Finding elements repeating in many arrays in Rails

Question

I have problem with comparing many arrays in one array. I need to get element which exists in every array. It's look like this one:

array= [[11,12,13,14],[55,66,13],[13,15,17,22,34],[4,6,8,13]]

I need to get only: 13 - because its on every array, how to get it ?

https://docs.ruby-lang.org/en/2.0.0/Array.html#method-i-26 – Brad Werth Jul 25 '18 at 15:32 — Brad Werth, Jul 25 '18 at 15:32

score 5 · Answer 1 · answered Jul 25 '18 at 15:36

5

This should work

a.inject(:&)

answered Jul 25 '18 at 15:36

Nithin

3,679
3
30
55

score -1 · Answer 2 · answered Jul 25 '18 at 17:57

You could use inject as mentioned by Nithin in another answer.

Another option is to use reduce:

ary = _
 => [
      [11, 12, 13, 14],
      [55, 66, 13],
      [13, 15, 17, 22, 34],
      [4, 6, 8, 13]
    ]

ary.reduce(:&)
 => [13]

# which is a short-hand for:
ary.reduce { |out, elem| out & elem }
 => [13]

Finding elements repeating in many arrays in Rails

2 Answers2