Flatten

flatten.rb

class Flatten
  def run(params = [])
    result = []
    params.each do |value|
      if value.is_a?(Array)
        result = result | run(value)
      else
        result = result << value
      end
    end
    result
  end
end

flatten_spec.rb

require 'rspec'
require_relative 'flatten'

describe 'Flatten' do
  let(:array) { [[1,2,[3]],4] }

  it 'flattens the array' do
    result = Flatten.new.run(array)
    expect(result).to eq([1,2,3,4])
  end
end