public static Level Replace(Level level, int rowOffset, int columnOffset, Level replacement)
{
Level newLevel = new Level(level);
bool lostSokoban = false;
for (int row = 1; row < replacement.Height - 1; row++)
{
for (int column = 1; column < replacement.Width - 1; column++)
{
if (replacement[row, column] != Cell.Undefined)
{
int rowTarget = row - 1 + rowOffset;
int columnTarget = column - 1 + columnOffset;
if (!level.IsValid(rowTarget, columnTarget))
{
return ExpandAndReplace(level, rowOffset, columnOffset, replacement);
}
if (level.IsSokoban(rowTarget, columnTarget) && !replacement.IsSokoban(row, column))
{
lostSokoban = true;
}
newLevel[rowTarget, columnTarget] = replacement[row, column];
}
}
}
if (lostSokoban)
{
// Find an empty cell to relocate the sokoban to.
foreach (Coordinate2D coord in replacement.Coordinates)
{
if (replacement[coord] == Cell.Empty)
{
newLevel.MoveSokoban(coord.Row - 1 + rowOffset, coord.Column - 1 + columnOffset);
return newLevel;
}
}
}
return newLevel;
}
private static Level TryNormalizeLoops(Level level)
{
// A loop is a tunnel that you cannot push a box through.
// Any square that it is impossible or not useful to push
// a box to is a no-box square. All the squares in a loop
// are no-box squares. A level may have several disconnected
// no-box regions. Within one no-box region we can
// optimize the path by removing islands that only
// lengthen the loop without changing its function.
// Finally, a normalized loop only needs to be one square
// wide.
// Copy the level and get island and no-box maps.
bool modifiedLevel = false;
Level newLevel = new Level(level);
Array2D<bool> islandMap = LevelUtils.GetIslandMap(level);
Array2D<int> noBoxMap = LevelUtils.GetNoBoxMap(level);
// Any island that only contacts other walls and one or more
// no-box squares in the same region can be removed.
foreach (Coordinate2D coord in newLevel.Coordinates)
{
if (islandMap[coord])
{
int wallCount = 0;
int noBoxCount = 0;
int region = 0;
foreach (Coordinate2D neighbor in coord.FourNeighbors)
{
if (newLevel.IsWall(neighbor))
{
wallCount++;
}
else if (noBoxMap[neighbor] != 0)
{
// Check whether we've encountered any no-box regions.
if (region == 0)
{
region = noBoxMap[neighbor];
}
// Only count no-box squares that match the first region.
if (noBoxMap[neighbor] == region)
{
noBoxCount++;
}
}
}
if (wallCount + noBoxCount == 4 && noBoxCount >= 1)
{
newLevel[coord] = Cell.Empty;
noBoxMap[coord] = 1;
islandMap[coord] = false;
modifiedLevel = true;
}
}
}
// Make a map of all the inside squares we want to keep, initialized to false.
Array2D<bool> keepMap = new Array2D<bool>(newLevel.Height, newLevel.Width);
foreach (Coordinate2D coord in newLevel.InsideCoordinates)
{
if (noBoxMap[coord] != 0)
{
// Keep all the no-box squares that contact box islands.
foreach (Coordinate2D neighbor in coord.EightNeighbors)
{
if (newLevel.IsValid(neighbor) && islandMap[neighbor])
{
keepMap[coord] = true;
break;
}
}
// Keep all the no-box squares that contact box squares.
foreach (Coordinate2D neighbor in coord.FourNeighbors)
{
if (newLevel.IsFloor(neighbor) && noBoxMap[neighbor] == 0)
{
keepMap[coord] = true;
break;
}
}
}
else
{
// Keep all the box squares.
keepMap[coord] = true;
}
}
// Fill in the no-box squares that we can safely remove.
Coordinate2D sokobanCoord = newLevel.SokobanCoordinate;
foreach (Coordinate2D coord in newLevel.InsideCoordinates)
{
if (!keepMap[coord])
{
newLevel[coord] = Cell.Wall;
modifiedLevel = true;
}
}
// If the sokoban was on one of the cells we didn't keep,
// move it to a nearby box square.
if (!newLevel.IsSokoban(sokobanCoord))
{
Level boxLevel = FillBoxSquaresWithBoxes(level, noBoxMap);
PathFinder finder = PathFinder.CreateInstance(boxLevel);
finder.Find(sokobanCoord);
foreach (Coordinate2D coord in finder.AccessibleCoordinates)
{
if (newLevel.IsEmpty(coord))
{
newLevel[coord] = Cell.Sokoban;
break;
}
}
}
// Return the new level only if we made changes.
if (modifiedLevel)
{
return newLevel;
}
return null;
}
