LeetCode 2095. Delete the Middle Node of a Linked List

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var deleteMiddle = function(head) {
    if (!head.next) {
        head = null;
        return head;
    }
    
    let f = head;
    let s = head;
    let prev = null;
    while (s.next && s.next.next) {
        s = s.next.next;
        prev = f;
        f = f.next;
    }
    // Two middle nodes
    if (s.next) {
        prev = f;
        f = f.next;
    }
    if (prev && prev.next && !prev.next.next) {
        prev.next = null;
    }
    if (prev && prev.next && prev.next.next) {
        prev.next = prev.next.next;
    }

    return head;
};

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* deleteMiddle(ListNode* head) {
        // Single node list
        if (head->next == nullptr) {
            delete head;
            return nullptr;
        }
        
        ListNode* slow = head;
        ListNode* fast = head;
        ListNode* prev = nullptr;
        
        while (fast && fast->next) {
            prev = slow;
            slow = slow->next;
            fast = fast->next->next;
        }
        
        prev->next = slow->next;
        
        return head;
    }
};