flats_ranking.rb

def euclidean_distance(flat, target, criteria)
  sum_of_squares = criteria.sum do |criterion|
    (flat[criterion] - target[criterion]) ** 2
  end
  Math.sqrt(sum_of_squares)
end

def rank_flats(flats, target)
  criteria = target.keys

  flats_with_proximity = flats.map do |flat|
    proximity = euclidean_distance(flat, target, criteria)
    { flat: flat, proximity: proximity }
  end

  flats_with_proximity.sort_by { |flat| flat[:proximity] }
end

flats = [
  { id: 1, price: 20, size: 40, location: 5 },
  { id: 2, price: 40, size: 60, location: 8 },
  { id: 3, price: 60, size: 80, location: 7 },
  { id: 4, price: 70, size: 100, location: 6 }
]

target = { price: 45, size: 75 }

puts rank_flats(flats, target)