P2860 [USACO06JAN]冗余路径Redundant Paths 题目描述 为了从F(1≤F≤5000)个草场中的一个走到另一个,贝茜和她的同伴们有时不得不路过一些她们讨厌的可怕的树．奶牛们已经厌倦了被迫走某一条路,所以她们想建一些新路,使每一对草场之间都会至少有两条相互分离的路径,这样她们就有多一些选择． 每对草场之间已经有至少一条路径．给出所有R(F-1≤R≤10000)条双向路的描述,每条路连接了两个不同的草场,请计算最少的新建道路的数量, 路径由若干道路首尾相连而成．两条路径相…

题目描述 In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to another field, Bessie and the rest of the herd are forced to cross near the Tree of Rotten Apples. The cows are now tired of often being forced to t…

题目描述 In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to another field, Bessie and the rest of the herd are forced to cross near the Tree of Rotten Apples. The cows are now tired of often being forced to t…

原题链接 题意实际上就是让你添加尽量少的边,使得每个点都在至少一个环上. 显然对于在一个边双连通分量里的点已经满足要求,所以可以用\(tarjan\)找边双并缩点. 对于缩点后的树,先讲下我自己的弱鸡做法,每次找直径,因为将直径改为环显然使得新添的边贡献最大,这样贪心的连下去,直到所有点满足要求为止. 而实际上有一个简单结论,该题答案就是缩点后树的叶子节点个数除\(2\)(向上取整). 代码是用的我自己的弱鸡做法. #include<cstdio> using namespace std; c…

传送门 解题思路 刚开始是找的桥,后来发现这样不对,因为一条链就可以被卡.后来想到应该缩点后找到度数为1 的点然后两两配对. #include<iostream> #include<cstdio> #include<cstring> #include<cstdlib> #include<set> using namespace std; ; ; inline int rd(){ ,f=;char ch=getchar(); :;ch=getcha…

题目链接:https://www.luogu.org/problemnew/show/P2860 考虑在无向图上缩点. 运用到边双.桥的知识. 缩点后统计度为1的点. 度为1是有一条路径,度为2是有两条路径. #include <stack> #include <cstdio> #include <cstring> #include <iostream> #include <algorithm> using namespace std; cons…

题目描述 In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1-F) to another field, Bessie and the rest of the herd are forced to cross near the Tree of Rotten Apples. The cows are now tired of often being forced to ta…

题目链接 https://www.luogu.org/problemnew/show/P2860 思路 缩点,之后就成了个树一般的东西了 然后(叶子节点+1)/2就是答案,好像贪心的样子,lmc好像讲过诶 cpp #include <iostream> #include <cstdio> #include <vector> #include <bits/stdc++.h> #define iter vector<int>::iterator us…

题解: 首先要边双缩点这很显然 然后变成树上问题 发现dp,dfs好像不太对 考虑一下度数 发现只要在度数为1的点之间连边 但我好像不太会证明这个东西.. 网上也没有看到比较正确的证明方法和连边策略.. 另外从桥上考虑这题是错的 举出链的反例就很容易能发现了…

题目描述 In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to another field, Bessie and the rest of the herd are forced to cross near the Tree of Rotten Apples. The cows are now tired of often being forced to t…