Dupli.rb

def dupli (d)

    uniqDups = d.uniq
    dups = Array.new
    uniqDups.each { |e|
        if d.grep(e).size > 1
            dups.push(e)
        end
    }
    return dups
end
dup = 'aaabbbcccccccccdddde'
p dupli(dup.split(""))