Sort array of string with digits and characters in ruby

Question

I have an array with the given strings

array = [
  "1mo-30-super",
  "1mo-40-classic",
  "1mo-30-classic",
  "1mo-110-super",
  "1mo-20-extra",
  "6mo-21-super",
  "6mo-11-super",
  "12mo-21-classic",
  "12mo-21-super"
]

How can I sort the array so that it goes in numerical order, then alphabetical order so the array displays like so:

array = [
  "1mo-20-extra",
  "1mo-30-classic",
  "1mo-30-super",
  "1mo-40-classic",
  "1mo-110-super",
  "6mo-11-super",
  "6mo-21-super",
  "12mo-21-classic",
  "12mo-21-super"
]

Please be more specific about sorting numerically, considering that each string begins with one or two digits and there are two or three digits between the hyphens. Similarly, what do you mean by the second sort criterion, considering that there are strings of letters in two places as well? — Cary Swoveland
– Cary Swoveland, Commented Nov 28, 2018 at 0:34
I wanted it sorted so the first section is sorted by number, then with all the ones with the same first number the second section is sorted by number, then the within those the last section is sorted alphabetically. — KBouldin9
– KBouldin9, Commented Nov 28, 2018 at 15:10

mu is too short · Accepted Answer · 2018-11-28 00:09:08Z

1

You're looking for a "natural" sort where the numeric substrings will be compared as numbers as the non-numeric parts will be compared like strings. Conveniently enough, arrays in Ruby compare element-by-element and your format is fairly regular so you can get away with a #sort_by call and a bit of mangling to convert "12mo-21-classic" to [12, 'mo-', 21, '-classic']. Something like this for example:

# This is a bit complicated so we'll give the logic a name.
natural_parts = ->(s) { s.match(/(\d+)(\D+)(\d+)(\D+)/).to_a.drop(1).map.with_index { |e, i| i.even?? e.to_i : e } }
array.sort_by(&natural_parts)

answered Nov 28, 2018 at 0:09

mu is too short

436k71 gold badges863 silver badges822 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Cary Swoveland · Accepted Answer · 2018-11-28 04:11:14Z

array.sort_by { |s| [s.to_i, s[/(?<=-)\d+/].to_i, s.gsub(/\A.+-/,'')] }
  #=> ["1mo-20-extra", "1mo-30-classic", "1mo-30-super", "1mo-40-classic", "1mo-110-super",
  #    "6mo-11-super", "6mo-21-super", "12mo-21-classic", "12mo-21-super"]

When sorting arrays the method Arrays#<=> is used to order pairs of arrays. See the third paragraph of the doc for an explanation of how that is done.

The arrays used for the sort ordering are as follows.

array.each do |s|
  puts "%-15s -> [%2d, %3d, %s]" % [s, s.to_i, s[/(?<=-)\d+/].to_i, s.gsub(/\A.+-/,'')]
end

1mo-30-super    -> [ 1,  30, super]
1mo-40-classic  -> [ 1,  40, classic]
1mo-30-classic  -> [ 1,  30, classic]
1mo-110-super   -> [ 1, 110, super]
1mo-20-extra    -> [ 1,  20, extra]
6mo-21-super    -> [ 6,  21, super]
6mo-11-super    -> [ 6,  11, super]
12mo-21-classic -> [12,  21, classic]
12mo-21-super   -> [12,  21, super]

(?<=-) is a positive lookbehind. It requires that the match be immediately preceded by a hyphen. /\A.+-/ matches the beginning of the string followed by one or more characters followed by a hyphen. Because regular expressions are by default greedy, it concludes the match on the second hyphen.

Note that it is not necessary to use regular expressions:

array.sort_by { |s| [s.to_i, s[s.index('-')+1..-1].to_i, s[s.rindex('-')+1..-1]] }

mrzasa · Accepted Answer · 2018-11-27 23:34:03Z

0

You can chain several #sort method calls, each sorting by a different part of a string (starting with one with smallest priority):

array.sort { |a,b| a.match(/-(.*)$/)[1] <=> b.match(/-(.*)-/)[1] } # sort by last element ('classic', 'super')
     .sort { |a,b| a.match(/-(\d+)-/)[1].to_i <=> b.match(/-(\d+)-/)[1].to_i } # sort by the number between dashes 
     .sort { |a,b| a.to_i <=> b.to_i  } # sort by the initial number

=> ["1mo-20-extra",
 "1mo-30-classic",
 "1mo-30-super",
 "1mo-40-classic",
 "1mo-110-super",
 "6mo-11-super",
 "6mo-21-super",
 "12mo-21-super",
 "12mo-21-classic"]

answered Nov 27, 2018 at 23:34

mrzasa

23.4k11 gold badges60 silver badges96 bronze badges

Collectives™ on Stack Overflow

Sort array of string with digits and characters in ruby

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related