Java: Object Array assignment in for loop

Posted by Hackster on Stack Overflow See other posts from Stack Overflow or by Hackster
Published on 2012-12-01T04:18:14Z Indexed on 2012/12/01 5:04 UTC
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I am trying to use Dijkstra's algorithm to find the shortest path from a specific vertex (v0) to the rest of them. That is solved and works well with this code from this link below: http://en.literateprograms.org/index.php?title=Special:DownloadCode/Dijkstra%27s_algorithm_(Java)&oldid=15444

I am having trouble with assigning the Edge array in a for loop from the user input, as opposed to hard-coding it like it is here.

Any help assigning a new edge to Edge[] adjacencies from each vertex? Keeping in mind it could be 1 or multiple edges.

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);
    }
}
}

The above code works well in finding the shortest path from v0 to all the other vertices. The problem occurs when assigning the new edge[] to edge[] adjacencies.

For example this does not produce the correct output:

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)};
        }
        }
    }

As opposed to this:

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

How can I take the user input and make an Edge[], to pass it to adjacencies? The problem is it could be 0 edges or many.

Any help would be much appreciated Thanks!

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