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w1zeman1p's solution

to Flatten Array in the Ruby Track

Published at Jul 13 2018 · 0 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.

Take a nested list and return a single flattened list with all values except nil/null.

The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.

For Example

input: [1,[2,3,null,4],[null],5]

output: [1,2,3,4,5]


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 flatten_array_test.rb

To include color from the command line:

ruby -r minitest/pride flatten_array_test.rb

Source

Interview Question https://reference.wolfram.com/language/ref/Flatten.html

Submitting Incomplete Solutions

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

flatten_array_test.rb

require 'minitest/autorun'
require_relative 'flatten_array'

# Common test data version: 1.1.0 d7a3c09
class FlattenArrayTest < Minitest::Test
  def test_no_nesting
    # skip
    fa = FlattenArray.flatten([0, 1, 2])
    assert_equal [0, 1, 2], fa
  end

  def test_flattens_array_with_just_integers_present
    skip
    fa = FlattenArray.flatten([1, [2, 3, 4, 5, 6, 7], 8])
    assert_equal [1, 2, 3, 4, 5, 6, 7, 8], fa
  end

  def test_5_level_nesting
    skip
    fa = FlattenArray.flatten([0, 2, [[2, 3], 8, 100, 4, [[[50]]]], -2])
    assert_equal [0, 2, 2, 3, 8, 100, 4, 50, -2], fa
  end

  def test_6_level_nesting
    skip
    fa = FlattenArray.flatten([1, [2, [[3]], [4, [[5]]], 6, 7], 8])
    assert_equal [1, 2, 3, 4, 5, 6, 7, 8], fa
  end

  def test_6_level_nest_list_with_null_values
    skip
    fa = FlattenArray.flatten([0, 2, [[2, 3], 8, [[100]], nil, [[nil]]], -2])
    assert_equal [0, 2, 2, 3, 8, 100, -2], fa
  end

  def test_all_values_in_nested_list_are_null
    skip
    fa = FlattenArray.flatten([nil, [[[nil]]], nil, nil, [[nil, nil], nil], nil])
    assert_equal [], fa
  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 1, BookKeeping::VERSION
  end
end
class FlattenArray
  VERSION = 1

  def self.flatten(arrays)
    arrays.inject([]) do |result, el|
      result + (el.is_a?(Array) ? flatten(el) : [el])
    end.compact
  end
end

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