【LeetCode】Reverse Nodes in k-Group

ListNode *newTail = new ListNode(0);//new a fake head node
	ListNode *newPtr = newTail;
	ListNode *ptr = head;
	ListNode *next;
	while (ptr != NULL)
	{
		next = ptr;
		int len = k;
		while (len > 0 && next != NULL)//find the scope of k
		{
			next = next->next;
			len--;
		}
		if (len == 0)                 //this start reverse K-Scope
		{
			while (ptr != next)
			{
				ListNode *tmp = ptr;
				ptr = ptr->next;
				tmp->next = newPtr->next;
				newPtr->next = tmp;
			}
		}
		else                       //put the last ListNode connect it
		{
			newPtr->next = ptr;
			break;
		}
		while (newPtr->next != NULL) //start a new process
		{
			newPtr = newPtr->next;
		}
	}
	return newTail->next;