【题解】poj3417 Network 树上差分+lca

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于 2018-09-19 06:57:41 发布 · 501 阅读

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#树上差分 #LCA

这篇博客介绍了如何利用树上差分算法解决SN公司网络防御问题。DN公司的黑客可以破坏两条通道，目标是将SN的网络分割成至少两部分。博客提供了一个输入输出示例，并解释了如何通过统计每条主要边被覆盖的次数来计算分割网络的方式数量。最后，博主总结这是一道关于树上差分的好题。

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题目链接

Description

Yixght is a manager of the company called SzqNetwork(SN). Now she’s very worried because she has just received a bad news which denotes that DxtNetwork(DN), the SN’s business rival, intents to attack the network of SN. More unfortunately, the original network of SN is so weak that we can just treat it as a tree. Formally, there are N nodes in SN’s network, N-1 bidirectional channels to connect the nodes, and there always exists a route from any node to another. In order to protect the network from the attack, Yixght builds M new bidirectional channels between some of the nodes.

As the DN’s best hacker, you can exactly destory two channels, one in the original network and the other among the M new channels. Now your higher-up wants to know how many ways you can divide the network of SN into at least two parts.