#!/usr/bin/env ruby
 
class CharsRepeat
  def self.number_of_repeaters string
    chars = Hash.new 0
    string.each_char { |char| chars[char] += 1 }
    chars.select { |char,count| count > 1 }
  end
end
 
p CharsRepeat.number_of_repeaters 'teestting'