摘要：
Problem DescriptionThese days, you can do all sorts of things online. For example, you can use various websites to make virtual friends. For some people, growing their social network (their friends, their friends' friends, their friends' friends' friends, and so on), has become an addict 阅读全文
摘要：
Problem DescriptionFive hundred years later, the number of dragon balls will increase unexpectedly, so it's too difficult for Monkey King(WuKong) to gather all of the dragon balls together.His country has N cities and there are exactly N dragon balls in the world. At first, for the ith dragon ba 阅读全文