dijkstra | 易学教程

Dijkstra's algorithm in python

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问题 I am trying to implement Dijkstra's algorithm in python using arrays. This is my implementation. def extract(Q, w): m=0 minimum=w[0] for i in range(len(w)): if w[i]<minimum: minimum=w[i] m=i return m, Q[m] def dijkstra(G, s, t='B'): Q=[s] p={s:None} w=[0] d={} for i in G: d[i]=float('inf') Q.append(i) w.append(d[i]) d[s]=0 S=[] n=len(Q) while Q: u=extract(Q,w)[1] S.append(u) #w.remove(extract(Q, d, w)[0]) Q.remove(u) for v in G[u]: if d[v]>=d[u]+G[u][v]: d[v]=d[u]+G[u][v] p[v]=u return d, p B

Go, Dijkstra : print out the path, not just calculate the shortest distance

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Go, Dijkstra : print out the path, not just calculate the shortest distance. http://play.golang.org/p/A2jnzKcbWD I was able to find the shortest distance using Dijkstra algorithm, maybe not. The code can be found here. But it would be useless if I can't print out the path. With a lot of pointers going on, I can't figure out how to print out the final path that takes the least amount of weights. In short, how do I not only find the shortest distance, but also print out the shortest path on this given code? The link is here: http://play.golang.org/p/A2jnzKcbWD And the snippet of the code is

Dijkstra's Algorithm Issue

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I'm working on a program where I have to find the shortest path between 12 cities, starting in Seattle and ending in Miami. I'm using Dijkstra's Algorithm because the paths are weighted. Here is my code so far, it all works except the answer I get is not the one I need, although it is correct. This part of the code sets everything up as well as creates the sorting algorithm. class Graph { Dictionary<string, Dictionary<string, int>> vertices = new Dictionary<string, Dictionary<string, int>>(); public void add_vertex(string name, Dictionary<string, int> edges) { vertices[name] = edges; } public

[模板]Dijkstra

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　前言　　考试前几天才发现一直写的Dijkstra是错的，有点惭愧，现在打了个板子放在这里，以示后人　　题目链接 : https://www.luogu.org/problem/P4779 　 Code 1 #include <iostream> 2 #include <cstdio> 3 #include <queue> 4 #include <cstring> 5 using namespace std; 6 typedef long long ll; 7 const int N=100002; 8 const int M=200002; 9 const int inf=2147483647; 10 inline int read() 11 { 12 char ch=getchar(); 13 int x=0;bool f=false; 14 while (!isdigit(ch)) f^=!(ch^45),ch=getchar(); 15 while (isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar(); 16 if (f) x=-x;return x; 17 } 18 int n,m,s; 19 int head[N],to[M],nex[M],cnt=0; 20 ll val[M]; 21 ll dis[N]; 22

graph - Shortest path with Vertex Weight

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问题 Here is an excise: In certain graph problems, vertices have can have weights instead of or in addi- tion to the weights of edges. Let Cv be the cost of vertex v, and C(x,y) the cost of the edge (x, y). This problem is concerned with finding the cheapest path between vertices a and b in a graph G. The cost of a path is the sum of the costs of the edges and vertices encountered on the path. (a) Suppose that each edge in the graph has a weight of zero (while non-edges have a cost of ∞).Assume

Shortest path between raw geo coordinates and a node of a graph

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I have implemented a simple Dijkstra's algorithm for finding the shortest path on an .osm map with Java. The pathfinding in a graph which is created from an .osm file works pretty well. But in case the user's current location and/or destination is not a node of this graph (just raw coordinates) how do we 'link' those coordinates to the graph to make pathfinding work? The simple straightforward solution "find the nearest to the current location node and draw a straight line" doesn't seem to be realistic. What if we have a situation like on the attached picture? (UPD) The problem here is that

Dijkstra on “Software Engineering” [closed]

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问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 10 years ago . Edsger Dijkstra, who could be somewhat abrasive at times (he called "Carl Friedrich Gauss, the Prince of Mathematicians but also somewhat of a coward") said in his essay "On the cruelty of really teaching

Dijkstra堆优化

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转载自 https://www.cnblogs.com/captain1/p/8552809.html Dijkstra是一个非常不错的最短路算法，它使用两层循环进行枚举，通过每次更新蓝白点的方式更新最短路，时间复杂度为O（n^2），优于floyd的O（n^3），不过只能用于计算单源最短路，而且无法处理负权边。今天我们尝试用堆来优化它。这里我们使用了STL中的set和pair。set本身相当于一个小根堆，内部自动从小到大排序。（据说内部使用平衡树实现？蒟蒻瑟瑟发抖。）操作方式大致就是insert（插入）和erase（删除），不过他会把相同的数据融合到一起，如果不想这样可以使用multiset。对于堆的遍历我们不能像数组一样直接遍历，而是要使用迭代器。（用法下面代码有）而pair相当于一个有两个成员的且已经重定义的struct，使用makepair来新构造一个pair。具体怎么做呢？我们从起点出发，然后枚举每一条能走到的边（这里使用了邻接表存图），之后在选取最短的一条边时，我们使用堆即可，也就是将贪心变成了堆，这样时间复杂度就变为了O(nlogn)。直接上代码看一下就好啦！ #include<cstdio> #include<vector> #include<cmath> #include<iostream> #include<algorithm> #include

How do I define a custom distance in Boost Dijkstra?

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I'm currently looking at the documentation of Boost Dijkstra - http://www.boost.org/doc/libs/1_52_0/libs/graph/doc/dijkstra_shortest_paths.html ; my objective is to modify the distance combining to get a "max" instead of a "plus" when computing my distances. The doc says this: IN: distance_combine(CombineFunction cmb) This function is used to combine distances to compute the distance of a path. The CombineFunction type must be a model of Binary Function. The first argument typ of the binary function must match the value type of the DistanceMap property map and the second argument type must

Find shortest path from Vertex u to v passing through a vertex w?

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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? Find the shortest path from u to w, then the shortest path from w to v. 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 you can also apply the Floyd-Warshall algorithm. Zach Langley This problem is NP-hard, so finding a polynomial