Ruby Extract array from multi-dimensional array

Question

I have a multidimensional array like:

arr1 = [["text1", 1], ["text2", 2], ["&nbsp;&nbsp;&nbsp;&nbsp;text3", 3], ["&nbsp;&nbsp;&nbsp;&nbsp;text4", 4], ["text5", 5], ["text6", 6], ["text7", 7]]

and another

arr2 = [2,3,6]

I want to extract entire array if it contains elements of arr2. So, result should be:

arr = [["text2", 2], ["&nbsp;&nbsp;&nbsp;&nbsp;text3", 3], ["text6", 6]].

I've tried many ways but unable to get the result. Attempts such as:

arr1.each { |elem| arr2.each { |x| elem.delete_if{ |u| elem.include?(x) } } }

and

arr2.map { |x| arr1.map{|key, val| val.include?(x) }}

Can anyone please help?

Ursus · Accepted Answer · 2017-02-17 18:09:06Z

3

Try this one

arr1.select { |a| a.any? { |item| arr2.include? item } }
 => [["text2", 2], ["&nbsp;&nbsp;&nbsp;&nbsp;text3", 3], ["text6", 6]]

answered Feb 17, 2017 at 18:09

Ursus

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1 Comment

Stefan Dorunga Over a year ago

I prefer this or the first comment of the accepted answer as it is more clearly related to what the code is trying to do, i.e. finding something.

Aleksei Matiushkin · Accepted Answer · 2017-02-17 18:10:39Z

1

arr1.select { |(_, d)| arr2.include? d }

answered Feb 17, 2017 at 18:10

Aleksei Matiushkin

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3 Comments

Andrey Deineko Over a year ago

Not very generic solution - having the position of integer in an array changed it will fail, as well as having the arr2 changed will make this solution invalid :) P.S. I know you know

Aleksei Matiushkin Over a year ago

@AndreyDeineko I am not sure I follow. I believe those are dumped elements with ids in arr1 and ids themselves in arr2. It will also fail on non-unique multiple values in arr2 etc, but for the stated question this solution is robust enough.

Andrey Deineko Over a year ago

Whatever those are, the question/request is I want to extract entire array if it contains elements of arr2, which your solution does not satisfy given the input data slightly changed. Even though with the provided examplary input it does solve it. arr1 = [[1, "text1"], [2, 'text'], [5, "text5"], [6, "text6"], [7, "text7"]], which with your solution will result in [], while it should result in [[2, "text"], [6, "text6"]]

Andrey Deineko · Accepted Answer · 2017-02-17 19:09:52Z

0

arr1.inject([]) { |result, array| (array & arr2).any? ? result << array : result }
#=> [["text2", 2], ["&nbsp;&nbsp;&nbsp;&nbsp;text3", 3], ["text6", 6]]

Slightly shorter and more correct from the goal perspective:

arr1.select { |array| (array & arr2).any? }

edited Feb 17, 2017 at 19:09

answered Feb 17, 2017 at 18:09

Andrey Deineko

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2 Comments

mu is too short Over a year ago

Why not arr1.select { |a| (a & arr2).any? } or arr1.find_all { |a| (a & arr2).any? } since you are selecting/finding things rather than a more general injection/reduction?

Andrey Deineko Over a year ago

@muistooshort selecting is definitely better than building a new array (which I did), I'll edit the answer (i did not do that before because solutions with select were already given)..

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