Class: SingleLinkedList

Inherits:
Object
  • Object
show all
Defined in:
lib/singly_linked_list.rb

Overview

singly linked list

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SingleLinkedList 



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# File 'lib/singly_linked_list.rb', line 5

def initialize
  @sentinel = SingleLink.new(nil)
end

Instance Attribute Details

#sentinel ⇒ Object (readonly)

Returns the value of attribute sentinel.



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# File 'lib/singly_linked_list.rb', line 3

def sentinel
  @sentinel
end

Instance Method Details

#pop ⇒ Object 



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# File 'lib/singly_linked_list.rb', line 9

def pop
  prev, last = walkthrough
  raise "cannot pop from empty list" if prev.nil?
  prev.next = nil

  last.val
end

#push(val) ⇒ Object 



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# File 'lib/singly_linked_list.rb', line 17

def push(val)
  link = SingleLink.new(val)
  _, last_link = walkthrough
  last_link.next = link

  self
end

#shift ⇒ Object 



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# File 'lib/singly_linked_list.rb', line 25

def shift
  first_link = @sentinel.next
  raise "cannot shift from empty list" if first_link.nil?
  val = first_link.val
  @sentinel.next = first_link.next

  val
end

#unshift(val) ⇒ Object 



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# File 'lib/singly_linked_list.rb', line 34

def unshift(val)
  link = SingleLink.new(val)
  @sentinel.next, link.next = link, @sentinel.next
  
  self
end