Ruby: Get all keys in a hash (including sub keys)

Question

let\'s have this hash:

hash = {\"a\" => 1, \"b\" => {\"c\" => 3}}
hash.get_all_keys 
=> [\"a\", \"b\", \"c\"]

how can i get all key

Answer 1

def get_all_keys(hash)
  hash.map do |k, v|
    Hash === v ? [k, get_all_keys(v)] : [k]
  end.flatten
end