Duplicate elements of array in ruby

Question

I find a lot of reference about removing duplicates in ruby but I cannot find how to create duplicate.

If I have an array like [1,2,3] how can I map it to a

Answer 1

Try this one

[1, 2, 3].flat_map { |i| [i, i] }
 => [1, 1, 2, 2, 3, 3]