乒乓球比赛知识，你知道吗？
参加比赛的队或运动员之间轮流比赛一次，称为单循环赛。这种方法能使参加比赛的各队或运动员之间都有比赛的机会，并能比较准确地决出参赛队或运动员的名次。但单循环赛比赛时间长，需用的场地、器材多，因此参加单循环赛的队数或人数不宜过多，否则，应采用分组循环的办法来进行。
我们以7人为例来讲讲乒乓球单循环赛
第一轮
1——0
2——7
3——6
4——5
第二轮
1——7
0——6
2——5
3——4
第三轮
1——6
7——5
0——4
2——3
第四轮
1——5
6——4
7——3
0——2
第五轮
1——4
5——3
6——2
7——0
第六轮
1——3
4——2
5——0
6——7
第七轮
1——2
3——0
4——7
5——6
共需要7轮21场比赛，也就是场比赛。以上是1号位固定逆时针轮转法，它是体育比赛单循环普遍采用的方法，它的好处是选手间歇时间一致，而且不会打漏和打重复。
这里讲的是人员数为奇数时的情况，与0对应的成员轮空一场，也就是说这场为空，一共需要轮空7场。人员数为偶数时就更简单了，这里就不做详细讲解了。
总结一下，若人员数或队数为N，当N为奇数时，一共需要打N轮N(N-1)/2场比赛；当N为偶数时，一共需要打N-1轮也是N(N-1)/2场比赛。
英文翻译：
The participating teams or players take turns to compete once, which is called a single round robin. This method enables all teams or athletes participating in the competition to have a chance to compete, and can more accurately determine the ranking of the participating teams or athletes. However, the single round-robin competition takes a long time and requires a lot of venues and equipment. Therefore, the number of teams or the number of people participating in the single round-robin competition should not be too large. Otherwise, the group cycle method should be adopted.
Let’s take 7 people as an example to talk about a single round table tennis match
first round
1——0
2——7
3——6
4——5
second round
1——7
0——6
2——5
3——4
Third round
1——6
7——5
0——4
2——3
Fourth round
1——5
6——4
7——3
0——2
Fifth round
1——4
5——3
6——2
7——0
Sixth round
1——3
4——2
5——0
6——7
Seventh round
1——2
3——0
4——7
5——6
A total of 7 rounds and 21 games are required, that is, 1 game. The above is a fixed counterclockwise rotation method for the No. 1 position. It is a commonly used method for a single cycle of sports competitions. Its advantage is that the players have the same intermittent time and will not miss and repeat.
Here is the situation when the number of personnel is an odd number. The member corresponding to 0 has a bye, that is to say, this is empty, and a total of 7 byes are required. It is even simpler when the number of personnel is even, so I wont explain it in detail here.
To sum up, if the number of personnel or the number of teams is N, when N is an odd number, a total of N rounds of N(N-1)/2 games need to be played; when N is an even number, a total of N-1 rounds need to be played also N( N-1)/2 games.
参考资料：百度；
英文翻译来源于Google翻译；
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