Question

我试图使用Dijkstra的算法来找到从特定顶点（v0）到其余顶点的最短路径。这已得到解决，并且可以使用以下链接中的代码运行良好：http://en.literateprograms.org/index.php?title=Special:DownloadCode/Dijkstra%27s_algorithm_(Java)&oldid=15444

我在用户输入的for循环中分配Edge数组时遇到了麻烦，而不是像在这里那样进行硬编码。

是否有任何帮助为每个顶点的Edge []邻接分配新边？请记住，它可以是1个或多个边缘。

class Vertex implements Comparable<Vertex>
{
    public final String name;
    public Edge[] adjacencies;
    public double minDistance = Double.POSITIVE_INFINITY;
    public Vertex previous;
    public Vertex(String argName) { name = argName; }
    public String toString() { return name; }

    public int compareTo(Vertex other){
    return Double.compare(minDistance, other.minDistance);
    }
}


class Edge{
    public final Vertex target;
    public final double weight;

    public Edge(Vertex argTarget, double argWeight){
        target = argTarget; weight = argWeight; }
    }

public static void main(String[] args)
{
    Vertex v[] = new Vertex[3];
    Vertex v[0] = new Vertex("Harrisburg");
    Vertex v[1] = new Vertex("Baltimore");
    Vertex v[2] = new Vertex("Washington");

    v0.adjacencies = new Edge[]{ new Edge(v[1],  1),
                             new Edge(v[2],  3) };
    v1.adjacencies = new Edge[]{ new Edge(v[0], 1),
                             new Edge(v[2],  1),};
    v2.adjacencies = new Edge[]{ new Edge(v[0],  3),
                                 new Edge(v[1],  1)  };

    Vertex[] vertices = { v0, v1, v2};
       /*Three vertices with weight: V0 connects (V1,1),(V2,3)
                                     V1 connects (V0,1),(V2,1)
                                     V2 connects (V1,1),(V2,3)
       */  
    computePaths(v0);
    for (Vertex v : vertices){
    System.out.println("Distance to " + v + ": " + v.minDistance);
    List<Vertex> path = getShortestPathTo(v);
    System.out.println("Path: " + path);
    }
}
}

上述代码可以很好地找到从v0到所有其他顶点的最短路径。将新边[]分配给边[]邻接时会出现问题。

例如，这不会产生正确的输出：

for (int i = 0; i < total_vertices; i++){
        s = br.readLine();
        char[] line = s.toCharArray();
        for (int j = 0; j < line.length; j++){  
           if(j % 4 == 0 ){ //Input: vertex weight vertex weight: 1 1 2 3
            int vert = Integer.parseInt(String.valueOf(line[j]));
            int w = Integer.parseInt(String.valueOf(line[j+2]));
            v[i].adjacencies = new Edge[] {new Edge(v[vert], w)};
        }
        }
    }

与此相反：

v0.adjacencies = new Edge[]{ new Edge(v[1],  1),
                         new Edge(v[2],  3) };

如何获取用户输入并制作Edge []，将其传递给邻接？问题是它可能是0边或许多。

非常感谢任何帮助谢谢！

Answer 1

在你的情况下，你为j的每次迭代分配v [i] .adjacencies ...这意味着它是line.length = 8，然后v [i] .adjacencies被分配2次。我不认为这是你的意图。

    for (int j = 0; j < line.length; j++){  
       if(j % 4 == 0 ){ //Input: vertex weight vertex weight: 1 1 2 3
        int vert = Integer.parseInt(String.valueOf(line[j]));
        int w = Integer.parseInt(String.valueOf(line[j+2]));
        v[i].adjacencies = new Edge[] {new Edge(v[vert], w)};
    }

您可以更改类似的代码......

    Edge[] edges = new Edge[line.length/4];  
    for (int j = 0; j < line.length; j++){           
       if(j % 4 == 0 ){ //Input: vertex weight vertex weight: 1 1 2 3
        int vert = Integer.parseInt(String.valueOf(line[j]));
        int w = Integer.parseInt(String.valueOf(line[j+2]));
        edges[j/4] =  {new Edge(v[vert], w)};
    }
   v[i].adjacencies = edges;

它可能不是确切的代码，但你必须指出循环。

Java：for循环中的对象数组赋值

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