Given a singly linked list, delete the middle of the linked list.

Note:

• If there are even nodes, then there would be two middle nodes, we need to delete the second middle element.
• If the input linked list has a single node, then it should return NULL.

Examples:

Input: LinkedList: 1->2->3->4->5
Output: 1->2->4->5
Explanation:

Input: LinkedList: 2->4->6->7->5->1
Output: 2->4->6->5->1
Explaination:

Input: LinkedList: 7 
Output: <empty linked list>
Explanation: There was only one node and it was deleted.

Constraints:
1 <= number of nodes <= 10⁵
1 <= node->data <= 10⁹