AK
arr.Where(x => arr.Where(y => x == y).Count() == 1).Count()
Size: a a a
AK
SB
arr.Where(x => arr.Where(y => x == y).Count() == 1).Count()
arr.Select(x=>x).Distinct().Count();
AM
arr.Select(x=>x).Distinct().Count();
S1
AM
SB
SB
ЕА
arr.Select(x=>x).Distinct().Count();
AM
AM
SB
МР
МР
МР
МР
arr.Select(x=>x).Distinct().Count();
МР
AM
AM