I looked at other posts regarding this here at SO.
I am trying to find the shortest path between nodes in a graph. Each edge between nodes has a coordinate (X, Y).
I want to calculate the shortest distance from Node Ito Node J. After that, I want to add all the X values and Y values from the coordinates to the shortest path.
I am stuck with this for hours and would like some insight.
Here is the code:
class Vertex implements Comparable<Vertex> {
private int id;
private List<Edge> adjacencyList;
private Vertex previousVertex;
private double minDistance;
private Coordinate point;
public Vertex(int id, Coordinate point) {
this.id = id;
this.point = point;
this.adjacencyList = new ArrayList<>();
}
public int getID() {
return this.id;
}
public Coordinate getPoint() {
return this.point;
}
public List<Edge> getAdjacencyList() {
return this.adjacencyList;
}
public void addNeighbour(Edge edge) {
this.adjacencyList.add(edge);
}
public Vertex getPreviousVertex() {
return this.previousVertex;
}
public void setPreviousVertex(Vertex previousVertex) {
this.previousVertex = previousVertex;
}
public double getMinDistance() {
return this.minDistance;
}
public void setMinDistance(double minDistance) {
this.minDistance = minDistance;
}
public int compareTo(Vertex other) {
return Double.compare(this.minDistance, other.minDistance);
}
}
class Edge {
private double weight;
private Vertex targetVertex;
public Edge(double weight, Vertex targetVertex) {
this.weight = weight;
this.targetVertex = targetVertex;
}
public double getWeight() {
return this.weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public Vertex getTargetVertex() {
return this.targetVertex;
}
public void setTargetVertex(Vertex targetVertex) {
this.targetVertex = targetVertex;
}
}
class Algorithm {
public void shortestPath(Vertex startVertex) {
startVertex.setMinDistance(0);
PriorityQueue<Vertex> queue = new PriorityQueue<>();
queue.add(startVertex);
while (!queue.isEmpty()) {
Vertex actualVertex = queue.poll();
for (Edge edge : actualVertex.getAdjacencyList()) {
Vertex v = edge.getTargetVertex();
double weight = edge.getWeight();
double currentDistance = actualVertex.getMinDistance() + weight;
if (currentDistance < v.getMinDistance()) {
queue.remove(v);
v.setMinDistance(currentDistance);
v.setPreviousVertex(actualVertex);
queue.add(v);
}
}
}
}
public List<Vertex> getShortestPathTo(Vertex targetVertex){
List<Vertex> path = new ArrayList<Vertex>();
for (Vertex vertex = targetVertex; vertex != null; vertex = vertex.getPreviousVertex()){
path.add(vertex);
}
Collections.reverse(path);
return path;
}
}
class Coordinate {
private int x;
private int y;
Coordinate(int x, int y) {
this.x = x;
this.y = y;
}
public int getX() {
return this.x;
}
public int getY() {
return this.y;
}
public static Coordinate readInput(Scanner in) {
String[] temp = in.nextLine().split(" ");
return new Coordinate(Integer.parseInt(temp[0]), Integer.parseInt(temp[1]));
}
}
If I read from this text file
3 // # coordinates
0 0 // (x, y)
1 1 // (x, y)
2 0 // (x, y)
1 2 // edge between coordinates 1 - 2
2 3 // edge between coordinates from 2 to 3
My test case will look like this:
class Test {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
String[] constants = s.nextLine().split(" ");
final int N = Integer.parseInt(constants[0]);
List<Coordinate> junctions = new ArrayList<>();
List<Coordinate> paths = new ArrayList<>();
List<Vertex> vertices = new ArrayList<>();
for(int i = 0; i < N; i++) {
junctions.add(Coordinate.readInput(s));
}
for(int i = 0; i < N-1; i++) {
paths.add(Coordinate.readInput(s));
}
for(int i = 0; i < N-1; i++) {
int x = junctions.get(paths.get(i).getX() - 1).getX();
int x1 = junctions.get(paths.get(i).getY() - 1).getX();
int y = junctions.get(paths.get(i).getX() - 1).getY();
int y1 = junctions.get(paths.get(i).getY() - 1).getY();
Vertex vertex1 = new Vertex(paths.get(i).getX(), new Coordinate(x, y));
Vertex vertex2 = new Vertex(paths.get(i).getY(), new Coordinate(x1, y1));
double distance = Math.sqrt(Math.pow(x - x1, 2) + Math.pow(y - y1, 2));
vertex1.addNeighbour(new Edge(distance, vertex2));
vertices.add(vertex1);
vertices.add(vertex2);
}
Algorithm a = new Algorithm();
int x = 0;
int y = 0;
for(int i = 0; i < vertices.size(); i++) {
a.shortestPath(vertices.get(i));
for(Vertex vertex : a.getShortestPathTo(vertices.get(i+1))) {
x += vertices.get(vertex.getID()).getPoint().getX();
y += vertices.get(vertex.getID()).getPoint().getY();
}
}
System.out.println("Total X: " + x + " Total Y: " + y);
}
}