void digraph::sortAdjLists() {
// Sort all the adjacency lists and initialize li values.
vertex u;
edge e;
for (u = 1; u <= n(); u++) {
sortAlist(u);
// now recompute li values
li[u] = Null;
for (e = first(u); e != term(u); e = next(u,e)) {
if (u == head(e)) li[u] = e;
}
}
}
/** Sort all the adjacency lists. */
void Graph::sortAdjLists() {
for (vertex u = 1; u <= n(); u++) sortAlist(u);
}