rdrey / heap

Heap data structure for Elixir.

Heap

A Heap is a very useful data structure, because it sorts, quickly, at insert time.

See also: https://en.wikipedia.org/wiki/Heap_(data_structure)

You can use it for things like:

• Help with scientific computing
• Quickly sorting
• Priority queues

Installation

This package is available in Hex:

1. Add heap to your list of dependencies in mix.exs:

   def deps do
     [{:heap, "~> 2.0"}]
   end

2. Run mix deps.get

Examples

Create a min heap and use it to find the smallest element in a collection:

1..500 |> Enum.shuffle |> Enum.into(Heap.min) |> Heap.root
# => 1

Likewise, for max heaps:

1..500 |> Enum.shuffle |> Enum.into(Heap.max) |> Heap.root
# => 500

A priority queue:

Tuples are compared by their elements in order, so you can push tuples of {priority, term} into a Heap for sorting by priority:

Heap.new
|> Heap.push({4, :jam})
|> Heap.push({1, :milk})
|> Heap.push({2, :eggs})
|> Heap.push({1, :bread})
|> Heap.push({3, :butter})
|> Heap.push({2, :coffee})
|> Enum.map(fn {_, what} -> what end)
# => [:bread, :milk, :coffee, :eggs, :butter, :jam]

The heap can also be constructed with a custom comparator:

Heap.new(&(Date.compare(elem(&1, 0), elem(&2, 0)) == :gt))
|> Heap.push({~D[2017-11-20], :jam})
|> Heap.push({~D[2017-11-21], :milk})
|> Heap.push({~D[2017-10-21], :bread})
|> Heap.push({~D[2017-10-20], :eggs})
|> Enum.map(fn {_, what} -> what end)
# => [:milk, :jam, :bread, :eggs]

To access the root and the rest of the heap in one line use Heap.split/1:

{root, rest} = Heap.split(heap)
{root, rest} == {Heap.root(heap), Heap.pop(heap)}
# => true

Documentation

Full API documentation is available on (hexdocs.pm)[https://hexdocs.pm/heap]

Contributing

1. Fork it ( https://github.com/jamesotron/heap/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