// Textbook fragment 13.15
/* Dijkstra's algorithm for the single-source shortest path problem
 * in an undirected graph whose edges have non-negative integer weights.  */
public class Dijkstra<V, E> {
  /** Infinity value. */
  protected static final Integer INFINITE = Integer.MAX_VALUE;
  /** Input graph. */
  protected Graph<V, E> graph;
  /** Decoration key for edge weights */
  protected Object WEIGHT;
  /** Decoration key for vertex distances  */
  protected Object DIST = new Object();
  /** Decoration key for entries in the priority queue */
  protected Object ENTRY = new Object();
  /** Auxiliary priority queue. */
  protected AdaptablePriorityQueue<Integer, Vertex<V>> Q;
  /** Executes Dijkstra's algorithm.
    * @param g Input graph
    * @param s Source vertex
    * @param w Weight decoration object */
  public void execute(Graph<V, E> g, Vertex<V> s, Object w) {
    graph = g;
    WEIGHT = w;
    DefaultComparator dc = new DefaultComparator();
    Q = new HeapAdaptablePriorityQueue<Integer, Vertex<V>>(dc);
    dijkstraVisit(s);
  }
  /** Get the distance of a vertex from the source vertex.
   * @param u Start vertex for the shortest path tree */
  public int getDist(Vertex<V> u) {
    return (Integer) u.get(DIST);
  }