/// <summary>
/// Determines whether the Sokoban can move from the source node to <paramref name="pos"/>, and if
/// so, adds this as a newly-discovered node to the <paramref name="priorityQueue"/>. This is used
/// only to add the first four items into the priority queue at the beginning of the algorithm.
/// </summary>
/// <param name="arrIndex">Index of the node the Sokoban is moving to.</param>
/// <param name="pos">Co-ordinates of the cell the Sokoban is moving to.</param>
/// <param name="priorityQueue">The priority queue.</param>
private void addIfValid(int arrIndex, Point pos, specialHeap priorityQueue)
{
if (_moveFinder.Get(pos))
{
_pushLength[arrIndex] = 1;
_moveLength[arrIndex] = _moveFinder.PathLength(pos) + 1;
priorityQueue.Add(arrIndex);
}
}
/// <summary>
/// Relaxes an edge, which is Dijkstrian for: Given that going from <paramref name="fromNode"/> to <paramref name="toNode"/>
/// requires <paramref name="pushLength"/> pushes and <paramref name="moveLength"/> moves, check if this gives rise to a
/// shorter way to reach <paramref name="toNode"/> from the source node, and if so, update the node with the new path
/// lengths and the new predecessor, and insert it into the priority queue.
/// </summary>
private void relaxEdge(int fromNode, int toNode, int pushLength, int moveLength, specialHeap priorityQueue)
{
if (
// Either we haven't discovered this node yet...
_pushLength[toNode] == 0 ||
// ...or we can reduce its push length...
_pushLength[toNode] > _pushLength[fromNode] + pushLength ||
// ...or its push length is the same, but we can reduce the move length
(_pushLength[toNode] == _pushLength[fromNode] + pushLength && _moveLength[toNode] > _moveLength[fromNode] + moveLength)
)
{
_pushLength[toNode] = _pushLength[fromNode] + pushLength;
_moveLength[toNode] = _moveLength[fromNode] + moveLength;
_predecessor[toNode] = fromNode;
priorityQueue.Add(toNode);
}
}
