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paulfioravanti's solution

to Anagram in the Elixir Track

Published at Jun 27 2019 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

Given a word and a list of possible anagrams, select the correct sublist.

Given "listen" and a list of candidates like "enlists" "google" "inlets" "banana" the program should return a list containing "inlets".

Running tests

Execute the tests with:

$ elixir anagram_test.exs

Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

Source

Inspired by the Extreme Startup game https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

anagram_test.exs

if !System.get_env("EXERCISM_TEST_EXAMPLES") do
  Code.load_file("anagram.exs", __DIR__)
end

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)

defmodule AnagramTest do
  use ExUnit.Case

  # @tag :pending
  test "no matches" do
    matches = Anagram.match("diaper", ["hello", "world", "zombies", "pants"])
    assert matches == []
  end

  @tag :pending
  test "detect simple anagram" do
    matches = Anagram.match("ant", ["tan", "stand", "at"])
    assert matches == ["tan"]
  end

  @tag :pending
  test "detect multiple anagrams" do
    matches = Anagram.match("master", ["stream", "pigeon", "maters"])
    assert matches == ["stream", "maters"]
  end

  @tag :pending
  test "do not detect anagram subsets" do
    matches = Anagram.match("good", ~w(dog goody))
    assert matches == []
  end

  @tag :pending
  test "detect anagram" do
    matches = Anagram.match("listen", ~w(enlists google inlets banana))
    assert matches == ["inlets"]
  end

  @tag :pending
  test "multiple anagrams" do
    matches = Anagram.match("allergy", ~w(gallery ballerina regally clergy largely leading))
    assert matches == ["gallery", "regally", "largely"]
  end

  @tag :pending
  test "anagrams must use all letters exactly once" do
    matches = Anagram.match("patter", ["tapper"])
    assert matches == []
  end

  @tag :pending
  test "detect anagrams with case-insensitive subject" do
    matches = Anagram.match("Orchestra", ~w(cashregister carthorse radishes))
    assert matches == ["carthorse"]
  end

  @tag :pending
  test "detect anagrams with case-insensitive candidate" do
    matches = Anagram.match("orchestra", ~w(cashregister Carthorse radishes))
    assert matches == ["Carthorse"]
  end

  @tag :pending
  test "anagrams must not be the source word" do
    matches = Anagram.match("corn", ["corn", "dark", "Corn", "rank", "CORN", "cron", "park"])
    assert matches == ["cron"]
  end

  @tag :pending
  test "do not detect words based on checksum" do
    matches = Anagram.match("mass", ["last"])
    assert matches == []
  end
end
defmodule Anagram do
  @doc """
  Returns all candidates that are anagrams of, but not equal to, 'base'.
  """
  @spec match(String.t(), [String.t()]) :: [String.t()]
  def match(base, candidates) do
    word = String.downcase(base)
    letters = to_sorted_letters(word)

    candidates
    |> Enum.filter(&anagram?(String.downcase(&1), word, letters))
  end

  defp to_sorted_letters(word) do
    word
    |> String.graphemes()
    |> Enum.sort()
  end

  defp anagram?(candidate, word, letters) do
    not same_word?(word, candidate) and same_letters?(letters, candidate)
  end

  defp same_word?(word, candidate), do: word == candidate

  defp same_letters?(letters, candidate) do
    letters == to_sorted_letters(candidate)
  end
end

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