P1550 [USACO08OCT]打井Watering Hole 题目背景 John的农场缺水了!!! 题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or con…

题面:P1550 [USACO08OCT]打井Watering Hole 题解:无 代码: #include<cstdio> #include<cstring> #include<iostream> #include<algorithm> #define ll long long using namespace std; ; ,edge_head[maxn]; ll Z,ans; *maxn*maxn]; inline void Add_edge(int f…

P1550 [USACO08OCT]打井Watering Hole   对于自己建水库的情况,新建一个虚拟结点,和其他点的边权即为自建水库的费用 这样问题就转化为一个裸最小生成树问题了. 这里用堆优化prim解决. #include<iostream> #include<cstdio> #include<cstring> #include<cctype> #include<queue> #define re register using name…

P1550 [USACO08OCT]打井Watering Hole 题目背景 John的农场缺水了!!! 题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or con…

题目背景 John的农场缺水了!!! 题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or connecting the pasture via a pipe to…

题面 题目背景 John的农场缺水了!!! 题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or connecting the pasture via a pipe…

本题看似很难,实际上思路非常简单--如果你想通了. 首先有一个问题:图中有几个点?大部分的人会回答\(n\)个点.错了,有\(n+1\)个. 多出来的那个点在哪?关键在于你要理解每一个决策的意义.实际上,多出来的那个点是地下的天然矿泉水.当我们打井时,我们实际上是在往地下连边.理解了这一点,代码就没有任何难度了. 构图时,我们只需多加一个点,对于每个点\(i\),我们连边\(i→n+1\),边权为\(w_i\).然后直接跑最小生成树就没了.就没了.(转载from here) #include<b…

题面(翻译有点问题,最后一句话) 农民John 决定将水引入到他的n(1<=n<=300)个牧场.他准备通过挖若 干井,并在各块田中修筑水道来连通各块田地以供水.在第i 号田中挖一口井需要花费W_i(1<=W_i<=100,000)元.连接i 号田与j 号田需要P_ij (1 <= P_ij <= 100,000 , P_ji=P_ij)元. 请求出农民John 需要为使所有农场都与有水的农场相连或拥有水井所需要的钱数. 题意 有n个点,每个点之间都有边权,但是每个点也…

题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or connecting the pasture via a pipe to another pasture whi…

题目の传送门:https://www.luogu.org/problem/show?pid=1550 精简版题意(本来就精简了不是么):n个点,每个点可以选择打井或从别的有水的点引水,求所有点都有水用的最小费用.(我是不是一说反而更不懂了) 这题其实并不是很难,讲道理贪心都能过.. 令我感到有趣的是这题中一种非常神奇的解题思路.. 首先,如果这个题没有打井的选项,显然是最小生成树 然而我们现在要打井,就不能直接用最小生成树做了.. 殊不知,这题还是一个最小生成树~ 这就需要一些小小的.巧妙的办法…

题目描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or connecting the pasture via a pipe to another pasture whi…

题意:有N个牧场,每个牧场修水井花费Wi,连接牧场花费Pij,问最小花费,使得每个牧场要么有水井,要么和有水井的牧场有通道. 思路:加一个格外的节点O,连接O表示修井,边权是修井的费用.     那么这N+1个点求最MST即可. 刘同学想到的解法: 先找到修井费用最低的的牧场,然后和上面一样,由于最低的那个必选,所以异曲同工. #include<bits/stdc++.h> #define rep(i,a,b) for(int i=a;i<=b;i++) using namespace…

描述 Description 农民约翰被选为他们镇的镇长!他其中一个竞选承诺就是在镇上建立起互联网,并连接到所有的农场.当然,他需要你的帮助.约翰已经给他的农场安排了一条高速的网络线路,他想把这条线路共享给其他农场.为了用最小的消费,他想铺设最短的光纤去连接所有的农场.你将得到一份各农场之间连接费用的列表,你必须找出能连接所有农场并所用光纤最短的方案.每两个农场间的距离不会超过100000 输入格式 Input Format 第一行: 农场的个数,N(3<=N<=100). 第二行..结尾:…

[USACO08OCT]Watering Hole 题目大意: Farmer John 有\(n(n\le300)\)个牧场,他希望灌溉他的所有牧场.牧场编号为\(1\sim n\),要灌溉一个牧场有两种方式,一个是直接在这个牧场建设一个小型水库,另一个是从别的牧场向这个牧场引水.在第\(i\)个牧场建立小型水库需要\(W_i\)美元,而从第\(i\)个牧场向第\(j\)个牧场引水需要\(P_{i,j}\)美元.即便牧场\(j\)没有建设小型水库,只要有别的有水的水库向它引水,那它自己也有水,而…

打井 题目 该题是一个最小生成树的好题,但是比起一般的最小生成树来说他不仅仅有各个井相连,而且还要和地下水相连,所以地下水我们也可以看成一口井. 代码 #include <bits/stdc++.h> using namespace std; struct edge { int a, b, c; }e[100100]; bool cmp(const edge &a, const edge &b) { return a.c < b.c; } int cnt, fa[1001…

Farmer John希望把水源引入他的N (1 <= N <= 300) 个牧场,牧场的编号是1~N.他将水源引入某个牧场的方法有两个,一个是在牧场中打一口井,另一个是将这个牧场与另一个已经有水源的牧场用一根管道相连.在牧场i中打井的费用是W_i (1 <= W_i <= 100000).把牧场i和j用一根管道相连的费用是P_ij (1 <= P_ij <= 100000, P_ij = P_ji, P_ii = 0).请你求出Farmer John最少要花多少钱才能…

这是USACO2008年的一道最小生成树题,感谢dzj老师那天教的图论. 要引渠让每一个村庄都可以接到水,然后从某一个村庄到另一个村庄修剪水道要花费w元,并且还要打井(至少一个)(而输入数据也包括了在每一个村庄打井的费用),需要为使所有农场都与有水的村庄相连或拥有水井所需要的钱数.很明显,这个题只有建成一个联通的图,然后求最小权值和即可.所以我选用了kruskal算法求最小生成树.但是这里还有一个问题,就是怎么判断是打井还是连水道的问题.那么我们则用到了“超级元”的思想,让水井代表0号节点,则边…

描述 Farmer John has decided to bring water to his N (1 <= N <= 300) pastures which are conveniently numbered 1..N. He may bring water to a pasture either by building a well in that pasture or connecting the pasture via a pipe to another pasture which…

传送门 总算是做上一道LCA的应用题了... 题意:有$n$个牧场, $m$根管道分别连接编号为$u,v$的牧场花费$p_{i}$,在第$i$个牧场挖口井需要花费$w_{i}$,有$P$根管道直接连通着$u,v$,即免费连上$u,v$ 对每根免费管道输出让所有牧场都有水的最小花费 先是最小生成树,用0去连每一个点,边权就是每个点的权值,然后正常建,跑一遍最小生成树,把用到的边重新建一次图,然后就对每次询问的$u,v$,减掉他们之间的路径的最长边就是答案了 因为删去这其中一条边,再免费连上$u,v…

目录 一.最小生成树的相关知识 1. 树的性质 2. 生成树 3. 最小生成树 4. 最小生成树的性质 二.Kruskal算法求最小生成树 1. 核心思想 2. 具体流程 3. 图示 4. 代码实施 三.例题 例1:P2212 [USACO14MAR]浇地Watering the Fields 例2:P1550 [USACO08OCT]打井Watering Hole 例3:P1547 Out of Hay 例4:P1340 兽径管理 一.最小生成树的相关知识 1. 树的性质 树实际上是图的特殊形…

线段树 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'watering hole' and drank a few too many beers before dinner. When it was time to line up for the…

Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 9669   Accepted: 6228 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'watering hole' an…

Lost Cows Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 10354 Accepted: 6631 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'watering h…

Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 10996   Accepted: 7059 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'watering hole' a…

Lost Cows Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 402    Accepted Submission(s): 203 Problem Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular…

Lost Cows Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 10609   Accepted: 6797 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'wateri…

Language: Default Lost Cows Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 9207   Accepted: 5922 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the nei…

主题链接:http://poj.org/problem? id=2182 Lost Cows Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 9152   Accepted: 5879 Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, t…

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Lost Cows Time Limit: 1000 MS Memory Limit: 65536 KB Description N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood 'watering hole' and drank a few too many beers b…