How to draw basketball in lottery games?

The upper part of 1-8 and the lower part of 9- 18. Draw lots first, 1- 18, and then the two teams play. Whether it is 1 and 2 or 1 and18,2 and 17 can be arranged by yourself. There are nine teams left, two more teams will be drawn and one team will be eliminated. For example, 1 vs 2, 3 vs 4, the winners of these two teams can be arranged to play another game. This is relatively fair, because drawing lots is your luck. Hehe, there are eight teams left in the end, and then two teams and two teams. By analogy, only the winning teams in the upper half and the lower half will enter the final. Do it. Ha ha. Understand? You can draw a tree diagram yourself. I just finished the lottery in our school. Hmm. How interesting