Class SudokuNode

java.lang.Object

SearchNode

SudokuNode

All Implemented Interfaces:

java.lang.Cloneable

public class SudokuNode
extends SearchNode
implements java.lang.Cloneable

Field Summary

Fields

Modifier and Type	Field and Description
static int	SIZE number of square grid rows and columns
static int	UNKNOWN constant 0 indicating an unknown grid value

Fields inherited from class SearchNode

depth, parent

Constructor Summary

Constructors

Constructor and Description
SudokuNode(int[][] grid) Constructs a SudokuNode using the given 9-by-9 grid of cell values, either ranging from 1 to 9 or being the UNKNOWN value.
SudokuNode(java.util.Scanner scanner) Constructs a SudokuNode using the given Scanner to read a text Sudoku grid with periods marking unknown values.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	clone() Create a deep clone of this SudokuNode using the int[][] grid copy constructor.
java.util.ArrayList<SearchNode>	expand() Return a list of children of this node.
int	getCell(int row, int column) Return the current cell value given the row and column of the cell.
boolean	isGoal() Return whether or not the grid contains no UNKNOWN values.
java.lang.String	toString() Return a String representation of the Sudoku grid with periods marking unknown values.

Methods inherited from class SearchNode

childClone

Methods inherited from class java.lang.Object

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

Field Detail

SIZE

public static final int SIZE

number of square grid rows and columns

See Also:

Constant Field Values

UNKNOWN

public static final int UNKNOWN

constant 0 indicating an unknown grid value

See Also:

Constant Field Values

Constructor Detail

SudokuNode

public SudokuNode(java.util.Scanner scanner)

Constructs a SudokuNode using the given Scanner to read a text Sudoku grid with periods marking unknown values. Input should be nine lines with nine characters per line consisting of digits 1-9 or '.'.

Parameters:

scanner - a Scanner object for reading a text Sudoku grid with periods marking unknown values.

SudokuNode

public SudokuNode(int[][] grid)

Constructs a SudokuNode using the given 9-by-9 grid of cell values, either ranging from 1 to 9 or being the UNKNOWN value. This constructor should not merely assign the given grid to a Sudoku node field, but should make its own field copy of the grid, i.e. there should be a step where you allocate a new grid 2D int array.

Parameters:

grid - initial 9-by-9 grid of cell values, either ranging from 1 to 9 or being the UNKNOWN value.

Method Detail

getCell

public int getCell(int row,
                   int column)

Return the current cell value given the row and column of the cell.

Parameters:

row - row of the cell

column - column of the cell

Returns:

the current cell value given the row and column of the cell.

toString

public java.lang.String toString()

Return a String representation of the Sudoku grid with periods marking unknown values. The String should consist of nine newline-terminated lines with nine characters per line consisting of digits 1-9 or '.' for UNKNOWN.

Overrides:

toString in class java.lang.Object

isGoal

public boolean isGoal()

Return whether or not the grid contains no UNKNOWN values.

Specified by:

isGoal in class SearchNode

Returns:

whether or not the grid contains no UNKNOWN values

expand

public java.util.ArrayList<SearchNode> expand()

Return a list of children of this node. The children are computed as follows:

• Find the minimum row, minimum column (in that order) grid cell with value UNKNOWN. If no such cell exists, return an empty list.
• If such a cell exists, compute all candidate values 1-9 which do not occur in the same row, same column, or same 3x3 block of cells in the grid.
• For each candidate value,
  • Create a deeply-cloned child using the childClone method.
  • Fill in the candidate value in the UNKNOWN cell.
  • Add this child to the list of children to be returned.
• Return the list of children.

Specified by:

expand in class SearchNode

Returns:

a list of children of this node

clone

public java.lang.Object clone()

Create a deep clone of this SudokuNode using the int[][] grid copy constructor.

Overrides:

clone in class SearchNode

Returns:

an Object value