[gecode-users] How to construct constraints which count distinct values?

[Jeffrey]

I'm trying to assign n number of students into 3 groups.
each student is teach by a certain instructor.

I'd like to evenly distributed the students into the groups (assume the total no. of student is divisible by the 3 groups.)
Given an array where the 1st element holds the instructor (in enum) of the 1st student and so on...

How should I model the constratint to enforce that:
     for each group, the total no. of distinct instructors are the same.

?? Big Big thanks!



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