/// <summary>
/// This is the key method and houses the key parts of the algorithm. Initially,
/// checks are made to the maze parameter that has been inputted from the 'Start'
/// class. These either fail and return the relevant error message or pass and
/// the process begins. The details of each part will be discussed in their
/// relevant sections.
/// </summary>
/// <param name="maze"> </param>
/// <returns>
/// A string.
/// If the maze parameter is valid, the maze directions.
/// If not, an error message, the type of which depends on the maze parameter.
/// </returns>
public static string AStarSearch(List <String> maze)
{
// Checks if maze is empty.
if (maze.Count == 0)
{
return("\nThe maze provided is empty, please input a valid Maze.\n");
}
/*
* Nested foreach loops, the first converts each string (line) to a char
* array, allowing the second to go through each character and check if
* the correct characters for this maze type are within (in this case;
* A, B, x and .).
*/
var isAInMaze = false;
var isBInMaze = false;
var isXInMaze = false;
var isDotInMaze = false;
foreach (var line in maze)
{
var ca = line.ToCharArray();
foreach (var c in ca)
{
if (c.Equals('A'))
{
isAInMaze = true;
}
if (c.Equals('B'))
{
isBInMaze = true;
}
if (c.Equals('x'))
{
isXInMaze = true;
}
if (c.Equals('.'))
{
isDotInMaze = true;
}
}
}
// Checks if the maze is in invalid.
if (isAInMaze == false | isBInMaze == false | isXInMaze == false | isDotInMaze == false)
{
return("\nThe maze provided is not valid, please input a valid Maze.\n");
}
/*
* Creates a new Node object called start and assigns it's Y value to
* the index value of that which contains 'A' - the start point. This
* process takes advantage of the C# LINQ framework (although the use
* of LINQ is minimised as much possible for efficiency purposes). The
* X value is then assigned using the value of Y as a reference point.
*/
var start = new Node
{
Y = maze.FindIndex(s => s.Contains("A"))
};
start.X = maze[start.Y].IndexOf("A");
// This process is identical to the above.
var end = new Node
{
Y = maze.FindIndex(s => s.Contains("B"))
};
end.X = maze[end.Y].IndexOf("B");
/*
* Here we create two queues, one called openPriorityQueue which is a
* SimplePriorityQueue (this is a third-party data structure, designed
* for pathfinding use cases - the reference of which can be found in
* the ReadMe) and is used for queuing the nodes that may be visited.
* This queue has a priority level for each node enqueued and it is
* this priority level which is used to dictate which nodes shall be
* visited at any given time.
*
* The second queue is called the ClosedQueue and it is a HashSet. This
* queue is used to store all the previously visited nodes, and as
* such grows rapidly in size in relation to maze complexity. A HashSet
* was therefore chosen for its performance, and from testing the
* difference between implementing it as a HashSet rather than a
* SimplePriorityQueue was around 2-3x faster.
*/
var openPriorityQueue = new SimplePriorityQueue <Node>();
var closedQueue = new HashSet <Node>();
// Adds the start node to the openPriorityQueue.
openPriorityQueue.Enqueue(start, 0);
// Initialises an int called gCost.
var gCost = 0;
// The start of the main loop.
while (openPriorityQueue.Count > 0)
{
/*
* This assigns the node current to the value of the node at the top
* of the queue, which should have the lowest fCost.
*/
var current = openPriorityQueue.First;
/*
* If the final node has been reached, assign the string variable to
* the result of the PrintDirections method. This will contain the
* NSEW directions and then return them.
*/
if (current.X == end.X && current.Y == end.Y)
{
var mazeDirections = PrintDirections(current);
return(mazeDirections);
}
// Adds the current node to the closed queue (visited).
closedQueue.Add(current);
// Removes the head of the queue from the open queue.
openPriorityQueue.Dequeue();
/*
* If the destination is within the closed list, then the Path has
* been found, and the while loop is broken.
*/
//var endFound = false;
foreach (var node in closedQueue)
{
if ((node.X == end.X) && (node.Y == end.Y))
{
var mazeDirections = PrintDirections(current);
return(mazeDirections);
}
}
/*
* Assign the HashSet neighbours to the value of the GetNeighbours
* method, which will contain 0-4 of the surrounding nodes.
*/
var neighbours = GetNeighbours(maze, current);
// Increment the gCost.
gCost = current.gCost + 1;
/*
* A foreach loop is used to iterate through the neighbours to find
* the best path moving forward.
*/
foreach (var neighbour in neighbours)
{
// If the neighbour is already in the closed queue, it's ignored.
var neighbourInClosedQueue = false;
foreach (var node in closedQueue)
{
if ((node.X == neighbour.X) && (node.Y == neighbour.Y))
{
neighbourInClosedQueue = true;
break;
}
}
if (neighbourInClosedQueue == true)
{
continue;
}
/*
* If the neighbour is not within the open queue, then CalculateNodeCost
* is called, which generates the costs of the node. The parent of the
* neighbour is set as the current node being dealt with. Following this
* a foreach loop is used to sort through the nodes of the open queue and
* if the neighbour fCost is lower, then it's assigned a higher priority
* (lower priority number), if the fCost is equal, it remains at the same
* priority, and if the fCost is higher, it's assigned a lower priority
* (high priority number). The initial if statement uses LINQ, as it was
* the only appropriate way to check if a node within the open queue is
* equal to neighbour's X and Y value.
*/
if (openPriorityQueue.FirstOrDefault(node => node.X == neighbour.X && node.Y == neighbour.Y) == null)
{
CalculateNodeCost(gCost, end, neighbour);
neighbour.parent = current;
openPriorityQueue.Enqueue(neighbour, 1);
foreach (var node in openPriorityQueue)
{
if (node.fCost < neighbour.fCost)
{
openPriorityQueue.UpdatePriority(node, 0);
}
else if (node.fCost > neighbour.fCost)
{
openPriorityQueue.UpdatePriority(node, 2);
}
}
}
}
}
// If the maze cannot be solved, a message is returned saying so.
return("\nThis maze cannot be escaped from...\n");
}
public ActionResult _CrearCSPF(CSPFViewModel newModel)
{
//Proyecto proyectoActual = new Proyecto(newModel.idProyecto);
NodoDijkstra RouterOrigen = new NodoDijkstra(newModel.nRouterOrigen, newModel.idProyecto);
SimplePriorityQueue<NodoDijkstra> routerQueue = new SimplePriorityQueue<NodoDijkstra>();
routerQueue = Dijkstra.GenerarRutas(RouterOrigen, newModel.idProyecto);
NodoDijkstra RouterDestino = routerQueue.FirstOrDefault(x => x.idRouter == newModel.nRouterDestino);
List<NodoDijkstra> result = new List<NodoDijkstra>();
result = Dijkstra.GetRutaMasCortaHasta(RouterDestino);
return Json(1);
}
