com.act365.sudoku
Class MaskFactory

java.lang.Object
  com.act365.sudoku.MaskFactory

All Implemented Interfaces:

java.util.Enumeration

public class MaskFactory

extends java.lang.Object

implements java.util.Enumeration

The MaskFactory class iterates through the complete set of possible masks (a mask is a boolean[][] array that indicates whether the corresponding cells in Su Doku grids should have their initial values exposed) of a given size. The masks are guaranteed to have rotational symmetry of order two, as demanded by the Su Doku puzzle. No mask will be a reflection of a mask that appeared earlier in the sequence.

Constructor Summary

MaskFactory(int cellsInRow, int filledCells)
Creates a new MaskFactory.

MaskFactory(int cellsInRow, int filledCells, boolean randomize)
Creates a new MaskFactory.

MaskFactory(int cellsInRow, int filledCells, boolean[][] mask)
Creates a new MaskFactory.

MaskFactory(int cellsInRow, int filledCells, int boxesAcross)
Creates a new MaskFactory.

MaskFactory(int cellsInRow, int filledCells, int[] gaps)
Creates a new MaskFactory.

MaskFactory(java.lang.String s)
Creates a new MaskFactory.

Method Summary

int	getCellsInRow() Returns the mask dimension.
int	getFilledCells() Returns the number of filled cells in the mask.
boolean	hasMoreElements() Indicates whether the MaskFactory has cycled through the complete set of all possible masks.
static boolean	isSymmetricLeftRight(boolean[][] mask) Determines whether the mask is symmetric in a line that extends from the left centre of the grid to the right centre.
static boolean	isSymmetricOrder2(boolean[][] mask) Determines whether a mask has rotational symmetry of order 2.
static boolean	isSymmetricOrder4(boolean[][] mask) Determines whether a mask has rotational symmetry of order 4.
static boolean	isSymmetricTopBottom(boolean[][] mask) Determines whether the mask is symmetric in a line that extends from the top centre of the grid to the bottom centre.
static boolean	isSymmetricTopLeftBottomRight(boolean[][] mask) Determines whether the mask is symmetric in a line that extends from the top-left corner of the grid to the bottom-right.
static boolean	isSymmetricTopRightBottomLeft(boolean[][] mask) Determines whether the mask is symmetric in a line that extends from the top-right corner of the grid to the bottom-left.
static void	main(java.lang.String[] args) Class test program takes the form MaskFactory [-c cellsInRow] [-r|-i|-a boxes across] [-d] filledCells.
java.lang.Object	nextElement() Returns the next mask.
java.lang.String	toString() Writes the mask as a string.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MaskFactory

public MaskFactory(int cellsInRow,
                   int filledCells)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence starts in its natural start position, which is usually some distance from the masks that are likely to lead to successful puzzles.

Parameters:

cellsInRow - size of grid

filledCells - number of true elements to appear in mask

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

MaskFactory

public MaskFactory(int cellsInRow,
                   int filledCells,
                   boolean randomize)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence starts at an optionally random position.

Parameters:

cellsInRow - size of grid

filledCells - number of true elements to appear in mask

randomize - whether the start position should be randomized

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

MaskFactory

public MaskFactory(int cellsInRow,
                   int filledCells,
                   boolean[][] mask)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence starts at the given mask.

Parameters:

cellsInRow - size of grid

filledCells - number of true elements to appear in mask

mask - start mask

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

MaskFactory

public MaskFactory(int cellsInRow,
                   int filledCells,
                   int[] gaps)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence starts at the mask specified by a given gap sequence.

Parameters:

cellsInRow - size of grid

filledCells - number of true elements to appear in mask

gaps - gap sequence that defines the start mask

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

MaskFactory

public MaskFactory(java.lang.String s)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence starts at the mask specified by the string, which should be in the format used by toString().

Parameters:

s - string representation of start mask

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

MaskFactory

public MaskFactory(int cellsInRow,
                   int filledCells,
                   int boxesAcross)
            throws java.lang.Exception

Creates a new MaskFactory. The sequence will start from a mask with uniformly-distributed filled cells.

Parameters:

cellsInRow - size of grid

filledCells - number of true elements to appear in mask

boxesAcross - grid dimension

Throws:

java.lang.Exception - thrown if cellsInRow and filledCells are incompatible

Method Detail

toString

public java.lang.String toString()

Writes the mask as a string.

hasMoreElements

public boolean hasMoreElements()

Indicates whether the MaskFactory has cycled through the complete set of all possible masks.

Specified by:

hasMoreElements in interface java.util.Enumeration

nextElement

public java.lang.Object nextElement()

Returns the next mask. The returned mask will simply be a reference to a member of the MaskFactory object, so the caller might well have to clone.

Specified by:

nextElement in interface java.util.Enumeration

getCellsInRow

public int getCellsInRow()

Returns the mask dimension.

getFilledCells

public int getFilledCells()

Returns the number of filled cells in the mask.

isSymmetricLeftRight

public static boolean isSymmetricLeftRight(boolean[][] mask)

Determines whether the mask is symmetric in a line that extends from the left centre of the grid to the right centre.

isSymmetricTopBottom

public static boolean isSymmetricTopBottom(boolean[][] mask)

Determines whether the mask is symmetric in a line that extends from the top centre of the grid to the bottom centre.

isSymmetricTopLeftBottomRight

public static boolean isSymmetricTopLeftBottomRight(boolean[][] mask)

Determines whether the mask is symmetric in a line that extends from the top-left corner of the grid to the bottom-right.

isSymmetricTopRightBottomLeft

public static boolean isSymmetricTopRightBottomLeft(boolean[][] mask)

Determines whether the mask is symmetric in a line that extends from the top-right corner of the grid to the bottom-left.

isSymmetricOrder2

public static boolean isSymmetricOrder2(boolean[][] mask)

Determines whether a mask has rotational symmetry of order 2.

isSymmetricOrder4

public static boolean isSymmetricOrder4(boolean[][] mask)

Determines whether a mask has rotational symmetry of order 4.

main

public static void main(java.lang.String[] args)

Class test program takes the form MaskFactory [-c cellsInRow] [-r|-i|-a boxes across] [-d] filledCells. When the -a option is stipulated, the factory will ensure that the sequence starts at a mask where the filled cells are distributed evenly across the grid. When -r is selected, the sequence will start at a random position while when -i is selected, the initial mask will be read from standard input. The option -t requests trace output. Defaults are nine cells in a row and no debug.