// number of nodes = 2^(n+1) - 1
int level = 0;
while (level < levels) {
int nnodes = (int)Math.pow(2, level);
for (int i = 0; i < nnodes; i++) {
Node n = (Node)queue.deq();
Node ln = builder.buildNode();
ln.setObject(n.getObject() + ".0");
id2node.put(ln.getObject(), ln);