Class: List

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/Prct07/List.rb

Overview

Author:

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ List

Returns a new instance of List.



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# File 'lib/Prct07/List.rb', line 11

def initialize
  @head = @tail = nil
  @size = 0
end

Instance Attribute Details

#size ⇒ Object (readonly)

Returns the value of attribute size.



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# File 'lib/Prct07/List.rb', line 9

def size
  @size
end

Instance Method Details

#back ⇒ Object

returns the last element of the list



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# File 'lib/Prct07/List.rb', line 81

def back
  @tail.value
end

#each ⇒ Object

necessary for enumerable module



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# File 'lib/Prct07/List.rb', line 104

def each
  aux = @head
  while aux!= nil do
    yield aux.value
    aux = aux.next
  end
end

#empty ⇒ Object

checks if the list is empty



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# File 'lib/Prct07/List.rb', line 42

def empty
  @size == 0
end

#front ⇒ Object

returns the first element of the list



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# File 'lib/Prct07/List.rb', line 86

def front
  @head.value
end

#getAt(index) ⇒ Object

returns the element specificated by the index



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# File 'lib/Prct07/List.rb', line 91

def getAt index
  if (index >= @size)
    nil
  else
    aux = @head
    for i in 0..index - 1
      aux = aux.next
    end
    aux.value
  end
end

#pop_back ⇒ Object

extracts the last element of the list and returns it



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# File 'lib/Prct07/List.rb', line 64

def pop_back
  @size = @size - 1
  if (@head == nil)
    nil
  else
    aux = @tail
    if (@tail.prev != nil)
      @tail = @tail.prev
      @tail.next = nil
    else
      @head = nil
    end
    aux.value
  end
end

#pop_front ⇒ Object

extracts the first element of the list and returns it



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# File 'lib/Prct07/List.rb', line 47

def pop_front
  @size = @size - 1
  if (@head == nil)
    nil
  else
    aux = @head
    if (@head.next != nil)
      @head = @head.next
      @head.prev = nil
    else
      @head = nil
    end
    aux.value
  end
end

#push_back(element) ⇒ Object

inserts elements by the tail of the list



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# File 'lib/Prct07/List.rb', line 17

def push_back element
  @size = @size + 1
  if (@head == nil)
    @head = @tail = Node.new element, nil, nil
  else
    @tail.next = Node.new element, @tail, nil
    @tail = @tail.next
  end
  true
end

#push_front(element) ⇒ Object

inserts elements by the head of list



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# File 'lib/Prct07/List.rb', line 29

def push_front element
  @size = @size + 1
  if (@head == nil)
    @head = @tail = Node.new element, nil, nil
  else
    aux = @head
    @head = Node.new element, nil, aux
    aux.prev = @head
  end
  true
end