Sorry I arrive late at this game.

However, could someone describe the technique I am using.

Seems failproof, no guess work even on the difficult ones (does take a lot a fun out of solving theses).

Here's an attempt at explaining what I am doing:

(1)I divide each little square into 9 smaller square- similar to your phone pad...

(2)If a number , eg 5, is present, I check all the 5's in that column, row and 3X3 area.

(3)Do that for all numbers given.

Most of the time, it's then just fill in the blank, and it's done.

On the harder ones,

(4)I look at each tiny column/ row I created on the phone pad, and usually there is one number in the phone pad that is obvious, because all the number in that tiny row or column are already checked, and repeat the procedures (1) to (2) all over again.

(5) Fill in the blank on the phone pad and solve each phone pad row/ column individually.

Eg:

Nick70 wrote:Animator wrote:I can see one thing you guess about and that is the cell you chose.

You normally (or atleast I) look at a specific number, row, column or box, but never on one particular cell.

I can't believe I'm reading something like this. This really looks like a denial phase.Animator wrote:I'm not sure on this yet, but I'm begining to believe that for each 'Trial and Error'-case there is a 'Foreched chain'-case.

This isn't so. Up to now, I've compiled about 18,000 problems. About 12,000 can be solved using common techniques. About 2,000 can be solved using advanced coloring (which includes swordfish and foreched chains). About 4,000 my program still cannot solve without guessing (9 times in one case).

Note: I haven't yet implemented naked/hidden triples in my program so this changes a bit the figures above.

Should anyone be interested in the 9-guesses problem, here it is; I don't expect it to be solvable by logic.

- Code: Select all
`..1.9.8.5`

.326.....

4........

.....5...

..3.1.6..

...4.....

........4

.....712.

8.9.6.3..

Once you have done step (1) and (2),

then r6,c6 can only be =6,

fill in slowly the phone pad for r6c6 and see what other number becomes obvious.

etc...

Or I'm I off somewhere?