/** Find a negative cost cycle in the residual graph.
* @return some vertex on the cycle, or 0 if no negative
* cycle is present in the residual graph; The edges in the
* cycle are found by traversing the pEdge pointers, starting
* at pEdge[returnedVertex].
*/
vertex mcfCycRed::findCyc() {
vertex u,v,last; edge e;
int c[wfg->n()+1];
List q(wfg->n());
for (u = 1; u <= wfg->n(); u++) {
pEdge[u] = 0; c[u] = 0; q.addLast(u);
}
last = q.last(); // each pass completes when last removed from q
while (!q.empty()) {
u = q.first(); q.removeFirst();
for (e = wfg->firstAt(u); e != 0; e = wfg->nextAt(u,e)) {
if (wfg->res(u,e) == 0) continue;
v = wfg->mate(u,e);
if (c[v] > c[u] + wfg->cost(u,e)) {
pEdge[v] = e;
c[v] = c[u] + wfg->cost(u,e);
if (!q.member(v)) q.addLast(v);
}
}
if (u == last) {
v = cycleCheck();
if (v != 0) return v;
last = q.last();
}
}
return 0;
}
void DFS_M::dfs(int iRoot)
{
Stack2< Pair<int,int> > fringe;
//Queue< Pair<int,int> > fringe;
fringe.push(Pair<int,int>(-1,iRoot));
int precount = 0; // pre-order counter
int poscount = 0; // post-order counter
int inocount = 0; // in-order counter
int P = -1;
int forest=0;
int cyclecount = 0; // number of cycles found so far
while (precount < _graph.getVertexSize())
{
while ( !fringe.empty() )
{
Pair<int,int> pair = fringe.getTop(); fringe.pop();
int v0 = pair.first();
int v1 = pair.second();
if (v0==-2) {
_postorder[v1]=poscount;
++poscount;
continue;
}
if ( !_visited[v1] )
{
// first time we see this vertex, push a dummy edge on the fringe
// before pushing all its children. When the dummy edge will be popped
// that means all the subtrees rooted under this vertex v1, will have been
// explored completely, and we can assign the postorder index to the vertex
fringe.push(Pair<int,int>(-2,v1));
_preorder[v1]=precount; ++precount;
_visited[v1]=1;
_parent[v1]=v0;
_forest[v1]=forest;
if ( v0 > -1 )
{
_matrix[v0][v1]='T';
}
//std::cout << "(" << v1 << ")" << std::endl;
for ( GraphEdgeIter it = _graph.getEdgeIter(v1); !it.end(); ++it )
{
int v2 = *it;
if (!_visited[v2]) {
fringe.push(Pair<int,int>(v1,v2));
} else { // already visited
char edgeType = tagEdge(v1,v2);
cycleCheck(edgeType, v1, v2, cyclecount);
}
}
} else { // already visited
char edgeType = tagEdge(v0,v1);
cycleCheck(edgeType, v0, v1, cyclecount);
}
}
if (fringe.empty() && precount<_graph.getVertexSize())
{
for (int i=0; i<_graph.getVertexSize(); ++i)
{
if (!_visited[i])
{
fringe.push(Pair<int,int>(-1,i));
break;
}
}
++forest;
}
}
}
