http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=46279 Brief description: 给定长度为 N 的置换集合 S，|S| = M，求满足一下条件的集合 G 的最小的阶。 $$S\subset G$$ $$\forall \sigma, \tau \in G, \sigma \tau^{-1} \in G$$ Analysis: … “A subset H of the group G is a subgroup of G if and only if it is nonempty and closed un……