/// <summary>
/// Returns an enumerator that solves the maze by creating a solution path using the Recursive Backtracking Algorithm
/// </summary>
/// <param name="service"></param>
public override IEnumerator SolveMazeRoutine(MazeSolvingService service)
{
//create datastructues necessary for algorithm to work
Stack <MazeCell> stack = new Stack <MazeCell>();
//set starting point and store exit for loop condition
MazeCell exitCell = service.ExitCell;
MazeCell entrance = service.EntranceCell;
entrance.MarkAsPartOfSolution();
stack.Push(entrance);
//loop until the next cell in path is the exit
MazeCell nextCellInPath = null;
while (nextCellInPath != exitCell)
{
//look at the cell at the top of the stack and get the next cells in the path relative to it
MazeCell cell = stack.Peek();
List <MazeCell> cellsNextInPath = service.GetNextCellsInPath(cell);
//check if the path is a dead end or not
if (cellsNextInPath.Count > 0)
{
//fetch a random cell that is next in the path and mark it as part of the solution
nextCellInPath = cellsNextInPath[Random.Range(0, cellsNextInPath.Count)];
nextCellInPath.MarkAsPartOfSolution();
//mark the walls as part of the solution aswell
cell.MarkWallAsPartOfSolution(nextCellInPath);
nextCellInPath.MarkWallAsPartOfSolution(cell);
//push the next cell to the stack
stack.Push(nextCellInPath);
}
else
{
//mark the dead end and its broken walls as checked, so not part of the solution anymore
cell.MarkAsChecked();
cell.MarkBrokenWallsAsChecked();
//pop the stack to backtrack
stack.Pop();
}
yield return(null);
}
CompletedRoutine();
}
/// <summary>
/// Returns an enumerator that marks the maze as checked from given walker cell until a junction is met
/// </summary>
/// <param name="walker"></param>
/// <param name="service"></param>
/// <returns></returns>
private IEnumerator CheckUntilJunctionRoutine(MazeCell walker, MazeSolvingService service)
{
walker.MarkAsChecked();
yield return(null);
//loop until a junction is found and is borken out of the loop
while (true)
{
//get the next cell in the current path
List <MazeCell> cellsNextInPath = service.GetNextCellsInPath(walker);
if (cellsNextInPath.Count == 1)
{
//save it is a junction
MazeCell nextCellInPath = cellsNextInPath[0];
bool isJunction = nextCellInPath.IsJunction;
//mark the walls as checked
walker.MarkWallAsChecked(nextCellInPath);
nextCellInPath.MarkWallAsChecked(walker);
if (isJunction)
{
//if the cell was a junction, break out of the loop
break;
}
else
{
//if the cell wasn't a junction, mark the cell as checked and continue from it
nextCellInPath.MarkAsChecked();
walker = nextCellInPath;
}
}
else
{
throw new System.InvalidOperationException($"Filling in until junktion failed :: there should be one next cell in {walker}'s path each time");
}
yield return(null);
}
}