private MazeGridpoint SearchForSolution(Queue <MazeGridpoint> queueToSolveMaze)
{
// As long as there are still elements in the queue to check, keep going
while (queueToSolveMaze.Any())
{
var currentMazeGridpoint = queueToSolveMaze.Dequeue();
currentMazeGridpoint.HasBeenVisited = true;
MazeToSolve.NotifyMazeHasBeenUpdated();
MazeToSolve.NotifyMazeToBeRedrawnUpdated();
_foundMazeFinishPoint = MazeToSolve.CheckIfAtFinish(currentMazeGridpoint);
// Quit now if the end of the maze was found
if (_foundMazeFinishPoint)
{
return(currentMazeGridpoint);
}
// Investigate each direction available at the current gridpoint
foreach (var direction in currentMazeGridpoint.DirectionsAvailable.OpenPaths)
{
if (!MazeToSolve.IsValidPositionInMaze(currentMazeGridpoint, direction))
{
continue;
}
var nextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(currentMazeGridpoint, direction);
if (MazeToSolve.CheckIfAtDeadEnd(nextMazeGridpoint) || nextMazeGridpoint.HasBeenVisited)
{
continue;
}
// Set up the parent gridpoint for each direction that is valid
var nextMazeSolutionElement = PathToSolveMaze.Single(m => m.MazeGridpoint == nextMazeGridpoint);
nextMazeSolutionElement.ParentMazeGridpoint = currentMazeGridpoint;
nextMazeGridpoint.HasBeenVisited = true;
// Make sure we haven't found the end of the maze for each direction
_foundMazeFinishPoint = MazeToSolve.CheckIfAtFinish(nextMazeGridpoint);
if (_foundMazeFinishPoint)
{
return(nextMazeGridpoint);
}
// If its not the end of the maze, queue it up for another round down the line
queueToSolveMaze.Enqueue(nextMazeGridpoint);
Console.WriteLine("X : " + nextMazeGridpoint.Position.X + ", Y : " + nextMazeGridpoint.Position.Y + " Direction : " + direction);
}
}
throw new Exception("Maze Solver Error: Sorry, maze could not be solved. The maze image provided may be invalid.");
}
private void RecursivelySearchForSolution(MazeGridpoint currentMazeGridpoint, MazeSolutionElementTree parentMazeSolutionElementTree)
{
// No need to keep going on this call if the finish has already been found
if (_foundMazeFinishPoint)
{
return;
}
_mazeSolutionElementTree = parentMazeSolutionElementTree;
_foundMazeFinishPoint = MazeToSolve.CheckIfAtFinish(currentMazeGridpoint);
currentMazeGridpoint.HasBeenVisited = true;
MazeToSolve.NotifyMazeHasBeenUpdated();
MazeToSolve.NotifyMazeToBeRedrawnUpdated();
// Now that we've checked the current gridpoint, let's make sure we need to do more work
if (_foundMazeFinishPoint)
{
return;
}
// For each direction available that is valid, add an element to the tree and recursively
// call the search function again.
foreach (var direction in currentMazeGridpoint.DirectionsAvailable.OpenPaths)
{
if (!MazeToSolve.IsValidPositionInMaze(currentMazeGridpoint, direction))
{
continue;
}
var nextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(currentMazeGridpoint, direction);
if (MazeToSolve.CheckIfAtDeadEnd(nextMazeGridpoint) || nextMazeGridpoint.HasBeenVisited)
{
continue;
}
var nextMazeSolutionElement = new MazeSolutionElementTree
{
ParentSolutionElement = parentMazeSolutionElementTree,
MazeGridpoint = nextMazeGridpoint
};
Console.WriteLine("X : " + nextMazeGridpoint.Position.X + ", Y : " + nextMazeGridpoint.Position.Y + " Direction : " + direction);
RecursivelySearchForSolution(nextMazeGridpoint, nextMazeSolutionElement);
}
}
/// <summary>
/// Given a direction to proceed, this logic determines what the next maze gridpoint will be. In cases
/// where we have reached a dead-end, this may mean backtracking to the last gridpoint where another
/// choice was available.
/// </summary>
private MazeGridpoint DetermineNextMazeGridPoint(MazeGridpoint currentMazeGridpoint, DirectionEnum directionToProceed)
{
var nextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(currentMazeGridpoint, directionToProceed);
if (MazeToSolve.CheckIfAtDeadEnd(nextMazeGridpoint) || nextMazeGridpoint.HasBeenVisited)
{
// We have arrived at a dead-end, so this cannot have been the right direction to proceed
currentMazeGridpoint.DirectionsAvailable[directionToProceed] = false;
if (currentMazeGridpoint.DirectionsAvailable.Count == 1)
{
// Go back to the last gridpoint where there were more than two choices about the direction to proceed
var lastValidMazeSolutionElement = PathToSolveMaze.LastOrDefault(p => p.MazeGridpoint.DirectionsAvailable.Count > 2);
if (lastValidMazeSolutionElement == null)
{
throw new Exception("Maze Solver Error: Sorry, maze could not be solved. The maze image provided may be invalid.");
}
var directionProceededAtLastValidMazeGridPoint = lastValidMazeSolutionElement.DirectionProceeded;
// Since the path resulted in a dead-end, it cannot have been the reight direction to proceed
lastValidMazeSolutionElement.MazeGridpoint.DirectionsAvailable[directionProceededAtLastValidMazeGridPoint] = false;
// Truncate the path back to the last valid point to take a new direction
PathToSolveMaze = PathToSolveMaze.Where(p => p.StepNumber < lastValidMazeSolutionElement.StepNumber).ToList();
return(lastValidMazeSolutionElement.MazeGridpoint);
}
return(currentMazeGridpoint);
}
// The step numbers will be indexed starting with zero
var stepNumber = PathToSolveMaze.Count;
var mazeSolutionElement = new MazeSolutionElement
{
StepNumber = stepNumber,
MazeGridpoint = currentMazeGridpoint,
DirectionProceeded = directionToProceed
};
PathToSolveMaze.Add(mazeSolutionElement);
return(nextMazeGridpoint);
}
protected void MarkClosedPaths(Dictionary <CartesianCoordinate, MazeGridpoint> mazeGridpoints)
{
foreach (var mazeGridpoint in mazeGridpoints.Values)
{
// For each available direction, check what paths are closed and mark them
foreach (var direction in mazeGridpoint.DirectionsAvailable.OpenPaths)
{
if (MazeToSolve.IsValidPositionInMaze(mazeGridpoint, direction))
{
var nextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(mazeGridpoint, direction);
if (MazeToSolve.CheckIfAtDeadEnd(nextMazeGridpoint) ||
nextMazeGridpoint.HasBeenVisited)
{
mazeGridpoint.DirectionsAvailable[direction] = false;
}
}
}
}
}
/// <summary>
/// Removes redundant interior space in a maze.
/// </summary>
public override void PreTreatMazeToSolve()
{
var wallMazeGridpoints = MazeToSolve.MazeGridpoints
.Where(m => m.Value.IsWall)
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
// One round of the outer-loop below takes about 170 ms in debug mode.
// For 5,500 gridpoints, that's about 15 minutes.
if (wallMazeGridpoints.Count() > _maxiumGridpointsLimit)
{
return;
}
// First, focus only on the gridpoints that are walls or have been visited
foreach (var mazeGridpoint in wallMazeGridpoints)
{
// Now for each direction, find the wall-adjacent gridpoints that are not walls themselves
foreach (var direction in mazeGridpoint.Value.DirectionsAvailable.OpenPaths)
{
if (!MazeToSolve.IsValidPositionInMaze(mazeGridpoint.Value, direction))
{
continue;
}
var canAvoidThisGridpoint = true;
var wallAdjacentMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(mazeGridpoint.Value, direction);
if (MazeToSolve.CheckIfAtDeadEnd(wallAdjacentMazeGridpoint))
{
continue;
}
// For each gridpoint that is wall-adjacent and not a wall itself, check the gridpoints
// at each of its four directions.
foreach (var nextDirection in wallAdjacentMazeGridpoint.DirectionsAvailable.OpenPaths)
{
if (!MazeToSolve.IsValidPositionInMaze(wallAdjacentMazeGridpoint, nextDirection))
{
continue;
}
var nextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(wallAdjacentMazeGridpoint, nextDirection);
if (MazeToSolve.CheckIfAtDeadEnd(nextMazeGridpoint))
{
wallAdjacentMazeGridpoint.DirectionsAvailable[nextDirection] = false;
}
else
{
// If not at a dead-end go out a second layer of gridpoints from the gridpoints that
// are around the wall-adjacent gridpoint
foreach (var nextNextDirection in nextMazeGridpoint.DirectionsAvailable.OpenPaths)
{
if (!MazeToSolve.IsValidPositionInMaze(nextMazeGridpoint, nextNextDirection))
{
continue;
}
var nextNextMazeGridpoint = MazeToSolve.ProceedToNewGridpoint(nextMazeGridpoint, nextNextDirection);
if (MazeToSolve.CheckIfAtDeadEnd(nextNextMazeGridpoint))
{
nextMazeGridpoint.DirectionsAvailable[nextNextDirection] = false;
}
}
// If there's not at least two paths avaiable this far out, the wall-adjacent gridpoint
// likely cannot be avoided without closing off a potential solution path
if (nextMazeGridpoint.DirectionsAvailable.Count < 2)
{
canAvoidThisGridpoint = false;
break;
}
}
}
// Assuming each of the second layer gridpoints had at least two open paths, make sure
// that the wall-adjacent gridpoint has at least tree open paths
if (!canAvoidThisGridpoint ||
wallAdjacentMazeGridpoint.DirectionsAvailable.Count < 3)
{
break;
}
// If everything above was satisfied, we can safely ignore the wall-adjacent gridpoint
// without fear of closing off a solution path
wallAdjacentMazeGridpoint.HasBeenVisited = true;
MazeToSolve.NotifyMazeHasBeenUpdated();
MazeToSolve.NotifyMazeToBeRedrawnUpdated();
}
}
}