public Queue <Location> GetPath(Location start, Location end)
{
//Check if locations provided are in bounds. If not, exit.
if (!gameController.IsInBounds(start) || !gameController.IsInBounds(end))
{
Debug.LogError("Tried to get a path with start or end out of bounds: S " + start.x + "," + start.z + " E " + end.x + "," + end.z);
return(null);
}
else
{
//Early exit if start and end are identical
if (gameController.AreLocationsIdentical(start, end))
{
path.Enqueue(start);
return(path);
}
//Get map size limits from GameController
int xSize = gameController.xSize;
int zSize = gameController.zSize;
//Create variables used for pathfinding
Queue <Location> path = new Queue <Location> ();
PriorityQueue frontier = new PriorityQueue();
bool[,] visited = new bool[xSize, zSize];
Dictionary <PathNode, PathNode> leadingMap = new Dictionary <PathNode, PathNode> ();
float[,] scores = new float[xSize, zSize];
int steps = 0;
scores [start.x, start.z] = 0;
Location currentPosition = start;
PathNode currentNode;
while (true)
{
if (gameController.AreLocationsIdentical(currentPosition, end))
{
//When node being evaluated == end, path has been found
break;
}
else
{
steps++;
//To prevent freeze up, early exit if steps exceeds full tile grid size
if (steps > xSize * ySize)
{
Debug.LogError("Frontier while loop timed out.");
return(null);
}
currentNode = pathGrid.GetPathNode(currentPosition);
foreach (PathEdge edge in currentNode.edges)
{
int x = edge.end.location.x;
int z = edge.end.location.z;
//If tile has not been visited and is not currently in frontier, score, add to frontier, and add to leadingMap.
if (!visited [x, z] && !frontier.Contains(edge.end.location))
{
float f = ManhattenDistance(end, currentPosition);
float g = scores[currentPosition.x, currentPosition.z] + edge.moveCost;
scores [x, z] = f + g;
frontier.Enqueue(edge.end.location, scores [x, z]);
leadingMap.Add(edge.end, currentNode);
}
}
//Set visited for current tile to true and remove from frontier.
visited [currentPosition.x, currentPosition.z] = true;
currentPosition = frontier.Dequeue();
}
}
//To prevent freeze up, early exit if attempts exceeds full tile grid size
int attempts = 0;
//Path is gathered from end to start, so a stack is used before poping all locations in path in to a queue
Stack <Location> rev = new Stack <Location> ();
//Start at end
currentPosition = end;
//Start at end and use leadingMap to find all locations in best path.
while (true)
{
attempts++;
if (attempts > xSize * ySize)
{
Debug.LogError("While loop for stack population timed out.");
return(null);
}
if (gameController.AreLocationsIdentical(currentPosition, start))
{
break;
}
rev.Push(currentPosition);
currentPosition = leadingMap [pathGrid.GetPathNode(currentPosition)].location;
}
int pathCount = rev.Count;
//Reverse order of stack by popping in to queue.
for (int i = 0; i < pathCount; i++)
{
path.Enqueue(rev.Pop());
}
return(path);
}
}
