The Omnifarium - Sudoku

Notice

I am no longer posting new puzzles to this blog. For all of my Sudoku puzzles, old and new, please visit Sudoku in another section of this website. I will still create and offer new puzzles, in batches of a couple of hundred, once a week or so.

Sudoku #27

Category: Sudoku
Tue, 19 Jul 2005, 09:35

In my previous Sudoku blog entry (#26), I described a conundrum where taking a different path on the way to solving one particular solvable puzzle led to a roadblock. I mused that I must be missing some analytical technique. Thanks to Bryan Wolf, I now know what I missed!

In #11, I described the "elimination" technique. That is, if you have two cells in a group with the same two possibilities, the two can be eliminated from the other cells of the group. What I missed was that when you go to three or more cells, not all possibilities need to be represented in those cells.

For example, if you have three cells with the possibilities {1,2,3}, {1,2,3}, and {2,3}, the technique still applies, and the three possibilities can be eliminated from the other cells of the group. I had incorrectly assumed that all three cells had to have the exact same three possibilities.

This now begs the question: If you know all possible analytical techniques for solving Sudoku, can you actually get into a dead-end situation if you choose the wrong order of applying the analytical techniques? My intuition now tells me that the answer is probably no.

And now, todays puzzle. My program tells me that two different analytical techniques are needed for this. But that was the program with the less than perfect elimination technique. After I fix my program, you might find some tougher puzzles.

Hans

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