/// <summary>
/// This is a wrapper around <see cref="StronglyConnectedComponentFinder{T}.DetectCycle"/> that uses the same way to setup dependencies as <see cref="DetectCycles{T}"/>.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source">Required. The sequence of elements that need to be sorted.</param>
/// <param name="dependencySelector">Required. A delegate that takes an items of <see cref="source"/> and returns a sequence of dependencies.
/// <remarks>Can return null to indicate no dependency.</remarks></param>
/// <param name="comparer">Not required. A n implementation of <see cref="IEqualityComparer{T}"/>, this is used to compare the values with their dependencies.</param>
public static StronglyConnectedComponentList <T> ResolveStronglyConnectedComponents <T>(
IEnumerable <T> source, Func <T, IEnumerable <T> > dependencySelector, IEqualityComparer <T> comparer = null)
{
var valueComparer = comparer ?? EqualityComparer <T> .Default;
var vertexComparer = new VertexValueComparer <T>(valueComparer);
var finder = new StronglyConnectedComponentFinder <T>();
var vertices = VertexBuilder.BuildVertices(source, dependencySelector, valueComparer);
return(finder.DetectCycle(vertices, vertexComparer));
}
public void CycleWithDuplicates()
{
var testValues = new
{
A = TestValue.Create("a ", "e"),
B = TestValue.Create(" B", " c "),
A2 = TestValue.Create("A ", "C"),
C = TestValue.Create("C", "A", "D"),
D = TestValue.Create("d"),
E = TestValue.Create("E"),
};
var graph = new[]
{
testValues.A,
testValues.B,
testValues.C,
testValues.D,
testValues.E,
testValues.A2,
};
var ignoreCase = DerivedComparer.Create(StringComparer.OrdinalIgnoreCase, (string t) => t.Trim());
var equalityComparer = TestValue.CreateComparer(ignoreCase);
var vertexValueComparer = new VertexValueComparer <TestValue <string> >(equalityComparer);
var byValue = graph.ToLookup(t => t.Value, ignoreCase);
var vertices = VertexBuilder.BuildVertices(graph, s => s.DependsOn.SelectMany(d => byValue[d]), equalityComparer).ToList();
Assert.AreEqual(6, vertices.Count, "every source element should yield a vertex");
Assert.AreEqual(5, vertices.Distinct().Count(), "'A' and 'a ' should yield the exact same vertex");
var finder = new StronglyConnectedComponentFinder <TestValue <string> >();
var simpleComponents = finder.DetectCycle(vertices, vertexValueComparer);
var components = simpleComponents.ExtractCycles(equalityComparer);
Assert.AreEqual(4, components.Count, "It should be only 4 components");
Assert.AreEqual(3, components.IndependentComponents().Count(), "B, D & E are acylic");
Assert.AreEqual(1, components.Cycles().Count(), "Only 1 cycle should be found");
Assert.AreEqual
(2,
components.Take(2)
.SelectMany(t => t)
.Intersect(new[] { testValues.D, testValues.E })
.Count(),
"D & E should be the first components.");
var component3 = components.Skip(2).First();
var component4 = components.Skip(3).First();
Assert.AreEqual(component3.Count, 2, "3rd component should be a cycle of 2");
Assert.AreEqual
(component3.Intersect(new[] { testValues.A, testValues.C }).Count(),
2,
"3rd component should be a cycle of A & C");
Assert.AreEqual(testValues.B, component4.Single()); // 4th one has to be B (uses A)
}