dijkstra

问题 In a directed graph with non-negative edge weights I can easily find shortest path from u to v using dijkstra's. But is there any simple tweak to Dijkstra's so that I can find shortest path from u to v through a given vertex w. Or any other algorithm suggestions? 回答1: Find the shortest path from u to w, then the shortest path from w to v. 回答2: Find shortest path from u to w Find shortest path from w to v Then u->w->v is the shortest path. You can do it by running Dijkstra for two times, but

问题 On the Wikipedia page for Dijkstra's algorithm, they mark visited nodes so they wouldn't be added to the queue again. However, if a node is visited then there can be no distance to that node that is shorter, so doesn't the check alt < dist[v] already account for visited nodes? Am I misunderstanding something about the visited set? for each neighbor v of u: alt := dist[u] + dist_between(u, v); // accumulate shortest dist from source if alt < dist[v] && !visited[v]: dist[v] := alt; // keep the

问题 I am looking for an explanation why the AStar / A* algorithm is called AStar. All similar (shortest path problem) algorithms are often named like its developer(s), so what is AStar standing for? 回答1: There were algorithms called A1 and A2. Later, it was proved that A2 was optimal and in fact also the best algorithm possible, so he gave it the name A* which symbolically includes all possible version numbers. Source: In 1964 Nils Nilsson invented a heuristic based approach to increase the speed

问题 Find the shortest path through a graph in efficient time, with the additional constraint that the path must contain exactly n nodes. We have a directed, weighted graph. It may, or may not contain a loop. We can easily find the shortest path using Dijkstra's algorithm, but Dijkstra's makes no guarantee about the number of edges. The best we could come up with was to keep a list of the best n paths to a node, but this uses a huge amount of memory over vanilla Dijkstra's. 回答1: It is a simple

问题 The deadline for this project is closing in very quickly and I don't have much time to deal with what it's left. So, instead of looking for the best (and probably more complicated/time consuming) algorithms, I'm looking for the easiest algorithms to implement a few operations on a Graph structure. The operations I'll need to do is as follows: List all users in the graph network given a distance X List all users in the graph network given a distance X and the type of relation Calculate the

问题 So I came to this beautiful problem that asks you to write a program that finds whether a negative infinity shortest path exists in a directed graph. (Also can be thought of as finding whether a "negative cycle" exists in the graph). Here's a link for the problem: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=499 I successfully solved the problem by running Bellman Ford Algorithm twice by starting with any source in the graph. The second time I

问题 I came across this article about programming styles, seen by Edsger Dijsktra. To quickly paraphrase, the main difference is Mozart, when the analogy is made to programming, fully understood (debatable) the problem before writing anything, while Beethoven made his decisions as he wrote the notes out on paper, creating many revisions along the way. With Mozart programming, version 1.0 would be the only version for software that should aim to work with no errors and maximum efficiency. Also,

问题 So I'm working on reading in a ".txt" file to use it to implement Dijkstra's algorithm, but every time I try to compile it gives me a "FileReader is already defined in this compilation unit" error while highlighting where I imported it in the beginning. If I take this out, however, it throws a constructor error when I'm trying to read in the file that it's of the wrong type. What am I missing here?? Here is my code: import java.io.BufferedReader; import java.io.File; //import java.io

问题 I am looking for a Dijkstra's algorithm implementation, that also takes into consideration the number of nodes traversed. What I mean is, a typical Dijkstra's algorithm, takes into consideration the weight of the edges connecting the nodes, while calculating the shortest route from node A to node B. I want to insert another parameter into this. I want the algorithm to give some weightage to the number of nodes traversed, as well. So that the shortest route computed from A to B, under certain

问题 I have a series of point (x,y) linked by a path. There's an easy way in objective c to apply something like a Dijkstra shortest path alghoritm in order to know the shortest path among two variable points of these? The real problem is i have an image with a series of locations on it and the coordinate of all these location. Now i need the user to choose two of this location and getting the shortest path between the location choosen. 回答1: I found a way to do this. Here there is a perfect