int _IsolateOuterplanarObstruction(graphP theGraph, int v, int R)
{
int RetVal;
/* A subgraph homeomorphic to K_{2,3} or K_4 will be isolated by using the visited
flags, set=keep edge/vertex and clear=omit. Here we initialize to omit all, then we
subsequently set visited on all edges and vertices in the homeomorph. */
_ClearVisitedFlags(theGraph);
/* Next we determineg which of the non-outerplanarity Minors was encountered
and the principal bicomp on which the isolator will focus attention. */
if (_ChooseTypeOfNonOuterplanarityMinor(theGraph, v, R) != OK)
return NOTOK;
/* Find the path connecting the pertinent vertex w with the current vertex v */
if (theGraph->IC.minorType & MINORTYPE_B)
{
isolatorContextP IC = &theGraph->IC;
int SubtreeRoot = gp_GetVertexLastPertinentRootChild(theGraph, IC->w);
if (_FindUnembeddedEdgeToSubtree(theGraph, IC->v, SubtreeRoot, &IC->dw) != TRUE)
return NOTOK;
}
else
{
isolatorContextP IC = &theGraph->IC;
if (_FindUnembeddedEdgeToCurVertex(theGraph, IC->w, &IC->dw) != TRUE)
return NOTOK;
}
/* For minor E, we need to find and mark an X-Y path */
if (theGraph->IC.minorType & MINORTYPE_E)
{
if (_MarkHighestXYPath(theGraph) != TRUE)
return NOTOK;
}
/* Call the appropriate isolator */
if (theGraph->IC.minorType & MINORTYPE_A)
RetVal = _IsolateOuterplanarityObstructionA(theGraph);
else if (theGraph->IC.minorType & MINORTYPE_B)
RetVal = _IsolateOuterplanarityObstructionB(theGraph);
else if (theGraph->IC.minorType & MINORTYPE_E)
RetVal = _IsolateOuterplanarityObstructionE(theGraph);
else
RetVal = NOTOK;
/* Delete the unmarked edges and vertices, and return */
if (RetVal == OK)
RetVal = _DeleteUnmarkedVerticesAndEdges(theGraph);
return RetVal;
}
int _InitializeIsolatorContext(graphP theGraph)
{
isolatorContextP IC = &theGraph->IC;
/* Obtains the edges connecting X and Y to ancestors of the current vertex */
if (_FindUnembeddedEdgeToAncestor(theGraph, IC->x, &IC->ux, &IC->dx) != TRUE ||
_FindUnembeddedEdgeToAncestor(theGraph, IC->y, &IC->uy, &IC->dy) != TRUE)
return NOTOK;
/* For Minor B, we seek the last pertinent child biconnected component, which
is also future pertinent, and obtain the DFS child in its root edge.
This child is the subtree root containing vertices with connections to
both the current vertex and an ancestor of the current vertex. */
if (theGraph->IC.minorType & MINORTYPE_B)
{
int SubtreeRoot = gp_GetVertexLastPertinentRootChild(theGraph, IC->w);
IC->uz = gp_GetVertexLowpoint(theGraph, SubtreeRoot);
if (_FindUnembeddedEdgeToSubtree(theGraph, IC->v, SubtreeRoot, &IC->dw) != TRUE ||
_FindUnembeddedEdgeToSubtree(theGraph, IC->uz, SubtreeRoot, &IC->dz) != TRUE)
return NOTOK;
}
/* For all other minors, we obtain an unembedded connecting the current vertex to the
pertinent vertex W, and for minor E we collect the additional unembedded ancestor
connection for the future pertinent vertex Z. */
else
{
if (_FindUnembeddedEdgeToCurVertex(theGraph, IC->w, &IC->dw) != TRUE)
return NOTOK;
if (theGraph->IC.minorType & MINORTYPE_E)
if (_FindUnembeddedEdgeToAncestor(theGraph, IC->z, &IC->uz, &IC->dz) != TRUE)
return NOTOK;
}
return OK;
}
