Find values that each subarray of an array contains

Question

I've got an Array of arrays. There can be two or more subarrays:

array = [
  ["66892885", "66891801", "66924833", "66892255"],
  ["65167829", "65167828", "66924833"],
  ["66924833", "66891801"]
]

I need only the values found across each subarray. So in this case "66924833" would be the only match. For a value to show up in the result, each subarray has to contain it.

How can I do this?

what would the return be if there are more than 2 sub arrays? — lusketeer
– lusketeer, Commented Oct 14, 2019 at 22:19
@lusketeer even if there are 10 sub arrays, I still need the shared values across all 10 — bopritchard
– bopritchard, Commented Oct 14, 2019 at 22:21
@lusketeer yes...but the way my data is configured, there will ALWAYS be a match — bopritchard
– bopritchard, Commented Oct 14, 2019 at 22:23
okay, someone already posted what I wanted to post, should work for your case — lusketeer
– lusketeer, Commented Oct 14, 2019 at 22:24

Viktor · Accepted Answer · 2019-10-15 09:21:38Z

3

You can combine inject with Array's Set Intersection (#&) method like this

array.inject(:&)

to get the desired result:

array=[["66892885", "66891801", "66924833", "66892255", "1", "33"],
       ["65167829", "65167828", "66924833", "1", "33", "44"], 
       ["2344", "66924833", "1", "33"]]

array.inject(:&)
#=>["66924833", "1", "33"]

edited Oct 15, 2019 at 9:21

answered Oct 14, 2019 at 22:22

Viktor

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1 Comment

Stefan Over a year ago

Since & has special meaning in Ruby's syntax, it might be worth noting that here :& is merely a symbol referring to the operator method Array#&. So [a, b, c].inject(:&) translates to a & b & c

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