anchor.diff: -= Reverse a Singley Linked List
  += Reverse a Singly Linked List
   
   :hp-tags: coding_problem
   
  
positive.code: 
  So the idea here is to traverse the linked list from head to tail and simultaneously reverse the links. In other words while we travel through the linked list we will switch the `next` pointers so that they point to the previous node rather than the next.
  
  We have to be careful now, if we set the next pointer of a node in the wrong order we will end up detaching the node from the rest of the list.
  
  [source,java]
  ----
  
negative.code:    }
  }
  ----
  
  This solution will run in O(n) time and O(1) space.
  