private Couple <int> AStarTreeSearch()
{
Console.WriteLine("A* Tree Search:");
SortedList <AStarTreeNode> openedNodes = new SortedList <AStarTreeNode>()
{
new AStarTreeNode(distanceMethod, 0, startPosition)
};
int minSteps = -1;
int examinedNodes = 0;
while (openedNodes.Count > 0)
{
examinedNodes++;
AStarTreeNode currentNode = openedNodes[0];
openedNodes.RemoveAt(0);
if (IsGoal(currentNode))
{
minSteps = currentNode.DistanceFromRoot;
break;
}
openedNodes.AddAll(GetSuccessors(currentNode));
}
return(new Couple <int>(minSteps, examinedNodes));
}
private List <AStarGraphNode> GetSuccessors(AStarTreeNode node)
{
Couple <int> pos = node.Coorditates;
List <AStarGraphNode> successors = new List <AStarGraphNode>();
List <AStarGraphNode> nextPositions = new List <AStarGraphNode>
{
new AStarGraphNode(distanceMethod, node.DistanceFromRoot + 1, new Couple <int>(pos.First + 1, pos.Second)),
new AStarGraphNode(distanceMethod, node.DistanceFromRoot + 1, new Couple <int>(pos.First - 1, pos.Second)),
new AStarGraphNode(distanceMethod, node.DistanceFromRoot + 1, new Couple <int>(pos.First, pos.Second + 1)),
new AStarGraphNode(distanceMethod, node.DistanceFromRoot + 1, new Couple <int>(pos.First, pos.Second - 1))
};
foreach (AStarGraphNode newPos in nextPositions)
{
if (IsValidPosition(newPos.Coorditates))
{
successors.Add(newPos);
}
}
return(successors);
}
private int GetHeuristicDistance(AStarTreeNode node) => node.DistanceFromRoot + GetManhattanDistance(node.Coorditates);
private bool IsGoal(AStarTreeNode node) => endPosition == node.Coorditates;
