private void relabelToFront() {
assert (!V.isEmpty()) : "No vertices";
ListIterator<Vertex> iter = V.listIterator();
while (iter.hasNext()) {
Vertex v = iter.next();
// System.out.println("Considering vertex: " + v);
int oldHeight = v.getHeight();
discharge(v);
if (v.getHeight() > oldHeight) {
iter.remove();
V.addFirst(v);
iter = V.listIterator(1);
}
}
}
