Sort Ruby String Array by the number in the string

Question

If I have a string array that looks like this:

array = ["STRING1", "STRING05", "STRING20", "STRING4", "STRING3"]

or

array = ["STRING: 1", "STRING: 05", "STRING: 20", "STRING: 4", "STRING: 3"]

How can I sort the array by the number in each string (descending)?

I know that If the array consisted of integers and not strings, I could use:

sort_by { |k, v| -k }

I've searched all around but can't come up with a solution

Please clarify whether the numbers can have more than a single digit. If 'yes' I suggest you indicate that by simply changing the example to include at least one number greater than 9. If 'no', array.sort_by(&:reverse).reverse also works. — Cary Swoveland
– Cary Swoveland, Commented Mar 18, 2014 at 1:22
Thanks @CarySwoveland! I see what you mean, good to know that works. — user3127502
– user3127502, Commented Mar 18, 2014 at 2:29

bjhaid · Accepted Answer · 2014-03-18 01:22:55Z

23

The below would sort by the number in each string and not the string itself

array.sort_by { |x| x[/\d+/].to_i }
=> ["STRING: 1", "STRING: 2", "STRING: 3", "STRING: 4", "STRING: 5"]

descending order:

array.sort_by { |x| -(x[/\d+/].to_i) }
=> ["STRING: 5", "STRING: 4", "STRING: 3", "STRING: 2", "STRING: 1"]

edited Mar 18, 2014 at 1:22

answered Mar 18, 2014 at 0:59

bjhaid

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3 Comments

Gareth Over a year ago

Remember to convert this to an integer otherwise you'll get unexpected ordering when 1-digit numbers are compared to 2-digit numbers

Cary Swoveland Over a year ago

bjhaid, it's now hard to choose between your answer and @xdazz's. :-)

bjhaid Over a year ago

@CarySwoveland well I did provide the answer with the main idea first (4 minutes earlier than xdazz's) and modification came after the comments, it's the concept behind it that really matters, the remaining changes are obvious, you can check my edit history to confirm that

xdazz · Accepted Answer · 2014-03-18 01:02:38Z

3

sort the array by the number in each string (descending)

array.sort_by { |x| -x[/\d+/].to_i }

answered Mar 18, 2014 at 1:02

xdazz

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