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# angelikatyborska's solution

## to Series in the Ruby Track

Published at Jul 13 2018 · 2 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 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:

• 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 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``````

I believe you can simplify line 7 to just: if length > @numbers.size as you has in iteration 2. I'm curious why it changed?

Solution Author
commented over 5 years ago

I did that to account for non-positive and fractional arguments which are also invalid.

### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™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?