[] Data structure - single chain [the] base face questions

//1、单链表的逆置
node* Reverse(node* s1)
{
	Node* head = s1;
	Node* cur = head->next;
	head->_next = NULL;
	while (cur)
	{
		Node* prev = cur;
		cur = cur->_next;
		prev->_next = head;
		prev = head;
	}
}

//2、移除链表的元素
//输入：1->2->6->3->4->5->6  val=6
//输出：1->2->3->4->5
node* removeElements(node* head, int val)
{
	Node* cur = head;
	Node* prev = NULL;
	Node* next = cur->_next;
	while (cur)
	{
		Node* next = cur->_next;
		if (cur->data == val)
		{
			if (prev == NULL)
			{
				head = next;
			}
			else
			{
				prev->_next = next;
			}
			free(cur);
			cur = next;
		}
			prev = cur;
			cur = next;
	}
	return head;
}

//3、返回链表的中间节点   //1->2->6->3->4->5->6
node* MiddleNode(node* head)//法一：遍历一遍，找中间元素
{
	node* cur = head;
	int count = 0;
	while (cur)
	{
		count++;
		cur = cur->_next;
	}
	cur = head;
	count = count / 2;
	while (count--)
	{
		cur = cur->_next;
	}
	return cur;
}
node* MiddleNode(node* head)  //法二：快慢指针法
{
	node* fast = head;
	node* slow = head;
	while (fast&&fast->_next)
	{
		fast = fast->_next->next;
		slow = slow->_next;
	}
	return slow;
}

//4、合并两个有序链表
//输入：1->2->4，1->3->4
//输出：1->1->2->3->4->4
struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) 
{
	if (l1 == NULL)
	{
		return l2;
	}
	if (l1 != NULL)
	{
		return l1;
	}
	struct ListNode* head;
	struct ListNode* tail;
	if (l1->data < l2->data)
	{
		head = l1;
		l1 = l1->_next;
	}
	else
	{
		head = l2;
		l2 = l2->_next;
	}
	tail = head;
	while (l1&&l2)
	{
		if (l1->data < l2->data)
		{
			tail->_next = l1;
			tail = tail->_next;
			l1 = l1->next;
		}
		else
		{
			tail->_next = l2;
			tail = tail->_next;
			l2 = l2->next;
		}
	}
	if (l1)
	{
		tail->_next = l1;
	}
	else
	{
		tail->_next = l2;
	}
	return head;
}

//5、链表分割
//编写代码，以给定值x为基准将链表分割成两个部分，所有小于x的结点排在
//大于或者等于x的结点之前，给定一个链表的头指针ListNode* phead
//请返回重新排列后的链表的头指针。注意：分割后保持原来的数据顺序不变
ListNode* partition(ListNode* pHead, int x)
{
	ListNode* greattail=(ListNode*)malloc(sizeof(ListNode*));
	ListNode* lesshead=(ListNode*)malloc(sizeof(ListNode*));
	ListNode* greathead=greattail;
	ListNode* lesstail=lesshead;
	while (cur)
	{
		if (cur->data < x)
		{
			lesstail->_next = cur;
			lesstail = lesstail->_next;
		}
		else
		{
			greattail->_next = cur;
			greattail = greatertail->_next;
		}
		cur = cur->next;
	}
	//合并两个有序链表
	lesstail->_next = greathead->next;
	greattail->next = NULL;
	phead = lesshead->next;
	return phead;
}