Implement merge sort in ruby

merge_sort.rb

# Algorithms: https://www.geeksforgeeks.org/merge-sort/

def merge_sort(array)
    return array if array.length <= 1

    mid = (array.length / 2)
    left = merge_sort(array[0..mid - 1])
    right = merge_sort(array[mid..-1])
    merge(left, right)
  end

  def merge(left, right)
    print "#{left} --- #{right}\n"
    if left.empty?
      right
    elsif right.empty?
      left
    elsif left[0] < right[0]
      [left[0]] + merge(left[1..left.length], right)
    else
      [right[0]] + merge(left, right[1..right.length])
    end
  end
  
  puts '------------------------------MERGE SORT SORT O(nlogn)--------------------------'
  print merge_sort([3,7,8,4,10,16,2,1,12])