C语言无头节点单链表的实现

链表相对于顺序表来说，插入和删除更加方便，然而想要查找一个元素时却没有顺序表方便。

我们需要实现以下接口：

#ifndef __LINKLIST_H__ 
#define __LINKLIST_H__ 

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

typedef int DataType;
typedef struct Node
{
	DataType data;
	struct Node* next;
}Node, *pNode, List, *pList;

void InitLinkList(pList* pplist);
pNode BuyNode(DataType d);
void DestroyLinkList(pList* pplist);
void PushBack(pList* pplist, DataType d);
void PopBack(pList* pplist);
void PushFront(pList* pplist, DataType d);
void PopFront(pList* pplist);
pNode Find(pList plist, DataType d);
void Insert(pList* pplist, pNode pos, DataType d);//在指定位置之前插入一个值 
void Erase(pList* pplist, pNode pos);//指定位置删除 
void Remove(pList* pplist, DataType d);
void RemoveAll(pList* pplist, DataType d);
void ReMoveP(pList* pplist, DataType d);

void EraseNotTailNode(pNode pos);
void PrintLinkList(pList plist);
int GetListLength(pList plist);
void PrintTailToHead1(pList plist);//逆序打印单项链表 
void PrintTailToHead2(pList plist)//逆序打印单项链表 

#endif //__LINKLIST_H__ 

实现主函数及测试接口：

#define _CRT_SECURE_NO_WARNINGS 1
#include "List.h"

static pNode plist;
void TestBack()
{
	PushBack(&plist, 1);
	PushBack(&plist, 2);
	PushBack(&plist, 3);
	PushBack(&plist, 4);
	PushBack(&plist, 5);
	PushBack(&plist, 6);
	PrintLinkList(plist);
	PopBack(&plist);
	PrintLinkList(plist);
}
void TestFront()
{
	
	PushFront(&plist, 1);
	PushFront(&plist, 2);
	PushFront(&plist, 3);
	PushFront(&plist, 4);
	PushFront(&plist, 5);
	PushFront(&plist, 6);
	PrintLinkList(plist);
	PopFront(&plist);
	PrintLinkList(plist);
}
void TestFind()
{
	PushFront(&plist, 1);
	PushFront(&plist, 2);
	PrintLinkList(plist);
	PushFront(&plist, 3);
	PrintLinkList(plist);
	PushFront(&plist, 4);
	PushFront(&plist, 5);
	PushFront(&plist, 6);
	PrintLinkList(plist);
	pNode tmp = NULL;
	tmp = Find(plist, 3);
	if (tmp)
	{
		printf("找到了，他的值为：%d\n", tmp->data);
	}
	Insert(&plist, tmp, 3);//在指定位置之前插入一个值 
	Insert(&plist, tmp, 3);//在指定位置之前插入一个值 
	Erase(&plist, tmp);//指定位置删除 
	PrintLinkList(plist);
	//EraseNotTailNode(tmp);
	PrintLinkList(plist);
}
void TestRemove()
{
	PushFront(&plist, 1);
	PushFront(&plist, 2);
	PushFront(&plist, 6);
	PushFront(&plist, 4);
	PushFront(&plist, 5);
	PushFront(&plist, 6);
	PrintLinkList(plist);
	Remove(&plist, 6);
	PrintLinkList(plist);
	//RemoveAll(&plist, 6);
	//PrintLinkList(plist);

}
void TestLength()
{
	PushFront(&plist, 1);
	PushFront(&plist, 2);
	PushFront(&plist, 3);
	PushFront(&plist, 4);
	PushFront(&plist, 5);
	PushFront(&plist, 6);
	PrintLinkList(plist);
	int len = GetListLength(plist);
	printf("len = %d\n", len);
}
void TestPrintTailToHead()
{
	PushFront(&plist, 1);
	PushFront(&plist, 2);
	PushFront(&plist, 3);
	PushFront(&plist, 4);
	PushFront(&plist, 5);
	PushFront(&plist, 6);
	PrintLinkList(plist);
	PrintTailToHead2(plist);//逆序打印单项链表 
}

int main()
{
	InitLinkList(&plist);
	//TestBack();
	//TestFront();
	//TestFind();
	//TestRemove();
	//TestLength();
	TestPrintTailToHead();
	DestroyLinkList(&plist);
	system("pause");
	return 0;
}

实现子函数：

#define _CRT_SECURE_NO_WARNINGS 1
#include "List.h"

void InitLinkList(pList* pplist)
{
	(*pplist)= NULL;
}
pNode BuyNode(DataType d)
{
	pNode newNode = (pNode)malloc(sizeof(Node));
	if (newNode == NULL)
	{
		perror("malldc error");
		exit(EXIT_FAILURE);
	}
	newNode->data =d;
	newNode->next = NULL;
	return newNode;
}
void DestroyLinkList(pList* pplist)
{
	assert(pplist);
	pNode cur = NULL;
	cur = *pplist;
	while (cur)
	{
		pNode del = cur;
		cur = cur->next;
		free(del);
		del = NULL;
	}
	*pplist = NULL;
}
void PushBack(pList* pplist, DataType d)
{
	assert(pplist);
	pNode newNode = BuyNode(d);
	if ((*pplist) == NULL)
	{
		*pplist = newNode;
	}
	else
	{
		pNode cur = NULL;
		cur = *pplist;
		while (cur->next)
		{
			cur = cur->next;
		}
		cur->next = newNode;
	}
}
void PopBack(pList* pplist)
{
	assert(pplist);
	if ((*pplist)==NULL)
	{
		printf("链表为空！\n");
		return;
	}
	else
	{
		pNode cur = NULL;
		pNode del = NULL;
		cur = *pplist;
		del = cur->next;
		while (cur->next->next)
		{
			cur = cur->next;
			del = cur->next;
		}
		cur->next = del->next;
		free(del);
		del = NULL;
	}
}
void PushFront(pList* pplist, DataType d)
{
	pNode newNode = BuyNode(d);
	assert(pplist);
	if ((*pplist) == NULL)
	{
		*pplist = newNode;
	}
	else
	{
		pNode cur = *pplist;
		newNode->next = cur;
		*pplist = newNode;
	}
}
void PopFront(pList* pplist)
{
	assert(pplist);
	if ((*pplist) == NULL)
	{
		printf("链表为空！\n");
		return;
	}
	else
	{
		pNode del = NULL;
		del = *pplist;
		*pplist = (*pplist)->next;
		free(del);
		del = NULL;
	}
}
pNode Find(pList plist, DataType d)
{
	if (plist == NULL)
	{
		printf("链表为空！\n");
		return NULL;
	}
	else
	{
		pNode cur = plist;
		while (cur)
		{
			if (cur->data == d)
			{
				return cur; 
			}
			cur = cur->next;
		}
		return NULL;
	}
}
void Insert(pList* pplist, pNode pos, DataType d)//在指定位置之前插入一个值 
{
	assert(pplist);
	assert(pos);
	assert(*pplist);
	pNode newNode = BuyNode(d);
	if (pos == (*pplist))
	{
		newNode->next = *pplist;
		*pplist = newNode;
	}
	else
	{
		pNode cur = *pplist;
		while (cur&&cur->next != pos)
		{
			cur = cur->next;
		}	
		if (cur)
			{
				newNode->next = pos;
				cur->next = newNode;
			}
	}
}
void Erase(pList* pplist, pNode pos)//指定位置删除 
{
	assert(pplist);
	assert(pos);
	if ((*pplist)==NULL)
	{
		return;
	}
	if ((*pplist)==pos)
	{
		*pplist = pos->next;
		free(pos);
		pos = NULL;
	}
	else
	{
		pNode cur = *pplist;
		while (cur&&cur->next != pos)
		{
			cur = cur->next;
		}
		if (cur)
		{
			cur->next = pos->next;
			free(pos);
			pos = NULL;
		}
	}
}
void Remove(pList* pplist, DataType d)
{
	assert(pplist);
	pNode cur = *pplist;
	if ((*pplist) == NULL)
	{
		return;
	}
	if ((*pplist)->data == d)
	{
		*pplist = cur->next;
		free(cur);
		cur = NULL;
	}
	else
	{
		pNode del = cur;
		while (cur&&del->data != d)
		{
			cur = cur->next;
			del = cur->next;
		}
		if (cur)
		{
			cur->next = del->next;
			free(del);
			del = NULL;
		}
	}
}
void RemoveAll(pList* pplist, DataType d)
{
	assert(pplist);
	pNode cur = *pplist;
	if ((*pplist) == NULL)
	{
		return;
	}
	pNode pre = *pplist;
	while (cur)
	{
		
		if ((*pplist)->data == d)
		{
			cur = *pplist;
			*pplist = (cur)->next;
			free(cur);
			cur = *pplist;
		}
		else if (cur->data == d)
		{
			pre->next = cur->next;
			free(cur);
			cur = pre->next;
		}
		pre = cur;
		cur = cur->next;	
	}
}
void EraseNotTailNode(pNode pos)
{
	assert(pos);
	assert(pos->next);
	pNode del = NULL;
	del = pos->next;
	pos->data = pos->next->data;
	pos->next = del->next;
	free(del);
	del = NULL;
}
void PrintLinkList(pList plist)
{
	pNode cur = plist;
	while (cur)
	{
		printf("%d->", cur->data);
		cur = cur->next;
	}
	printf("NULL\n");
}
int GetListLength(pList plist)
{
	int count = 0;
	pNode cur = plist;
	while (cur)
	{
		count++;
		cur = cur->next;
	}
	return count;
}
void PrintTailToHead1(pList plist)//逆序打印单项链表 
{
	if (plist == NULL)
		return;
	PrintTailToHead1(plist->next);
	printf("%d ", plist->data);
}
void PrintTailToHead2(pList plist)//逆序打印单项链表 
{

	pNode tail = NULL;
	pNode cur = plist;
	if (plist == NULL)
		return;
	
	while (plist != tail)
	{
		while (cur->next != tail)
		{
			cur = cur->next;
		}
		printf("%d ", cur->data);
		tail = cur;
		cur = plist;
	}

}

无头节点的单链表就完成了!