Ruby: Remove middle node from Linked List

Question

Currently, I'm going over the CTCI, I'm working on the problem removing the middle node. I'm using Ruby to go over these problems. I have the following solution.

 def remove_middle_node
    node = @head
    count = 1

    while(node = node.next )
      count += 1
    end
    # reset node to point to head
    node = @head
    middle = (count / 2)
    count = 1

    while(node = node.next)

      if(count == (middle - 1))
        node.next = node.next.next
        return
      end
      count += 1
    end
  end

Instead of having a previos_node I subtract one from the middle. In this case when traversing the Linked List, when I get to the (middle - 1), meaning the previous node before the middle node in the linked list. I delete the middle node and set it to next.

I would like to get feedback on this implementation. In my understanding, this is O(n) and time complexity is also O(n). Although I warn you, this Big O notation still a bit unclear to me so time and space complexity might be wrong.

Here is the full Linked List class.

https://github.com/theasteve/ds_and_algos/blob/master/linked_list.rb here is the test I used.

# TEST
list = LinkedList.new

list.append(1)
list.append(2)
list.append(8)
list.append(3)
list.append(7)
list.append(0)
list.append(4)

list.display
puts '-----------------------------------'
list.remove_middle_node
list.display

Answer 1

• document/comment your code. In the code.
• re-checking .next in the second loop is unusually defensive
• do not have a comment repeat what a statement "does" (reset node to point to head):
  have it illuminate what is achieved/what-for/why something is done (the way it is)
• the ruby way to have a statement executed, say, middle times may be

  middle.times do
      node = node.next
  

(Eyeballing remove_middle_node, it uses O(1) additional space and Θ(n) time.)