/// <summary>
/// Marks the square in the matrix to indicate the direction we're moving through the
/// square. This allows us to render the path simply using ASCII art.
/// </summary>
/// <param name="tracker">The current square in the maze that we're looking at</param>
/// <param name="outDirection">The direction the path takes when leaving the current
/// tracker square (up, right, down or left).</param>
private static void MarkTravelDirection(Square tracker, Direction outDirection)
{
SquareState currentSquareTravel = SquareState.OnThePath;
if (outDirection == Direction.UP)
{
if (tracker.CurrentSquare == startingSquare.CurrentSquare)
{
return;
}
else if (tracker.PreviousSquare.X == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelNS;
}
else if (tracker.PreviousSquare.X - 1 == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelNE;
}
else if (tracker.PreviousSquare.X + 1 == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelNW;
}
}
else if (outDirection == Direction.RIGHT)
{
if (tracker.CurrentSquare == startingSquare.CurrentSquare)
{
return;
}
else if (tracker.PreviousSquare.Y == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelWE;
}
else if (tracker.PreviousSquare.Y - 1 == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelNE;
}
else if (tracker.PreviousSquare.Y + 1 == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelSE;
}
}
else if (outDirection == Direction.DOWN)
{
if (tracker.CurrentSquare == startingSquare.CurrentSquare)
{
return;
}
else if (tracker.PreviousSquare.X == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelNS;
}
else if (tracker.PreviousSquare.X - 1 == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelSE;
}
else if (tracker.PreviousSquare.X + 1 == tracker.CurrentSquare.X)
{
currentSquareTravel = SquareState.TravelSW;
}
}
else if (outDirection == Direction.LEFT)
{
if (tracker.CurrentSquare == startingSquare.CurrentSquare)
{
return;
}
else if (tracker.PreviousSquare.Y == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelWE;
}
else if (tracker.PreviousSquare.Y - 1 == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelNW;
}
else if (tracker.PreviousSquare.Y + 1 == tracker.CurrentSquare.Y)
{
currentSquareTravel = SquareState.TravelSW;
}
}
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = currentSquareTravel;
}
/// <summary>
/// Gets the state of a square adjacent to the specified one.
/// </summary>
/// <param name="direction">The direction to look in (left, right, up or down)</param>
/// <param name="square">The reference square.</param>
/// <returns>Whether the square is empty, the start or finish point, an obstacle or
/// one that's on the current path</returns>
private static SquareState GetAdjoiningSquareState(Direction direction, Square square)
{
int xOffset = 0;
int yOffset = 0;
if (direction == Direction.UP && square.CurrentSquare.Y + 1 < SquareSize)
yOffset = 1;
else if (direction == Direction.DOWN && square.CurrentSquare.Y - 1 >= 0)
yOffset = -1;
else if (direction == Direction.RIGHT && square.CurrentSquare.X + 1 < SquareSize)
xOffset = 1;
else if (direction == Direction.LEFT && square.CurrentSquare.X - 1 >= 0)
xOffset = -1;
else
return SquareState.InvalidSquare;
return matrix[square.CurrentSquare.X + xOffset, square.CurrentSquare.Y + yOffset];
}
/// <summary>
/// All good things have to start somewhere.
/// </summary>
/// <param name="args">None, ignored.</param>
static void Main(string[] args)
{
// Setup a matrix to test with.
matrix = SetupMatrixTest(grid1);
// Open a log file so we can write out the paths we find.
string logFile = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "WPC35-solutions.txt");
sw = new StreamWriter(logFile);
sw.WriteLine("Olimex Weekend Programming Challenge 35 - 30 Nov 2013");
sw.WriteLine("-----------------------------------------------------");
sw.WriteLine();
// Starting square
startingSquare = new Square(0, 0);
startingSquare.PreviousSquare = new Point(-1, -1);
startingSquare.SquareCounter = 1;
// Start recursing...
CheckSquare(startingSquare);
// Finished. Close the log file.
string message = string.Format("Finished!! Number of paths found = {0}", solutionsFound);
Console.WriteLine();
Console.WriteLine(message);
sw.WriteLine();
sw.WriteLine(message);
sw.Close();
// Wait for user to close the console.
Console.ReadLine();
}
/// <summary>
/// The main recursion routine that checks whether a square is valid for the current path and
/// moves the path along to that square. Then we call ourself again to recurse further along
/// the path.
/// </summary>
/// <param name="tracker">The current square we're looking at in the maze.</param>
/// <returns>true when a valid solutin is found (all squares occupied); false otherwise</returns>
private static bool CheckSquare(Square tracker)
{
Square clone;
// Check if we've reached the start/finish point
if (tracker.CurrentSquare == startingSquare.CurrentSquare)
{
// Check whether all the squares in the maze are occupied. If they are, we have
// a valid solution.
if (AllSquaresFilled())
{
// It's a valid path!
solutionsFound++;
DrawSolutionPath();
return true;
}
}
// We could have occupied all squares in the maze but hit a dead-end. This detects that
// and quits the recursion to back-track to the previous square.
if (tracker.SquareCounter >= targetLength)
{
// Reset the current square to an empty one
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
return false;
}
// Get the state of the squares adjoining the current one
SquareState squareAboveState = GetAdjoiningSquareState(Direction.UP, tracker);
SquareState squareRightState = GetAdjoiningSquareState(Direction.RIGHT, tracker);
SquareState squareBelowState = GetAdjoiningSquareState(Direction.DOWN, tracker);
SquareState squareLeftState = GetAdjoiningSquareState(Direction.LEFT, tracker);
// If it's OK to move up, do so
if (squareAboveState == SquareState.Empty || squareAboveState == SquareState.StartFinish)
{
// Mark the square as being on the path.
if (squareAboveState == SquareState.Empty || squareLeftState == SquareState.StartFinish)
MarkTravelDirection(tracker, Direction.UP);
// Create a clone of the current square to pass into the next recursion
clone = new Square(tracker);
// Bump the counter that keeps track of the number of squares are along the path
clone.SquareCounter++;
// Move to the square above
clone.PreviousSquare.X = clone.CurrentSquare.X;
clone.PreviousSquare.Y = clone.CurrentSquare.Y;
clone.CurrentSquare.Y++;
// And check that.
if (CheckSquare(clone))
{
// Reset the current square
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
return false;
}
}
// If it's OK to move right, do so
if (squareRightState == SquareState.Empty || squareRightState == SquareState.StartFinish)
{
// Mark the square as being on the path.
if (squareRightState == SquareState.Empty || squareLeftState == SquareState.StartFinish)
MarkTravelDirection(tracker, Direction.RIGHT);
// Create a clone of the current square to pass into the next recursion
clone = new Square(tracker);
// Bump the counter that keeps track of the number of squares are along the path
clone.SquareCounter++;
// Move to the square to the right
clone.PreviousSquare.X = clone.CurrentSquare.X;
clone.PreviousSquare.Y = clone.CurrentSquare.Y;
clone.CurrentSquare.X++;
// And check that.
if (CheckSquare(clone))
{
// Reset the current square
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
return false;
}
}
// If it's OK to move down, do so
if (squareBelowState == SquareState.Empty || squareBelowState == SquareState.StartFinish)
{
// Mark the square as being on the path.
if (squareBelowState == SquareState.Empty || squareLeftState == SquareState.StartFinish)
MarkTravelDirection(tracker, Direction.DOWN);
// Create a clone of the current square to pass into the next recursion
clone = new Square(tracker);
// Bump the counter that keeps track of the number of squares are along the path
clone.SquareCounter++;
// Move to the square below
clone.PreviousSquare.X = clone.CurrentSquare.X;
clone.PreviousSquare.Y = clone.CurrentSquare.Y;
clone.CurrentSquare.Y--;
// And check that.
if (CheckSquare(clone))
{
// Reset the current square
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
return false;
}
}
// If it's OK to move left, do so
if (squareLeftState == SquareState.Empty || squareLeftState == SquareState.StartFinish)
{
// Mark the square as being on the path.
if (squareLeftState == SquareState.Empty || squareLeftState == SquareState.StartFinish)
MarkTravelDirection(tracker, Direction.LEFT);
// Create a clone of the current square to pass into the next recursion
clone = new Square(tracker);
// Bump the counter that keeps track of the number of squares are along the path
clone.SquareCounter++;
// Move to the square to the left
clone.PreviousSquare.X = clone.CurrentSquare.X;
clone.PreviousSquare.Y = clone.CurrentSquare.Y;
clone.CurrentSquare.X--;
// And check that.
if (CheckSquare(clone))
{
// Reset the current square
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
return false;
}
}
// No more routes available from the current square so it's not viable.
// As long as the current square is not the start/finish, clear it and go back to
// the caller to try another route from the previous square along the path.
if (matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] != SquareState.StartFinish)
{
matrix[tracker.CurrentSquare.X, tracker.CurrentSquare.Y] = SquareState.Empty;
}
return false;
}