http://codeforces.com/problemset/problem/274/D 这道题解题思路: 对每一行统计,以小值列作为弧尾,大值列作为弧头,(-1除外,不连弧),对得到的图做拓扑排序即可. 但本题数据较大,所以需要进行缩点,把相同数值的点缩在一起,成为一个新的大点,原先的小值列向大点连接,再由大点向大值列连接,可以减少边数 举例来说,原本取值为1的有4个点,取值为2的有5个点, 不缩点,就需要20条边 缩点,只需要4+1+5=10条边 (不过我还是觉得这个方法有点投机取巧??…

Priest John's Busiest Day Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 8170   Accepted: 2784   Special Judge Description John is the only priest in his town. September 1st is the John's busiest day in a year because there is an old le…

Fox And Names time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the…

传送门 Description Furik and Rubik love playing computer games. Furik has recently found a new game that greatly interested Rubik. The game consists ofn parts and to complete each part a player may probably need to complete some other ones. We know that…

1924: [Sdoi2010]所驼门王的宝藏 Time Limit: 5 Sec  Memory Limit: 128 MBSubmit: 787  Solved: 318[Submit][Status][Discuss] Description Input 第一行给出三个正整数 N, R, C. 以下 N 行,每行给出一扇传送门的信息,包含三个正整数xi, yi, Ti,表示该传送门设在位于第 xi行第yi列的藏宝宫室,类型为 Ti.Ti是一个1~3间的整数, 1表示可以传送到第 xi行任意…

     Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K       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 tim…

这道题要判断一张有向图是否是单连通图,即图中是否任意两点u和v都存在u到v或v到u的路径. 方法是,找出图中所有强连通分量,强连通分量上的点肯定也是满足单连通性的,然后对强连通分量进行缩点,缩点后就变成DAG. 现在问题就变成,如何判断DAG是否是单连通图——用拓扑排序——如果拓扑排序过程中出现1个以上入度为0的点那就不是单连通图,因为有2个入度0的点,那这两个点肯定都无法到达对方. 另外,注意题目没说给的图是连通的!.. #include<cstdio> #include<cstrin…

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…

Going from u to v or from v to u? Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 14789   Accepted: 3915 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…