SplayTree

A self-balancing binary tree optimised for fast access to frequently used nodes. Useful for implementing caches and garbage collection algorithms.

Features

• Familiar Hash like access
• Easy instantiation with default value

Installation

Add this line to your application's Gemfile:

gem "splay_tree"

And then execute:

$ bundle

Or install it yourself as:

$ gem install splay_tree

Contents

• 1. Usage
  • 1.1 insert
  • 1.2 fetch
  • 1.3 default
  • 1.4 delete
  • 1.5 empty?
  • 1.6 each

1. Usage

SplayTree operations are similar to that of Hash:

tree = SplayTree.new
tree[:foo] = :bar

tree[:foo]  # => :bar
tree.size   # => 1

1.1 insert

To assign a value to a given key do the following:

tree = SplayTree.new
tree[:foo] = 1
tree[:bar] = 2

Note: The inserted key will be subjected to splaying, which means the tree will be rearranged to help with quicker access on subsequent calls.

1.2 fetch

To retrieve a value at a given key do:

tree = SplayTree.new
tree[:foo]  #  => nil

tree[:foo] = 1
tree[:foo]  #  => 1

Note: Frequently accessed keys will move nearer to the root where they can be accessed more quickly.

1.3 default

You can set a default value for a missing key. This can be done during initialization:

tree = SplayTree.new
tree.default  # => UndefinedValue

tree = SplayTree.new(1)
tree.default  # => 1
tree[:foo]    # => 1

Or using default method:

tree = SplayTree.new
tree.default = 1

tree[:foo] # => 1

You can also use a block to set the default value:

tree = SplayTree.new
tree.default_proc  # => nil

tree = SplayTree.new { 1 }
tree.default_proc  # => #<Proc...>
tree[:foo]         # => 1

1.4 delete

In order to remove an entry from a splay tree use delete method. If a key is not found, the default value is returned, otherwise nil.

tree = SplayTree.new
tree[:foo] = 1
tree.delete(:foo)  # => 1
tree.delete(:bar)  # => nil

1.5 empty?

Use empty? to check if a tree contains any elements:

tree = SplayTree.new
tree.empty?  # => true

tree[:foo] = 1
tree.empty?  # => false

1.6 each

Use each method to iterate over all tree nodes like so:

tree = SplayTree.new
tree[:foo] = 1
tree[:bar] = 2

tree.each { |key, value| puts "#{key}: #{value}" }
# =>
# bar: 2
# foo: 1

You can also use each_key and each_value to enumerate only keys or values:

tree.each_key { |key| ... }
tree.each_value { |value| ... }

If no block is given, an enumerator is returned instead.

Contributing

1. Fork it ( https://github.com/piotrmurach/splay_tree/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Code of Conduct

Everyone interacting in the SplayTree project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

Copyright

Copyright (c) 2014 Piotr Murach. See LICENSE for further details.