Question

我对Dijkstra算法的实现有问题。我用所有顶点（Node）和相对边（Edge）创建了图形。当我运行方法computePath（节点源）时，它正确地将priorityQueue添加到它遇到的第一个节点但不是以下节点。通过这种方式，在第二次迭代中，它不会找到插入节点的边缘。

类Node是这样的：

public class Node implements Comparable<Node>{
public final String id;
public Vector <Edge> adjacencies;
public double minDistance = Double.POSITIVE_INFINITY;
public Node previous;
//here there are all the methods included compareTo(Node other)

类Edge就是这样：

public class Edge{
public final Nodo target;
public final double weight;
//here there all the methods

分配所有方法的Edge的功能如下：

Vector <Arch> totArchs = this.getArchs();
for(int i=0;i<this.getNodes().size();i++)
this.getNodes().get(i).setAdjacenies(this.trovaAdiacenze(this.getNodes().get(i),totArchs));

，其中

public Vector <Edge> trovaAdiacenze(Node n,Vector <Arch> archs){
Vector <Edge> adiacenze = new Vector <Edge>();
for(int i=0;i<archs.size();i++){  
if(n.getId().equalsIgnoreCase(archs.get(i).getInitialNode().getId()))
Edge e = new Edge(archs.get(i).getFinalNode(),archs.get(i).getCost());
adiacenze.add(e);}
}
return adiacenze;}

computePath方法的代码是

public static void computePaths(Node source){
 source.minDistance = 0.;
 PriorityQueue<Node> vertexQueue = new PriorityQueue<Node>();
 vertexQueue.add(source);
 while (!vertexQueue.isEmpty()){
Node u = vertexQueue.poll();

for (Edge e : u.adjacencies){
    Node v = e.target;      
    double weight = e.weight;
    double distanceThroughU = u.minDistance + weight;

    if (distanceThroughU < v.minDistance) 
    {
          vertexQueue.remove(v);
      v.minDistance = distanceThroughU;
      v.previous = u;
      vertexQueue.add(v);
     }  
   }
    }
  }

尽管节点具有所有正确的边缘，但实现并未找到第三个节点的邻接。

我可以用代码的输出更好地解释。

Added nodes:2 having 2 adjacencies
Added nodes:5 having 0 adjacencies
Added nodes:35 having 0 adjacencies
Added nodes:67 having 0 adjacencies

但是，在方法之外，它们有相邻性

for(Nodo n:ist.getNodes())
System.out.println("Node: "+n.id+ " having "+n.adjacencies.size()+" adjacencies");

，相对输出为

Node: 2 having 2 adjacencies
Node: 5 having 2 adjacencies
Node: 35 having 2 adjacencies
Node: 67 having 2 adjacencies

有人可以帮助我吗？

生成最短路径

0 个答案: