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| defmodule PriorityQueue do | |
| @moduledoc """ | |
| A priority queue in Elixir. | |
| """ | |
| @type priority :: integer() | nil | |
| @type element :: any() | |
| @type t :: %__MODULE__{set: :gb_sets.set({priority(), element()})} | |
| defstruct [set: :gb_sets.empty()] | |
| @doc """ | |
| Create a new priority queue. | |
| """ | |
| @spec new() :: t() | |
| @spec new([{priority(), element()}]) :: t() | |
| def new(), do: %__MODULE__{set: :gb_sets.empty()} | |
| def new([]), do: new() | |
| def new([{_priority, _element} | _] = list), do: %__MODULE__{set: :gb_sets.from_list(list)} | |
| @doc """ | |
| Add an element with a priority. | |
| """ | |
| @specc add_with_priority(t(), element(), priority()) :: t() | |
| def add_with_priority(%__MODULE__{} = queue, element, priority) do | |
| %{queue | set: :gb_sets.add({priority, element}, queue.set)} | |
| end | |
| @doc """ | |
| Get the size of the queue. | |
| """ | |
| @spec size(t()) :: non_neg_integer() | |
| def size(%__MODULE__{} = queue) do | |
| :gb_sets.size(queue.set) | |
| end | |
| @doc """ | |
| Extract the element with the lowest priority. | |
| """ | |
| @spec extract_min(t()) :: {{priority(), element()}, t()} | |
| def extract_min(%__MODULE__{} = queue) do | |
| case :gb_sets.size(queue.set) do | |
| 0 -> :empty | |
| _else -> | |
| {{priority, element}, set} = :gb_sets.take_smallest(queue.set) | |
| {{priority, element}, %{queue | set: set}} | |
| end | |
| end | |
| defimpl Inspect do | |
| import Inspect.Algebra | |
| def inspect(%PriorityQueue{} = queue, opts) do | |
| concat(["#PriorityQueue.new(", to_doc(:gb_sets.to_list(queue.set), opts), ")"]) | |
| end | |
| end | |
| end |
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Originally from: https://blog.ftes.de/elixir-dijkstras-algorithm-with-priority-queue-f6022d710877