/// <summary>
///
/// </summary>
/// <param name="graph"></param>
/// <param name="vertexDistances"></param>
/// <param name="startVertex"></param>
/// <returns></returns>
public static IEnumerable <int> WalkToMin(EdgeGraph graph, float[] vertexDistances, int startVertex)
{
int v0 = startVertex;
float d0 = vertexDistances[v0];
while (true)
{
// edge to lowest neighbour
int eMin = -1;
float dMin = float.MaxValue;
// find edge to neighbour with smallest distance
foreach (var ei in graph.GetIncidentEdges(v0))
{
var v1 = graph.GetEdge(ei).Other(v0);
var d1 = vertexDistances[v1];
if (d1 < dMin)
{
eMin = ei;
dMin = d1;
}
}
// if less than current distance, take a step
if (dMin < d0)
{
yield return(eMin);
// update current vertex and distance
v0 = graph.GetEdge(eMin).Other(v0);
d0 = dMin;
}
else
{
yield break;
}
}
}
/// <summary>
///
/// </summary>
public static void GetVertexDistances(EdgeGraph graph, float[] edgeLengths, IEnumerable <int> sources, float[] result, IEnumerable <int> ignore = null)
{
// initialize depths
for (int i = 0; i < graph.VertexCount; i++)
{
result[i] = float.MaxValue;
}
// create queue
var queue = new Queue <int>();
// initialize source(s)
foreach (int source in sources)
{
queue.Enqueue(source);
result[source] = 0.0f;
}
// initialize ignored
if (ignore == null)
{
ignore = Enumerable.Empty <int>();
}
foreach (int index in ignore)
{
result[index] = 0.0f;
}
// search
while (queue.Count > 0)
{
int v0 = queue.Dequeue();
float d0 = result[v0];
// iterate over edges incident to v0
foreach (var ei in graph.GetIncidentEdges(v0))
{
// calculate distance to v1
int v1 = graph.GetEdge(ei).Other(v0);
float d1 = d0 + edgeLengths[ei];
// if less than the current distance then update
if (d1 < result[v1])
{
queue.Enqueue(v1);
result[v1] = d1;
}
}
}
}