🎉 Exercism Research is now launched. Help Exercism, help science and have some fun at research.exercism.io 🎉
Avatar of remcopeereboom

remcopeereboom's solution

to Anagram in the Ruby Track

Published at Jul 13 2018 · 3 comments
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code 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".


For installation and learning resources, refer to the exercism help page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby anagram_test.rb

To include color from the command line:

ruby -r minitest/pride anagram_test.rb

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.rb

require 'minitest/autorun'
require_relative 'anagram'

# Common test data version: 1.0.1 196fc1a
class AnagramTest < Minitest::Test
  def test_no_matches
    # skip
    detector = Anagram.new('diaper')
    anagrams = detector.match(["hello", "world", "zombies", "pants"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_detects_simple_anagram
    skip
    detector = Anagram.new('ant')
    anagrams = detector.match(["tan", "stand", "at"])
    expected = ["tan"]
    assert_equal expected, anagrams
  end

  def test_does_not_detect_false_positives
    skip
    detector = Anagram.new('galea')
    anagrams = detector.match(["eagle"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_detects_two_anagrams
    skip
    detector = Anagram.new('master')
    anagrams = detector.match(["stream", "pigeon", "maters"])
    expected = ["maters", "stream"]
    assert_equal expected, anagrams.sort
  end

  def test_does_not_detect_anagram_subsets
    skip
    detector = Anagram.new('good')
    anagrams = detector.match(["dog", "goody"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_detects_anagram
    skip
    detector = Anagram.new('listen')
    anagrams = detector.match(["enlists", "google", "inlets", "banana"])
    expected = ["inlets"]
    assert_equal expected, anagrams
  end

  def test_detects_three_anagrams
    skip
    detector = Anagram.new('allergy')
    anagrams = detector.match(["gallery", "ballerina", "regally", "clergy", "largely", "leading"])
    expected = ["gallery", "largely", "regally"]
    assert_equal expected, anagrams.sort
  end

  def test_does_not_detect_identical_words
    skip
    detector = Anagram.new('corn')
    anagrams = detector.match(["corn", "dark", "Corn", "rank", "CORN", "cron", "park"])
    expected = ["cron"]
    assert_equal expected, anagrams
  end

  def test_does_not_detect_non_anagrams_with_identical_checksum
    skip
    detector = Anagram.new('mass')
    anagrams = detector.match(["last"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_detects_anagrams_case_insensitively
    skip
    detector = Anagram.new('Orchestra')
    anagrams = detector.match(["cashregister", "Carthorse", "radishes"])
    expected = ["Carthorse"]
    assert_equal expected, anagrams
  end

  def test_detects_anagrams_using_case_insensitive_subject
    skip
    detector = Anagram.new('Orchestra')
    anagrams = detector.match(["cashregister", "carthorse", "radishes"])
    expected = ["carthorse"]
    assert_equal expected, anagrams
  end

  def test_detects_anagrams_using_case_insensitive_possible_matches
    skip
    detector = Anagram.new('orchestra')
    anagrams = detector.match(["cashregister", "Carthorse", "radishes"])
    expected = ["Carthorse"]
    assert_equal expected, anagrams
  end

  def test_does_not_detect_a_word_as_its_own_anagram
    skip
    detector = Anagram.new('banana')
    anagrams = detector.match(["Banana"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_does_not_detect_a_anagram_if_the_original_word_is_repeated
    skip
    detector = Anagram.new('go')
    anagrams = detector.match(["go Go GO"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_anagrams_must_use_all_letters_exactly_once
    skip
    detector = Anagram.new('tapper')
    anagrams = detector.match(["patter"])
    expected = []
    assert_equal expected, anagrams
  end

  def test_capital_word_is_not_own_anagram
    skip
    detector = Anagram.new('BANANA')
    anagrams = detector.match(["Banana"])
    expected = []
    assert_equal expected, anagrams
  end

  # Problems in exercism evolve over time, as we find better ways to ask
  # questions.
  # The version number refers to the version of the problem you solved,
  # not your solution.
  #
  # Define a constant named VERSION inside of the top level BookKeeping
  # module, which may be placed near the end of your file.
  #
  # In your file, it will look like this:
  #
  # module BookKeeping
  #   VERSION = 1 # Where the version number matches the one in the test.
  # end
  #
  # If you are curious, read more about constants on RubyDoc:
  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html

  def test_bookkeeping
    skip
    assert_equal 2, BookKeeping::VERSION
  end
end
class Anagram
  def initialize(word)
    @word = word
  end

  def match(anagrams)
    anagrams.select { |w| anagram?(w) }
  end

  private

  attr_reader :word

  def anagram?(string)
    same_characters?(string) && different_word?(string)
  end

  def different_word?(string)
    string.downcase != word.downcase
  end

  def same_characters?(string)
    @characters ||= word.downcase.chars.sort
    string.downcase.chars.sort == @characters
  end
end

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of monkbroc

Clever idea to defer calculation of @characters to same_characters?

Avatar of remcopeereboom

Thanks!

Avatar of revdan

I like the method names :)

You could probably move the downcase further up to avoid repetition.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?