摘要：小希的迷宫 上次Gardon的迷宫城堡小希玩了很久（见Problem B），现在她也想设计一个迷宫让Gardon来走。但是她设计迷宫的思路不一样，首先她认为所有的通道都应该是双向连通的，就是说如果有一个通道连通了房间A和B，那么既可以通过它从房间A走到房间B，也可以通过它从房间B走到房间A，为了提高 阅读全文

摘要：Deepest Root A graph which is connected and acyclic can be considered a tree. The hight of the tree depends on the selected root. Now you are supposed 阅读全文

摘要：Battle Over Cities It is vitally important to have all the cities connected by highways in a war. If a city is occupied by the enemy, all the highways 阅读全文