Permutation Partitions CodeForces - 1326C(组合数学+思维)
Youaregivenapermutationp1,p2,…,pnofintegersfrom1tonandanintegerk,suchthat1≤k≤n.Apermutationmeansthateverynumberfrom1toniscontainedinpexactlyonce.Let’sconsiderallpartitionsofthispermutationintokdisjoin