鏈表的增刪改查

1、增加（尾插）

void backnode(node** ppnode, int num, typedata data )//尾插
{
	node *pnewnode = (node *)malloc(sizeof(node));
	pnewnode->num = num;//賦值
	pnewnode->data = data;
	pnewnode->next = NULL;
	if(*ppnode == NULL)
	{
		*ppnode = pnewnode;//存儲地址
		
	}
	else
	{
		node *p = *ppnode;
		while(p->next != NULL)
		{
			p = p->next;
		}
		p->next = pnewnode;
	}

}

調用時

node *pnode = NULL;

	backnode(&pnode,1,11);

另一種尾插

node* backnode(node *pnode, int num, typedata data )
{
	node *pnewnode = (node *)malloc(sizeof(node));
	pnewnode->num = num;//賦值
	pnewnode->data = data;
	pnewnode->next = NULL;
	if(pnode == NULL)
	{
		pnode = pnewnode;//存儲地址
		
	}
	else
	{
		node *p = pnode;
		while(p->next != NULL)
		{
			p = p->next;
		}
		p->next = pnewnode;
	}
	return pnode;

}

調用時

node *pnode = NULL;
pnode = backnode2(pnode,1,11);

從以上兩種尾插法可知，要改變指針，需要傳遞指針的地址，即用二級指針或是用返回值。

頭插法

node *headnode(node *pnode, int num, typedata data)
{
	node *pnewnode = (node *)malloc(sizeof(node));
	pnewnode->num = num;//賦值
	pnewnode->data = data; 
	pnewnode->next = NULL;
	if(pnode == NULL)
	{
		pnode = pnewnode;
		pnewnode = NULL;
	}
	else
	{
		pnewnode->next = pnode;
		pnode = pnewnode;
	}
	return pnode;
}

2、查找

node *findfirst(node *pnode,int num)
{
	for(node *p = pnode; p != NULL; p = p->next)
	{
		if(p->num == num)
		{
			return p;
			break;
		}
	}
	return NULL;

}

調用時

node *pnode = NULL;
	pnode = headnode(pnode,1,11);
	pnode = headnode(pnode,2,12);
	pnode = headnode(pnode,3,13);
	pnode = headnode(pnode,4,14);
	node *find = findfirst(pnode,3);
	if(find == NULL)
	{
		printf("\n沒有找到\n");
	}
	else
	{
		printf("\n%d,%d,%p\n",find->num, find->data, find);
	}

3、修改

int change(node *pnode, int oldnum, int newnum)//正常替換返回1，不正常替換返回0
{
	for(node *p = pnode; p != NULL; p = p->next)
	{
		if(p->num == oldnum)
		{
			p->num = newnum;
			return 1;
			break;
		}
	}
	return 0;
}

4、逆轉

node *reverse(node *pnode)
{
	node *p1, *p2, *p3;
	p1 = p2 = p3 = NULL;//避免野指針

	if(pnode == NULL || pnode->next == NULL)
	{
		return pnode;
	}

	else
	{
		p1 = pnode;
		p2 = pnode->next;
		while(p2 != NULL)
		{
			p3 = p2->next;
			p2->next = p1;//地址轉向
			p1 = p2;
			p2 = p3;
		}
		pnode->next = NULL;
		pnode = p1;
		return pnode;
	}
	
}

5、刪除節點

node *deletenode(node *pnode, int num)
{
	node *p1, *p2;
	p1 = p2 = NULL;
	p1 = pnode;
	while(p1 != NULL)
	{
		if(p1->num == num)
			break;
		else
		{
			p2 = p1;
			p1 = p1->next;
		}

	}
	if(p1 == pnode)
	{
		pnode = p1->next;
		free(p1);
	}
	else
	{
		p2->next = p1->next;
		free(p1);
	}
	return pnode;
}

6、插入節點

node *insert(node *pnode, int findnum, int newnum, typedata newdata)
{
	node *p1, *p2;
	p1 = p2 = NULL;
	p1 = pnode;
	while(p1 != NULL)
	{
		if(p1->num == findnum)
		{
			break;
		}
		else
		{
			p2 = p1;
			p1 = p1->next;
		}
	}
	node *pnewnode = (node *)malloc(sizeof(node));
	pnewnode->num = newnum;
	pnewnode->data = newdata;
	if(p1 == pnode)
	{
		pnewnode->next = p1;
		pnode = pnewnode;
	}
	else
	{
		pnewnode->next = p1;
		p2->next = pnewnode;
	}
	return pnode;
}