The New Sudoku Players' Forum

[The Robman]

I have created a simple Excel spreadsheet that will help you solve your puzzles. Basically, as you enter in numbers in the grid, it will remove them from the relevant "pencil marks".

I wouldn't recommend using it with the "easy" puzzles as you will be able to complete the puzzle with absolutely no thought power whatsoever, but it might be useful for the more tricky ones.

Here it is...
http://www.hifi-remote.com/sudoku.xls

Each Sudoku cell is represented by 3 Excel cells (arranged vertically) where the middle cell is the one where you enter your numbers. The smaller cell above will automatically calculate what numbers remain valid for this cell based solely on the vertical column, horizontal row and box. It doesn't try to look for doubles, triples, etc (after all, some of the fun has to be left to the player).

The smaller cell below the entry cell is where you can enter numbers that you have determined are not valid for the cell. These numbers will automatically be moved from the valid list.

Enjoy.

[gapfaat]

I am a university student in HK and I am very interested in the game - SUDOKU. I have the following questions that hope you could kindly give me the answer:

1) How many numbers should be given (the numbers that cannot be changed) at the beginning to graurantee an unique answer?

2) And where should these given numbers be placed?

Thanks!

[underquark]

17
symetrically

[PaulIQ164]

17
symetrically

If I may expand a little, 17 is the smallest known number of givens (the numbers that can't be changed) to create a valid sudoku puzzle. That doesn't mean, however, that having 17 givens guarantees a unique answer (by my quick working, you could make an (admittedly very stupid) puzzle with as many as 77 givens and it could still have more than one solution). The number of givens any particular puzzle has is (by definition) entirely dependent on the puzzle itself, but is highly unlikely to be more than thirty-some.

As for the placement, there is no particular way to place them. Most people prefer symmetrical sudokus (I say without any justification), but there's no objective reason the givens can't be arranged completely haphazardly.