摘要：
题目： There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a di 阅读全文
摘要：
题目： There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you ha 阅读全文
摘要：
题目： There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you ha 阅读全文