Delete the Middle Node of a Linked List LeetCode solution in JavaScript

1
/**
2
 * Definition for singly-linked list.
3
 * function ListNode(val, next) {
4
 * this.val = (val===undefined ? 0 : val)
5
 * this.next = (next===undefined ? null : next)
6
 * }
7
 */
8
/**
9
 * @param {ListNode} head
10
 * @return {ListNode}
11
 */
12
// Two Pointer: Fast & Slow | O(N) | O(1)
13
var deleteMiddle = function (head) {
14
  if (!head.next) return null;
15

16
  let prev = head;
17
  let slow = head;
18
  let fast = head.next;
19
  let size = 2;
20

21
  while (fast && fast.next) {
22
    prev = slow;
23
    slow = slow.next;
24
    fast = fast.next.next;
25
    size += fast ? 2 : 1;
26
  }
27

28
  if (size % 2 === 0) slow.next = slow.next.next;
29
  else prev.next = slow.next;
30

31
  return head;
32
};