Fin bilan dijkstra
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2 changed files with 178 additions and 3 deletions
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@ -1,5 +1,16 @@
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package org.insa.graphs.algorithm.shortestpath;
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import java.util.ArrayList;
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import java.util.Collections;
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import org.insa.graphs.algorithm.AbstractInputData.Mode;
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import org.insa.graphs.algorithm.AbstractSolution.Status;
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import org.insa.graphs.algorithm.utils.BinaryHeap;
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import org.insa.graphs.model.Arc;
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import org.insa.graphs.model.Label;
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import org.insa.graphs.model.Node;
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import org.insa.graphs.model.Path;
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public class DijkstraAlgorithm extends ShortestPathAlgorithm {
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public DijkstraAlgorithm(ShortestPathData data) {
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@ -9,9 +20,124 @@ public class DijkstraAlgorithm extends ShortestPathAlgorithm {
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@Override
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protected ShortestPathSolution doRun() {
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final ShortestPathData data = getInputData();
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ShortestPathSolution solution = null;
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// TODO:
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return solution;
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int numberOfNodes = data.getGraph().size();
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double shortestCostToDestination = Double.POSITIVE_INFINITY;
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// it's the cost of the last marked node. In order to stop algorithm when it's not
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// useful
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double lastMarkedNodeCost = 0;
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// Dijkstra Init
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Label[] labels = new Label[numberOfNodes];
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for(Node node : data.getGraph().getNodes()) {
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labels[node.getId()] = new Label(node);
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}
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// Let's set the origin cost at 0
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labels[data.getOrigin().getId()].setNewCost(null, 0d);
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// We need to add a binaryMinHeap to get min at each iteration
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BinaryHeap<Label> minHeap = new BinaryHeap<Label>();
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// We add into our binaryMinHeap the origin
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minHeap.insert(labels[data.getOrigin().getId()]);
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// We can start searching for the shortestPath
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// We stop the algorithm when the cost of last marked point is equal to the shortest found path
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// or if we searched all the graph
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while(lastMarkedNodeCost < shortestCostToDestination && !minHeap.isEmpty()) {
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//We get the shortest not marked label
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Label minLabel = minHeap.deleteMin();
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//We mark it
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minLabel.setMarked();
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lastMarkedNodeCost = minLabel.getCost();
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//We look at their successors
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for(Arc successor : minLabel.getCurrent().getSuccessors()) {
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//We see if we need to update
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Label label = labels[successor.getDestination().getId()];
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if(!label.isMarked() ) {
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//We calculate new costs
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double newCost;
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// If the arc can't be reached thanks to transport mode (car, bike)
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// Then it's like the cost to reach it is equal to infinity
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if(!data.isAllowed(successor)) {
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newCost = Double.POSITIVE_INFINITY;
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}
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else if(data.getMode() == Mode.TIME) {
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newCost = minLabel.getCost() + successor.getMinimumTravelTime();
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}
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else {
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newCost = minLabel.getCost() + successor.getLength();
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}
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if(newCost < label.getCost()) {
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//we need to update !
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//if the result is finite, then we need to remove first
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//on the heap
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if(Double.isFinite(label.getCost())) {
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minHeap.remove(label);
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}
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label.setNewCost(successor, newCost);
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minHeap.insert(label);
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//we see if we have updated the destination
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if(successor.getDestination().equals(data.getDestination())) {
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shortestCostToDestination = newCost;
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}
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}
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}
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}
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}
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//Here we have calculated minimum cost to destination, or no destination is unreachable
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//We see if we find something
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if(labels[data.getDestination().getId()].getFather() == null) {
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//here there is no route available
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return new ShortestPathSolution(data, Status.INFEASIBLE);
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}
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//There is a path, let's find it
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ArrayList<Arc> path = new ArrayList<Arc>();
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//First arc
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Arc arc = labels[data.getDestination().getId()].getFather();
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while(arc != null) {
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//while there is a father
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//add the arc to the path
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path.add(arc);
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arc = labels[arc.getOrigin().getId()].getFather();
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}
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// We need to reverse the path to get in the right order
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Collections.reverse(path);
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// Send the solution
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return new ShortestPathSolution(data, Status.OPTIMAL, new Path(data.getGraph(), path));
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}
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}
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@ -0,0 +1,49 @@
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package org.insa.graphs.model;
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public class Label implements Comparable<Label>{
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private Node current;
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private boolean marked;
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private double cost;
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private Arc father;
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public Label(Node current) {
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this.current = current;
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this.cost = Double.POSITIVE_INFINITY;
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this.father = null;
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this.marked = false;
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}
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public void setNewCost(Arc father, double cost) {
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this.father = father;
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this.cost = cost;
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}
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public void setMarked() {
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this.marked = true;
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}
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public boolean isMarked() {
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return this.marked;
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}
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public double getCost() {
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return this.cost;
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}
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public Node getCurrent() {
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return this.current;
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}
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public Arc getFather() {
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return this.father;
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}
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@Override
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public int compareTo(Label arg0) {
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return Double.compare(this.cost, arg0.cost);
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}
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}
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