A SUDOKU MUSING
One of the things I'm a little bit proud of in my journey of sorting out how to solve Sudoku puzzles is that I've never looked for any advice. Early on I wrote some VBA code to quickly get past the easy 'giveaway' answers, which was fun in itself, but since then I've only relied on methods and rules I've come up with or set for myself. Neither am I a master of it by any stretch of the imagination, I make a lot of stupid mistakes and keep getting the feeling that I'm missing something in my logical analysis, hoping that another revelation or strategy will appear.
To start with I like the simple approach, it's either this or it's that, binary if you will. However I've not yet got a foolproof notation of such which I think leads to misinterpreting my notes. After the Excel VBA phase I decided that too many notes were not helping me, a cluttered grid gets in the way. In a row, column or square of 9 I'll note two possible places for a number (which I'm thinking sometimes gets me into trouble). More reliable, I think, is determining that a given cell can only be one of two numbers, so I'll note that too. I don't want the clutter of more than two possibilities happening for a given cell, although that still happens sometimes with my current approach.
But that's not what I wanted to talk about here. There's a pattern I've seen but have not yet drawn any conclusions from, so I thought I'd walk through where I am at the moment then see how this particular example plays out in hopes of learning something. So let us start with the 5-star puzzle ("by Dave Green") presented in the Akron Beacon Journal, Sunday October 3, 2021.
In order to discuss this, I'll need a way of identifying cells. I'm sure folks have come up with their own ways of talking about this but as with all other things Sudoku thus far, I'm doggedly blazing my own way. The first and perhaps simplest approach that came to mind was simply to ID each cell by row and column, AA through II. This pays no regard to squares of 9. That would work but...
I like this second approach that came to me. Each square-of-9 (call it a GROUP) will be identified with a letter A through I. Each cell within a group will be identified in the same way with a second letter. Rightly or wrongly I thought that might steer us/me through the grid faster. As with the first ID approach, the very top left cell would be AA, but now the fourth cell in the top row becomes BA.