is
Checks if the tile specified by the given position is a blank tile.
Return
true if the tile specified by the given position is a blank tile; false, otherwise.
Parameters
position
Position of the tile in the puzzle grid (zero-based, following row-major order).
puzzleState
Current puzzle state (flattened into one dimension, following row-major order).
blankTileMarker
Indicator that the tile is blank.