Question

I’m trying to generate valid trees given certain graph edges (which can be considered as a network). Following is the code which reads the graph edges from a file;

    FILE *fin = fopen("somefile.txt", "r");

    for (int i = 0; i <=edges; i++) {
    fscanf(fin, "%d%d%d", &u, &v, &w);
            graph[u][v]=w;
    }
    fclose(fin);

Now I want to generate the maximum number of possible trees (or topology) for a given root u and a given size N given these edges.

For example, if there are edges; 1—>2 ;1—>3; 3—>4. Now if N is 1; possible trees from u=1 is 1—->2 and 1—>3. If N is 2, then possible trees are 1—>2 & 3 or 1—>3—->4
What would be the best way of achieving this? I’m not concerned about complexity issues. I’ll appreciate the help!

Answer 1

it may not the best implementation but
something like this should work

map<vertex,list<edge>> vertexToedgeThatIncludeIt
void Coloredge(edgeList)
{
  for each edge in list:
     edge.color=True
}


void init()
{
   for each edge:
   {
    vertexToedgeThatIncludeIt[edge.vertex1].append(edge)
    vertexToedgeThatIncludeIt[edge.vertex2].append(edge)
   }
}

edge* findUnColoredvertex(edgeList,startPoistion,founfAt)
{
    skip to startPoistion
    for each edge In edgeList:
          if edge not colored return edge 
    update founfAt
    return NULL
}

void spanTree(vertexToedgeThatIncludeIt,spanTreeList,lastvertex)
{
   if(spanTreeList.size==NumberOfTotalvertex)
   {
        print spanningTree
        return 
   }
   nextedge=findUnColoredvertex(vertexToedgeThatIncludeIt[lastvertex],0,founfAt)
   while(nextedge!=NULL)
   {           
       spanTreeList.append(nextedge);
       Coloredge(vertexToedgeThatIncludeIt[lastvertex]);
       spanTree(vertexToedgeThatIncludeIt,spanTreeList,nextedge.othervertex)
       spanTreeList.pop();
       UnColoredge(vertexToedgeThatIncludeIt[lastvertex])
       nextedge=findUnColoredvertex(vertexToedgeThatIncludeIt[lastvertex],founfAt,founfAt)
   }

 }