dijkstra

Apply Dijkstra's algorithm in a undirected graph with negative weights

由 冷暖自知 提交于 2019-12-13 09:15:36
问题 Can anyone apply Dijkstra's algorithm in the undirected graph with negative weights above? Even if the algorithm fails. Adjancency's list: A -> (B, 3), (C, 2), (D, 4) B -> (A, 3), (C, -2), (F, 6) C -> (A, 2), (B, -2), (E, 5) D -> (A, 4), (E, 3), (F, 2) E -> (C, 5), (D, 3), (F, -2) F -> (B, 6), (D, 2), (E, -2) 回答1: Seed the traversal list with source node A, and it's cost with 0. Add an infinite cost for every other node: {}, [A=0, B=inf, C=inf, D=inf, E=inf, F=inf] Then take the lowest

Regarding the query speed of dijkstra and A* algorithm

由 南楼画角 提交于 2019-12-13 07:04:39
问题 I am trying to profile the speed of A* and Dijkstra algorithm. I am using the code available at http://www.boost.org/doc/libs/1_38_0/libs/graph/example/astar-cities.cpp and http://www.boost.org/doc/libs/1_50_0/libs/graph/doc/dijkstra_shortest_paths.html. I tried a simple graph with 500 edges and 300 nodes. I was expecting A* to perform better than Dijkstra since in Dijkstra the shortest distance from the source vertex to every other vertex is found. On the other hand in A* the shortest

Understanding Dijkstra Algorithm

由 主宰稳场 提交于 2019-12-13 05:43:29
问题 I'm trying to understand the Dijkstra Algorithm for finding the shortest path. I've came up to this example, where the top table corresponds to the image in the bottom left corner. Now, my problem is that I don't understand the transition from step 1 to step 2: When we are in UX we can travel to UXV by adding the cost of X to V (which is 2) to our current cost (which is 1; the cost of UX). So the sum would be 3, but since this I bigger then the 2 we already found we don't change it. In step 1

Decide Whether All Shortest Paths From s to t Contain The Edge e

由 喜夏-厌秋 提交于 2019-12-13 04:20:44
问题 Let G = (V;E) be a directed graph whose edges all have non-negative weights. Let s,t be 2 vertices in V, and let e be an edge in E. Describe an algorithm that decides whether all shortest paths from s to t contain the edge e. Well, this is how you can achieve Dijsktra's time complexity: Simply run Dijkstra from s and calculate delta(s,t) (the weight of the shortest path from s to t). Remove the edge e, and run Djikstra again from s in the new graph. If delta(s,t) in the new graph has

最短路之旅行（Dijkstra解法）

由 我与影子孤独终老i 提交于 2019-12-13 02:43:49
链接：https://ac.nowcoder.com/acm/problem/14550 来源：牛客网 题目描述 小z放假了，准备到RRR城市旅行，其中这个城市有N个旅游景点。小z时间有限，只能在三个旅行景点进行游玩。小明租了辆车，司机很善良，说咱不计路程，只要你一次性缴费足够，我就带你走遍RRR城。 小z很开心，直接就把钱一次性缴足了。然而小z心机很重，他想选择的路程尽量长。 然而司机也很聪明，他每次从一个点走到另外一个点的时候都走最短路径。 你能帮帮小z吗？ 需要保证这三个旅行景点一个作为起点，一个作为中转点一个作为终点。（一共三个景点，并且需要保证这三个景点不能重复）. 输入描述: 本题包含多组输入，第一行输入一个整数t，表示测试数据的组数 每组测试数据第一行输入两个数N,M表示RRR城一共有的旅游景点的数量，以及RRR城中有的路的数量。 接下来M行，每行三个数，a，b，c表示从a景点和b景点之间有一条长为c的路 t<=40 3<=N,M<=1000 1<=a,b<=N 1<=c<=100 输出描述: 每组数据输出两行， 每组数据包含一行，输出一个数，表示整条路程的路长。 如果找不到可行解，输出-1. 输入 4 7 7 1 2 100 2 3 100 1 4 4 4 5 6 5 6 10 1 6 4 6 7 8 7 3 1 2 1 1 3 1 1 3 2 7 3 1 2 1

Calling Functions From Main in C++ [duplicate]

由 雨燕双飞 提交于 2019-12-13 02:27:38
问题 This question already has answers here : Static Functions in C++ (8 answers) Closed 6 years ago . I'm trying to call my Dijkstra() method from Main.cpp. #include <iostream> #include "Alg.h" int main(int argc, char **argv) { Alg::dijkstra(); return 1; } It is delcared in my Alg class in my header file: #ifndef Alg_ #define Alg_ #include <iostream> #include <stack> using namespace std; class Alg { public: void tracePath(int x); void output(); void printArray(); void Initialize(); void dijkstra(

Shortest path algorithm (eg. Dijkstra's) for 500+ waypoints/nodes?

由 江枫思渺然 提交于 2019-12-12 21:18:41
问题 I've asked about a shortest path algorithm here: 2D waypoint pathfinding: combinations of WPs to go from curLocation to targetLocation (To understand my situation, please read that question as well as this one.) It appears that the Dijkstra shortest path algorithm would be able to do what I need. However, I have about 500 to 1000 nodes in my routes map. The implementations I have seen so far limited the amount of nodes to something under 50. My question is: should I still use the Dijkstra

Dijkstra with a heap. How to update the heap after relaxation?

由 有些话、适合烂在心里 提交于 2019-12-12 19:01:16
问题 I am trying to implement Dijkstra algorithm. foreach distance d d = INFINITY d[source] = 0 create_heap_based_on_Distances(); while(true) bestedge = heap[0] remove_minimum_from_heap //it will be heap[0] foreach adjacency of bestedge if (weight + bestedge_distance < current_distance) { current_distance = weight + bestedge_distance // Now I have to update heap, how can I do that? } if (heap_empty) break So, in the relaxation, how can I update the heap, so it would have the correct order? I don't

Boost dijkstra string edge weight

由 孤街醉人 提交于 2019-12-12 18:43:53
问题 is it possible to use string value instead of double properties typedef adjacency_list < vecS, vecS, directedS, property<vertex_name_t, string>, property < edge_weight_t, string> > Graph; My goal is to use the dijkstra algorithm. PS: I already tried replacing the double with string and it generates an error within the algorithm. std::vector<vertexd> P(num_vertices(g)); std::vector<string> d(num_vertices(g)); vertexd s = vertex(0, g); dijkstra_shortest_paths(g, s, predecessor_map(boost::make

Python Dijkstra Algorithm

由 孤者浪人 提交于 2019-12-12 15:55:32
问题 I am trying to write Dijkstra's Algorithm, however I am struggling on how to 'say' certain things in code. To visualize, here are the columns I want represented using arrays: max_nodes A B C Length Predecessor Visited/Unvisited A 0 1 2 -1 U B 1 0 1 -1 U C 2 1 0 -1 U So, there will be several arrays, as seen in my code below: def dijkstra (graph, start, end) network[max_nodes][max_nodes] state [max_nodes][length] state2 [max_nodes][predecessor] state3 [max_nodes][visited] initialNode = 0 for
订阅 dijkstra