Create Dijkstra's Algorithm.java

Dijkstra's Algorithm.java

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+import java.util.*;
+public class GFG {
+    private int dist[];
+    private Set<Integer> settled;
+    private PriorityQueue<Node> pq;
+    private int V;
+    List<List<Node> > adj;
+    public GFG(int V)
+    {
+        this.V = V;
+        dist = new int[V];
+        settled = new HashSet<Integer>();
+        pq = new PriorityQueue<Node>(V, new Node());
+    }
+
+    public void dijkstra(List<List<Node> > adj, int src)
+    {
+        this.adj = adj;
+
+        for (int i = 0; i < V; i++)
+            dist[i] = Integer.MAX_VALUE;
+        pq.add(new Node(src, 0));
+        dist[src] = 0;
+
+        while (settled.size() != V) {
+            if (pq.isEmpty())
+                return;
+            int u = pq.remove().node;
+            if (settled.contains(u))
+                continue;
+            settled.add(u);
+
+            e_Neighbours(u);
+        }
+    }
+
+    // Main driver method
+    public static void main(String arg[])
+    {
+
+        int V = 5;
+        int source = 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));
+        GFG dpq = new GFG(V);
+        dpq.dijkstra(adj, source);
+        System.out.println("The shorted path from node :");
+
+        for (int i = 0; i < dpq.dist.length; i++)
+            System.out.println(source + " 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;
+    }
+}