/// <summary>
/// Checks if a given graph is planar.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="graph">Undirected graph.</param>
/// <returns></returns>
public bool IsPlanar <T>(IGraph <T> graph)
{
if (graph.IsDirected)
{
throw new ArgumentException("The graph must not be directed", nameof(graph));
}
if (graph.VerticesCount == 0)
{
return(true);
}
var alias = new IntGraph <T>(graph, () => new UndirectedAdjacencyListGraph <int>());
// Prepare edges for the C++ code
var edges = new List <int>();
foreach (var edge in alias.Edges)
{
edges.Add(edge.From);
edges.Add(edge.To);
}
return(BoostWrapper.IsPlanar(edges.ToArray(), edges.Count, alias.VerticesCount));
}
private int[][] GetFaces(int verticesCount, List <Tuple <int, int> > edges)
{
var edgesSerialized = new int[edges.Count * 2];
for (var i = 0; i < edges.Count; i++)
{
var edge = edges[i];
edgesSerialized[2 * i] = edge.Item1;
edgesSerialized[2 * i + 1] = edge.Item2;
}
var faces = new int[2 * edges.Count];
var facesBorders = new int[2 * edges.Count];
var success = BoostWrapper.GetFaces(edgesSerialized, edgesSerialized.Length, verticesCount, faces, facesBorders, out var facesCount);
if (!success)
{
return(null);
}
var result = new int[facesCount][];
var counter = 0;
for (var i = 0; i < facesCount; i++)
{
result[i] = new int[facesBorders[i]];
for (var j = 0; j < facesBorders[i]; j++)
{
result[i][j] = faces[counter++];
}
}
return(result);
}