#2095 - Delete the Middle Node of a Linked List

Medium • View on LeetCode • View on GitHub

Problem Description

You are given the head of a linked list. Delete the middle node, and return the head of the modified linked list.

The middle node of a linked list of size n is the ⌊n / 2⌋th node from the start using 0-based indexing, where ⌊x⌋ denotes the largest integer less than or equal to x.

For n = 1, 2, 3, 4, and 5, the middle nodes are 0, 1, 1, 2, and 2, respectively.

Solution

/**
 * 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) {
  let slow = new ListNode(0, head);
  let fast = head;

  if (!head.next) {
    return null;
  }

  while (fast && fast.next) {
    slow = slow.next;
    fast = fast.next.next;
  }

  slow.next = slow.next.next;

  return head;
};