SUDOKU Rules: A puzzle looks like the one on the previous page: a 9x9 grid with some numbers filled in. The challenge is to fill in each empty space with a digit 1 through 9, so that no digit is repeated in any row, column or “block”. “Block” is my name for the nine 3x3 blocks outlined in thicker black lines in the picture.
Your Assignment: In the Eclipse workspace of your choice, create a new Java project containing package “sudoku”. Import the 4 starter files that you downloaded with this assignment: Evaluation.java, Grid.java, Solver.java, and TestGridSupplier.java. You won't need to change Evaluation.java or TestGridSupplier.java. Your assignment is to finish Grid.java and Solver.java.
Grid: This class models a Sudoku puzzle that is unsolved, partially solved, or completely solved. The class has a 9x9 array of ints, called “values”. If a Sudoku square is empty, the corresponding cell in “values” is zero; otherwise the cell in “values” contains the number in the Sudoku square. The starter class has a ctor and a toString() method that you should not change. It also has 4 empty methods that you need to write: next9Grids(), isLegal(), isFull(), and equals(). Do not change their names, arg lists, or return types. The comments on the unfinished methods tell you all you need to know about what they should do. It’s ok to add more methods to this class.
You don’t need to provide this class with hashCode() or compareTo() methods. The equals() method is just so that you can compare your puzzle solutions to solutions in TestGridSupplier. (That is, you won’t be collecting Grid instances into a hash set a tree set.)
Solver: Most of this class has already been written. Complete the solveRecurse() method using the backtracking technique you saw in lecture and lab. Also complete the evaluate() method. The main() method is for you to use while testing your code with the puzzles and solutions in TestGridSupplier.
Evaluation: You saw this enum in lecture and lab. It contains 3 values that represent the 3 possible outcomes of the evaluate() method of the Grid class. Look at the source code. Sometimes enums can be complicated, but this one is not. You might need to write a simple enum for the next midterm.
TestGridSupplier: This class contains static methods that return Grid instances. Some of them are puzzles, some are solutions, and some are for testing your code
