题目 Tour operator Your Personal Holiday organises guided bus trips across the Benelux. Every day the bus moves from one city S to another city F. On this way, the tourists in the bus can see the sights alongside the route travelled. Moreover, the bus…

http://poj.org/problem?id=3621 全文翻译参自洛谷:https://www.luogu.org/problemnew/show/P2868 题目大意:一个有向图,每个点都有一个价值,每条路通过需要一定时间,求出一个回路使得价值和/时间和最大.(重复经过一个点不会额外增加价值) 按照01分数规划的套路,我们显然可以将路的边权更改为时间*枚举的答案-目的地价值,然后找一个环. 如果这个环是一个负环,那么显然答案还可以变得更大,反之则需要变小. 所以我们需要用spfa判断图…

题面 这道题是一道标准的01分数规划: 但是有一些细节可以优化: 不难想到要二分一个mid然后判定图上是否存在一个环S,该环是否满足∑i=1t(Fun[vi]−mid∗Tim[ei])>0 但是上面的算法并不好实现,所以可以将两边同时乘上-1,使式子变为∑i=1t​(mid∗Tim[ei​]−Fun[vi​])<0 那么该问题就转化成了在每一个图中跑一边SPFA来寻找是否存在负环,若存在则l=mid,否则r=mid: #include <bits/stdc++.h> #define…

题目: 题意: 找到从s到t与最短路长度相差少于1的路径总数. 分析: 首先,搞明白题意之后,我们来考虑一下怎么处理这个1,怎样找相差为1的路径呢?我们这样想,如果有相差为1的路径,那么它将会是严格的次短路,所以我们可以再跑最短路的时候顺带着跑了次短路(严格的),然后判断一下和最短路是不是相差一然后就计算一下就好了,当然,这个的时间复杂度其实就是常数大了的E*logE的,所以时间复杂度是没问题的,然后就是代码: #include <cstdio> #include <cstring>…

Sightseeing Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 1023    Accepted Submission(s): 444 Problem Description Tour operator Your Personal Holiday organises guided bus trips across the Ben…

http://poj.org/problem?id=3463 Sightseeing Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 6420   Accepted: 2270 Description Tour operator Your Personal Holiday organises guided bus trips across the Benelux. Every day the bus moves from…

Sightseeing tour Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 8628   Accepted: 3636 Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beauti…

Sightseeing Cows Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8915   Accepted: 3000 Description Farmer John has decided to reward his cows for their hard work by taking them on a tour of the big city! The cows must decide how best to…

描述 The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beautiful city. They want to construct the tour so that every street in the city is visited exactly once. The bus s…

嗯,这是我上一篇文章说的那本宝典的第二题,我只想说,真TM是本宝典……做的我又痛苦又激动……(我感觉ACM的日常尽在这张表情中了) 题目链接:http://poj.org/problem?id=1637 Time Limit: 1000MS Memory Limit: 10000K Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that t…