/// <summary>Returns an <c>IPath</c> for the optimal path from coordinates <paramref name="source"/> to <paramref name="target"/>.</summary>
/// <param name="board">An object satisfying the interface <c>INavigableBoardFwd</c>.</param>
/// <param name="source">Coordinates for the <c>first</c> step on the desired path.</param>
/// <param name="target">Coordinates for the <c>last</c> step on the desired path.</param>
/// <returns>A <see cref="IPath{THex}"/> for the shortest path found, or null if no path was found.</returns>
/// <remarks>
/// <para>Note that the Heuristic provided by <paramref name="board"/> must be <b>consistent</b>
/// in order for the algorithm to perform properly.</para>
/// </remarks>
public static IPath <THex> GetPathBiDiAlt <THex>(this ILandmarkBoard <THex> board, THex source, THex target)
where THex : class, IHex
{
if (board?.Landmarks == null || source == null || target == null)
{
return(new Path <THex>(null, source, target, null, null));
}
else
{
source.TraceFindPathDetailInit(target);
var pathHalves = board.NewPathHalves(source, target);
var pathfinderFwd = pathHalves.NewAltPathfinder(false);
var pathfinderRev = pathHalves.NewAltPathfinder(true);
// Alternate searching from each direction and calling the other direction
pathfinderFwd.Partner = pathfinderRev;
var pathfinder = pathfinderRev.Partner
= pathfinderFwd;
while (!pathfinder.IsFinished())
{
pathfinder = pathfinder.Partner;
}
pathHalves.ClosedSet.Count.TraceFindPathDone();
return(new Path <THex>(pathHalves.PathFwd, source, target, pathHalves.ClosedSet, null));
}
}
public PathHalves(ILandmarkBoard board, HexCoords start, HexCoords goal)
{
Board = board;
Start = start;
Goal = goal;
ClosedSet = new HashSet <HexCoords>();
BestSoFar = int.MaxValue;
}
/// <summary>.</summary>
/// <param name="board">Board on which this path search is taking place.</param>
/// <param name="source">Start hex for this half of the bidirectional path search.</param>
/// <param name="target">Goal hex for this this half of the bidirectional path search.</param>
public PathHalves(ILandmarkBoard <THex> board, THex source, THex target)
{
Board = board;
Source = source;
Target = target;
ClosedSet = new HashSet <HexCoords>();
BestSoFar = int.MaxValue;
}
/// <summary>.</summary>
/// <typeparam name="THex"></typeparam>
/// <param name="board"></param>
/// <param name="source"></param>
/// <param name="target"></param>
/// <returns></returns>
internal static IPathHalves <THex> NewPathHalves <THex>(this ILandmarkBoard <THex> board, THex source, THex target)
where THex : class, IHex
=> new PathHalves <THex>(board, source, target);
/// <summary>Calculates an <see cref="IDirectedPath"/> for the optimal path from coordinates.</summary> /// <param name="board">An object satisfying the interface <c>INavigableBoardFwd</c>.</param> /// <remarks> /// <para>Note that the Heuristic provided by <paramref name="board"/> <b>must</b> be monotonic /// in order for the algorithm to perform properly.</para> /// <seealso cref="StandardPathfinder"/> /// </remarks> public BidirectionalAltPathfinder(ILandmarkBoard board) => Board = board;
