ICPC North Central NA Contest 2017 - Is-A? Has-A? Who Knowz-A? (Floyd求传递闭包)
题目链接Twofamiliarconceptsinobjectorientedprogrammingaretheis-aandhas-arelationships.GiventwoclassesAandB,wesaythatAis-aBifAisasubclassofB;wesayAhas-aBifoneofthefieldsofAisoftypeB.Forexample,wecouldimagi