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:
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
A subset of the Problem 8 at Project Euler http://projecteuler.net/problem=8
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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
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Community comments
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?
I did that to account for non-positive and fractional arguments which are also invalid.