median.rb

# original solution in ruby tapas 150

class Median

  def self.avdi(list)
    sorted = list.sort
    q, r = sorted.size.divmod(2)
    middle = sorted[q - 1 + r, 2 - r]
    middle.reduce(:+) / middle.size
  end

  def self.jed(list)
    list = list.sort
    length = list.size / 2
    # create two arrays one going up one going down
    last_half = list.slice(length..-1).reverse
    first_half = list.take(length)
    # tuples are the complimentary positions in each array
    tuples = last_half.zip(first_half)
    # the last tuple either has [number, nil] or [number, number]
    # we abstract away the conditional using list processing
    res = tuples.last.compact
    res.reduce(:+) / res.length
  end
end

arr1 = [1,2,3,4,5,6,7,8,9]
arr2 = [1,2,3,4,5,6,7,8,9,10]

puts Median.jed(arr1)
puts Median.avdi(arr1)
puts Median.jed(arr2)
puts Median.avdi(arr2)