Round Robin Tournament Scheduling

### Modified round robin, 11 teams, 1 triple ea round

ndodge · 5 · 4262

#### ndodge

• Newbie
• Posts: 20
on: July 27, 2017, 01:24:19 AM
I am running a volleyball tournament where I have a lot of nets, enough to do a full round robin of 11 teams where 10 of the teams are playing each time and 1 sitting.  However, there is a volleyball variant called tri-ball where two nets separate 3 teams.  I'd like to add this and have 3 teams playing this each round, and the other 8 teams playing against each other on the other courts, with normal 2 teams per court.

I was hoping to take a standard 11 team round robin schedule, and for each round, pull 2 teams off the schedule to play tri-ball along with the team that otherwise would have had a bye.  If I do this each round in a balanced fashion, I believe that everyone would play tri-ball 3 times.  I tried, by hand, to pull 2 teams off of the standard round robin schedule in each round so that each team got pulled off twice total, but I can't seem to pick the right pairs from the standard schedule so every team gets pulled off only twice.

Is this easy to do programmatically ?

#### wbport

• Senior Member
• Posts: 129
Reply #1 on: July 27, 2017, 07:18:18 AM
This shows how the RR actually works.  Chose "By board number" with 12 opponents--the one playing 12 and another board you choose (and keep constant) would do the tri-ball. rrpair.htm

#### Ian Wakeling

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Reply #2 on: July 27, 2017, 09:24:54 AM
That works, but does not consider the number of times teams play each other.  If the one playing 12 plays with the two teams in the next column, then the pairs (1 6) & (1 7) both play one standard game and two tri-ball games against each other.  No matter which column you choose similar problems will arise.   It would be nice if no pair of teams plays together more than twice, but I am not sure how to do this.
« Last Edit: July 27, 2017, 09:25:44 AM by Ian »

#### Ian Wakeling

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Reply #3 on: July 27, 2017, 10:56:35 AM
I had some inspiration and think the solution below will work well.  From the perspective of one team,  all 8 normal volleyball opponents are unique, and all 6 tri-ball opponents are unique.   Of course there are only 10 possible opponents so there must be overlap, therefore each team will oppose 4 of the other teams twice, once as a normal opponent and once as a tri-ball opponent.

`( 4  6)  ( 8 11)  (10  5)  ( 2  1)  ( 3  7  9)( 5  7)  ( 9  1)  (11  6)  ( 3  2)  ( 4  8 10)( 6  8)  (10  2)  ( 1  7)  ( 4  3)  ( 5  9 11)( 7  9)  (11  3)  ( 2  8)  ( 5  4)  ( 6 10  1)( 8 10)  ( 1  4)  ( 3  9)  ( 6  5)  ( 7 11  2)( 9 11)  ( 2  5)  ( 4 10)  ( 7  6)  ( 8  1  3)(10  1)  ( 3  6)  ( 5 11)  ( 8  7)  ( 9  2  4)(11  2)  ( 4  7)  ( 6  1)  ( 9  8)  (10  3  5)( 1  3)  ( 5  8)  ( 7  2)  (10  9)  (11  4  6)( 2  4)  ( 6  9)  ( 8  3)  (11 10)  ( 1  5  7)( 3  5)  ( 7 10)  ( 9  4)  ( 1 11)  ( 2  6  8)`

#### ndodge

• Newbie
• Posts: 20
Reply #4 on: July 28, 2017, 12:00:49 AM
Thank you, this will work perfectly.