dijkstra

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Can somebody tell me why Dijkstra's algorithm for single source shortest path assumes that the edges must be non-negative. I am talking about only edges not the negative weight cycles. 回答1: Recall that in Dijkstra's algorithm, once a vertex is marked as "closed" (and out of the open set) - the algorithm found the shortest path to it , and will never have to develop this node again - it assumes the path developed to this path is the shortest. But with negative weights - it might not be true. For example: A / \ / \ / \ 5 2 / \ B--(-10)-->C V=

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am trying to understand why Dijkstra's algorithm will not work with negative weights. Reading an example on Shortest Paths , I am trying to figure out the following scenario: 2 A-------B \ / 3 \ / -2 \ / C From the website: Assuming the edges are all directed from left to right, If we start with A, Dijkstra's algorithm will choose the edge (A,x) minimizing d(A,A)+length(edge), namely (A,B). It then sets d(A,B)=2 and chooses another edge (y,C) minimizing d(A,y)+d(y,C); the only choice is (A,C) and it sets d(A,C)=3. But it never finds the

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm looking for advices to speed up my implementation of Dijkstra Shortest Path Search on a weighted graph which is a square matrix N x N. The weight on horizontal vertice is called H (resp. V on vertical ones). A picture is worth a thousand words: A picture is worth a thousand words! http://lionelgermain.free.fr/img/graphe.png Of course, this is part of a bigger application, but I've extracted the relevant bit here: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; const

　　这次我第一次写博客，起了一个特别中二的名字fancyaboy_(:з」∠)_。 　　fancyaboy还有三天就要考算法了，今晚在复习图算法的时候，突然想到以前打建模在网上没有找到能用的dijkstra算法的matlab代码。 　　就当做是复习，今晚写了一个matlab版的dijkstra。 　　因为觉得matlab实现堆比较麻烦，就直接用sort来实现最小堆了，不喜忽喷_(:з」∠)_ 　　代码如下 function [load, w] = dijkstra(Matrix, src, dst) Matrix(isnan(Matrix)) = inf; N = size(Matrix, 1 ); d = zeros(1 , N); pred = zeros(1 , N); for i = 1 :N d(i) = inf; color(i) = ‘ W ‘ ; end d(src) = 0; pred(src) = 0; [ ~, index] = sort(d); temp = repmat( ‘ B ‘ , 1 , length(d)); while (~ strcmp(color, temp)) for j = 1 :length(d) if color(index(j)) == ‘ W ‘ u = index(j); break ; end end index(j) =

刚开始想用dfs，后来想想，这要是用dfs的话节点之间的边过多那么，一方面容易爆栈，另一方面容易超时。 转换另一种思路，最段路径。 只有52个节点，用Dijkstra算法， 刚开始想这倒着算，但要是遇到城镇的化不好进行计算。 还是正着算好，但正着算又该如何计算呢，吴永辉老师告诉我们，直接二分模拟就好。从p到2的20次方，二分最多进行20次就好了。 但还得注意二分的方法。。。。。 害得我wa了，还是吴老师的二分写得好。 在迪杰斯特拉算法中，模拟他的思想，对于本题，选取最大的中间节点以他为跳板进行松弛， ac代码如下： #include<iostream> #include<cstdio> #include<algorithm> #include<cstring> #include<string> #include<map> #include<vector> #include<cmath> #include<cstdlib> #include<list> #include<queue> #define mm(a,b) memset(a,b,sizeof(a)) #define ACCELERATE (ios::sync_with_stdio(false),cin.tie(0)) typedef long long ll; typedef long double ld; typedef

In this earlier question the OP asked how to find a shortest path in a graph that goes from u to v and also passes through some node w. The accepted answer, which is quite good, was to run Dijkstra's algorithm twice - once to get from u to w and once to get from w to v. This has time complexity equal to two calls to Dijkstra's algorithm, which is O(m + n log n). Now consider a related question - you are given a sequence of nodes u 1 , u 2 , ..., u k and want to find the shortest path from u 1 to u k such that the path passes through u 1 , u 2 , ..., u k in order. Clearly this could be done by

在图形应用中，常常需要求从图中某个结点至其余各结点的最短路径，如对于一个物流配送系统计算从配送中心到各订货点的最短路径。 Dijkstra's Algorithm 基本思想： 若给定带权有向图G=(V,E)和源顶点v0，构筑一个源集合S，将v0加入其中。 ③ 重复 步骤①②。直至所有的顶点都加到集合S 中为止。 算法求解过程图式： 步骤： 小结： Dijkstra's 算法与最小生成树的区别在于： ① 最小生成树是对全图而言的，而Dijkstra's算法是对某个结点而言的。 ③ 若Dijkstra's算法依次应用于每个顶点，最后可以得到任意两个顶点之间的最短路径，这就是通常所说的任意顶点对之间的最短路径问题（all-pairs shortest paths,APAP） 文章来源: 迪克斯特拉算法-- Dijkstra's Algorithm

I am looking for an implementation of bidirectional search (a.k.a. "meet in the middle" algorithm) for Dijkstra (or any other source-to-destination shortest path algorithm) in Java. As bidirectional search processing is trickier than it looks like ( Graph Algorithms, p.26 ), I want to consider an existing implementation before reinventing the wheel! P.S.: I am talking about bidirectional search , not to be confused with a bidirectional graph) Here is an example of a tricky graph: Yes, there is at least in Java: https://github.com/coderodde/GraphSearchPal/blob/master/src/main/java/net/coderodde