题意:判断一个有向图中的任意两点u.v,是否可以由其中一个点到达另一个点. 分析:这个问题转化以后就是:将该图强连通缩点后再判断其是否是单向连通的.缩点用Tarjan处理强连通分量. 有一个定理是这样的:一个有向图是单项连通的当且仅当其拓扑排序唯一.那么将这个子问题再转化为其缩点之后的图拓扑排序是否唯一. 如果一个有向图拓扑排序唯一,那么在根据入度求拓扑排序的过程中,不会有超过一个点在同一时刻同时为0. #include<stack> #include<stdio.h> #incl…

题目链接:http://poj.org/problem?id=2762 题意是 有t组样例,n个点m条有向边,取任意两个点u和v,问u能不能到v 或者v能不能到u,要是可以就输出Yes,否则输出No.注意一点,条件是或者!所以不是判断双连通图的问题. 我一开始没看到'or'这个条件,所以直接tarjan判断是否只有一个强连通分量,果断WA. 所以需要给原图缩点,用tarjan把图变成一个有向无环图,要是只有一个scc,那就直接输出Yes.那接下来讨论多个scc,要是新图中有两个及以上的点的入度为…

http://poj.org/problem?id=2762 Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 12733   Accepted: 3286 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. The cave has…

职务地址:id=2762">POJ 2762 先缩小点.进而推断网络拓扑结构是否每个号码1(排序我是想不出来这点的. .. ).由于假如有一层为2的话,那么从此之后这两个岔路的点就不可能从一点到还有一点的. 代码例如以下: #include <iostream> #include <string.h> #include <math.h> #include <queue> #include <algorithm> #include…

http://poj.org/problem?id=2762 题意:给出有向图,判断任意两个点u和v,是否可以从u到v或者从v到u. 思路: 判断图是否是单连通的. 首先来一遍强连通缩点,重新建立新图,接下来我们在新图中找入度为0的点,入度为0的点只能有1个,如果有多个那么这些个点肯定是不能相互到达的. 如果只有一个入度为0的点,走一遍dfs判断新图是否是单链,如果有分支,那么分支上的点肯定是不能相互到达的. #include<iostream> #include<algorithm&g…

题目链接: http://poj.org/problem?id=2762 Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 14546   Accepted: 3837 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. The cav…

id=2762">http://poj.org/problem?id=2762 Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 14573   Accepted: 3849 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. T…

Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 17089   Accepted: 4590 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. The cave has n rooms, and one-way corridors…

Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 15812   Accepted: 4194 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. The cave has n rooms, and one-way corridors…

Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 17104   Accepted: 4594 Description In order to make their sons brave, Jiajia and Wind take them to a big cave. The cave has n rooms, and one-way corridors connecting some rooms. Each time,…