Class: Containers::RubyDeque

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/containers/deque.rb

Overview

rdoc

A Deque is a container that allows items to be added and removed from both the front and back,
acting as a combination of a Stack and Queue.

This implementation uses a doubly-linked list, guaranteeing O(1) complexity for all operations.

MIT License

Copyright (c) 2009 Kanwei Li

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Defined Under Namespace

Classes: Node

Instance Method Summary collapse

Constructor Details

#initialize(ary = []) ⇒ RubyDeque

Create a new Deque. Takes an optional array argument to initialize the Deque.

d = Containers::Deque.new([1, 2, 3])
d.front #=> 1
d.back #=> 3



39
40
41
42
43
44
 
# File 'lib/containers/deque.rb', line 39

def initialize(ary=[])
  @front = nil
  @back = nil
  @size = 0
  ary.to_a.each { |obj| push_back(obj) }
end

Instance Method Details

#back ⇒ Object

Returns the object at the back of the Deque but does not remove it.

d = Containers::Deque.new
d.push_front(1)
d.push_front(2)
d.back #=> 1



82
83
84
 
# File 'lib/containers/deque.rb', line 82

def back
  @back && @back.obj
end

#clear ⇒ Object

Removes all the objects in the Deque.



52
53
54
55
 
# File 'lib/containers/deque.rb', line 52

def clear
  @front = @back = nil
  @size = 0
end

#each_backward ⇒ Object Also known as: reverse_each

Iterate over the Deque in LIFO order.



176
177
178
179
180
181
182
183
 
# File 'lib/containers/deque.rb', line 176

def each_backward
  return unless @back
  node = @back
  while node
    yield node.obj
    node = node.left
  end
end

#each_forward ⇒ Object Also known as: each

Iterate over the Deque in FIFO order.



165
166
167
168
169
170
171
172
 
# File 'lib/containers/deque.rb', line 165

def each_forward
  return unless @front
  node = @front
  while node
    yield node.obj
    node = node.right
  end
end

#empty? ⇒ Boolean

Returns true if the Deque is empty, false otherwise.

Returns:

  • (Boolean) 


47
48
49
 
# File 'lib/containers/deque.rb', line 47

def empty?
  @size == 0
end

#front ⇒ Object

Returns the object at the front of the Deque but does not remove it.

d = Containers::Deque.new
d.push_front(1)
d.push_front(2)
d.front #=> 2



72
73
74
 
# File 'lib/containers/deque.rb', line 72

def front
  @front && @front.obj
end

#pop_back ⇒ Object

Returns the object at the back of the Deque and removes it.

d = Containers::Deque.new
d.push_front(1)
d.push_front(2)
d.pop_back #=> 1
d.size #=> 1



150
151
152
153
154
155
156
157
158
159
160
161
162
 
# File 'lib/containers/deque.rb', line 150

def pop_back
  return nil unless @back
  node = @back
  if @size == 1
    clear
    return node.obj
  else
    @back.left.right = nil
    @back = @back.left
  end
  @size -= 1
  node.obj
end

#pop_front ⇒ Object

Returns the object at the front of the Deque and removes it.

d = Containers::Deque.new
d.push_front(1)
d.push_front(2)
d.pop_front #=> 2
d.size #=> 1



129
130
131
132
133
134
135
136
137
138
139
140
141
 
# File 'lib/containers/deque.rb', line 129

def pop_front
  return nil unless @front
  node = @front
  if @size == 1
    clear
    return node.obj
  else
    @front.right.left = nil
    @front = @front.right
  end
  @size -= 1
  node.obj
end

#push_back(obj) ⇒ Object

Adds an object at the back of the Deque.

d = Containers::Deque.new([1, 2, 3])
d.push_back(4)
d.pop_back #=> 4



109
110
111
112
113
114
115
116
117
118
119
120
 
# File 'lib/containers/deque.rb', line 109

def push_back(obj)
  node = Node.new(nil, nil, obj)
  if @back
    node.left = @back
    @back.right = node
    @back = node
  else
    @front = @back = node
  end
  @size += 1
  obj
end

#push_front(obj) ⇒ Object

Adds an object at the front of the Deque.

d = Containers::Deque.new([1, 2, 3])
d.push_front(0)
d.pop_front #=> 0



91
92
93
94
95
96
97
98
99
100
101
102
 
# File 'lib/containers/deque.rb', line 91

def push_front(obj)
  node = Node.new(nil, nil, obj)
  if @front
    node.right = @front
    @front.left = node
    @front = node
  else
    @front = @back = node
  end
  @size += 1
  obj
end

#size ⇒ Object Also known as: length

Return the number of items in the Deque.

d = Containers::Deque.new([1, 2, 3])
d.size #=> 3



61
62
63
 
# File 'lib/containers/deque.rb', line 61

def size
  @size
end