Codeforces题号:#510C 出处: Codeforces 主要算法:判环+拓扑 难度:4.2 思路分析: 要是把这道题联系到图上就很容易想了. 如何建图?由于最后要求名字满足字典序,所以不妨以字母为节点,然后按照题意的顺序从小的到大的连边.建图了又什么用?如果图存在环,那么也就意味着矛盾了——因为这比自己小的节点比自己大.因此是否存在一个合法的字典序的判断依据就是建的图是否存在环. 第二步,如何输出任意一个方案?这很简单,由于有可能有的字母根本没有参与建图,所以这些字母就不需要管了.对…

C. Fox And Names 题目连接: http://codeforces.com/contest/510/problem/C Description Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in…

C. 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: t…

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…

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…

题目链接:http://codeforces.com/problemset/problem/510/C Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in the lexicographical order.…

Description Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in the lexicographical order. After checking some examples, she found…

题目链接:http://codeforces.com/contest/510/problem/C 题目大意:构造一个字母表,使得按照你的字母表能够满足输入的是按照字典序排下来. 递归建图:竖着切下来,将每个名字的第x个字母从上到下连接建图.然后求拓扑排序. 之所以要拓扑排序,因为要判断在x-1里面有a-->b  在x中有b-->a,这样就形成了一个环.这样一来,就不能够构造字母表了. [经验教训]:在递归建图的函数中开了两个数组,用来记录字母第一次出现和最后一次出现的位置..结果就RE在12上…

题目传送门 /* 给出n个字符串,求是否有一个“字典序”使得n个字符串是从小到大排序 拓扑排序 详细解释:http://www.2cto.com/kf/201502/374966.html */ #include <cstdio> #include <iostream> #include <cstring> #include <string> #include <map> #include <algorithm> #include &…

题意:给出n串名字,表示字典序从小到大,求符合这样的字符串排列的字典序 先挨个地遍历字符串,遇到不相同的时候,加边,记录相应的入度 然后就是bfs的过程,如果某一点没有被访问过,且入度为0,则把它加入队列中,并将它指向的节点的入度减去1 另外如果len[i]<len[i-1],说明第i个字符串是i-1个字符串的前缀,但是它还排在后面,这样肯定不存在符合的字典序,直接输出“Impossible” #include<iostream> #include<cstdio> #incl…