Non-unique Elements

Non-unique Elements

If you have 50 different plug types, appliances wouldn't be available and would be very expensive. But once an electric outlet becomes standardized, many companies can design appliances, and competition ensues, creating variety and better prices for consumers.
-- Bill Gates

You are given a non-empty sequence of integers. For this task, you should return Array consisting of only the non-unique elements from the initial sequence. To do so you will need to remove all unique elements (elements which are contained in a given sequence only once). When solving this task, do not change the order of the elements. Example: in [1, 2, 3,...

You should be an authorized user in order to see the full description and start solving this mission.
19