/** Prints the keys of the tree in the order given by a level-order traversal. */
public void levelOrderPrint() {
LLQueue<NodePlusDepth> q = new LLQueue<NodePlusDepth>();
// Insert the root into the queue if the root is not null.
if (root != null) q.insert(new NodePlusDepth(root, 0));
// We continue until the queue is empty. At each step,
// we remove an element from the queue, print its value,
// and insert its children (if any) into the queue.
// We also keep track of the current level, and add a newline
// whenever we advance to a new level.
int level = 0;
while (!q.isEmpty()) {
NodePlusDepth item = q.remove();
if (item.depth > level) {
System.out.println();
level++;
}
System.out.print(item.node.key + " ");
if (item.node.left != null) q.insert(new NodePlusDepth(item.node.left, item.depth + 1));
if (item.node.right != null) q.insert(new NodePlusDepth(item.node.right, item.depth + 1));
}
}
private LLQueue getLLQueue() {
return LLQueue.get();
}