How do I find keys in my hash to map to elements t

Question

I have a hash that maps integers to arrays. For example

{1 => ["abc"], 2 => ["ccc", "ddd"]}

How do I get all the keys from my hash that have arrays with at least 2 elements in them?

Answer 1

{1 => ["abc"], 2 => ["ccc", "ffffd"]}.select{|_, a| a.length > 1}.keys
# => [2]

Answer 2

One more possible solution :)

{1 => ["abc"], 2 => ["ccc", "ffffd"]}.map { |k, v| k if v.size > 1 }.compact
# => [2]

Answer 3

Anything like this?

hash.each_key.select { |key| hash[key].count >= 2 }