思路:正向建边,一遍Dijkstra,反向建边,再一遍Dijkstra.ans加在一起输出最大值. (SPFA也行--) // by SiriusRen #include <queue> #include <cstdio> #include <cstring> #include <algorithm> using namespace std; #define N 1005 int n,m,X,tot=0,maxx=0,first[N],v[N*N],w[N*…

题目链接 :http://poj.org/problem?id=3268 Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roa…

Silver Cow Party One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads connects pairs of farms; road…

题目传送门 1 2 题意:有向图,所有点先走到x点,在从x点返回,问其中最大的某点最短路程 分析:对图正反都跑一次最短路,开两个数组记录x到其余点的距离,这样就能求出来的最短路以及回去的最短路. POJ 3268 //#include <bits/stdc++.h> #include <cstdio> #include <queue> #include <algorithm> #include <cstring> using namespace…

POJ 3268 Silver Cow Party Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads connects…

Silver Cow Party Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Submit Status Practice POJ 3268 Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to b…

http://poj.org/problem?id=2387 一个dijkstra的模板题 #include <stdio.h> #include <string.h> #define inf 999999; ][ ]; ]; int m,n; void dijkstra() { ],k,Min; ]; ; i <= n ; i++) //对d[i]进行初始化 { mark[ i ] = false; d[ i ] = graph[ ][ i ]; } ; i <= n…

单源最短路问题(SSSP)常用的算法有Dijkstra,Bellman-Ford,这两个算法进行优化,就有了Dijkstra+heap.SPFA(Shortest Path Faster Algorithm)算法.这两个算法写起来非常相似.下面就从他们的算法思路.写法和适用场景上进行对比分析.如果对最短路算法不太了解,可先看一下相关ppt:最短路 为了解释得简单点,以及让对比更加明显,我就省略了部分细节. 我们先看优化前的: \(O(V^2 + E)\)的Dijkstra n-1次循环 -->找…

POJ 3268 Silver Cow Party (最短路径) Description One cow from each of N farms (1 ≤ N ≤ 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 ≤ X ≤ N). A total of M (1 ≤ M ≤ 100,000) unidirectional (one-way roads c…

在NOIP比赛中,如果出图论题最短路径应该是个常考点. 求解最短路径常用的算法有:Floyed算法(O(n^3)的暴力算法,在比赛中大概能过三十分) dijkstra算法 (堆优化之后是O(MlogE),再加些玄学优化一般就是正解了,100分做法) SPFA算法  ( 个人是不建议学习的,在NOIP提高组中出题人是故卡SPFA,它的复杂度是不确定的,它是基于ballman-Fold算法(O(N*E))的队列优化版) 这个应该都是比较简单的,直接上代码吧 dijkstra #include<ios…