Multiple random distrubution of a list without repetetion

[Bangeel]

Hi every body....
I work in a college were students are randomly distributed into groups every block (block=2 months)...
i made a simple VBA code for this but I've faced a problem: by chance, some students were distributed into the same group more than once e.g. student who is in groups 3 still in the same groups next block which in unacceptable.
can anybody Help Me.....

 

[Bangeel]

Hi every body....
I work in a college were students are randomly distributed into groups every block (block=2 months)...
i made a simple VBA code for this but I've faced a problem: by chance, some students were distributed into the same group more than once e.g. student who is in groups 3 still in the same groups next block which in unacceptable.
can anybody Help Me.....

N.B: here is the file a made: http://ifile.it/mxfgi4a

 

[energman58]

If this is a no-one can sit with the same person twice problem it gets very hard very quickly - depending on how far back the rule goes. There is a whole literature on the mathematics around it!

If you are only interested in two or three turns then you can do it by setting up a matrix for each table which determines who is available based on previous events and then picking the group members one at a time and updating your matrix each time (as your availability matrix gets smaller and smaller very quickly as it excludes everyone who has been with anyone in the group). This gets very hard as it gets bigger.

You will find that - depending on how restrictive your rules are - that the combinations become impossible and you have to keep trying until you fnd a combination that works.