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Weighted Voting

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.9", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Weighted Voting

In the previous Counting Votes exercise, we created a module to count a list of votes. For example, users would vote for their favorite animal to decide if :birds, :dogs, or :cats were more popular.

Now, you're going to create a WeightedVoting.count/2 that can count the number of votes for a single value such as :dogs or :cats. provided in a keyword list.

WeightedVoting.count([cats: 10, dogs: 20, dogs: 20], :dogs)
40

You're also going to create a WeightedVoting.tally/1 function that will count the votes provided in a keyword list, and return the results as a keyword list like so.

WeightedVoting.tally([cats: 10, dogs: 20, dogs: 20])
[cats: 10, dogs: 40]
Example Solution 
defmodule WeightedVoting do
  def count(votes, vote_to_count) do
    Enum.reduce(votes, 0, fn {key, value}, acc ->
      if key == vote_to_count do
        acc + value
      else
        acc
      end
    end)
  end

  def tally(votes) do
    Enum.reduce(votes, [], fn {key, vote_count}, acc ->
      Keyword.update(acc, key, vote_count, fn existing_value ->
        existing_value + vote_count
      end)
    end)
  end

  def tally_map(votes) do
    Enum.reduce(votes, %{}, fn {key, vote_count}, acc ->
      Map.update(acc, key, vote_count, fn existing_value ->
        existing_value + vote_count
      end)
    end)
  end
end

Implement the WeightedVoting module as documented below.

defmodule WeightedVoting do
  @doc """
  Count the total number of votes for some key in a keyword list.

  ## Examples

    iex> WeightedVoting.count([dogs: 20, dogs: 10], :dogs)
    30
    iex> WeightedVoting.count([cats: 10, dogs: 20, dogs: 30], :dogs)
    50
    iex> WeightedVoting.count([cats: 10, dogs: 20, dogs: 10, cats: 30], :cats)
    40
  """
  def count(votes, vote_to_count) do
  end

  @doc """
  Tally the total number of votes in a keyword list, and return
  the results as a keyword list.

  The keyword list should be sorted in alphabetical order.

  ## Examples

    iex> WeightedVoting.tally([dogs: 20, dogs: 10])
    [dogs: 30]
    iex> WeightedVoting.tally([cats: 10, dogs: 20, dogs: 10])
    [cats: 10, dogs: 30]
    iex> WeightedVoting.tally([cats: 10, dogs: 20, cats: 20, dogs: 10, birds: 20])
    [birds: 20, cats: 30, dogs: 30]
  """
  def tally(votes) do
  end
end

Bonus: Tally Map

Create a WeightedVoting.tally_map/1 function which returns a map instead of a keyword list. You may copy the following code into the WeightedVoting module above to get started.

  @doc """
  Tally the total number of votes in a keyword list, and return
  the results as a map.

  ## Examples

    iex> WeightedVoting.tally_map([dogs: 20, dogs: 10])
    %{dogs: 30}
    iex> WeightedVoting.tally_map([cats: 10, dogs: 20, dogs: 10])
    %{cats: 10, dogs: 30}
    iex> WeightedVoting.tally_map([cats: 10, dogs: 20, cats: 20, dogs: 10, birds: 20])
    %{birds: 20, cats: 30, dogs: 30}
  """
  def tally_map(votes) do
  end

Commit Your Progress

DockYard Academy now recommends you use the latest Release rather than forking or cloning our repository.

Run git status to ensure there are no undesirable changes. Then run the following in your command line from the curriculum folder to commit your progress.

$ git add .
$ git commit -m "finish Weighted Voting exercise"
$ git push

We're proud to offer our open-source curriculum free of charge for anyone to learn from at their own pace.

We also offer a paid course where you can learn from an instructor alongside a cohort of your peers. We will accept applications for the June-August 2023 cohort soon.

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