programming-examples/ruby/Data_Structures/doubly_linked_list.rb

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Ruby
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2019-11-15 12:59:38 +01:00
require_relative 'node.rb'
class LinkedList
include Enumerable
attr_accessor :length
def initialize
@length = 0
@index = -1
end
def [](pos)
return if pos >= length || pos < 0 # bounds check
delta = pos > @index ? 1 : -1 # set direction
until @index == pos # traverse
@current = delta == 1 ? @current.next : @current.previous
@index += delta
end
@current.data
end
def []=(pos, data)
return if pos < 0 # bounds check
create_head if index == -1
delta = pos > @index ? 1 : -1 # set direction
until @index == pos # traverse
create_next_node if @index == @length - 1 # create missing nodes
@current = delta == 1 ? @current.next : @current.previous
@index += delta
end
@current.data = data
end
def <<(value)
self[@length] = value
end
def each
(0...@length).each do |x|
yield self[x]
end
end
def first
@head.data
end
def last
@tail.data
end
private
def create_head
@head = Node.new
@tail = @head
@index = 0
@length = 1
end
def create_next_node
@tail.next = Node.new
@tail = @tail.next
@length += 1
end
end