Interview Question

flatten.rb

#!/usr/bin/env ruby

# the custom flatten function 
#
# This function will flatten an array.
#
# param 1: the base array to add data to
# param 2: the array to be flattened
def flatten(array, items)
  # iterate through each item in the array to be flattened
  items.each do |item|
    if item.kind_of?(Array)
      # if the item is an array, recursively call the 
      # flatten fuction
      array = flatten(array, item)
    else
      # if the item is not an array, just add it to the base array
      array << item
    end
  end
  
  # return the array
  array
end

# the input array
input = [[1,2,[3]],4]

# call the function
output = flatten([], input)

# print out result
puts output