TOP bubble sort assignment

bubble_sort.rb

def bubble_sort(arr)
  # drop ignores previous sorted elems
  arr.each_with_index do |dum, drop_i|
    arr.drop(drop_i).each_with_index do |elem, i|
      if arr[i+1] != nil && arr[i] > arr[i + 1]
        temp = arr[i] 
        arr[i] = arr[i+1]
        arr[i+1] = temp
      end
    end
  end 
  return arr
end

puts bubble_sort([4,3,78,2,0,2]).inspect