给定整数n，产生所有[2n]上的匹配（matching） //将其视为一个所有块大小均为2的集合分拆 //输出格式为 a1 a2 - b1 b2 - c1 c2 - ... //满足a1<a2, b1<b2, ... //且 a1 < b1 < c1 <-given integer n, have all [2n] on the matching (matching)// will be considered as an all pieces are