bfs.java

Author: Mayank Kumar Jha

bfs.java

@@ -0,0 +1,42 @@
+import java.util.*;
+
+public class App{
+	
+	public static void bfs(byte [][] a,int vertices,int source){  //passing adjacency matrix and no of vertices
+		byte []b=new byte[vertices];    //flag container containing status of each vertices
+		Arrays.fill(b,(byte)-1);   //status initialization
+		/*       code   status 
+				 -1  =  ready
+				  0  =  waiting
+				  1  =  processed       */
+				
+		Queue <Integer> st=new LinkedList<>();     //operational stack
+		st.add(source);                                                 //assigning source
+		while(!st.isEmpty()){
+			b[st.peek()]=(byte)0;                                   //assigning waiting status
+			System.out.println(st.element());
+			int pop=st.element();
+			b[pop]=(byte)1;               //assigning processed status
+			st.remove();                  //removing head of the queue 
+			for(int i=0;i<vertices;i++){
+				if(a[pop][i]!=0 && b[i]!=(byte)0 && b[i]!=(byte)1 ){
+					st.add(i);
+					b[i]=(byte)0;                        //assigning waiting status
+				}}}
+	}
+	
+	
+		public static void main(String args[]){
+		Scanner in=new Scanner(System.in);
+		int vertices=in.nextInt(),source=in.nextInt();
+		byte [][]a=new byte [vertices][vertices];
+		//initially all elements of a are initialized with value zero
+		
+		for(int i=0;i<vertices;i++){
+			int size =in.nextInt(); 
+			for(int j=0;j<size;j++){
+				a[i][in.nextInt()]=1;      //taking adjacency entries by assigning 1
+			}
+		}
+		bfs(a,vertices,source);         //function call
+	}}