Serpentine system

The serpentine system (also called snake seeding) is a method employed in the organization of a competition to define the seeded teams and arrange them in pools. The n ranked teams that will be involved in the tournament are distributed in m pools according to the following algorithm:

Pool 1	Pool 2	. . .	Pool m − 1	Pool m
1	2	. . .	m − 1	m
2m	2m − 1	. . .	m + 2	m + 1
2m + 1	2m + 2	. . .	3m − 1	3m
...

For instance, 12 teams would be organized in four-team pools, according to the serpentine system, as follows:

Pool 1	Pool 2	Pool 3
1	2	3
6	5	4
7	8	9
12	11	10

To improve competitivity, this method is sometimes used in conjunction with the drawing of lots method: the serpentine system is used only for some of the teams involved in a competition ("seeds"); the rest are distributed in pools following a drawing of lots.