"Overlap" of two arrays

array_overlap.rb

require 'minitest/autorun'

class Array
  def max_overlap(a)
    clone = self.clone

    a.each do |n|
      if clone.index(n)
        clone.delete_at(clone.index(n))
      end
    end

    (a + clone).sort
  end

  def min_overlap(a)
    self_uniq = self.uniq

    a_uniq = a.uniq

    r = []

    self_uniq.each do |n|
      count = [self.count(n), a.count(n)].min

      if count == 0
        count = [self.count(n), a.count(n)].max
      end

      count.times do
        r << n
      end

      a_uniq.delete(n)
    end

    a_uniq.each do |n|
      count = [self.count(n), a.count(n)].min

      if count == 0
        count = [self.count(n), a.count(n)].max
      end

      count.times do
        r << n
      end
    end

    r.sort
  end
end

describe Array do
  before do
    @x = [2, 3, 4, 5, 5, 6, 6, 7, 8, 8, 8, 8]

    @y = [2, 2, 3, 8, 8, 11]
  end

  describe '#max_overlap' do
    it 'should find the maximum overlap of two arrays' do
      @x.max_overlap(@y).must_equal [2, 2, 3, 4, 5, 5, 6, 6, 7, 8, 8, 8, 8, 11]
    end

    it 'should be the same either way' do
      @x.max_overlap(@y).must_equal @y.max_overlap(@x)
    end
  end

  describe '#min_overlap' do
    it 'should find the minimum overlap of two arrays' do
      @x.min_overlap(@y).must_equal [2, 3, 4, 5, 5, 6, 6, 7, 8, 8, 11]
    end

    it 'should be the same either way' do
      @x.min_overlap(@y).must_equal @y.min_overlap(@x)
    end
  end
end