/// <inheritdoc/>
public UndirectedIndexedIncidenceGraph ToGraph()
{
int n = _vertexCount;
int m = _tailByEdge.Count;
Debug.Assert(_tailByEdge.Count == _headByEdge.Count, "_tailByEdge.Count == _headByEdge.Count");
int dataLength = 2 + n + m + m + m + m;
#if NET5
int[] data = GC.AllocateUninitializedArray <int>(dataLength);
#else
int[] data = new int[dataLength];
#endif
data[0] = n;
data[1] = m;
Span <int> destEdgesOrderedByTail = data.AsSpan(2 + n, m + m);
int invertedEdgeCount = 0;
for (int edge = 0; edge < m; ++edge)
{
destEdgesOrderedByTail[edge] = edge;
int head = _headByEdge[edge];
int tail = _tailByEdge[edge];
if (head != tail)
{
destEdgesOrderedByTail[m + invertedEdgeCount++] = ~edge;
}
}
int directedEdgeCount = m + invertedEdgeCount;
Array.Sort(data, 2 + n, directedEdgeCount,
new UndirectedIndexedEdgeComparer(_tailByEdge.Array, _headByEdge.Array));
Span <int> destUpperBoundByVertex = data.AsSpan(2, n);
destUpperBoundByVertex.Clear();
for (int i = 0; i < directedEdgeCount; ++i)
{
int edge = destEdgesOrderedByTail[i];
int tail = edge < 0 ? _headByEdge[~edge] : _tailByEdge[edge];
++destUpperBoundByVertex[tail];
}
for (int vertex = 1; vertex < n; ++vertex)
{
destUpperBoundByVertex[vertex] += destUpperBoundByVertex[vertex - 1];
}
Span <int> destHeadByEdge = data.AsSpan(2 + n + m + m, m);
_headByEdge.AsSpan().CopyTo(destHeadByEdge);
Span <int> destTailByEdge = data.AsSpan(2 + n + m + m + m, m);
_tailByEdge.AsSpan().CopyTo(destTailByEdge);
_headByEdge = ArrayPrefixBuilder.Release(_headByEdge, false);
_tailByEdge = ArrayPrefixBuilder.Release(_tailByEdge, false);
_vertexCount = 0;
return(new UndirectedIndexedIncidenceGraph(data));
}
/// <inheritdoc/>
public IndexedIncidenceGraph ToGraph()
{
int n = _vertexCount;
int m = _tailByEdge.Count;
Debug.Assert(_tailByEdge.Count == _headByEdge.Count, "_tailByEdge.Count == _headByEdge.Count");
int dataLength = 2 + n + m + m + m;
#if NET5
int[] data = GC.AllocateUninitializedArray <int>(dataLength);
#else
int[] data = new int[dataLength];
#endif
data[0] = n;
data[1] = m;
Span <int> destReorderedEdges = data.AsSpan(2 + n, m);
for (int edge = 0; edge < m; ++edge)
{
destReorderedEdges[edge] = edge;
}
if (NeedsReordering)
{
Array.Sort(data, 2 + n, m, new IndexedEdgeComparer(_tailByEdge.Array));
}
Span <int> destUpperBoundByVertex = data.AsSpan(2, n);
destUpperBoundByVertex.Clear();
for (int edge = 0; edge < m; ++edge)
{
int tail = _tailByEdge[edge];
++destUpperBoundByVertex[tail];
}
for (int vertex = 1; vertex < n; ++vertex)
{
destUpperBoundByVertex[vertex] += destUpperBoundByVertex[vertex - 1];
}
Span <int> destHeadByEdge = data.AsSpan(2 + n + m, m);
_headByEdge.AsSpan().CopyTo(destHeadByEdge);
Span <int> destTailByEdge = data.AsSpan(2 + n + m + m, m);
_tailByEdge.AsSpan().CopyTo(destTailByEdge);
_currentMaxTail = 0;
_headByEdge = ArrayPrefixBuilder.Release(_headByEdge, false);
_tailByEdge = ArrayPrefixBuilder.Release(_tailByEdge, false);
_vertexCount = 0;
return(new IndexedIncidenceGraph(data));
}