public static Result SolveAStar(Maze maze)
{
// The set of nodes already evaluated
var closedSet = new PositionSet();
// The set of currently discovered nodes that are not evaluated yet.
// Initially, only the start node is known.
var openSet = new PositionSet();
openSet.Add(maze.Start);
// For each node, which node it can most efficiently be reached from.
// If a node can be reached from many nodes, cameFrom will eventually contain the
// most efficient previous step.
var cameFrom = new PositionMap <Position>();
// For each node, the cost of getting from the start node to that node.
var gScore = new GScore(maze, 0);
//map with default value of Infinity
// For each node, the total cost of getting from the start node to the goal
// by passing by that node. That value is partly known, partly heuristic.
var fScore = new FScore(maze, HeuristicCostEstimate(maze.Start, maze.End));
// For the first node, that value is completely heuristic.
while (openSet.Count > 0)
{
Position current = fScore.GetLowest(openSet);
//the node in openSet having the lowest fScore[] value
if (current.Equals(maze.End))
{
return(new Result(ReconstructPath(cameFrom, current), maze));
}
openSet.Remove(current);
closedSet.Add(current);
foreach (var neighbor in GetNeighbours(maze, current))
{
if (closedSet.Contains(neighbor))
{
continue; // Ignore the neighbor which is already evaluated.
}
if (!openSet.Contains(neighbor))
{ // Discover a new node
openSet.Add(neighbor);
}
// The distance from start to a neighbor
//the "dist_between" function may vary as per the solution requirements.
double tentative_gScore = gScore[current] + GetDistanceBetweenCost(current, neighbor);
if (tentative_gScore >= gScore[neighbor])
{
continue; // This is not a better path.
}
// This path is the best until now. Record it!
cameFrom[neighbor] = current;
gScore[neighbor] = tentative_gScore;
fScore.Add(neighbor, gScore[neighbor] + HeuristicCostEstimate(neighbor, maze.End));
}
}
return(new Result(maze));
}
