algorithms.rb

def insertion_sort(collection)
  collection.count.times do |i|
    index = i
    next if index.zero?
    right_value = collection[i]

    while index > 0
      index -= 1
      left_value = collection[index]
      if right_value < left_value
        collection[index] = right_value
        collection[i] = left_value
        next
      end
    end
  end

  collection
end

def selection_sort(source_collection)
  new_collection = [source_collection.first]

  source_collection.each.with_index do |number, index|
    next if index.zero?

    didInsert = false

    new_collection.each.with_index do |new_collection_number, i|
      if number <= new_collection_number
        new_collection.insert(i, number)
        didInsert = true
        break
      end
    end

    new_collection.push(number) unless didInsert
  end

  return new_collection
end

def bubble_sort(collection)
  isUnsorted = true

  while isUnsorted
    isUnsorted = false
    collection.count.times do |i|

      left_value = collection[i]
      right_value = collection[i + 1]

      if left_value && right_value && left_value > right_value
        collection[i] = right_value
        collection[i + 1] = left_value
        isUnsorted = true
      end
    end
  end

  collection
end

if __FILE__ == $0
  require 'minitest/spec'
  require 'minitest/autorun'

  describe 'algorithms' do
    let(:collection) { 1000.times.map { rand(1000) } }

    describe "insertion_sort" do
      it 'correctly sorts' do
        insertion_sort(collection).must_equal collection.sort
      end
    end

    describe "bubble_sort" do
      it 'correctly sorts' do
        bubble_sort(collection).must_equal collection.sort
      end
    end

    describe "seleciton_sort" do
      it 'correctly sorts' do
        selection_sort(collection).must_equal collection.sort
      end
    end
  end
end