Dynamic intersection in Ruby Arrays

Question

I have an set of Arrays. The number of Arrays is dynamic, it could be one, could be 100. In this example it's 3:

arr = [[1,2,3,4], [2,4], [2,3,4]]

What I need as result is to find same (intersecting) value(s) from all arrays. So result should be:

#=> [2,4]

How it could be done a proper way?

Have you already looked at the simpler 2 case example? stackoverflow.com/questions/10230227/… — jkeuhlen
– jkeuhlen, Commented Jul 21, 2015 at 13:36
Sure. But my arr is dynamic as I mentioned before. It could be [[1] [1,2,3,4]] or like it the example above. — There Are Four Lights
– There Are Four Lights, Commented Jul 21, 2015 at 13:39

Jörg W Mittag · Accepted Answer · 2015-07-21 13:40:57Z

6

You can use Array#& to find the (set) intersection of arrays:

arr.inject(:&)
# => [2, 4]

answered Jul 21, 2015 at 13:38

Jörg W Mittag

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Aleksei Matiushkin · Accepted Answer · 2015-07-21 13:38:08Z

5

arr.reduce &:&
#⇒ [
#  [0] 2,
#  [1] 4
# ]

answered Jul 21, 2015 at 13:38

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