【初阶数据结构】深入解析单链表:探索底层逻辑（无头单向非循环链表）

SLNode* CreateNode(SLNDataType x)
{
	SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
	if (newnode==NULL)
	{
		perror("malloc fail!!!");
		 return (-1);
	}
	newnode->next = NULL;
	newnode->val = x;
	return newnode;
}

void SLTPushBack(SLNode** phead,SLNDataType x)
{
	assert(phead);
	SLNode* newnode = CreateNode(x);//值已经有了,创建一个新节点
	if (*phead == NULL)//这里需要二级指针去改变了，外的头了
	{
		*phead = newnode;
	}
	else
	{
		//找尾
		SLNode* cur =*phead;//拷贝一份
		while (cur->next != NULL)
		{
			cur = cur->next;
		}
		cur->next = newnode;//newnode已经搞下一次是空了	
	}	
}

void SLTPushFront(SLNode** pphead, SLNDataType x)
{
	assert(pphead);
	SLNode* newnode = CreateNode(x);
	if (*pphead == NULL)
	{
		*pphead = newnode;
	}
	else
	{
		SLNode* cur = *pphead;
		*pphead = newnode;
		newnode->next = cur;
	}
}

void SLTPopBack(SLNode** pphead)
{
	assert(pphead);
	assert(*pphead);//空的时候
	//一个节点和多个节点
	//这里不创建一个cur变量，当只有一个节点的时候，直接pphead
	SLNode* cur = *pphead;
	if (cur->next == NULL)
	{
		*pphead = NULL;
		free(cur);
		cur = NULL;
	}
	else
	{
		while (cur->next->next!= NULL)
		{
			cur = cur->next;//上一个节点
		}
		free(cur->next);
		cur->next = NULL;
	}
}

void SLTPopFront(SLNode** pphead)
{
	assert(pphead);
	assert(*pphead);
	SLNode* cur = *pphead;
	if (cur->next == NULL)
	{
		*pphead = NULL;
		free(cur);
		cur = NULL;
	}
	else
	{
		*pphead = cur->next;
		free(cur);
		cur = NULL;
	}
}

SLNode* SLTFind(SLNode* pphead, SLNDataType x)
{
	SLNode* cur = pphead;
	while (cur!=NULL)
	{
		if (cur->val == x)
			return cur;
		else
			cur = cur->next;
	}
	return NULL;
}

void SLTInsert(SLNode** pphead,SLNode *pos,SLNDataType x)//pos指定之前插入
{
	assert(pphead);
	assert(*pphead);
	if (pos == NULL)//没有节点
	{
		SLTPushFront(pphead, x);
	}
	if (*pphead == pos)//一个节点
	{
		SLTPushFront(pphead, x);
	}
	else//多个节点
	{
		SLNode* newnode = CreateNode(x);
		SLNode* cur = *pphead;
		while (cur->next != pos)//上面避免了pos等于cur
		{
			cur = cur->next;
		}
		cur->next = newnode;
		newnode->next = pos;
	}
}

void SLTEeara(SLNode** pphead, SLNode* pos)
{
	assert(pphead);//防止用户传个空指针
	assert(*pphead);
	assert(pos);
	SLNode* next = pos->next;
	SLNode* cur = *pphead;

	if (cur==pos)
	*pphead = NULL;
        free(cur);
		cur = NULL;
	else
	{
		while (cur->next != pos)
		{
			cur = cur->next;
		}
		cur->next = next;
		free(pos);
		pos = NULL;
	}
}

void SLTInsertAfter(SLNode **pphead,SLNode* pos, SLNDataType x)
{
	assert(pphead);
	assert(*pphead);
	if (pos == NULL)//没有节点
	{
		SLTPushFront(pphead, x);
	}
	if (*pphead == pos)//一个节点
	{
		SLTPushBack(pphead, x);
	}
	else//多个节点
	{
		SLNode* newnode = CreateNode(x);
		SLNode* back = pos->next;
		newnode->next = back;
		pos->next = newnode;
	}
}

void SLTEearaAfter(SLNode **pphead,SLNode* pos)
{
	assert(pphead);
	assert(*pphead);
	assert(pos);
	SLNode* cur = *pphead;
	SLNode* back = pos->next;
	if (cur == pos)//只有一个结点
		SLTPopBack(pphead);
	if(back->next==NULL)
	{
		free(back);
		back = NULL;
		pos->next = NULL;
	}
	else
	{
		pos->next = back->next;
		free(back);
		back = NULL;
	}
}

void SLTPrint(SLNode** pphead)//二级指针改变外的结构体指针类型
{
	assert(pphead);
	SLNode* cur = *pphead;
	while (cur!= NULL)
	{
		printf("%d->", cur->val);
		cur = cur->next;
	}
	printf("NULL\n");
}

void SLTDestroy(SLNode** pphead)
{
	assert(pphead);
	SLNode* cur = *pphead;
	while (cur)
	{
		SLNode* next = cur->next;
		free(cur);
		//这里cur不要赋空，还需要使用的
		cur = next;
}
	*pphead = NULL;
}