do a BFS and print: printBSTLevels(Node n) { Queue q = new Queue(); q.enqueue(n); while(!q.isEmpty()) { n = q.dequeue(); if(n.left != null) q.enqueue(n.left); if(n.right != null) q.enqueue(n.right); System.out.println(n.val); } }

The above solution is correct but it doesn't print each level on the same line. You can use two stacks or queues to do that.