/// <summary>
/// Creates the vertices in the level graph and fills the level matrix and connected
/// subgraph dictionary with them.
/// </summary>
private void CreateVertices()
{
for (int row = 0; row < _rows; row++)
{
for (int column = 0; column < _columns; column++)
{
var vertex = new Vertex(row, column);
_levelMatrix[row, column] = vertex;
_connectedSubgraphs[vertex] = new ConnectedSubgraph(vertex);
_availableVertices.Add(vertex);
}
}
}
/// <summary>
/// Attempts to remove an edge entering a specific vertex from the strongly connected
/// portion of a specific connected subgraph and replace it with another edge towards an
/// edge from a weakly connected portion of the connected subgraph, thus expanding the
/// strongly connected portion.
/// </summary>
/// <param name="connectedSubgraph">The connected subgraph which contains a weakly
/// connected portion.</param>
/// <param name="vertex">The vertex from the strongly connected portion of the connected
/// subgraph.</param>
/// <returns><see langword="true"/> if the edge was successfully added.</returns>
private bool AddStronglyConnectingEdgeEnteringVertex(
ConnectedSubgraph connectedSubgraph,
Vertex vertex)
{
Vertex otherVertex = null;
List<Vertex> adjacentVertices = GetAdjacentVertices(vertex);
while (adjacentVertices.Count > 0)
{
int vertexIndex = _random.Next(adjacentVertices.Count);
Vertex adjacentVertex = adjacentVertices[vertexIndex];
if (!vertex.IsConnectedToVertex(adjacentVertex)
&& connectedSubgraph.ContainsVertex(adjacentVertex)
&& !connectedSubgraph.IsVertexStronglyConnected(adjacentVertex))
{
if (connectedSubgraph.CheckWillConnectStrongly(vertex, adjacentVertex))
{
if (!CheckCanConnectVertices(vertex, adjacentVertex))
{
// If the two vertices cannot be connected without causing an
// intersection, remove the other edge
Vertex crossVertex1 = _levelMatrix[vertex.Row, adjacentVertex.Column];
Vertex crossVertex2 = _levelMatrix[adjacentVertex.Row, vertex.Column];
RemoveEdgeBetweenVertices(crossVertex1, crossVertex2);
}
// Check if the other vertex has the maximum number of edges entering it
// and if so, remove a random edge entering it
if (adjacentVertex.ConnectedVertexCount == _maxEdges)
RemoveEdgeEnteringVertex(adjacentVertex);
otherVertex = adjacentVertex;
break;
}
}
adjacentVertices.RemoveAt(vertexIndex);
}
// If no suitable other vertex was found, give up
if (otherVertex == null)
return false;
// Check if the specified vertex has the maximum number of edges entering it and if so,
// remove a random edge entering it
if (vertex.ConnectedVertexCount == _maxEdges)
RemoveEdgeEnteringVertex(vertex);
// Add the edge to the level graph
AddEdgeBetweenVertices(vertex, otherVertex);
return true;
}
/// <summary>
/// Adjusts the connected subgraph assignment for a specific vertex.
/// </summary>
/// <param name="vertex">The vertex whose connected subgraph should be adjusted.
/// </param>
/// <param name="recalculateCurrent">Specifies whether the vertex's currently assigned
/// connected subgraph should be recalculated before adjusting the assignment.</param>
private void AdjustConnectedSubgraphs(Vertex vertex, bool recalculateCurrent)
{
ConnectedSubgraph currentGraph = _connectedSubgraphs[vertex];
// Recalculate the currently assigned connected subgraph if needed
if (recalculateCurrent)
currentGraph.RecalculateConnectedVertices();
// If the specified vertex does not belong to its currently assigned connected
// subgraph, create a new connected subgraph object using the specified vertex as a
// main vertex for it and then assign it to all vertices that belong to it
if (!currentGraph.ContainsVertex(vertex))
{
var newGraph = new ConnectedSubgraph(vertex);
foreach (Vertex connectedVertex in newGraph.ConnectedVertices)
{
_connectedSubgraphs[connectedVertex] = newGraph;
}
}
}
/// <summary>
/// Attempts to remove an edge entering a specific vertex in a specific connected subgraph
/// and replace it with another edge towards a different connected subgraph, thus merging
/// the two connected subgraphs.
/// </summary>
/// <param name="connectedSubgraph">The connected subgraph which should be merged with
/// another one.</param>
/// <param name="vertex">The vertex from the strongly connected portion of the connected
/// subgraph.</param>
/// <returns><see langword="true"/> if the edge was successfully added.</returns>
private bool AddExternalEdgeEnteringVertex(
ConnectedSubgraph connectedSubgraph,
Vertex vertex)
{
// Attempt to find another vertex from a different connected subgraph that can be
// connected to the specified vertex; if an edge prevents the two vertices from being
// connected, remove it
Vertex otherVertex = null;
List<Vertex> adjacentVertices = GetAdjacentVertices(vertex);
while (adjacentVertices.Count > 0)
{
int vertexIndex = _random.Next(adjacentVertices.Count);
Vertex adjacentVertex = adjacentVertices[vertexIndex];
if (!connectedSubgraph.ContainsVertex(adjacentVertex))
{
if (!CheckCanConnectVertices(vertex, adjacentVertex))
{
// If the two vertices cannot be connected without causing an intersection,
// remove the other edge
Vertex crossVertex1 = _levelMatrix[vertex.Row, adjacentVertex.Column];
Vertex crossVertex2 = _levelMatrix[adjacentVertex.Row, vertex.Column];
RemoveEdgeBetweenVertices(crossVertex1, crossVertex2);
}
// Check if the other vertex has the maximum number of edges entering it and if
// so, remove a random edge entering it
if (adjacentVertex.ConnectedVertexCount == _maxEdges)
RemoveEdgeEnteringVertex(adjacentVertex);
otherVertex = adjacentVertex;
break;
}
adjacentVertices.RemoveAt(vertexIndex);
}
// If no suitable other vertex was found, give up
if (otherVertex == null)
return false;
// Check if the specified vertex has the maximum number of edges entering it and if so,
// remove a random edge entering it
if (vertex.ConnectedVertexCount == _maxEdges)
RemoveEdgeEnteringVertex(vertex);
// Add the edge to the level graph
AddEdgeBetweenVertices(vertex, otherVertex);
return true;
}
