Contest Clarifications

kentczf | 2015-01-03 20:32:29Author

admin | 2015-01-03 20:34:56# 1

RE:如果边是无向的，何来子树一说？

I think, tree is a special undirected graph that it has a root.

admin | 2015-01-03 20:35:39# 2

RE:如果边是无向的，何来子树一说？

And it doesn't contain any circle.