参见博客：[点这里](https://www.luogu.org/blog/70177/wan-quan-bei-bao-wen-ti-fei-gun-dong-shuo-zu-post)
里面解释的很详细
by big_news @ 2018-03-11 20:05:22
顺序不一样......
这个是顺着循环......
by Armand @ 2018-05-19 06:18:36