How to convert a string of values with a range to an array in Ruby

Question

I'm trying to parse a string of numbers and ranges joined by ",", and convert it to a numerical array. I have this as input: "1,3,6-8,5", and would like to have an array like this: [1,3,5,6,7,8].

I can only do it without the range, like this:

"12,2,6".split(",").map { |s| s.to_i }.sort #=> [2, 6, 12]

With a range, I cannot do it:

a = "12,3-5,2,6"
b = a.gsub(/-/, "..")               #=> "12,3..5,2,6"
c = b.split(",")                    #=> ["12", "3..5", "2", "6"]
d = c.sort_by(&:to_i)               #=> ["2", "3..5", "6", "12"]
e = d.split(",").map { |s| s.to_i } #>> Error

How can I do this?

I was also thinking to use the splat operator in map, but splat doesn't accept strings like [*(3..5)].

Aleksei Matiushkin · Accepted Answer · 2018-04-08 15:48:16Z

4

"12,3-5,2,6".
  gsub(/(\d+)-(\d+)/) { ($1..$2).to_a.join(',') }.
  split(',').
  map(&:to_i)
#⇒ [12, 3, 4, 5, 2, 6]

answered Apr 8, 2018 at 15:48

Aleksei Matiushkin

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2 Comments

Brian Tompsett - 汤莱恩 Over a year ago

For the benefit of the wider community it is usual to add some explanation to code only answers, otherwise they end up in the LQP queue for review like this one did....

not2qubit Over a year ago

Definitely the most easy answer to wrap my head around. No maps, and no if/then loops. Accepted.

Фил · Accepted Answer · 2018-04-08 14:10:16Z

3

"1,3,6-8,5".split(',').map do |str|
  if matched = str.match(/(\d+)\-(\d+)/)
    (matched[1].to_i..matched[2].to_i).to_a
  else
    str.to_i
  end
end.flatten

or

"1,3,6-8,5".split(',').each_with_object([]) do |str, output|
  if matched = str.match(/(\d+)\-(\d+)/)
    output.concat (matched[1].to_i..matched[2].to_i).to_a
  else
    output << str.to_i
  end
end

or strict

RANGE_PATTERN = /\A(\d+)\-(\d+)\z/
INT_PATTERN   = /\A\d+\z/

"1,3,6-8,5".split(',').each_with_object([]) do |str, output|
  if matched = str.match(RANGE_PATTERN)
    output.concat (matched[1].to_i..matched[2].to_i).to_a

  elsif str.match(INT_PATTERN)
    output << str.to_i

  else
    raise 'Wrong format given'
  end
end

edited Apr 8, 2018 at 14:10

answered Apr 8, 2018 at 13:42

Фил

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Comments

Cary Swoveland · Accepted Answer · 2018-04-08 17:58:20Z

1

"1,3,6-8,5".split(',').flat_map do |s|
  if s.include?('-')
    f,l = s.split('-').map(&:to_i)
    (f..l).to_a
  else
    s.to_i
  end
end.sort
  #=> [1, 3, 5, 6, 7, 8]

answered Apr 8, 2018 at 17:58

Cary Swoveland

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Comments

sawa · Accepted Answer · 2018-04-09 04:54:14Z

1

"1,3,6-8,5"
.scan(/(\d+)\-(\d+)|(\d+)/)
.flat_map{|low, high, num| num&.to_i || (low.to_i..high.to_i).to_a}
#=> [1, 3, 6, 7, 8, 5]

answered Apr 9, 2018 at 4:54

sawa

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