linkedList.rb

#!/usr/bin/env ruby

class Node 
	attr_accessor :data, :next_node

	def initialize(data, next_node=nil)
		@data = data
		@next = next_node
	end	

end


class LinkedList
	def initialize(*items)
		@head = nil
		if items
			self.prepend(*items)
		end
	end

	def prepend(*items)
		items.reverse.each do |item|
			old_head = @head
			@head = Node.new(item)
			@head.next_node = old_head

		end
	end

	def append(*items)
		last = @head

		while last.next_node
			last = last.next_node
		end 
		
		items.each do |item|
			new_node = Node.new(item)
			last.next_node = new_node
			last = new_node
		end
	end

	def delete(target)
		current = @head
		last = @head

		while current && current.data != target
			last = current
			current = current.next_node
		end

		if current
			last.next_node = current.next_node
		end
	end

	def length
		count = 0
		current = @head

		while current
			count += 1
			current = current.next_node
		end

		return count
	end 

	def show
		current = @head
		
		while current
			puts current.data
			current = current.next_node
		end
	end

	def show_reverse
		def rec(current)
			if current
				return "#{rec(current.next_node)} <- |#{current.data}|"
			else
				return 'Tail'
			end
		end
		puts "#{rec(@head)} <- Head"
	end
end

list = LinkedList.new('a','b','c')
list.append('d', 'f', 'g')
list.show()
puts list.length()
list.show_reverse()