DCEL.h

struct Vertex;
struct HalfEdge;
struct Face;

struct Vertex
{
        int data;
        HalfEdge* edge;         //one edge with this vertex as head
};

struct HalfEdge
{
        Vertex* tail() const { return next->head; }

        int data;
        Vertex* head;
        Face* face;
        HalfEdge* next;
        HalfEdge* adj;
};

struct Face
{
        bool HasEdge(const Edge* e) const {
                HalfEdge* e = edge;
                do
                {
                        if(e->adj->face == f)
                                return true;
                        e = e->next;
                }
                while(e != edge);
                return false;
        }
        HalfEdge AdjEdge(const Face* f) const {
                HalfEdge* e = edge;
                do
                {
                        if(e->adj->face == f)
                                return e;
                        e = e->next;
                }
                while(e != edge);
                return NULL;
        }
        bool IsAdj(const Face* f) const {
                HalfEdge* e = AdjEdge(f);
                return (e != NULL);
        }

        int data;
        HalfEdge* edge;
};