dailysudoku.com

[alanr555]

Documenting Solution Steps
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Several contributions to various fora refer to backtracking or reviewing
what one has done so far.

A computer solution can prepare elaborate and excellent trails to a
solution but what is an easy way to document the solution process
when working manually?

Pencil marks can be used to work towards a solution but once a digit
has been eliminated, how can one know that it was still a possibility
three, six or ten moves previously? Short of taking a snapshot after
each move, one must develop an "audit trail" of some kind.

Do other solvers maintain such a trail?
What tips and tricks are there for working back from a mistake (or even
from a trial/error "stuck" position)?

Alan Rayner BS23 2QT
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[David Bryant]

Usually I don't worry about backtracking. I just forge boldly ahead.

Once in a while I get stuck on a very tough puzzle. Then I start trying to keep track of the order in which I make each move. I don't have a particularly good system for doing this, though. I generally mark possibilities within a single cell like this

3/7

in tiny letters at the top of a cell. When I'm trying to track the order of moves I just number the moves sequentially, with a tiny circled numeral in the upper left corner of each cell.

The biggest problem I have with tough puzzles is misidentifying the possibilities for a single cell. I haven't even considered tracking the order in which I identify various sets of possibilities like 3/7. That would involve too much detail. dcb

[Sam]

Evrything I've read says if you find you've made that type of error, start over. Not what I do, but perhaps the logic is exactly the point you're raising...it is so diificult to identify where you make the mistake. I have noticed I tend to make certain types of mistakes, e.g. I start eliminating the options, going too fast, and I "read the wrong row, ending up including other number options" So, i check those first. Ah....logic