upwork_test.rb

require 'rspec'

class Stats
  def self.mean(array)
    array.inject(:+) / array.size.to_f
  end

  def self.median(array)
    mid = array.length / 2
    sorted = array.sort
    array.length.odd? ? sorted[mid] : (sorted[mid] + sorted[mid - 1]) / 2.0
  end
end

class Sorter
  def self.quick_sort!(elems)
    sort(elems, 0, elems.length - 1)
  end

  private

  def self.partition(elems, left, right)
    x = elems[right]
    i = left - 1
    for j in left..right - 1
      if elems[j] <= x
        i += 1
        elems[i], elems[j] = elems[j], elems[i]
      end
    end
    elems[i + 1], elems[right] = elems[right], elems[i + 1]
    i + 1
  end

  def self.sort(elems, left, right)
    if left < right
      pivot = partition(elems, left, right)
      sort(elems, left, pivot - 1)
      sort(elems, pivot + 1, right)
    end
    elems
  end
end


RSpec.describe 'Test' do
  let(:array) { [5, 3, 2, 1, 4] }

  describe Sorter do
    describe '#quick_sort!' do
      it 'sorts using quick sort algorithm' do
        expect(Sorter.quick_sort!(array)).to eq [1, 2, 3, 4, 5]
      end
    end
  end

  describe Stats do
    describe '#mean' do
      it 'returns the mean' do
        expect(Stats.mean(array)).to eq(3.0)
      end
    end

    describe '#median' do
      it 'returns the median' do
        expect(Stats.median(array)).to eq(3.0)
      end
    end
  end
end