Question

I have an array:

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

And more arrays:

b =[[1,2,3], [1,1,4], [7,3,4], [1,5,6,1]]

For each element in b, b_i, I want to know:

• is there some b_i such that a & b_i == b_i, and
• what is that b_i

This is what I am thinking

def get_matching(a, b)
   b.each {|b_i|
      return b_i if (a & b_i) == b_i
   }
end

Where can I check whether the return value is nil or not to determine the answer to the first question? Though, maybe I can implement them as two separate functions so that checking whether such a matching exists doesn’t need to actually return the matching.

Assume I only need the first matching if there are many.

Is there a more efficient way to do this?

Answer 1

This is probably not any more efficient but it is a little more ruby-esque using Enumerable#detect

def get_matching(a, b)
  b.detect{ |b_i| (a & b_i) == b_i }
end