Hash#smash

gistfile1.rb

class Hash
  def smash(prefix = nil)
    inject({}) do |acc, (k, v)|
      key = prefix.to_s + k
      if Hash === v
        acc.merge(v.smash(key + '-'))
      else
        acc.merge(key => v)
      end
    end
  end
end

hash = {
  'f' => 100,
  'z' => {'j' => 25},
  'a' => {'b' => {'c' => 1}}
}

puts hash.smash # => {"f"=>100, "z-j"=>25, "a-b-c"=>1}