110 lines
2.5 KiB
Java
110 lines
2.5 KiB
Java
package graph;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.LinkedHashMap;
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import java.util.List;
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import java.util.Map;
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import feature.StreetSegment;
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import feature.StreetSegmentObserver;
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/**
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* Base implementation for shortest-path algorithms.
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*/
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public abstract class AbstractShortestPathAlgorithm implements ShortestPathAlgorithm
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{
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private Collection<StreetSegmentObserver> observers;
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/**
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*
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*/
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public AbstractShortestPathAlgorithm()
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{
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observers = new ArrayList<StreetSegmentObserver>();
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}
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@Override
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public abstract Map<String, StreetSegment> findPath(int origin, int destination,
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StreetNetwork net);
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@Override
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public void addStreetSegmentObserver(final StreetSegmentObserver observer)
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{
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if (observer != null)
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{
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observers.add(observer);
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}
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}
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@Override
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public void removeStreetSegmentObserver(final StreetSegmentObserver observer)
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{
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observers.remove(observer);
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}
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@Override
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public void notifyStreetSegmentObservers(final List<String> segmentIDs)
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{
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for (StreetSegmentObserver observer : observers)
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{
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observer.handleStreetSegments(segmentIDs);
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}
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}
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/**
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* @param segmentID the segment id
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*/
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protected void notifyStreetSegmentObservers(final String segmentID)
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{
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List<String> one = new ArrayList<String>();
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one.add(segmentID);
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notifyStreetSegmentObservers(one);
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}
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/**
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* @param labels the labels
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* @param origin the origin id
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* @param destination the destination id
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* @return ordered path map
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*/
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protected Map<String, StreetSegment> buildPath(final LabelManager labels, final int origin,
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final int destination)
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{
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LinkedHashMap<String, StreetSegment> path =
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new LinkedHashMap<String, StreetSegment>();
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if (labels == null)
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{
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return path;
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}
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Label destinationLabel = labels.getLabel(destination);
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if (destinationLabel == null || Double.isInfinite(destinationLabel.getValue()))
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{
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return path;
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}
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ArrayList<StreetSegment> reversed = new java.util.ArrayList<StreetSegment>();
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Label current = destinationLabel;
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while (current != null && current.getID() != origin)
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{
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StreetSegment predecessor = current.getPredecessor();
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if (predecessor == null)
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{
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break;
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}
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reversed.add(predecessor);
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current = labels.getLabel(predecessor.getTail());
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}
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for (int i = reversed.size() - 1; i >= 0; i--)
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{
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StreetSegment segment = reversed.get(i);
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path.put(segment.getID(), segment);
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}
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return path;
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}
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}
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