题意:求其他所有牛都认为其牛的牛的个数. 解题关键:targin算法模板题,缩点形成一棵树,并不一定是棵树,可能含有多个入度为0的点,寻找出度为0的点(缩点之后的点)的个数,如果个数大于0,则无解,否则输出该强连通分量内的个数. 注意targin算法的数组不需要memset. #include<iostream> #include<cstring> #include<cstdio> #include<cstdlib> #include<cmath>…

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…

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: 35644   Accepted: 14532 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 题意:一只牛崇拜另外一只牛,这种崇拜关系可以传导.A->B,B->C =>A->C.现在给出所有的关系问你有多少牛被其他所有的牛都崇拜. 思路:就是一个tarjan裸模板求出所有的点的low和dfn值,让后通过缩点的方法,确定那些出度为0的点.符合条件的牛肯定就在tarjan求出的所有强连通分量里.缩点后它不会有出度.如果缩点后有多个出度为0的点那么就不存在符合条件的牛了. int n,m,top,c,ti,low[N],Stack[N],vis[N],d…

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: 39115   Accepted: 15937 Description Every cow's dream is to become th…

Popular Cows Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 23445   Accepted: 9605 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 &l…

Popular Cows Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 29642   Accepted: 11996 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 &…

题目解析: 这题题意没什么好说的,解法也挺简单的,只要会tarjan算法+只有一个出度为0的强连通分量题目有解这题就迎刃而解了. #include <iostream> #include <string.h> #include <stdio.h> #include <algorithm> #define N 100002 using namespace std; int n,m,tt,time,cnt,e,a[N],b[N],sum[N]; struct n…