// get the node ids in 1-connected components
void Get1CnCom(const PUNGraph& Graph, TCnComV& Cn1ComV) {
//TCnCom::GetWccCnt(Graph, SzCntV); IAssertR(SzCntV.Len() == 1, "Graph is not connected.");
TIntPrV EdgeV;
GetEdgeBridges(Graph, EdgeV);
if (EdgeV.Empty()) { Cn1ComV.Clr(false); return; }
PUNGraph TmpG = TUNGraph::New();
*TmpG = *Graph;
for (int e = 0; e < EdgeV.Len(); e++) {
TmpG->DelEdge(EdgeV[e].Val1, EdgeV[e].Val2); }
TCnComV CnComV; GetWccs(TmpG, CnComV);
IAssert(CnComV.Len() >= 2);
const TIntV& MxWcc = CnComV[0].NIdV;
TIntSet MxCcSet(MxWcc.Len());
for (int i = 0; i < MxWcc.Len(); i++) {
MxCcSet.AddKey(MxWcc[i]); }
// create new graph: bridges not touching MxCc of G with no bridges
for (int e = 0; e < EdgeV.Len(); e++) {
if (! MxCcSet.IsKey(EdgeV[e].Val1) && ! MxCcSet.IsKey(EdgeV[e].Val2)) {
TmpG->AddEdge(EdgeV[e].Val1, EdgeV[e].Val2); }
}
GetWccs(TmpG, Cn1ComV);
// remove the largest component of G
for (int c = 0; c < Cn1ComV.Len(); c++) {
if (MxCcSet.IsKey(Cn1ComV[c].NIdV[0])) {
Cn1ComV.Del(c); break; }
}
}
// GIRVAN-NEWMAN algorithm
// 1. The betweenness of all existing edges in the network is calculated first.
// 2. The edge with the highest betweenness is removed.
// 3. The betweenness of all edges affected by the removal is recalculated.
// 4. Steps 2 and 3 are repeated until no edges remain.
// Girvan M. and Newman M. E. J., Community structure in social and biological networks, Proc. Natl. Acad. Sci. USA 99, 7821–7826 (2002)
// Keep removing edges from Graph until one of the connected components of Graph splits into two.
void CmtyGirvanNewmanStep(PUNGraph& Graph, TIntV& Cmty1, TIntV& Cmty2) {
TIntPrFltH BtwEH;
TBreathFS<PUNGraph> BFS(Graph);
Cmty1.Clr(false); Cmty2.Clr(false);
while (true) {
TSnap::GetBetweennessCentr(Graph, BtwEH);
BtwEH.SortByDat(false);
if (BtwEH.Empty()) { return; }
const int NId1 = BtwEH.GetKey(0).Val1;
const int NId2 = BtwEH.GetKey(0).Val2;
Graph->DelEdge(NId1, NId2);
BFS.DoBfs(NId1, true, false, NId2, TInt::Mx);
if (BFS.GetHops(NId1, NId2) == -1) { // two components
TSnap::GetNodeWcc(Graph, NId1, Cmty1);
TSnap::GetNodeWcc(Graph, NId2, Cmty2);
return;
}
}
}
