poj2186 popular cows   Every cow's dream is to become the most popular cow in the herd. In a herd of N (1 <= N <= 10,000) cows, you are given up to M (1 <= M <= 50,000) ordered pairs of the form (A, B) that tell you that cow A thinks that cow…

http://poj.org/problem?id=2186 (题目链接) 题意 给出一个n个点m条边的有向图,求其中没有出度强连通分量所包含的点有几个 Solution 其实这道题的题解已经在“题意”中给出了= =,先Tarjan跑出强连通分量,之后模拟给缩点后的图连边(其实并不用真的连边),来统计缩点后每个节点的出度.输出出度为0的强连通分量所包含的点即可,若有多个强连通分量出度为0,输出0(不要问我为什么,有时候事情就是这么不讲道理). 代码 // poj2186 #include<alg…

这里的Tarjan是基于DFS,用于求有向图的强联通分量. 运用了一个点dfn时间戳和low的关系巧妙地判断出一个强联通分量,从而实现一次DFS即可求出所有的强联通分量. §有向图中, u可达v不一定意味着v可达u.    相互可达则属于同一个强连通分量    (Strongly Connected Component, SCC) §有向图和它的转置的强连通分量相同 §所有SCC构成一个DAG(有向无环图) dfn[u]为节点u搜索的次序编号(时间戳),即首次访问u的时间 low[u]为u或u的…

不裸缩点>...POJ2186受欢迎的牛 :first-child { margin-top: 0; } blockquote > :last-child { margin-bottom: 0; } img { border: 0; max-width: 100%; height: auto !important; margin: 2px 0; } table { border-collapse: collapse; border: 1px solid #bbbbbb; } td, th {…

两题都是水题,1236第一问求缩点后入度为0的点数,第二问即至少添加多少条边使全图强连通,属于经典做法,具体可以看白书 POJ2186即求缩点后出度为0的那个唯一的点所包含的点数(即SCC里有多少点) //poj1236 #include<iostream> #include<cstdio> #include<string.h> #define maxn 6000 int now=0,next[maxn],head[maxn],point[maxn],num=0,dfn…

强连通分量:两个点能够互相连通. 算法分解:第一步.正向dfs全部顶点,并后序遍历 第二步,将边反向,从最大边dfs,构成强连通分量 标号最大的节点属于DAG头部,cmp存一个强连通分量的拓扑序. poj2186 解就是拓扑后的最后一个强连通分量 #include<cstdio> #include<algorithm> #include<vector> #include<iostream> #include<cstring> #include&l…

P2341 [HAOI2006]受欢迎的牛/POJ2186:Popular Cows 题目背景 本题测试数据已修复. 题目描述 每头奶牛都梦想成为牛棚里的明星.被所有奶牛喜欢的奶牛就是一头明星奶牛.所有奶 牛都是自恋狂,每头奶牛总是喜欢自己的.奶牛之间的“喜欢”是可以传递的——如果A喜 欢B,B喜欢C,那么A也喜欢C.牛栏里共有N 头奶牛,给定一些奶牛之间的爱慕关系,请你 算出有多少头奶牛可以当明星. 输入输出格式 输入格式:  第一行:两个用空格分开的整数:N和M  第二行到第M + 1行…

Popular Cows Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 31241   Accepted: 12691 Description Every cow's dream is to become the most popular cow in the herd. In a herd of N (1 <= N <= 10,000) cows, you are given up to M (1 <= M &…

Popular Cows Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 29773   Accepted: 12080 Description Every cow's dream is to become the most popular cow in the herd. In a herd of N (1 <= N <= 10,000) cows, you are given up to M (1 <= M &…

Description Every cow's dream is to become the most popular cow in the herd. In a herd of N (1 <= N <= 10,000) cows, you are given up to M (1 <= M <= 50,000) ordered pairs of the form (A, B) that tell you that cow A thinks that cow B is popula…