insert-a-node-at-a-specific-position-in-a-linked-list.js

/**
 * @title Insert a node at a specific position in a linked list
 * @difficulty Easy
 * @link https://www.hackerrank.com/challenges/insert-a-node-at-a-specific-position-in-a-linked-list/problem
 */

/* global SinglyLinkedListNode b:writable */
const insertNodeAtPosition = (head, data, position) => {
  const newNode = new SinglyLinkedListNode(data);
  if (position === 0) {
    newNode.next = head;
    head = newNode;

    return head;
  }

  let pre = head;
  let cur = pre.next;
  let index = 1;
  while (index !== position) {
    pre = cur;
    cur = cur.next;
    index++;
  }
  newNode.next = pre.next;
  pre.next = newNode;

  return head;
};