/// <summary>
/// Enumerates edges of the graph in a breadth-first order.
/// </summary>
/// <param name="graph">The graph.</param>
/// <param name="source">The source.</param>
/// <param name="vertexCount">The number of vertices.</param>
/// <returns>An enumerator to enumerate the edges of a depth-first search tree.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="graph"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentOutOfRangeException">
/// <paramref name="vertexCount"/> is less than zero.
/// </exception>
public IEnumerator <TEdge> EnumerateEdges(TGraph graph, int source, int vertexCount)
{
if (graph == null)
{
throw new ArgumentNullException(nameof(graph));
}
if (vertexCount < 0)
{
throw new ArgumentOutOfRangeException(nameof(vertexCount));
}
if (unchecked ((uint)source >= vertexCount))
{
yield break;
}
byte[] exploredSet = ArrayPool <byte> .Shared.Rent(vertexCount);
Array.Clear(exploredSet, 0, exploredSet.Length);
var queue = new Internal.Queue <int>();
try
{
SetHelpers.Add(exploredSet, source);
queue.Add(source);
while (queue.TryTake(out int u))
{
#if DEBUG
Debug.Assert(SetHelpers.Contains(exploredSet, u));
#endif
TEdgeEnumerator outEdges = graph.EnumerateOutEdges(u);
while (outEdges.MoveNext())
{
TEdge e = outEdges.Current;
if (!graph.TryGetHead(e, out int v))
{
continue;
}
if (SetHelpers.Contains(exploredSet, v))
{
continue;
}
yield return(e);
SetHelpers.Add(exploredSet, v);
queue.Add(v);
}
}
}
finally
{
// The Dispose call will happen on the original value of the local if it is the argument to a using statement.
queue.Dispose();
ArrayPool <byte> .Shared.Return(exploredSet);
}
}
/// <summary>
/// Enumerates edges of the graph in a depth-first order starting from the single source.
/// </summary>
/// <param name="graph">The graph.</param>
/// <param name="source">The source.</param>
/// <param name="vertexCount">The number of vertices.</param>
/// <returns>An enumerator to enumerate the edges of a depth-first search tree.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="graph"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentOutOfRangeException">
/// <paramref name="vertexCount"/> is less than zero.
/// </exception>
public IEnumerator <TEdge> EnumerateEdges(TGraph graph, int source, int vertexCount)
{
if (graph == null)
{
throw new ArgumentNullException(nameof(graph));
}
if (vertexCount < 0)
{
throw new ArgumentOutOfRangeException(nameof(vertexCount));
}
if (unchecked ((uint)source >= vertexCount))
{
yield break;
}
byte[] exploredSet = ArrayPool <byte> .Shared.Rent(vertexCount);
Array.Clear(exploredSet, 0, exploredSet.Length);
var stack = new Internal.Stack <TEdgeEnumerator>();
try
{
SetHelpers.Add(exploredSet, source);
stack.Add(graph.EnumerateOutEdges(source));
while (stack.TryTake(out TEdgeEnumerator outEdges))
{
if (!outEdges.MoveNext())
{
continue;
}
stack.Add(outEdges);
TEdge e = outEdges.Current;
if (!graph.TryGetHead(e, out int v))
{
continue;
}
if (SetHelpers.Contains(exploredSet, v))
{
continue;
}
yield return(e);
SetHelpers.Add(exploredSet, v);
stack.Add(graph.EnumerateOutEdges(v));
}
}
finally
{
stack.Dispose();
ArrayPool <byte> .Shared.Return(exploredSet);
}
}