Concatenate arrays items

Question

I have two arrays:

x = [ ["0", "#0"], ["1", "#1"] ]
y = [ ["00", "00 description"], ["10", "10 description"] ]

What i need is to merge them so i get the following as result:

result = [ ["000", "#0 00 description"], ["010", "#0 10 description"],
   ["100", "#1 00 description"], ["110", "#1 10 description"] ]

Is there a method for that? Or I'll need to use collect or something like this?

Thanks in advance.

Answer 1

In your example you seem to be applying special rules for concatenating the digits of specific decimal representations of integers, which doesn't work in any simple manner (e.g. when you write 00 it's just 0 to the interpreter). However, assuming simple string concatenation is what you meant:

x = [ ["0", "#0"], ["1", "#1"] ]
y = [ ["00", "00 description"], ["10", "10 description"] ]
z = []
x.each do |a|
  y.each do |b|
    c = []
    a.each_index { |i| c[i] = a[i] + b[i] }
    z << c
  end
end
p z

Edit: The originally posted version of the question had integers as the first elements of each sub-array, the preface to the solution refers to that. The question has since been edited to have strings as assumed here.

Answer 2

You can use Array#product method:

x = [ ['0', "#0"], ['1', "#1"] ]
#=> [["0", "#0"], ["1", "#1"]]
y = [ ['00', "00 description"], ['10', "10 description"] ]
#=> [["00", "00 description"], ["10", "10 description"]]
x.product(y).map{|a1,a2| [a1[0]+a2[0], a1[1] + ' ' + a2[1]]}
#=> [["000", "#0 00 description"], ["010", "#0 10 description"], ["100", "#1 00 description"], ["110", "#1 10 description"]]

And if you wouldn't need different kinds of concatenation above (second one is inserting space between), even:

x.product(y).map{|a1,a2|
  a1.zip(a2).map{|e|
    e.inject(&:+)
  }
}

And here's a variant without Array#product, admittedly less readable:

x.inject([]){|a,xe|
  a + y.map{|ye|
    xe.zip(ye).map{|e|
      e.inject(&:+)
    }
  }
}

Answer 3

In your example you're concatenating the first elements without spaces, but the second elements with spaces. If you can do them both the same way, this can be just:

x.product(y).map {|a,b| a.zip(b).map(&:join)}
=> [["000", "#000 description"], ["010", "#010 description"], ["100", "#100 description"], ["110", "#110 description"]]

If the different concatenations are required, this'll do:

x.product(y).map {|a,b| [a[0]+b[0],a[1]+' '+b[1]]}
=> [["000", "#0 00 description"], ["010", "#0 10 description"], ["100", "#1 00 description"], ["110", "#1 10 description"]]