Implement heap sort in ruby

max_heap_sort.rb

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

module MaxHeapSort
  extend self

  @heap = Array.new
  @sorted = Array.new

  def create_heap(arr)
    arr.each_with_index { |num, index| insert(index, num) }
    @heap
  end

  def insert(index, node)
    @heap[index] = node
    bubble_up(index)
  end

  def bubble_up(index)
    parent_index = (index - 1) / 2
    child_index = index
    return if child_index.zero?

    if @heap[child_index] > @heap[parent_index]
      swap(parent_index, child_index)
      bubble_up(parent_index)
    end
  end

  def swap(parent_index, child_index)
    @heap[child_index], @heap[parent_index] = @heap[parent_index], @heap[child_index]
  end

  def extract_min
    while @heap.length > 0
      @sorted << @heap.first
      swap(0, @heap.length - 1)
      @heap.delete_at(@heap.length - 1)
      sink_down(0)
    end
    @sorted
  end

  def sink_down(parent_index)
    biggest_index = parent_index
    left_child = 2 * parent_index + 1
    right_child = 2 * parent_index + 2

    biggest_index = left_child if @heap[left_child] && @heap[left_child] > @heap[biggest_index]
    biggest_index = right_child if @heap[right_child] && @heap[right_child] > @heap[biggest_index]

    return if biggest_index == parent_index

    swap(parent_index, biggest_index)
    sink_down(biggest_index)
  end

  def sort(arr)
    puts '------------------------------MAX HEAP SORT O(nlogn)--------------------------'
    print create_heap(arr)
    puts ''
    print extract_min
    puts ''
  end
end


MaxHeapSort.sort([3,7,8,4,10,16,2,1,12])