BFS

Main.java

package com.company;

import java.util.Iterator;
import java.util.LinkedList;

public class Main {
    private int V; //number of vertices.
    private LinkedList<Integer> adj[];
    //Constructor that inialises and sets memory for the adj list
    Main(int v){
        V=v;
        adj= new LinkedList[v];
        for(int i=0;i<v;i++)
            adj[i] = new LinkedList<>();
    }
    //method to build the adj list.
    void addEdge(int v,int w){
        adj[v].add(w);
    }
    //pass the root
    void BFS(int root){
        boolean []visited =  new boolean[V];
        LinkedList<Integer> queue = new LinkedList<>();
        visited[root]=true;
        queue.add(root);
        while(queue.size()!=0) {
            root = queue.poll();
            System.out.println(" "+root);
            Iterator<Integer> i = adj[root].listIterator();
            while(i.hasNext()){
                int n = i.next();
                if(!visited[n]){
                    visited[n]=true;
                    queue.add(n);
                }
            }
        }
    }
    public static void main(String[] args) {
        Main g = new Main(4);
        g.addEdge(2,3);
        g.addEdge(3,3);
        g.addEdge(2,0);
        g.addEdge(0,2);
        g.addEdge(1, 2);
        g.addEdge(0, 1);
        g.BFS(2);
    }
}

Ouputs 2 3 0 1