Graph_BFS(breadth-first-search algorithm)

Main.java

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+import java.util.*;
+class Graph{
+
+    static HashMap<String,List<Node>> adj; //creating a adjacency List {source ->destinations}
+
+    public Graph(){
+        this.adj=new HashMap<>(); //constructor initializes the adjacency list
+    }
+
+    static class Node{ //Node class to store the destination place and the distance frome source to destination
+	String dest;
+	int dist;
+
+	Node(String dest,int dist){
+            this.dest=dest;
+	    this.dist=dist;
+	}
+    }
+
+    public static void insert(String src,String dest,int dist){
+           insert(src,new Node(dest,dist));  //Undirected weighted graph
+	   insert(dest,new Node(src,dist));
+    }
+
+    private static void insert(String src,Node n){
+         if(adj.isEmpty() || !adj.containsKey(src)){
+               adj.put(src,new ArrayList<>());
+	 }
+	 adj.get(src).add(n);
+    } 
+
+    public static void BFS(String src){ // BREADTH-FIRST-SEARCH
+          if(adj.isEmpty()) return;
+
+	  HashSet<String> set=new HashSet<>();
+	  Queue<String> q=new LinkedList<>();  //BFS uses Queue data structure
+	  q.offer(src);
+	  set.add(src);
+
+	  while(!q.isEmpty()){ 
+             String node=q.poll();
+	     System.out.print(node+" ");
+	     List<Node> neighbours=adj.get(src);
+	     if(neighbours!=null){
+                for(Node neighbour:neighbours){
+                    if(neighbour!=null && !set.contains(neighbour.dest)){
+                        q.offer(neighbour.dest);
+                        set.add(neighbour.dest);
+		    }
+		}
+	     }
+	  }
+    }
+
+}
+
+class Main{
+  public static void main(String[] args){
+      Graph graph=new Graph();              //instantiating Graph by making an object graph of GRAPH
+      graph.insert("DELHI","MUMBAI",990);
+      graph.insert("MUMBAI","PUNE",100);
+      graph.insert("PUNE","GOA",140);
+      graph.insert("BANGALORE","PUNE",453);
+      graph.insert("DELHI","PUNE",1056);
+      graph.insert("DELHI","HYDERABAD",1099);
+      graph.insert("VISHAKHAPATNAM","HYDERABAD",230);
+      graph.insert("BANGALORE","DELHI",1000);
+      graph.insert("CHENNAI","BANGALORE",600);
+      graph.insert("CHENNAI","DELHI",1300);
+
+      graph.BFS("DELHI");
+  }
+}