Solving a Sudoku.

[brassnuts]

I did two Sudoku puzzles a couple months ago from some National Inquirer sort of publication. Anyways, I found them pretty enjoyable but had basically forgot about their existence until yesterday, when someone mentioned www.websudoku.com to me.

I've messed around several puzzles. I still find them pretty enjoyable, nothing too great, but I am interested in methodology used to solve them. It seems to me, easy ones can be solved in many different ways, using many different strategies. However, it also seems that some of the difficult puzzles have many fewer possible ways to be solved, possibly just one start-to-finish line of logic to find a solution.

It's hard for me to say for sure because there are some that I haven't yet been able to solve (though I haven't been spending much time with the really tough ones.) I arrive at a point where I have only 2 possible squares for a certain number, I mentally call this a couplet. I'm looking for a very precise strategy at this point, rather than simply "guessing" and continuing on intil I find a contradiction that would give certainty to the position in the original couplet. Anyways, maybe there is no strategy other than to "guess". I put guess in quotes because it's not really guessing. You are choosing one number, and continuing with a strategy to find a contradiction further in the puzzle, but I wonder if there are better ways to solve them.

[DougShrapnel]

Sudoku's are alot of fun. I'll post some strategy later.

[hmkpoker]

Thanks for the puzzle, I enjoyed it ^_^

Sudoku strategy is somewhat similar to minesweeper logic, imho. I went straight to the "evil" ones, which wasn't really that hard. Here's the strategy:

1) Get a piece of paper and jot down the 9x9 board in big squares, marking the given numbers with big black pen.

2) Go through EACH unmarked cell, and list, in soft pencil, which ones they COULD be (eliminating numbers that already exist in the given square, column or row) Be careful to list all and only the correct numbers! This part is very annoying.

Now, we have an outline.

3) Skim through each square, column and row. See a cell that contains a number not possible in any other cells of that group? That's your number. Label it as such, and revise every row, column and square to which that cell belongs accordingly.

4) See a "couplet," as you mentioned? (A couplet is two cells in a square for which you have the other seven numbers figured out). Look at the row or column in which the couplet exists, and eliminate the couplet numbers from other cells in the row or column as possibilities.

Repeat 3 and 4 over and over again, and it'll solve itself.