How to find duplicates in a list?

Question

I have a list of unsorted integers and I want to find those elements which have duplicates.

val dup = List(1,1,1,2,3,4,5,5,6,100,101,101,102         


        

Answer 1

A bit late to the party, but here's another approach:

dup.diff(dup.distinct).distinct

diff gives you all the extra items above those in the argument (dup.distinct), which are the duplicates.