Segmentation fault( core dump)

[tushu]

using namespace std;
static int index = 0;
class neighbor
{
    public:
            int dest ;
            int weight;
            neighbor( int d= 0, int w= 0)
            {
               dest = d; weight = w;
            }
};
template<typename T>
class vertexInfo
{
    public:
            enum vertexColor { white , grey , black } ;
            typename  map< T, int>:: iterator vtxMapLoc;
            set<neighbor> edges;
             vertexInfo<T>(int index)
             {}
             vertexInfo<T>( typename  map<T, int> :: iterator& iter): vtxMapLoc{iter}
             {}     
};
template <typename T>
class graph
{
    private:

            typename  map< T, int > :: iterator iter;
            map <T,int> vtxMap;
            vector<vertexInfo<T> > vInfo;
            int numVertices;
            int numedges;
            stack<int> availStack;
            int getvInfoIndex(graph<T>& , const T& v);
    public:
            void addEdge( graph<T>& , const T& , const T&, int );
            set<T> get_Neighbor( graph<T>& , const T& v) ;
            void show(graph<T>& );


};
int main()
{
    graph<char> g;
    char neighbor;
    g.addEdge(g,'A','B', 2); // add edge AB of length 2
    g.addEdge(g,'A','C', 3);
    g.addEdge(g,'B','D', 5);
    g.addEdge(g,'C','D', 1);
    g.addEdge(g,'B','C', 7);
    g.addEdge(g,'D','E', 4);
    g.show(g);
    cout<<"Enter the node whose Neighbor you want  "<<endl;
    cin>> neighbor;
    set<char> adjVertices = g.get_Neighbor(g, neighbor);
    set<char> :: iterator iter;
    iter = adjVertices.begin();
    while( iter != adjVertices.end())
    {
        cout<< *iter<< "  ";
        iter++;
    }
    return 0;
}

template <typename T>
void graph<T> :: addEdge ( graph<T> & g, const T& v1 , const T& v2, int w)
{
    pair <map <char, int> :: iterator, bool> ret ;

     ret = g.vtxMap.insert(pair <char, int >( v1, index));

     if( ret.second)
     {
        index++;
        g.vInfo.push_back(index);
      }

     ret = g.vtxMap.insert(pair <char, int >(v2 , index));

     if( ret.second)
     {
        index++;
        g.vInfo.push_back(index);
      }
   }

template<typename T>
set<T> graph<T> :: get_Neighbor( graph<T>& g , const T& v)
{

    set<T> adjVertices;

    int pos =g.getvInfoIndex(g,v);

    const set<neighbor>& edgeSet = g.vInfo[pos].edges;
    set<neighbor> :: const_iterator setIter;
    int aPos;

    for(setIter = edgeSet.begin(); setIter != edgeSet.end(); setIter++ )
    {
        aPos = (*setIter).dest;
        adjVertices.insert((*g.vInfo[aPos].vtxMapLoc).first);
    }
    return adjVertices;
}

template<typename T>
int  graph<T> :: getvInfoIndex( graph<T>& g , const T& v)
{
     iter = g.vtxMap.find(v);
    int pos = (*iter).second;
    cout<< " position is "<< pos<<endl;
    return pos;
}
template<typename T>
void graph<T> :: show( graph<T>& g)
{
    for( g.iter = g.vtxMap.begin(); g.iter != g.vtxMap.end(); g.iter++)
         {
             cout<< (*(g.iter)).first <<" - >" << (*(g.iter)).second <<endl;
         }

}

I am getting following output :

Output :
A -> 0
B -> 1
C -> 2
D -> 3
E -> 4
Enter the node whose neighbor do you want
A
Segmentation fault (Core dumped)



It is basically a representation of a graph using map.
I tried to verify where is the fault by putting some cout<< statements I got that in function get_neighbor() , not a single statement is executing. What would be the error ??

[Peter87]

You are trying to dereference vtxMapLoc on line 96 and 107 but it has not been initialized.

[tushu]

@Peter87 Can I add photo here so that I can tell what exactly I want ??
if yes how to add photo ??

[tushu]

@Peter87 I removed that 96 lines. Now no error. But not getting desired output.
I will tell what exactly it is
Basically I am representing graph using map and set. So when I will addEdge( A, B, 2) , addEdge ( B, C, 3) map should store A->0 , B->1 , C->2 ( key -> index) Then this "index will be stored in vector vInfo.
Then vInfo[0] will point to some member functions like inDegree(), outDegree(), getNeighbor() etc.... of vertex A.
vInfo[1] will will point to same member functions but for vertex "B".
vInfo[2] will point to member function of vertex "C".
out of this member functions there is vtxMapLoc ( which is iterator) should point to map<T,int> again i.e. ( (*vInfo[0].vtxMapLoc).first = A
(*vInfo[1].vtxMapLoc).first = B.
*vInfo[2].vtxMapLoc).first = C etc...
So in above program , in get_neighbor () ( line no . 91 )
from line 102 to 106 is not being executed. ( for loop )