Java - BFS

import java.util.*;

public class Main {

    static final int MAX = 1000;

    static List<Integer>[] adj = (List<Integer>[]) new ArrayList[MAX];

    /* নিচের মত হচ্ছেনা তাই উপরে arrayList এর array ব্যবহার করেছি । declaration এ কোন প্রবলেম নাই */
//  static List<List<Integer>> adj = new ArrayList<List<Integer>>(MAX);

    static int[] distance = new int[MAX];
    static int[] visited = new int[MAX];
    static Queue<Integer> q = new LinkedList<Integer>();

    static void BFS(int source){
        q.add(source);
        distance[source] = 0;
        visited[source] = 1;
        System.out.println("Level " + distance[source] + " :  " + source);
        while (!q.isEmpty()) {
            int pop = q.peek();
            int temp;
            for (int i = 0; i < adj[pop].size(); i++) {
                temp = adj[pop].get(i);
                if (visited[temp] == 0) {
                    distance[temp] = distance[pop] + 1;
                    visited[temp] = 1;
                    q.add(temp);
                    System.out.println("Level " + distance[temp] + " :  " + temp);
                }
            }
            q.remove();
        }
    }

    public static void main(String[] args) {
        int edge, u, v, source;
        Scanner input = new Scanner(System.in);
        edge = input.nextInt();
        for (int i = 0; i < edge; i++) {
            u = input.nextInt();
            v = input.nextInt();
            if (adj[v]==null) adj[v] = new ArrayList<Integer>();
            adj[v].add(u);
            if (adj[u]==null) adj[u] = new ArrayList<Integer>();
            adj[u].add(v);

                        /* এইখানে প্রবলেম । রান করলে array out of bound exception দেখায় । stackOverFlow তে এইরকম একজন suggest করছিল */
        //  adj.get(u).add(v);
        //  adj.get(v).add(u);

        }
        source = input.nextInt();

       Arrays.fill(visited, 0);
       Arrays.fill(distance, 0);

       BFS(source);
    }

}