13 How to arrange basketball matches in groups and cycles?

1, draw lots and divide into two groups, with 6 or 7 teams in each group, and then do a single cycle. The top two in each group, A 1-B2 and B 1-A2.

2. Divide the draw into 4 groups, with 3 or 4 teams in each group, and then make a single cycle. The top two players in each group qualify, namely A 1-B2, B 1-A2, C 1-D2 and D 1-C2.