angelikatyborska's solution to Series on the Ruby track

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 string of digits, output all the contiguous substrings of length n in that string.

For example, the string "49142" has the following 3-digit series:

And the following 4-digit series:

4914
9142

And if you ask for a 6-digit series from a 5-digit string, you deserve whatever you get.

Note that these series are only required to occupy adjacent positions in the input; the digits need not be numerically consecutive.

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 series_test.rb

To include color from the command line:

ruby -r minitest/pride series_test.rb

Source

A subset of the Problem 8 at Project Euler http://projecteuler.net/problem=8

Submitting Incomplete Solutions

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

series_test.rb

require 'minitest/autorun'
require_relative 'series'

class SeriesTest < Minitest::Test
  def test_simple_slices_of_one
    series = Series.new('01234')
    assert_equal ['0', '1', '2', '3', '4'], series.slices(1)
  end

  def test_simple_slices_of_one_again
    skip
    series = Series.new('92834')
    assert_equal ['9', '2', '8', '3', '4'], series.slices(1)
  end

  def test_simple_slices_of_two
    skip
    series = Series.new('01234')
    assert_equal ['01', '12', '23', '34'], series.slices(2)
  end

  def test_other_slices_of_two
    skip
    series = Series.new('98273463')
    expected = ['98', '82', '27', '73', '34', '46', '63']
    assert_equal expected, series.slices(2)
  end

  def test_simple_slices_of_two_again
    skip
    series = Series.new('37103')
    assert_equal ['37', '71', '10', '03'], series.slices(2)
  end

  def test_simple_slices_of_three
    skip
    series = Series.new('01234')
    assert_equal ['012', '123', '234'], series.slices(3)
  end

  def test_simple_slices_of_three_again
    skip
    series = Series.new('31001')
    assert_equal ['310', '100', '001'], series.slices(3)
  end

  def test_other_slices_of_three
    skip
    series = Series.new('982347')
    expected = ['982', '823', '234', '347']
    assert_equal expected, series.slices(3)
  end

  def test_simple_slices_of_four
    skip
    series = Series.new('01234')
    assert_equal ['0123', '1234'], series.slices(4)
  end

  def test_simple_slices_of_four_again
    skip
    series = Series.new('91274')
    assert_equal ['9127', '1274'], series.slices(4)
  end

  def test_simple_slices_of_five
    skip
    series = Series.new('01234')
    assert_equal ['01234'], series.slices(5)
  end

  def test_simple_slices_of_five_again
    skip
    series = Series.new('81228')
    assert_equal ['81228'], series.slices(5)
  end

  def test_simple_slice_that_blows_up
    skip
    series = Series.new('01234')
    assert_raises ArgumentError do
      series.slices(6)
    end
  end

  def test_more_complicated_slice_that_blows_up
    skip
    slice_string = '01032987583'

    series = Series.new(slice_string)
    assert_raises ArgumentError do
      series.slices(slice_string.length + 1)
    end
  end

  def test_sequential_slices
    skip
    series = Series.new('1234')
    assert_equal ['12', '23', '34'], series.slices(2)
    assert_equal ['123', '234'], series.slices(3)
  end
end

class Series
  def initialize(string)
    @numbers = string.chars.map(&:to_i)
  end

  def slices(length)
    unless (1..@numbers.length).include?(length)
      fail ArgumentError, "Cannot divide a series of length #{ @numbers.length } into slices of length #{ length }"
    end

    @numbers.each_cons(length).to_a
  end
end

Community comments

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

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?

angelikatyborska's solution

to Series in the Ruby Track