static State AStar(State initial)
{
IComparer <State> comparer = new Comparer <State>();
IPriorityQueue <State> candidates = new C5.IntervalHeap <State>(comparer);
System.Collections.Generic.HashSet <string> visitedStates = new System.Collections.Generic.HashSet <string>();
//initialize state
candidates.Add(initial);
visitedStates.Add(initial.ToString());
while (candidates.Count > 0)
{
State currentBest = candidates.DeleteMin();
if (currentBest.GetManhattanDistance() == 0)
{
return(currentBest);
}
// move right
if (currentBest.PositionOf0.Y > 0)
{
var newPositionof0 = new Point(currentBest.PositionOf0.X, currentBest.PositionOf0.Y - 1);
AddCandidate(currentBest, newPositionof0, visitedStates, candidates);
}
//move left
if (currentBest.PositionOf0.Y < State.N - 1)
{
var newPositionof0 = new Point(currentBest.PositionOf0.X, currentBest.PositionOf0.Y + 1);
AddCandidate(currentBest, newPositionof0, visitedStates, candidates);
}
//move down
if (currentBest.PositionOf0.X > 0)
{
Point newPositionof0 = new Point(currentBest.PositionOf0.X - 1, currentBest.PositionOf0.Y);
AddCandidate(currentBest, newPositionof0, visitedStates, candidates);
}
// move up
if (currentBest.PositionOf0.X < State.N - 1)
{
Point newPositionof0 = new Point(currentBest.PositionOf0.X + 1, currentBest.PositionOf0.Y);
AddCandidate(currentBest, newPositionof0, visitedStates, candidates);
}
}
return(null);//this should never be reached but the compilator requires it
}
public Path GetShortestPath(string from, string to)
{
var fromNode = _nodes[from];
var toNode = _nodes[to];
Dictionary <Node, int> distances = new Dictionary <Node, int>();
foreach (var node in _nodes.Values)
{
distances.Add(node, int.MaxValue);
}
distances[fromNode] = 0;
IntervalHeap <NodeEntry> queue = new C5.IntervalHeap <NodeEntry>();
queue.Add(new NodeEntry(fromNode, 0));
Dictionary <Node, Node> previousNode = new Dictionary <Node, Node>();
System.Collections.Generic.HashSet <Node> visited = new System.Collections.Generic.HashSet <Node>();
while (queue.Count != 0)
{
var current = queue.DeleteMin().node;
visited.Add(current);
foreach (var edge in current.Edges)
{
if (visited.Contains(edge.to))
{
continue;
}
var newDistance = distances[current] + edge.weight;
if (newDistance < distances[edge.to])
{
distances[edge.to] = newDistance;
previousNode.Add(edge.to, current);
queue.Add(new NodeEntry(edge.to, newDistance));
}
}
}
return(BuildPath(previousNode, toNode));
}