### ... by: P Majumdar, Delhi, India.

I fully agree with the Comments from Mae (Thursday 9-Frb-2012.)

All easy, medium and other low-difficulty level tough Sudoku puzzles cover only the very few basic simple strategies, whereas, tough/diabolic puzzles cover the remaining galaxy of advanced stategies. It is a pity!

The creator/s of all tough/diabolic Sudoku puzzles, should, provide some minimum hint, at least by naming the strategies involved towards solving the puzzle.

### ... by: jennifer antonio

cool

### ... by: Mae

The so called easy Sudoku puzzles on Road Runner have just gotten too hard to make them fun any more.

Sometimes it is fun to just take a few minute break and work and easy Sudoku. How can you encourage people to begin playing Sudoku, if you make them this tough?

### ... by: Jonathan Carr-Hopkins

If, as Geoff in Australia offers, one cell can be only 3 or 5, then selecting one, and if that doesn't work, using the other, is this process, known as iteration, 'cheating', or is only a formulaic solution the only bona fide and acceptable one?

Jonathan

### ... by: Geoff

I have been doing the Sudokus out of the local paper (Queensland Times, Australia) and they are rated from One Star to Five Star.

I have just run across the first Five Star Sudoku where I am 3/4 finished but can not find any more hints.

Some of my friends tell me that you now need to start a 'trial & error' process ie if one cell can only be a 3 or a 5 - then pick on the 3 and see if it carries all the way through and if not, go back and pick on the 5.

I tend to think that there should always be a 'hint' to be found - is this correct?

Geoff

### ... by: Lloyd Welton

Thanks for the great book. Never seen so many strategies so well explained in one book. Maybe in any following editions it should be spiral bound, that way it would a bit easier to use it as a reference.

Thanks again.

### ... by: John C Raaen, Jr.

I blew it! The setup for a Virtual Wall is A1=1, A3=3, D2=4 and B4=4. Then A7, A9, C1, C2 and C3 are the "candidate squares for "4". Sorry!

### ... by: John C. Raaen, Jr

I see no examples of my concept of a wall or virtual wall. If boxes are A thru I and the squares are 1 thru 9, fill A1=1, A2=2, A3=3. This is a wall. Any number other than 1, 2 or 3 in box B or C, say B1=4. can be placed only on squares C1, C2 or C3, and on A7, A8 or A9. Usually some of those candidate squares are already occupied, often leading to an easy placement of, in this case, a "4". (Of course, the squares B and C, 1, 2 and 3 are excluded in the above.)

In a virtual wall, use the same setup but leave A2 blank and put the "2" on D2=2. Again, the "4" can be placed only on squares C1, C2 or C3 and on A7, A8 and A9.

I am sure this simple technique is included somewhere on this site.