title: Linked List insertion running time confusion
body: <p>I've tried to confirm the running time for the insertion for Linked List and it seems like there are two different answers. </p>
  
  <p>For inserting an element at the end of a Linked List, I would think that it would take O(n) since it has to traverse to the end of the list in order to access the tail. But some of the answers I've seen says O(1)? Are they assuming that all linked lists implementation of a pointer to the tail? If so, is that an acceptable assumption?</p>
  
  <p>Second, some places also suggest that insertion an element in the middle of a linked list is O(1) which I'm confused about due to the same reasoning of traverse to the middle of the list to insert it. </p>
  
  <p>Could someone please clarify? Thanks.</p>