ruby: how to find non-unique elements in array and print each with number of occurrences?

Question

I have

a = [\"a\", \"d\", \"c\", \"b\", \"b\", \"c\", \"c\"]

and need to print something like (sorted descending by number of occurrences)

Answer 1

How about:

a.sort.chunk{|x| a.count(x)}.sort.reverse.each do |n, v|
  puts "#{v[0]}:#{n}" if n > 1
end

Answer 2

I personally like this solution:

 a.inject({}) {|hash, val| hash[val] ||= 0; hash[val] += 1; hash}.
   reject{|key, value| value == 1}.sort.reverse.
   each_pair{|k,v| puts("#{k}:#{v}")}