How To Create Sudoku Puzzles Revealed!

I hesitate to tell you how to create Sudoku puzzles for yourself. 

Then again, when you see that it isn't all that easy to make Sudoku puzzles by hand with single solutions, you may be happy to return again.

If you want this inside knowledge to create a Sudoku computer program, then take it from me, there is a lot of competition. Should you create a new PC program, I am interested in reviewing your creation here.

So it is win - win. Here are the steps to make your own Sudoku puzzle and solutions.

Step 1: Create Sudoku Solution

Yes, the first step is to create your puzzle's solution. That is the easy part. You know the Sudoku rules.
Each row, column, and 3x3 grid must contain the numbers one through nine without duplicates. Fill in the grid completely obeying the rules and you have created a puzzle solution.

If you are creating your puzzle by hand, I suggest that you use my blank sudoku grid (or grille if you prefer) for a worksheet.

A faster way is to enter the solution on a new blank puzzle grid in Sudoku Dragon. (File > New Blank puzzle).
Anytime that you encounter a duplicate number, you must redo your grid, removing some or all of your numbers.

Then start over again. Fill in all the blank spaces again until each row, column, and 3x3 grids has only the numbers one through nine without duplicates.

Done with it? Great, you just created your first Sudoku puzzle answer. Save your puzzle.

Step 2: Remove Mirror Pairs

The next step is to begin removing numbers from your completed Sudoku puzzle solution.

If you want to create a symmetrical puzzle, you must remove mirror pairs from your puzzle. For example, if you are removing the number from the cell R1C1, then you must also remove the number from the cell which is R9C9.

These two cells are mirror images if the puzzle is folded in half diagonally.

Step 3: Test For A Single Solution

Each time you remove a mirror pair from your puzzle solution, you must test the puzzle to see if it has a single solution. If it does not have a single solution, it is an invalid puzzle.
The easiest way to test your puzzle is to enter the puzzle manually into a game like Sudoku Dragon mentioned above.

Then allow the software to test to see if your puzzle is solvable.

To do this open the Give Solution Hint window (Game > Hint) or press F9. Then select the first radio button "Check whether all allocations so far are correct".

Click the Show button. If you get an error message, you do not have a valid puzzle. Re-enter the removed number pairs and try again.

Repeat step 2 and step 3 until you can no longer remove mirror pairs without an error or creating an invalid puzzle that has multiple solutions.

It is simple, but not easy to create Sudoku puzzles.

I recommend reading Programming Sudoku by Wei-Meng Lee. This book explains in detail how to program Sudoku. Complete source code is given.

---

Grading Sudoku Puzzles
Ever wonder how grading Sudoku puzzles is done? My research has revealed what Sudoku patterns you are likely to find in different grades of puzzles and games.