74 lines
1.0 KiB
Ruby
74 lines
1.0 KiB
Ruby
# This file contains the Ruby code from book of
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# "Data Structures and Algorithms
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# with Object-Oriented Design Patterns in Ruby"
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# by Bruno R. Preiss.
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#
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# Copyright (c) 2004 by Bruno R. Preiss, P.Eng. All rights reserved.
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class DoubleLinkedList < SinglyLinkedList
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class Element < SinglyLinkedList < Element
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attr_accessor :prev
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def initialize(list, data, succ, prev)
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super(list, data, succ)
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@prev = prev
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end
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def insert_after(item)
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# Todo
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end
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def insert_before(item)
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# Todo
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end
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end
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attr_accessor :head, :tail
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def initialize
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@head = nil
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@tail = nil
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end
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def purge
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@head = nil
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@tail = nil
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end
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def empty?
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@head.nil?
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end
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def first
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if @head.nil?
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raise Error
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else
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@head.data
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end
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end
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def last
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if @tail.nil?
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raise Error
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else
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@tail.data
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end
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end
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def prepend(elem)
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# Todo
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end
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def append(elem)
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# Todo
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end
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def clone
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# Todo
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end
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def extract
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# Todo
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end
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end |