0019-remove-nth-node-from-end-of-list.js

/**
 * 19. Remove Nth Node From End of List
 * https://leetcode.com/problems/remove-nth-node-from-end-of-list/
 * Difficulty: Medium
 *
 * Given the head of a linked list, remove the nth node from the end of the list
 * and return its head.
 */

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
  const result = new ListNode();
  let slow = result;
  let fast = result;
  slow.next = head;

  for (let i = 0; i <= n; i++) {
    fast = fast.next;
  }

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

  slow.next = slow.next.next;

  return result.next;
};