Sudexel Discussion Board

[admin]

Let us have a look at the Sudoku puzzle in figure 1, below.

The first technique I am going to use simply looks a an empty cell and decides which number can go there, depending on the other numbers in its row, column and box of 9. I can see that a 6 must go in row 3 column 4 (the nimber 6 marked red in figure 2). The reason is that if I look at the numbers already in the row, column & box of nine (orange dashed lines & blue shaded box in figure 2), the only number not already there is a 6.

For the second technique, I look at a box. For this example it is the blue shaded box in figure 2. I look at the numbers not already in the box and decide if there is a unique empty cell which can contain any of them. In this example I again look at the number 6. I have indicated, in figure 3, with orange dashed lines any 6's which are already in rows or columns which are part of the shaded box. This shows that the only cell in the shaded box which can take a 6 is row 1 column 3 (red 6 in figure 3) as those marked a, b, c and d already have a 6 in their row or column.

The third technique is similar to the second only, this time, I am looking at rows and columns rather than boxes. In this case I'm looking at column 7 I look at the empty cells in this column and see that those marked a, b and call have a 1 in their associated column or box. The only cell, in this column, which can contain a 1 is, therefore row 1 (the red 1 in figure 4).

By reapplying all these techniques, it is possible to complete this puzzle and get the unique solution, figure 5.

These 3 techniques can be used to complete many of the less difficult puzzles found in newspapers and magazines around the world. More sophisticated methods may be required to solve the more difficult puzzles. We'll have a look at them later.

Admin

[dfisbein]

From the sample that you have at http://www.sudoku-xls.com/ I think that your Sudoku-xls use only one of the basic techniques. As it is very simple to add to the Excel file the formulas of the other basic technique, let me help you for improving your Sudoku-xls sheet. Regards,

Daniel Fisbein Bresler
Mobile: +34 678432858

[admin]

[jeffloeb]

Pete,

It might help to take a look at the solving document at the sudoku.org.uk site

Jeff

[dfisbein]

[jeffloeb]

When you go into sudoku.org.uk there are things listed on the right hand side of the screen, such as the daily sudoku, jigsaw sudoku, and killer sudoku. One of these items is the solving document - http://sudoku.org.uk/PDF/Solving_Sudoku.pdf . That's what I had in mind.

Jeff

[dfisbein]

[Irish Pete]

[jeffloeb]

One thing is key. Keep scanning. Scan rows. Scan columns. And scan boxes.

There is the "Rule of 45".

As well as something like, is a certain number goes in Row A and in Row C, then that number needs to go in Row B. If there's no room for that number in Row B, then scratch it from Row A and from Row C.