Printing BFS (Binary Tree) in Level Order with Specific Formatting

Question

To begin with, this question is not a dup of this one, but builds on it.

Taking the tree in that question as an example,

    1 
   / \\
  2   3
 /            


        

Answer 1

why not keep sentinal in queue and check when all the nodes in current level are processed.

public void printLevel(Node n) {
    Queue q = new ArrayBlockingQueue();
    Node sentinal = new Node(-1);
    q.put(n);
    q.put(sentinal);
    while(q.size() > 0) {
        n = q.poll();
        System.out.println(n.value + " "); 
        if (n == sentinal && q.size() > 0) {
           q.put(sentinal); //push at the end again for next level
           System.out.println();
        }
        if (q.left != null) q.put(n.left);
        if (q.right != null) q.put(n.right);
    }
}