600.108 Intro Programming Lab 				         		Week 8

PROBLEM STATEMENT: Write a program to be a Sudoku solution checker!
More specifically, the program must read a file containing numbers in
a 9x9 grid (9 integers per row, 9 rows), and then check to see if the
numbers are a valid solution to a sudoku puzzle.  A valid solution
contains each of the numbers 1 through 9 in every row, column and 3x3
sub-grid.  Get user input for the filename, and display the valid or
invalid result on the screen.  If the grid is invalid, give at least
one reason why (row number, column number or cube number).  (In the
posted examples, we give all reasons.)  When displaying invalid rows,
columns or cubes, refer to them with the numbers 1-9 (not 0-8) because
that will make more sense to the user.  Assume the numbers in the
input file are separated by spaces.  You can find a bunch of puzzles
on various websites.  A nice one that includes solutions (which you
can use to test your program) is www.dailysudoku.com

We have posted two sample input files: sudoku1.txt and sudoku2.txt. 
In addition to the input, the results of checking each grid are in
each file as well.  (Just ignore those lines when reading the files.)


PHASE 1: Problem Analysis & Design - Think about how you will need to
solve this problem.  Basically, you have to do the same kind of
checking for each row, column and sub-cube.  You should do an object
oriented solution which creates a Sudoku class to hold and manipulate
a puzzle, and a main program to control things.  Think about the data
and methods needed for the Sudoku class. Read through all the phases
below for some ideas on how to break things down.  Sketch the
structure of this class by writing headers for all the methods you
will use, include dummy values where needed to make it compile.

PHASE 2: Create a main program which should handle the input
processing details.  Make it so that it will get the name of an input
file from the user, create a puzzle object, read from the file to
initialize the puzzle, and then display the puzzle on
the screen.  The last two operations should call methods in your
Sudoku class to do the work.  Write the bodies of these methods.
Compile, run and test.

PHASE 3: In your Sudoku class, create a method which has a one
dimensional array of 9 integers as a parameter and checks whether it
contains each value 1 through 9 exactly once.  This method can be
static.  Now write an instance method to check all rows by calling
this method on each row in the puzzle, displaying the numbers of any
invalid ones.  Call the instance method which checks all rows from
main on your puzzle object.

PHASE 4: Now figure out how to use the static array check method to
deal with a column instead.  Once you have that worked out, add an
instance method in Sudoku to use it on every column.  Call this
instance method from main on your puzzle object.  (Hint: copy each
column into a 1 dimensional array.)

PHASE 5: Lastly, figure out how to similarly process each subcube.  If
you have time, combine the calls to check the rows, columns and
subcubes into one validate method in the Sudoku class.  Replace the
three separate method calls in main with one validate call.


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   MAKE SURE YOU DELETE YOUR FILES OFF THE LAB COMPUTER WHEN DONE!!!
             FAILURE TO DO SO IS AN ETHICS VIOLATION!  
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