题目传送门 晕牛Dizzy Cows 题目背景 Hzwer 神犇最近又征服了一个国家,然后接下来却也遇见了一个难题. 题目描述 The cows have taken to racing each other around the farm but they get very dizzy when running in circles, and everyone knows that dizzy cows don't produce any milk. Farmer John wants to…

前言:P大终于又更新了 正文 转送门 由于当时我这个ZZ不知怎么了,这份题解排版可能有些尴尬,建议大家读完题后,看我主程序前的代码的注释,然后看最下面的图片,然后看第一张图片,对不起,望多谅解 以样例为例.具体看代码及其中的注释,这样做的正确性,看最下面说明 #include<iostream>#include<cstdio>#include<queue>using namespace std;/*    晕牛:拓扑排序    根据题干可知,有向边不成环,所以通过拓扑排…

https://www.luogu.org/problem/P2017 题目背景 Hzwer 神犇最近又征服了一个国家,然后接下来却也遇见了一个难题. 题目描述 The cows have taken to racing each other around the farm but they get very dizzy when running in circles, and everyone knows that dizzy cows don't produce any milk. Farm…

P3056 [USACO12NOV]笨牛Clumsy Cows 题目描述 Bessie the cow is trying to type a balanced string of parentheses into her new laptop, but she is sufficiently clumsy (due to her large hooves) that she keeps mis-typing characters. Please help her by computing th…

正解:拓扑排序+dp 解题报告: 传送门 我好暴躁昂,,,怎么感觉HNOI每年总有那么几道题题面巨长啊,,,语文不好真是太心痛辣QAQ 所以还是要简述一下题意,,,就是说,本来是有一个DAG,然后后来又加入辣一条有向边(x,y),求形成的树的方案数 首先从比较简单的想起,假如加入之后依然麻油环,那就直接计算每个点的入度in,然后tot=Πin[i]就好,还是挺好理解的趴,就每个点可以选从所有指向自己的边中选一条就好,显然都是合法的QwQ 然后所以就会多算,多算的就是加入边(x,y)之后形成的环的…

[USACO09DEC] Dizzy Cows 拓扑序 先对有向边跑拓扑排序,记录下每个点拓扑序,为了使最后的图不存在环,加入的\(p2\)条无向边\(u,v\)必须满足\(u\)拓扑序小于\(v\)拓扑序,否则加入的无向边会破坏拓扑DAG结构,由此确定加入的无向边方向. #include <cstdio> #include <queue> using namespace std; #define MAXN 100010 int head[MAXN],nxt[MAXN*2],vv[…

洛谷P1522 [USACO2.4]牛的旅行 Cow Tours 题意: 给出一些牧区的坐标,以及一个用邻接矩阵表示的牧区之间图.如果两个牧区之间有路存在那么这条路的长度就是两个牧区之间的欧几里得距离. 对于一个联通块,称之为一个牧场,也就是说一个牧场内任意一个牧区都可以到达该牧场内的任意的另外一个牧区. 对于一个牧场,它的直径是这个联通块内最短路的最大值. 现在让你在恰当地选择两个牧场,在这两个牧场中各自选一个牧区,在这两个牧区之间建路,要求建路之后所有牧场中最大的直径最小.这里其实如果产生了…

P1821 [USACO07FEB]银牛派对Silver Cow Party 题目描述 One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads co…

一道\(0/1\)分数规划+负环 POJ原题链接 洛谷原题链接 显然是\(0/1\)分数规划问题. 二分答案,设二分值为\(mid\). 然后对二分进行判断,我们建立新图,没有点权,设当前有向边为\(z=(x,y)\),\(time\)为原边权,\(fun\)为原点权,则将该边权换成\(mid\times time[z]+fun[x]\),然后在上面跑\(SPFA\). 如果有一个环使得\(\sum\{mid\times time[z]+fun[x]\}<0\),则说明\(mid\)小了,而式子…

P2883 [USACO07MAR]牛交通Cow Traffic 随着牛的数量增加,农场的道路的拥挤现象十分严重,特别是在每天晚上的挤奶时间.为了解决这个问题,FJ决定研究这个问题,以能找到导致拥堵现象的瓶颈所在. 牧场共有M条单向道路,每条道路连接着两个不同的交叉路口,为了方便研究,FJ将这些交叉路口编号为1..N,而牛圈位于交叉路口N.任意一条单向道路的方向一定是是从编号低的路口到编号高的路口,因此农场中不会有环型路径.同时,可能存在某两个交叉路口不止一条单向道路径连接的情况. 在挤奶时间到…

传送门啦 这个题没有想象中复杂. 我们先有向边建立,因为我们无法改变有向边的方向. 建立完之后跑一边拓扑排序,我们按拓扑序小的指向大的就好了. 解释: 我们知道如果一个点在另一个点顺序的后面的话,如果我们添加这个点回去的边显然是不合理的,所以我们每读入一条无向边的时候我们判断这个点在拓扑排序里面位置的大小,如果 $ u > v $ 就代表 $ u $ 到$ v $ 可能有路线,但是 $ v $ 绝对不能返回 $ u $ ,那么此时如果有一条边要你选择,建立 $ u $ 到 $ v $ 不会使 $…

P2862 [USACO06JAN]把牛Corral the Cows 题目描述 Farmer John wishes to build a corral for his cows. Being finicky beasts, they demand that the corral be square and that the corral contain at least C (1 <= C <= 500) clover fields for afternoon treats. The co…

P2862 [USACO06JAN]把牛Corral the Cows 题目描述 Farmer John wishes to build a corral for his cows. Being finicky beasts, they demand that the corral be square and that the corral contain at least C (1 <= C <= 500) clover fields for afternoon treats. The co…

P2862 [USACO06JAN]把牛Corral the Cows 题目描述 Farmer John wishes to build a corral for his cows. Being finicky beasts, they demand that the corral be square and that the corral contain at least C (1 <= C <= 500) clover fields for afternoon treats. The co…

题目描述 Like everyone else, FJ is always thinking up ways to increase his revenue. To this end, he has set up a series of tolls that the cows will pay when they traverse the cowpaths throughout the farm. The cows move from any of the N (1 <= N <= 250)…

P2862 [USACO06JAN]把牛Corral the Cows 题目描述 Farmer John wishes to build a corral for his cows. Being finicky beasts, they demand that the corral be square and that the corral contain at least C (1 <= C <= 500) clover fields for afternoon treats. The co…

P2970 [USACO09DEC]自私的放牧Selfish Grazing 题目描述 Each of Farmer John's N (1 <= N <= 50,000) cows likes to graze in a certain part of the pasture, which can be thought of as a large one-dimeensional number line. Cow i's favorite grazing range starts at lo…

题目描述 One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads connects pairs of farms; road i requires…

P2969 [USACO09DEC]音符Music Notes 题目描述 FJ is going to teach his cows how to play a song. The song consists of N (1 <= N <= 50,000) notes, and the i-th note lasts for B_i (1 <= B_i <= 10,000) beats (thus no song is longer than 500,000,000 beats).…

P1821 [USACO07FEB]银牛派对Silver Cow Party 题目描述 One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads co…

P3088 [USACO13NOV]挤奶牛Crowded Cows 题目描述 Farmer John's N cows (1 <= N <= 50,000) are grazing along a one-dimensional fence. Cow i is standing at location x(i) and has height h(i) (1 <= x(i),h(i) <= 1,000,000,000). A cow feels "crowded"…

P2906 [USACO08OPEN]牛的街区Cow Neighborhoods 题目描述 Those Who Know About Cows are aware of the way cows group into 'Cow Neighborhoods'. They have observed Farmer John's N (1 <= N <= 100,000) cows (conveniently numbered 1..N) as they graze, each at her own…

题目描述 The cows are having a picnic! Each of Farmer John's \(K (1 ≤ K ≤ 100)\) cows is grazing in one of \(N (1 ≤ N ≤ 1,000)\) pastures, conveniently numbered \(1...N\). The pastures are connected by \(M (1 ≤ M ≤ 10,000)\) one-way paths (no path connec…

P1211 [USACO1.3]牛式 Prime Cryptarithm 187通过 234提交 题目提供者该用户不存在 标签USACO 难度普及- 提交  讨论  题解 最新讨论 题面错误 题目描述 下面是一个乘法竖式,如果用我们给定的那n个数字来取代*,可以使式子成立的话,我们就叫这个式子牛式. *** x     ** ---------- *** *** ---------- **** (请复制到记事本) 数字只能取代*,当然第一位不能为0,况且给定的数字里不包括0. 注意一下在美国的学…

传送门 给出一棵n" role="presentation" style="position: relative;">nn个点的树,每个点上有Ci" role="presentation" style="position: relative;">CiCi头牛,问每个点k" role="presentation" style="position: relat…

P1588 丢失的牛 158通过 654提交 题目提供者JOHNKRAM 标签USACO 难度普及/提高- 时空限制1s / 128MB 提交  讨论  题解 最新讨论更多讨论 答案下载下来是对的,但过不… 此题卡stl的queue? 假的编译器... 怎么A不了 题目描述 FJ丢失了他的一头牛,他决定追回他的牛.已知FJ和牛在一条直线上,初始位置分别为x和y,假定牛在原地不动.FJ的行走方式很特别:他每一次可以前进一步.后退一步或者直接走到2*x的位置.计算他至少需要几步追上他的牛. 输入输出…

题目描述 Farmer John has decided to reward his cows for their hard work by taking them on a tour of the big city! The cows must decide how best to spend their free time. Fortunately, they have a detailed city map showing the L (2 ≤ L ≤ 1000) major landma…

P2971 [USACO10HOL]牛的政治Cow Politics 农夫约翰的奶牛住在N (2 <= N <= 200,000)片不同的草地上,标号为1到N.恰好有N-1条单位长度的双向道路,用各种各样的方法连接这些草地.而且从每片草地出发都可以抵达其他所有草地.也就是说,这些草地和道路构成了一种叫做树的图.输入包含一个详细的草地的集合,详细说明了每个草地的父节点P_i (0 <= P_i <= N).根节点的P_i == 0, 表示它没有父节点.因为奶牛建立了1到K一共K (1…

P1211 [USACO1.3]牛式 Prime Cryptarithm 题目描述 下面是一个乘法竖式,如果用我们给定的那n个数字来取代*,可以使式子成立的话,我们就叫这个式子牛式. *** x ** ---------- *** *** ---------- **** (请复制到记事本) 数字只能取代*,当然第一位不能为0,况且给定的数字里不包括0. 注意一下在美国的学校中教的“部分乘积”,第一部分乘积是第二个数的个位和第一个数的积,第二部分乘积是第二个数的十位和第一个数的乘积. 写一个程序找…

P2868 [USACO07DEC]观光奶牛Sightseeing Cows 题目描述 Farmer John has decided to reward his cows for their hard work by taking them on a tour of the big city! The cows must decide how best to spend their free time. Fortunately, they have a detailed city map sh…