Intersecting non-empty arrays

Question

I have three arrays I want to intersect, but I want to ignore the ones that are empty.

This code seems too verbose. Is there a more efficient approach?

if a.empty? && b.empty?
  abc = c
elsif a.empty? && c.empty?
  abc = b
elsif b.empty? && c.empty?
  abc = a
elsif a.empty?
  abc = b & c
elsif b.empty?
  abc = a & c
elsif c.empty?
  abc = a & b
else
  abc = a & b & c
end

I assumed so and edited. I also assumed that a, b and c are arrays that may or may not me empty. — edgerunner
– edgerunner, Commented Nov 10, 2012 at 18:14

edgerunner · Accepted Answer · 2012-11-10 18:29:35Z

11

How about

abc = [a,b,c].reject(&:empty?).reduce(:&)

The first part, [a,b,c] puts your arrays in an array. The second bit with reject runs empty? on every element and rejects it if the result is true, returning an array of arrays where the empty arrays are removed. The last part, reduce runs the equivalent of your a & b & c but since we discarded all empty arrays in the previous step, you don't end up with an empty result.

edited Nov 10, 2012 at 18:29

answered Nov 10, 2012 at 18:12

edgerunner

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Comments

Cary Swoveland · Accepted Answer · 2013-10-19 22:08:53Z

0

A little late to the party...

a = [1,3,4,5]
b = []
c = [2,3,5,6]

t = a | b | c # => [1, 3, 4, 5, 2, 6]
[a,b,c].map {|e| e.empty? ? t : e}.reduce(:&) # => [3, 5]

answered Oct 19, 2013 at 22:08

Cary Swoveland

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