return p->next;
}
//返回节点个数(除去头节点)
int Get_length(PNode plist)
{
	assert(plist != NULL);
	PNode p = plist->next;
	int count = 0;
	while (p != NULL)
	{
		count++;
		p = p->next;
	}
	return count;
}
//清空链表
void Clear(PNode plist)
{
	assert(plist != NULL);
	while (!IsEmpty(plist))
	{
		Del_head(plist);
	}
}
//摧毁链表
void Destory(PNode plist)
{
	assert(plist != NULL);
	Clear(plist);
	free(plist);
	plist = NULL;
}
//打印链表数据
void Print(PNode plist)
{
	assert(plist != NULL);
	PNode p = plist->next;
	while (p!= NULL)
	{
		printf("%d ", p->data);
		p = p->next;
	}
	printf("\n");
}
int main()
{
	Node p = {};
	Init_list(&p);
	for (int i = 0; i < 3; i++)
	{
		Insert_back(&p, i + 1);
		Print(&p);
	}
	for (int i = 2; i>=0; i--)
	{
		Del_pos(&p,i);
		Print(&p);
	}
}