private EdgePair LocateEdge(int u, int v)
{
VertexPair pair = HelpSearchEdge(u, v);
if (pair == null)
{
return(null);
}
Vertex v1 = pair.V1;
Vertex v2 = pair.V2;
if (v1.marked || v2.marked)
{
return(null);
}
while (true)
{
Edge e1 = v1.outgoingHead;
Edge e2 = e1.next;
while (e2.key < v)
{
e1 = e2;
e2 = e2.next;
}
Lock(e1, e2);
if (ValidateEdge(e1, e2))
{
return(new EdgePair(e1, e2));
}
Unlock(e1, e2);
}
}
public void AddVertex(int key)
{
VertexPair pair = LocateVertex(key); // v1,v2 still locked at this point
Vertex v1 = pair.V1;
Vertex v2 = pair.V2;
if (v2.key != key || v2.marked) // if does not exist, or marked
{
Vertex v3 = new Vertex(key, version);
v3.next = v2; // same key might appear twice, but marked nodes are always last
v1.next = v3;
}
Unlock(v1, v2);
}
public void AddVertex(int key)
{
VertexPair pair = LocateVertex(key); // v1,v2 still locked at this point
Vertex v1 = pair.V1;
Vertex v2 = pair.V2;
if (v2.key != key) // if does not exist
{
Vertex v3 = new Vertex(key);
v3.next = v2;
v1.next = v3;
}
Unlock(v1, v2);
}
public bool ContainsEdge(int u, int v)
{
VertexPair pair = HelpSearchEdge(u, v);
if (pair == null)
{
return(false);
}
Edge e = pair.V1.outgoingHead;
while (e.key < v)
{
e = e.next;
}
return(e.key == v && !e.marked);
}
public void RemoveVertex(int key)
{
VertexPair pair = LocateVertex(key); // v1,v2 still locked at this point
Vertex v1 = pair.V1;
Vertex v2 = pair.V2;
if (v2.key == key)
{
v2.marked = true; // logically remove
v1.next = v2.next; // physically remove
Unlock(v1, v2);
RemoveIncomingEdge(key);
}
else
{
Unlock(v1, v2);
}
}
