public static List <MazePosition> FindFirstShortestPathBreadthFirst(MazePosition start, MazePosition end, char[][] maze, MazePosition mazeMax)
{
if (maze[start.Y][start.X] != 'S')
{
throw new Exception("Starting maze location should hold value of S.");
}
if (maze[end.Y][end.X] != 'E')
{
throw new Exception("Ending maze location should hold value of E.");
}
List <MazePosition> firstFoundPath = null;
var initialPathSoFar = new List <MazePosition>();
//use breadth first search and return first found path
var queueToVisit = new Queue <QueueItemToVisit>();
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(initialPathSoFar), new MazePosition(start.X - 1, start.Y)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(initialPathSoFar), new MazePosition(start.X + 1, start.Y)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(initialPathSoFar), new MazePosition(start.X, start.Y - 1)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(initialPathSoFar), new MazePosition(start.X, start.Y + 1)));
while (queueToVisit.Count != 0 && firstFoundPath == null)
{
visit(queueToVisit.Dequeue(), maze, mazeMax, queueToVisit, ref firstFoundPath);
}
return(firstFoundPath);
}
private static void visit(QueueItemToVisit queueItemToVisit, char[][] maze, MazePosition mazeMax, Queue <QueueItemToVisit> queueToVisit, ref List <MazePosition> firstFoundPath)
{
var pos = queueItemToVisit.PositionToVisit;
var pathSoFar = queueItemToVisit.PathSoFar;
if (pos.X < 0 || pos.Y < 0 || pos.X > mazeMax.X || pos.Y > mazeMax.Y)
{
return;
}
if (maze[pos.Y][pos.X] == 'E')//end
{
pathSoFar.Add(pos);
firstFoundPath = pathSoFar;
return;
}
if (maze[pos.Y][pos.X] != ' ')//empty
{
return;
}
maze[pos.Y][pos.X] = 'V';//mark visited
pathSoFar.Add(pos);
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(pathSoFar), new MazePosition(pos.X - 1, pos.Y)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(pathSoFar), new MazePosition(pos.X + 1, pos.Y)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(pathSoFar), new MazePosition(pos.X, pos.Y - 1)));
queueToVisit.Enqueue(new QueueItemToVisit(new List <MazePosition>(pathSoFar), new MazePosition(pos.X, pos.Y + 1)));
}
public QueueItemToVisit(List <MazePosition> pathSoFar, MazePosition positionToVisit)
{
PathSoFar = pathSoFar;
PositionToVisit = positionToVisit;
}
