DTL66的博客

E - Farthest Nodes in a TreeTime Limit:2000MS Memory Limit:32768KB 64bit IO Format:%lld & %llu SubmitStatus Description Given a tree (a connected graph with no cycles), you have to find the

B - Roads in the NorthTime Limit:1000MS Memory Limit:65536KB 64bit IO Format:%lld & %llu SubmitStatus Description Building and maintaining roads among communities in the far North is an expe

A - Cow MarathonTime Limit:2000MS Memory Limit:30000KB 64bit IO Format:%lld & %llu SubmitStatus Description After hearing about the epidemic of obesity in the USA, Farmer John wants his cows

D - ComputerTime Limit:1000MS Memory Limit:32768KB 64bit IO Format:%I64d & %I64u SubmitStatus Description A school bought the first computer some time ago(so this computer’s id is 1). During

C - Labyrinth Time Limit:2000MS Memory Limit:32768KB 64bit IO Format:%lld & %llu SubmitStatus Description The northern part of the Pyramid contains a very large and complicated labyrinth. T

a.树的性质： .树中所有节点都是连通的；树上的任意连两点间只有一跳通路，即数中不能含有环； 性质1&2->含有n个节点的树有n-1条边；树中任意节点的父节点只有一个，根节点除外；性质4决定了一棵树只能含有一个根节点。 注意：通过树的性质判断一个图是不是树。那就是判断图中所有节点是否连通（用并查集判断根节点是否唯一），图中是否含有环（判断边数是否为n-1）。一棵树的·根节点有且只有一个，