CODEWITHSUNDEEP
arraysruby
Exodus Reed
Exodus Reed

Reputation: 307

how to sort an array of strings and integers to show sorted integers first in ruby

I have an array containing integer values and string type characters as such _

Here is my array array = ["_", 2, 3, "_"] how can I sort them such that it returns like the following: [2, 3, "_", "_"] I have tried to sort it with the ruby .sort() method but it appears as if sort() does not compare integers with strings and therfore returns an error.

is there a ruby method I am not aware of? Any help or guidance is highly appreciated.

Upvotes: 1

Views: 125

Answers (1)

dawg
dawg

Reputation: 103864

The problem is you can't compare a string to an integer:

> 2<"2"
(irb):15:in `<': comparison of Integer with String failed (ArgumentError)

The fix (with your specific example) is to make array act as if it is all strings.

Given:

array = ["_", 2, 3, "_"]

If you just want the result to be a uniform string array:

> array.map{|e| e.to_s}.sort
=> ["2", "3", "_", "_"]

If you want the elements to maintain their type:

> array.map{|e| [e.to_s, e]}.sort.map{|e| e[1]}
=> [2, 3, "_", "_"]

Or, alternatively:

> array.sort_by{|e| e.to_s}
=> [2, 3, "_", "_"]

The potential issue here is that if you rely solely on a conversion to a string (which solved the example you gave) you will get a bad result with integers:

> array = ["10", 12, 3, "0", "b", "a"]
=> ["10", 12, 3, "0", "b", "a"]
> array.sort_by{|e| e.to_s}
=> ["0", "10", 12, 3, "a", "b"]   # desirable?

Which is not entirely solvable by using .to_i:

> array.sort_by{|e| e.to_i}
=> ["0", "b", "a", 3, "10", 12]   # fixed?

Which maybe is best solved by sorting on both:

> array.sort_by{|e| [e.to_i, e.to_s]}
=> ["0", "a", "b", 3, "10", 12]

Luckily Ruby makes it super easy to choose.

Note, .sort_by or the other enumerable sorts are not a stable sort so elements that compare equal are potentially returned in different order than given:

> array=[1,2,3,4,5,6,7,8,9]
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]
> array.sort_by{|e| 0}  # make them all compare equal 
=> [9, 2, 3, 4, 5, 6, 7, 8, 1]

To fix that now, add an index:

> array.each_with_index.sort_by{|e,i| [0,i]}.map(&:first)
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]

Or, as pointed out in comments:

> array.sort_by.with_index { |e, i| [0, i] }
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]

Upvotes: 3

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