Fibonacci Sequence

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.8.0", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"},
  {:benchee, "~> 1.1"}
])

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Setup

Ensure you type the ea keyboard shortcut to evaluate all Elixir cells before starting. Alternatively you can evaluate the Elixir cells as you read.

Fibonacci Sequence

The Fibonacci sequence is a series of the following numbers.

flowchart LR
a[0] --> b[1] --> c[1] --> d[2] --> e[3] --> f[5] --> g[8] --> h[13] --> i[21] --> k[34] --> ...

It’s created by taking the sum of the previous to numbers to get the next number.

So $fib(n) = fib(n-1) + fib(n - 2)$

Implement the Fibonacci.sequence/1 function below. Do not worry about performance for this solution.

defmodule Fibonacci do
  @doc """
  Generate the fibonacci sequence of a given length.

  ## Examples

    iex> 
  """
  def sequence(length) do
  end
end

Competition: Benchmark

In the Elixir cell below, create a FastFib module. The FastFib module should be the most performant version of the Fibonacci Sequence that you can create.

defmodule FastFib do
  def sequence(length) do
  end
end

Use Benchee to benchmark the performance of FastFib.sequence/1 function. The student in the class with the fastest FastFib time wins.

Benchee.run(
  %{
    fast_fib: fn n -> FastFib.sequence(n) end
  },
  inputs: %{
    "1: small" => 10,
    "2: medium" => 30
    # Uncomment the following if your solution can handle it! 
    # Make sure to add a comma above.
    # "3: large" => 100,
    # "4: xl" => 1000,
    # "6: 2xl" => 10000,
    # "7: 3xl" => 100_000
  },
  memory_time: 2
)

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "fibonacci_challenge_reading"
    "exercises" -> "fibonacci_challenge_exercise"
  end

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, save_name, false)

form =
  Kino.Control.form(
    [
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    ],
    report_changes: true
  )

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(
      progress_path,
      Jason.encode!(Map.put(existing_progress, save_name, completed), pretty: true)
    )
  end
end)

form

Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout -b fibonacci-challenge-exercise
$ git add .
$ git commit -m "finish fibonacci challenge exercise"
$ git push origin fibonacci-challenge-exercise

Create a pull request from your fibonacci-challenge-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your teacher by including @BrooklinJazz in your PR description to get feedback. You (or your teacher) may merge your PR into your solutions branch after review.

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