Create Dijkstra.java

Dijkstra.java

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+import java.util.*;
+public class Dijkstra{
+
+  public static void main(String[] arg){
+
+		Dijkstra obj = new Dijkstra();
+
+		// Create a new graph.
+		Graph g = new Graph(9);
+
+		// Add the required edges.
+		g.addEdge(0, 1, 4); g.addEdge(0, 7, 8);
+		g.addEdge(1, 2, 8); g.addEdge(1, 7, 11); g.addEdge(2, 1, 8);
+		g.addEdge(2, 8, 2); g.addEdge(2, 5, 4); g.addEdge(2, 3, 7);
+		g.addEdge(3, 2, 7); g.addEdge(3, 5, 14); g.addEdge(3, 4, 9); 
+		g.addEdge(4, 3, 9); g.addEdge(4, 5, 10); 
+		g.addEdge(5, 4, 10); g.addEdge(5, 3, 9); g.addEdge(5, 2, 4); g.addEdge(5, 6, 2);
+		g.addEdge(6, 7, 1); g.addEdge(6, 8, 6); g.addEdge(6, 5, 2);
+		g.addEdge(7, 0, 8); g.addEdge(7, 8, 7); g.addEdge(7, 1, 11); g.addEdge(7, 6, 1);
+		g.addEdge(8, 2, 2); g.addEdge(8, 7, 7); g.addEdge(8, 6, 6);
+
+		// Calculate Dijkstra.
+		obj.calculate(g.getVertex(0));	
+
+		// Print the minimum Distance.
+		for(Vertex v:g.getVertices()){
+			System.out.print("Vertex - "+v+" , Dist - "+ v.minDistance+" , Path - ");
+			for(Vertex pathvert:v.path) {
+				System.out.print(pathvert+" ");
+			}
+			System.out.println(""+v);
+		}
+
+	}
+
+	public void calculate(Vertex source){
+		// Algo:
+		// 1. Take the unvisited node with minimum weight.
+		// 2. Visit all its neighbours.
+		// 3. Update the distances for all the neighbours (In the Priority Queue).
+		// Repeat the process till all the connected nodes are visited.
+
+		source.minDistance = 0;
+		PriorityQueue<Vertex> queue = new PriorityQueue<Vertex>();
+		queue.add(source);
+
+		while(!queue.isEmpty()){
+
+			Vertex u = queue.poll();
+
+			for(Edge neighbour:u.neighbours){
+				Double newDist = u.minDistance+neighbour.weight;
+
+				if(neighbour.target.minDistance>newDist){
+					// Remove the node from the queue to update the distance value.
+					queue.remove(neighbour.target);
+					neighbour.target.minDistance = newDist;
+
+					// Take the path visited till now and add the new node.s
+					neighbour.target.path = new LinkedList<Vertex>(u.path);
+					neighbour.target.path.add(u);
+
+					//Reenter the node with new distance.
+					queue.add(neighbour.target);					
+				}
+			}
+		}
+	}
+
+}
+