MAKE YOUR OWN SUDOKU

Quite a few people use their spreadsheets to help them solve Sudoku puzzles. Can you use yours to create a new Sudoku puzzle?



First of all, you need to know what you are creating.





(a) Each row lists each of the numbers from 1 to 9 once only

(b) Each column lists each of the numbers from 1 to 9 once only.

(c) The grid contains 9 smaller squares listing the numbers 1 to 9 once.

A fourth rule needs to be stated if you are going to create a "good" puzzle: (d) Apart from rules (a), (b) and (c) above, the numbers should look as if they were randomly distributed.


Simply putting the numbers 1 to 9 in a 9x9 grid to fit these rules may look easy when you start. It gets much harder the further you go. So we have to find a way to work smarter not harder.


Strategy 1. Start with a ready-made puzzle and change the numbers.

Suppose we

1. Made all the 9's into 1's, and added 1 to each of all the other numbers?, OR

2. Made all the 9's into 2's , all the 8's into 1's and added 2 to each of the other numbers? OR

3. Set up a more random pattern of changes, e.g 1=4, 2=7, 3=1, 4=9, 5=3, 6=8, 7=5, 8=2, 9=6?

Spreadsheets can be set up to do these tasks automatically. Hints: Methods 1 and 2 involve nested IF formulae. Method 3 can be done using HLOOKUP or VLOOKUP functions.



Strategy 2. Move whole rows and whole columns in a ready-made Sudoku puzzle.

1. Exchange the positions of the whole first column and the whole second column (TRY IT!)

2. Exchange the positions of the whole last row and the whole third last row.

3. Make the whole first three columns the middle three columns

4. Try moving whole columns or whole rows more randomly.

Any moves like these will not break rule (a) or rule (b) but doing more random moves soon breaks rule (c)



Strategy 3.

1. Create a simple non-random puzzle that obeys rules (a) and (b)




2. Swap around whole rows and whole columns until
(i) Rule (c) is obeyed. and
(ii)Rule (d) (Random appearance) is obeyed.

NOTE FOR TEACHERS AND PARENTS

Obviously the last strategy is the simplest, particularly if you know how to select and move rectangular arrays of numbers in your spreadsheet.


HAVE FUN!