/*
* Returns the active c-node of RBC list containing "u".
* Traverses only nodes with label_b <= dfspos_num[w].
* Let z be the first element of RBC.
* All traversed nodes, but z, are inserted in "nl".
* Pre-conditions:
* - "u" is not the 1st element in RBC list;
* - ptritem[u] is the pointer to the item containing "u";
* - "u" is a node that is an ancestor of a neighbor of w;
* - state[v] == NOT_VISITED for each node v in RBC list that was not
* traversed.
*/
node PlanarityTestImpl::findActiveCNode(node u, node w, list<node> &nl) {
list<node> traversedNodesInRBC;
assert(isCNode(parent.get(u.id)));
if (state.get(u.id) != NOT_VISITED) {
assert(!isCNode(parent.get(parent.get(u.id).id)));
return parent.get(u.id);
}
BmdLink<node> *it1 = ptrItem.get(u.id); // ptrItem[u];
assert(it1 != nullptr);
state.set(u.id, VISITED_IN_RBC);
traversedNodesInRBC.push_back(u);
BmdLink<node> *it = searchRBC(1, it1, w, traversedNodesInRBC);
if (it == nullptr)
it = searchRBC(0, it1, w, traversedNodesInRBC);
assert(it != nullptr);
node v = it->getData();
node cNode;
if (it->prev() != nullptr && it->succ() != nullptr)
cNode = parent.get(v.id); // path compressed;
else
cNode = activeCNode[it];
assert(cNode != NULL_NODE);
node first = RBC[cNode].firstItem()->getData();
// path compression;
// forall(v, traversedNodesInRBC)
for (list<node>::iterator it = traversedNodesInRBC.begin(); it != traversedNodesInRBC.end();
++it) {
if (*it != first) {
if (*it != u)
nl.push_back(v);
parent.set((*it).id, cNode);
} else
state.set((*it).id, NOT_VISITED);
}
return cNode;
}
