Delete the Middle Node of a Linked List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteMiddle(ListNode head) {
        // base case == list = [1]
        if(head.next==null)
            return null;
        // O(n), O(1)
        ListNode slow = new ListNode(-1);
        slow.next = head;
        ListNode fast = head;
        while(fast!=null && fast.next!=null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        slow.next = slow.next.next;
        return head;
    }
}