occurences.rb

class Array  
  def most_popular(n = 1)
    get_occurrency_hash[n * -1].first
  end
  
  def occurrences(n = 1)
    get_occurrency_hash[n * -1].last
  end
  
  def has_duplicates?
    get_occurrency_hash.last.last > 1
  end
  
  def has_triplicates?
    get_occurrency_hash.last.last > 2
  end

  protected
  def get_occurrency_hash
    Hash.new(0).tap { |h|
      self.each { |e| h[e] += 1 }
    }.sort_by { |k, v| v }
  end
end

ary = (0...9).map{(65+rand(26)).chr} # [1, 2, 1, 2, 1]#

if ary.has_triplicates?
  puts "In #{ary} the second most popular element is \"#{ary.most_popular 2}\" (#{ary.occurrences 2} times)."
elsif ary.has_duplicates?
  puts "In #{ary} the most popular element is \"#{ary.most_popular}\" (#{ary.occurrences} times)."
else
  puts "#{ary} has not duplicate elements."
end