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…

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…

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 ta…

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…

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…

P2860 [USACO06JAN]冗余路径Redundant Paths 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．两条路径相互分离,是…

Luogu2860 [USACO06JAN]冗余路径Redundant Paths 给定一个连通无向图,求至少加多少条边才能使得原图变为边双连通分量 \(1\leq n\leq5000,\ n-1\leq m\leq10^4\) tarjan 边双无疑不用考虑,于是就可以边双缩点成一棵树 令现在要连的边为 \((u,\ v)\) ,当前树上 \(bl_u\) 到 \(bl_v\) 的链将会变为一个新的点双,可以将他们看为一个新的点 可以贪心地连边使得每次连边后,不复存在的点尽量多,当只剩一个点时…

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…

题目链接 https://www.luogu.org/problemnew/show/P2860 https://www.lydsy.com/JudgeOnline/problem.php?id=1718 分析 首先这题目的意思就是让任意两点之间至少有两条没有重复道路的路径,很显然,如果这个图不存在桥,就一定满足上述条件. 于是我们就是要求使这个图不存在桥需要连接的最小边数 如果把桥从图中去掉,很显然剩余的联通块中任意两点之间至少有两条没有重复道路的路径(当然也可能不是联通块而是孤立的点),对答…

(写题解不容易,来我的博客玩玩咯qwq~) 该题考察的知识点是边双连通分量 边双连通分量即一个无向图中,去掉一条边后仍互相连通的极大子图.(单独的一个点也可能是一个边双连通分量) 换言之,一个边双连通分量中不包含桥. 例如下图(样例)中的边双连通分量有(1),(2,3,5,6),(4),(7) 不难发现,在一个边双连通分量中,任意两点都存在至少两条互相分离的路径:(如1->2与1->3->2) 如若不在一个边双连通分量中,则可能经过桥(甚至不联通)如:2->4. 由于桥是必须通过的…

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…

Description 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 forc…

题目大意:给定一个 N 个点,M 条边组成的无向图,求至少在图中加入几条边才能使得整个图没有割边. 题解:求出该无向图的所有边双联通分量,每个边双联通分量可以理解成无向图的一个极大环,对该无向图进行缩点,形成一棵树.至少加入的边数和树中入度为 1 的节点个数有关,找找规律即可求得结果. 代码如下 #include <bits/stdc++.h> #define fi first #define se second #define pb push_back #define mp make_pai…

tarjan求边双连通分量, 然后就是一棵树了, 可以各种乱搞... ------------------------------------------------------------------------------- #include<cstdio> #include<cstring> #include<algorithm>   using namespace std;   const int maxn = 5009;   struct edge { int…

1718: [Usaco2006 Jan] Redundant Paths 分离的路径 Time Limit: 5 Sec  Memory Limit: 64 MBSubmit: 964  Solved: 503[Submit][Status][Discuss] Description In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to another f…

1718: [Usaco2006 Jan] Redundant Paths 分离的路径 Time Limit: 5 Sec  Memory Limit: 64 MBSubmit: 1132  Solved: 590[Submit][Status][Discuss] Description     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…

Redundant Paths 分离的路径 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 o…

Redundant Paths 分离的路径 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．两条路径相互分离,是指两条路径没有一条重合的…

POJ 3177 Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 12598   Accepted: 5330 Description 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 re…

Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 11047   Accepted: 4725 Description 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…

题目链接:http://poj.org/problem?id=3177 Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 15852   Accepted: 6649 Description In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to anoth…

Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13717   Accepted: 5824 Description 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…

在看了春晚小彩旗的E技能(旋转)后就一直在lol……额抽点时间撸一题吧…… Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8159   Accepted: 3541 Description In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to anot…

Redundant Paths Description 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…

Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 19316   Accepted: 8003 题目链接:http://poj.org/problem?id=3177 Description: In order to get from one of the F (1 <= F <= 5,000) grazing fields (which are numbered 1..F) to anot…

Redundant Paths Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13712   Accepted: 5821 Description 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…