public static Dictionary <ulong, double> BellmanFordDistances(
IWeightedGraph <FindingDirectionsState, double> graph,
FindingDirectionsState landmark
)
{
// TODO: move this to fast.search
// https://en.wikipedia.org/wiki/Bellman%E2%80%93Ford_algorithm
// this is a version of Bellman-Ford that assumes no prior knowledge
// of the full node set and only tracks reachable nodes, anything not
// in the result of this function should be considered infinite
// we also only care about the distances here and do not maintain prev
var result = new Dictionary <ulong, double>();
var openSet = new OpenSet <double, FindingDirectionsState>();
openSet.PushOrImprove(0d, landmark);
while (!openSet.IsEmpty)
{
var dist = openSet.MinCost;
var node = openSet.PopMin();
if (result.ContainsKey(node.NodeId))
{
continue;
}
result.Add(node.NodeId, dist);
var neighbors = graph.GetNeighbors(node);
foreach (var neighbor in neighbors)
{
openSet.PushOrImprove(dist + graph.GetEdgeWeight(node, neighbor), neighbor);
}
}
return(result);
}
public void TestSorting10()
{
var openSet = new OpenSet <int, int>();
var values = new int[] { 9, 2, 3, 8, 0, 4, 7, 5, 6, 1 };
for (int j = 0; j < 2; j++)
{
foreach (var i in values)
{
openSet.PushOrImprove(i, i);
}
}
int nextValue = 0;
while (!openSet.IsEmpty)
{
var val = openSet.PopMin();
if (val != nextValue)
{
break;
}
nextValue += 1;
}
Assert.Equal(nextValue, values.Length);
}
public void PopRemovesMin()
{
var openSet = new OpenSet <int, int>();
openSet.PushOrImprove(5, 99);
openSet.PushOrImprove(8, 33);
int minValue = openSet.PopMin();
Assert.Equal(99, minValue);
Assert.Equal(1, openSet.Size);
Assert.Equal(8, openSet.MinCost);
}
public void PoppingEmptySetFails()
{
var openSet = new OpenSet <int, int>();
try
{
openSet.PopMin();
Assert.True(false, "PopMin from an empty set did not throw InvalidOperationException.");
}
catch (InvalidOperationException)
{
Assert.True(true);
}
}
