Editorial code is wrong, if you try this input:

3
8
1 1 2 2 3 3 6 6
8
6 6 1 1 3 3 2 2
8
1 6 6 1 2 2 3 3

All of sets are the same(items in different order), and you will get 3, 2, 0, output! The code doesn't check all possible partitions:

(6, 6) or (3, 3, 2, 2, 1, 1) vs
(6, 3, 3) or (6, 2, 2, 1, 1) vs
(6, 3, 2, 1) or (6, 3, 2, 1) vs

Also it failse in this case:

1
5
3 4 5 6 8 

It outputs 0, instead of 1, (3,4,6),(5,8) The problem seems to be NP-Hard, so I don't think there is any optimal solution.