【Tarjan边双缩点】【CEOI2000】Roads

最新推荐文章于 2024-08-28 18:01:45 发布

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最新推荐文章于 2024-08-28 18:01:45 发布 · 1.6k 阅读

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#Tarjan #CEOI #OI

本文介绍了一个关于罗马尼亚道路升级的问题，需要在关闭单条道路时保持网络连通，通过 Tarjan 算法求解最小新增道路数及连接城镇对。讨论了算法实现中的细节和错误避免策略。

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题目描述

The Romanian Ministry of Transport decides to upgrade the Romanian roads. Each road is bidirectional and directly connects two towns. No two towns are directly connected by more than one road. The existing road network ensures direct or indirect links between any two towns in Romania.
However, upgrading the roads implies closing, in turn, each road and performing the necessary repairs. During these operations, it is necessary to preserve the road network connectivity. In order to do so, the Minister decides that new roads should be built, so that no matter which single road is closed at any given moment (exactly one road at a time), the traffic between any given pair of towns should still be possible. Of course, the number of these newly added roads should be minimized. Furthermore, no new road may directly connect two directly connected towns.
Write a program that determines the minimum number of the additional roads to be built and the pairs of towns to be connected with them. If there are several optimal solutions, only one is required.

输入

Line $1$ : $N$ $M$
two integers, separated by a blank, representing respectively the number of the towns and the number of the roads. The towns are labelled from $1$ to $N$ .
Lines