typedef int SLTDataType;//
typedef struct SListNode
{
	int data;//val，存儲(chǔ)的數(shù)據(jù)，此處假設(shè)存儲(chǔ)的數(shù)據(jù)為int型
	struct SListNode* next;//存儲(chǔ)下一個(gè)節(jié)點(diǎn)的位置
}SListNode,SLN;

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

void SListPushBack(SListNode** pphead, SLTDataType x)
{
	SListNode* newnode = BuySListNode(x);
	if (*pphead == NULL)
	{
		*pphead = newnode;
	}
	else
	{
		//找尾
		SListNode* tail = *pphead;
		while (tail->next != NULL)
		{
			tail = tail->next;
		}
		tail->next = newnode;
	}
}

while(tail!=NULL)
{
	tail = tail->next;
}
tail->next = newnode;

SListNode* BuySListNode(SLTDataType x)
{
	SListNode* newnode = (SListNode*)malloc(sizeof(SListNode));
	if (newnode == NULL)
	{
		printf("malloc fail\n");
		exit(-1);
	}
	else
	{
		newnode->data = x;
		newnode->next = NULL;
	}
	return newnode;
}

void SListPushFront(SListNode** pphead, SLTDataType x)
{
	SListNode* newnode = BuySListNode(x);
	newnode->next = *pphead;
	*pphead = newnode;
}

void SListPopBack(SListNode** pphead)
{
	assert(pphead);
	if (*pphead == NULL)//空鏈表
	{
		return;
	}
	else if ((*pphead)->next == NULL)//一個(gè)節(jié)點(diǎn)
	{
		free(*pphead);//*pphead就是plist的值
		*pphead = NULL;
	}
	else//多個(gè)節(jié)點(diǎn)
	{
		SListNode* tail = *pphead;
		SListNode* prev = NULL;//為什么要置為空呢？因?yàn)檫@個(gè)地方相當(dāng)于是指向第一個(gè)節(jié)點(diǎn)之前的節(jié)點(diǎn)，這個(gè)節(jié)點(diǎn)并不存在，設(shè)為空
		while (tail->next != NULL)
		{
			prev = tail;
			tail = tail->next;
		}
		free(tail);
		tail = NULL;
		prev->next = NULL;
	}
}

void SListPopBack(SListNode** pphead)
{
	assert(pphead);
	if (*pphead == NULL)//空鏈表
	{
		return;
	}
	else if ((*pphead)->next == NULL)//一個(gè)節(jié)點(diǎn)
	{
		free(*pphead);//*pphead就是plist的值
		*pphead = NULL;
	}
	else//多個(gè)節(jié)點(diǎn)
	{
		SListNode* tail = *pphead;
		while (tail->next->next != NULL)
		{
			tail = tail->next;
		}
		free(tail->next);//釋放尾節(jié)點(diǎn)
		tail->next = NULL;//將新尾節(jié)點(diǎn)的next置為NULL
	}
}

void SListPopFront(SListNode** pphead)
{
	assert(pphead);
	if (*pphead == NULL)//空鏈表
	{
		return;
	}
	else//非空鏈表
	{
		SListNode* next = (*pphead)->next;//next作為臨時(shí)變量存放的是被刪除的節(jié)點(diǎn)中next存儲(chǔ)的第二個(gè)節(jié)點(diǎn)的地址
		free(*pphead);
		*pphead = next;
	}
}

void SListInsertBefore(SListNode** pphead, SListNode* pos,SLTDataType x)
{
	assert(pphead);
	if (*pphead == pos)//pos是第一個(gè)節(jié)點(diǎn)，相當(dāng)于頭插
	{
		SListPushFront(pphead, x);
	}
	else
	{
		SListNode* prev = *pphead;
		while (prev->next != pos)
		{
			prev = prev->next;
		}
		SListNode* newnode = BuySListNode(x);
		prev->next = newnode;
		newnode->next = pos;
	}
}

void SListInsertAfter(SListNode* pos, SLTDataType x)
{
	assert(pos);
	SListNode* newnode = BuySListNode(x);
	
	newnode->next = pos->next;
	pos->next = newnode;
	//這兩行代碼順序是固定的，只能這個(gè)順序，無(wú)法進(jìn)行改變
}

void SListInsertAfter(SListNode* pos, SLTDataType x)
{
	assert(pos);
	SListNode* next = pos->next;
	SListNode* newnode = BuySListNode(x);

	newnode->next = next;
	pos->next = newnode;
	//這兩行代碼可以任意改變順序，誰(shuí)先誰(shuí)后都不影響最后的結(jié)果
}

void SListErase(SListNode** pphead, SListNode* pos)
{
	assert(pphead);
	assert(pos);
	if (pos == *pphead)//當(dāng)pos為頭節(jié)點(diǎn)的時(shí)候
	{
		SListPopFront(pphead);
	}
	else//當(dāng)pos為非頭節(jié)點(diǎn)的時(shí)候
	{
		SListNode* prev = *pphead;
		while (prev->next != pos)
		{
			prev = prev->next;
		}
		prev->next = pos->next;
		free(pos);
		pos = NULL;
	}
}

void SListEraseBefore(SListNode** pphead, SListNode* pos)//pos即為任意位置
{
	assert(pphead);
	assert(pos);
	if (pos == *pphead)
	{
		return;
	}
	else if(pos==(*pphead)->next)
	{
		SListPopFront(pphead);
	}
	else
	{
		SListNode* prev = *pphead;//prev用來(lái)存儲(chǔ)pos的前一個(gè)位置的前一個(gè)位置
		while (prev->next->next != pos)
		{
			prev = prev->next;
		}
		SListNode* next = prev->next;//保存pos前一個(gè)節(jié)點(diǎn)的地址
		prev->next = prev->next->next;//將prev和pos的兩個(gè)節(jié)點(diǎn)進(jìn)行連接
		free(next);//刪除pos的前一個(gè)節(jié)點(diǎn)
	}
}

void SListEraseAfter(SListNode* pos)
{
	assert(pos);
	SListNode* next = pos->next;
	if (next == NULL)//當(dāng)pos是最后一個(gè)節(jié)點(diǎn)的時(shí)候
	{
		return;
	}
	else
	{
		pos->next = next->next;
		free(next);
		next = NULL;
	}
}

void SListDestory(SListNode** pphead)
{
	assert(pphead);
	SListNode* cur = *pphead;
	SListNode* next = *pphead;//是為了存儲(chǔ)cur下一個(gè)節(jié)點(diǎn)的地址，因?yàn)閒ree(cur)之后，cur指針指向的內(nèi)存中的數(shù)據(jù)可能已經(jīng)稱為亂碼了，即不能再正常的使用
	while (cur)
	{
		next = cur->next;
		free(cur);
		cur = next;
	}
	*pphead = NULL;
}