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matheussilvasantos's solution

to Series in the Ruby Track

Published at Nov 27 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

Given a string of digits, output all the contiguous substrings of length n in that string in the order that they appear.

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

  • "491"
  • "914"
  • "142"

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 Ruby resources 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(digits)
    @digits = digits
  end

  def slices(length)
    raise ArgumentError if length > @digits.size

    @digits.each_char.each_cons(length).map(&:join)
  end
end

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