[d.p.l.t]

i am using the shortest path algorithm to determine the connection between individuals within a given array.
the array is written into the code and not read from external files.

when i am having problem is .. i am having problems how to prompt the user for the starting point or vertex and read that prompt to determine the starting point in the array.


i know that this code

 computePaths(v0); 

determines the starting point. i want to read "v0" from the user prompt.

any assistance or pointing in the right direction is appreciated

total code being used

import java.util.PriorityQueue;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
import java.io.IOException;
import java.util.Scanner;


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

            for (Edge e : u.adjacencies)
            {
                Vertex 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);
		}
            }
        }
    }

    public static List<Vertex> getShortestPathTo(Vertex target)
    {
        List<Vertex> path = new ArrayList<Vertex>();
        for (Vertex vertex = target; vertex != null; vertex = vertex.previous)
            path.add(vertex);
        Collections.reverse(path);
        return path;
    }

    public static void main(String[] args)
    {
        Vertex v0 = new Vertex("Andrew Marshall");
	Vertex v1 = new Vertex("Mark Williams");
	Vertex v2 = new Vertex("Carla Watson");
	Vertex v3 = new Vertex("Paul Morgan");
	Vertex v4 = new Vertex("Anthony Taylor");

	v0.adjacencies = new Edge[]{ new Edge(v1, 5),
	                             new Edge(v2, 13),
                               new Edge(v3, 8) };
	v1.adjacencies = new Edge[]{ new Edge(v0, 5),
	                             new Edge(v2, 7),
	                             new Edge(v4, 7) };
	v2.adjacencies = new Edge[]{ new Edge(v0, 10),
                               new Edge(v1, 3) };
	v3.adjacencies = new Edge[]{ new Edge(v0, 8),
	                             new Edge(v4, 2) };
	v4.adjacencies = new Edge[]{ new Edge(v1, 7),
                               new Edge(v3, 2) };
	Vertex[] vertices = { v0, v1, v2, v3, v4 };
        computePaths(v0);
        for (Vertex v : vertices)
	{
	    System.out.println("Connection to " + v + ": " + v.minDistance);
	    List<Vertex> path = getShortestPathTo(v);
	    System.out.println("Individual : " + path);
	}
    }
}

[macosxnerd101]

How about just read in the index from the user and parse that input to an int. It's straight-forward to access an array element given an index.

By the way- is this code you wrote or code you found online?

[d.p.l.t]

macosxnerd101, on 11 May 2014 - 08:24 PM, said:

How about just read in the index from the user and parse that input to an int. It's straight-forward to access an array element given an index.

By the way- is this code you wrote or code you found online?

code that was found and being modded to fit my application