Inserting an array into every nth element of another

Question

I have 2 arrays:

[\'a\', \'b\', \'c\', \'d\', \'e\', \'f\']
[\'g\', \'h\', \'i\']

I need to insert elements of second array after every sec

Answer 1

a=['a', 'b', 'c', 'd', 'e', 'f']
b=['g', 'h', 'i']
b.each.with_index(1) { |e,i| a.insert((3*i)-1,e) }

a
#=> ['a', 'b', 'g', 'c', 'd', 'h', 'e', 'f', 'i']

Answer 2

Something like this:

a = ['a', 'b', 'c', 'd', 'e', 'f']
b = ['g', 'h', 'i']
a.each_slice(2). # => [["a", "b"], ["c", "d"], ["e", "f"]]
  zip(b). # => [[["a", "b"], "g"], [["c", "d"], "h"], [["e", "f"], "i"]]
  flatten # => ['a', 'b', 'g', 'c', 'd', 'h', 'e', 'f', 'i']

Answer 3

You can always use a custom Enumerator:

a1 = ['a', 'b', 'c', 'd', 'e', 'f']
a2 = ['g', 'h', 'i']

enum = Enumerator.new do |y|
  e1 = a1.each
  e2 = a2.each
  loop do
    y << e1.next << e1.next << e2.next
  end
end

enum.to_a #=> ["a", "b", "g", "c", "d", "h", "e", "f", "i"]

Or for the general case:

n.times { y << e1.next }