/// <summary>
/// Executes one step in the search.
/// </summary>
public bool Step()
{
if (_heap.Count == 0)
{
return(false);
}
_current = _heap.Pop();
while (_current != null)
{ // keep trying.
LinkedEdgePath <T> edgePath = null;
if (!_visits.TryGetValue(_current.Vertex, out edgePath))
{ // this vertex has not been visited before.
_visits.Add(_current.Vertex, new LinkedEdgePath <T>()
{
Path = _current,
MinWeight = _current.Weight
});
break;
}
else
{ // vertex has been visited before, check if edge has.
if (!edgePath.HasPath(_current))
{ // current edge has not been used to get to this vertex.
_visits[_current.Vertex] = new LinkedEdgePath <T>()
{
Path = _current,
MinWeight = edgePath.MinWeight,
Next = edgePath
};
break;
}
}
_current = _heap.Pop();
}
if (_current == null)
{
return(false);
}
if (this.WasFound != null)
{
this.WasFound(_current);
}
// get relevant restrictions.
var restrictions = _getRestrictions(_current.Vertex);
// get the edge enumerator.
var currentSequence = _current.GetSequence2(_edgeEnumerator);
currentSequence = currentSequence.Append(_current.Vertex);
// get neighbours.
_edgeEnumerator.MoveTo(_current.Vertex);
// add the neighbours to the queue.
while (_edgeEnumerator.MoveNext())
{
bool?neighbourDirection;
var neighbourWeight = _weightHandler.GetEdgeWeight(_edgeEnumerator, out neighbourDirection);
if (neighbourDirection == null || (neighbourDirection.Value != _backward))
{ // the edge is forward, and is to higher or was not contracted at all.
var neighbourNeighbour = _edgeEnumerator.Neighbour;
var neighbourSequence = Constants.EMPTY_SEQUENCE;
if (_edgeEnumerator.IsOriginal())
{ // original edge.
if (currentSequence.Length > 1 && currentSequence[currentSequence.Length - 2] == neighbourNeighbour)
{ // this is a u-turn.
continue;
}
if (restrictions != null)
{
neighbourSequence = currentSequence.Append(neighbourNeighbour);
}
}
else
{ // not an original edge, use the sequence.
neighbourSequence = _edgeEnumerator.GetSequence1();
if (currentSequence.Length > 1 && currentSequence[currentSequence.Length - 2] == neighbourSequence[0])
{ // this is a u-turn.
continue;
}
if (restrictions != null)
{
neighbourSequence = currentSequence.Append(neighbourSequence);
}
}
if (restrictions != null)
{ // check restrictions.
if (!restrictions.IsSequenceAllowed(neighbourSequence))
{
continue;
}
}
// build route to neighbour and check if it has been visited already.
var routeToNeighbour = new EdgePath <T>(
neighbourNeighbour, _weightHandler.Add(_current.Weight, neighbourWeight), _edgeEnumerator.IdDirected(), _current);
LinkedEdgePath <T> edgePath = null;
if (!_visits.TryGetValue(_current.Vertex, out edgePath) ||
!edgePath.HasPath(routeToNeighbour))
{ // this vertex has not been visited in this way before.
if (!_weightHandler.IsSmallerThanAny(routeToNeighbour.Weight, _max))
{
continue;
}
_heap.Push(routeToNeighbour, _weightHandler.GetMetric(routeToNeighbour.Weight));
}
}
}
return(true);
}
