dijkstra算法最短路径java

Dijkstra算法最短路径Java代码示例如下：

import java.util.*;

public class DijkstraShortestPath {
    private int dist[];
    private Set<Integer> visited;
    private PriorityQueue<Node> pq;
    private int V;
    List<List<Node>> adj;

    public DijkstraShortestPath(int V) {
        this.V = V;
        dist = new int[V];
        visited = new HashSet<Integer>();
        pq = new PriorityQueue<Node>(V, new Node());
    }

    public void dijkstra(List<List<Node>> adj, int srcVertex) {
        this.adj = adj;

        for (int i = 0; i < V; i++) {
            dist[i] = Integer.MAX_VALUE;
        }

        pq.add(new Node(srcVertex, 0));

        dist[srcVertex] = 0;
        while (visited.size() != V) {

            int u = pq.remove().node;
            visited.add(u);

            e_Neighbours(u);
        }
    }

    private void e_Neighbours(int u) {
        int edgeDistance = -1;
        int newDistance = -1;

        for (int i = 0; i < adj.get(u).size(); i++) {
            Node vi = adj.get(u).get(i);
            if (!visited.contains(vi.node)) {
                edgeDistance = vi.cost;
                newDistance = dist[u] + edgeDistance;

                if (newDistance < dist[vi.node]) {
                    dist[vi.node] = newDistance;
                }
                pq.add(new Node(vi.node, dist[vi.node]));
            }
        }
    }

    public static void main(String arg[]) {
        int V = 5;
        int sourceVertex = 0;

        List<List<Node>> adj = new ArrayList<List<Node>>();

        for (int i = 0; i < V; i++) {
            List<Node> item = new ArrayList<Node>();
            adj.add(item);
        }

        adj.get(0).add(new Node(1, 9));
        adj.get(0).add(new Node(2, 6));
        adj.get(0).add(new Node(3, 5));
        adj.get(0).add(new Node(4, 3));

        adj.get(2).add(new Node(1, 2));
        adj.get(2).add(new Node(3, 4));

        DijkstraShortestPath dpq = new DijkstraShortestPath(V);
        dpq.dijkstra(adj, sourceVertex);

        System.out.println("The shorted path from node :");
        for (int i = 0; i < dpq.dist.length; i++)
            System.out.println(sourceVertex + " to " + i + " is "
                               + dpq.dist[i]);
    }
}

class Node implements Comparator<Node> {
    public int node;
    public int cost;

    public Node() {
    }

    public Node(int node, int cost) {
        this.node = node;
        this.cost = cost;
    }

    @Override
    public int compare(Node node1, Node node2) {
        if (node1.cost < node2.cost)
            return -1;
        if (node1.cost > node2.cost)
            return 1;
        return 0;
    }
}