array_flatten.rb

# I tried to avoid as many Ruby-isms as possible for this assignment, including
# Ruby's unique Array methods and Ruby's functional concepts...as I thought
# this got to the "heart" of the assignment.  I figure *most* languages
# support basic iteration and recursion and some method of adding an element
# to an array.  The one possible outlier here is using Ruby's splat operator.
# I'm not sure if this violates the intent of the assignment or not.  Also,
# since Minitest was removed from Ruby core, I just did some more basic tests.
#
# Additionally, the assignment mentioned flattening an array of integers, so
# I did not include a bunch of nil and type checks for input.

def andy_flatten(arr)
  flattened_array = []
  for i in 0..(arr.length - 1)
    element = arr[i]
    if element.is_a?(Array)
      flattened_array.push(*andy_flatten(element))
    else
      flattened_array.push(element)
    end
  end
  flattened_array
end

def assert_equal(expected, actual)
  raise "Expected: #{expected} does not == Actual: #{actual}" unless expected == actual
end

assert_equal andy_flatten([1]), [1]
assert_equal andy_flatten([1,2,3]), [1,2,3]
assert_equal andy_flatten([1,2,[3,4]]), [1,2,3,4]
assert_equal andy_flatten([1,2,[3,[4,5]]]), [1,2,3,4,5]