public void TestCycleDetector()
{
GraphExtensions <String> g = new GraphExtensions <string>();
// We want to construct a triangle
g.AddVertex("A");
g.AddVertex("B");
g.AddVertex("C");
g.AddEdge("A", "B", 100);
// At this point, we should definitely have no cycle!
Assert.IsFalse(g.ExistsCycleFrom("A"));
Assert.IsFalse(g.ExistsCycleFrom("B"));
Assert.IsFalse(g.ExistsCycleFrom("C"));
// Should still not have a cycle
g.AddEdge("B", "C", 100);
Assert.IsFalse(g.ExistsCycleFrom("A"));
Assert.IsFalse(g.ExistsCycleFrom("B"));
Assert.IsFalse(g.ExistsCycleFrom("C"));
// Let's fully connect our trinagle
g.AddEdge("C", "A", 100);
Assert.IsTrue(g.ExistsCycleFrom("A"));
Assert.IsTrue(g.ExistsCycleFrom("B"));
Assert.IsTrue(g.ExistsCycleFrom("C"));
// Let's add a branch from our triangle
g.AddVertex("D");
g.AddEdge("D", "A", 100);
// These should still be true
Assert.IsTrue(g.ExistsCycleFrom("A"));
Assert.IsTrue(g.ExistsCycleFrom("B"));
Assert.IsTrue(g.ExistsCycleFrom("C"));
// this is a branch, so no cycle from D exists
Assert.IsFalse(g.ExistsCycleFrom("D"));
// Let's connect D to B, making a cycle.
g.AddEdge("D", "B", 100);
// There are now multiple possible cycles from every node to every other
Assert.IsTrue(g.ExistsCycleFrom("A"));
Assert.IsTrue(g.ExistsCycleFrom("B"));
Assert.IsTrue(g.ExistsCycleFrom("C"));
Assert.IsTrue(g.ExistsCycleFrom("D"));
}
public void TestDijkstraSimple()
{
GraphExtensions <String> g = new GraphExtensions <string>();
// Add towns
g.AddVertex("Sydney");
g.AddVertex("Melbourne");
g.AddVertex("Adelaide");
// Draw a straight line between them
g.AddEdge("Sydney", "Melbourne", 100);
g.AddEdge("Melbourne", "Adelaide", 100);
/*
* We now have:
* Sydney <-> Melbourne <-> Adelaide
*/
List <String> l = g.ShortestPathBetween("Sydney", "Adelaide");
Assert.AreEqual("Sydney", l[0]);
Assert.AreEqual("Melbourne", l[1]);
Assert.AreEqual("Adelaide", l[2]);
Assert.AreEqual(3, l.Count);
// Adjacent vertices
l = g.ShortestPathBetween("Sydney", "Melbourne");
Assert.AreEqual("Sydney", l[0]);
Assert.AreEqual("Melbourne", l[1]);
Assert.AreEqual(2, l.Count);
// From self to self
l = g.ShortestPathBetween("Sydney", "Sydney");
Assert.AreEqual(0, l.Count);
// Add a new unconnected vertex
g.AddVertex("Rome");
// Not all roads lead to Rome!
l = g.ShortestPathBetween("Sydney", "Rome");
Assert.IsNull(l);
// TODO remove
g.AddVertex("Helsinki");
g.AddEdge("Sydney", "Rome", 400);
g.AddEdge("Sydney", "Helsinki", 500);
// Make a heavier but direct connection
g.AddEdge("Sydney", "Adelaide", 300);
// The following from earlier should still hold
Console.WriteLine("Here they come:");
l = g.ShortestPathBetween("Sydney", "Adelaide");
/*
* foreach (string i in l) {
* Console.WriteLine(i);
* }*/
Assert.AreEqual("Sydney", l[0]);
Assert.AreEqual("Melbourne", l[1]);
Assert.AreEqual("Adelaide", l[2]);
Assert.AreEqual(3, l.Count);
}