Stumped on Samurai

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Stumped on Samurai

Postby sigsky » Fri Feb 01, 2019 3:10 pm

I am stuck on the attached puzzle. I have circled the offending cell in box e5

The solver on the site where I got the puzzle indicates '8' is the proper entry citing the Digit Rule.

I don't see it! It appears to me that both '1' and '8' are possibles here and that '2' and '8' are possibles for the cell to the left,

I've been looking at this for 2 days and am sure I am missing something silly. Can anyone help?


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Re: Stumped on Samurai

Postby m_b_metcalf » Tue Feb 05, 2019 5:41 pm

Sorry to be so long replying, but I'm travelling. If you consider box 1 of the bottom right puzzle, we see that there is a naked pair in r1c1 and r3c1 with the values 1 and 6. Thus, neither value can appear in r3c3, leaving it containing a naked single, 8.

HTH

Mike
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Re: Stumped on Samurai

Postby sigsky » Wed Feb 06, 2019 12:16 am

Hi Mike

Yep, that works but I can't help but wonder how you got there. Obviously determining the possibles for every cell is the way and I should have done that at least for the box we are looking at here. Of course without the solver, I wouldn't have even known which box to examine. I find determining the possibles for a common sudoku is tedious, but for a samurai it borders on torture. Of course there are many sites which produce the possibles when you enter the knowns for a common sudoku. I'm not aware of one for samurais.

Thanks for your help, if I decide to continue pursuing this variant of sudoku, I will at least check the possibles in the problem box before seeking help.
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Re: Stumped on Samurai

Postby m_b_metcalf » Wed Feb 06, 2019 4:46 pm

Well, I looked at that box because you asked us to. But, in general, the overlapping regions are those subject to the most constraints, and so are an obvious place to start. Just look at box 7 of the top right puzzle.

Regards,

Mike
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Re: Stumped on Samurai

Postby enxio27 » Sat Feb 09, 2019 1:19 am

sigsky wrote:Of course there are many sites which produce the possibles when you enter the knowns for a common sudoku. I'm not aware of one for samurais.

I find calculating pencil marks (possibles) to be tedious and fraught with potential mistakes, as well. That's why I have software to do it for me. Richard Broughton's SudokuSolver will import samurais and calculate pencil marks. You can find it here:

http://www.rcbroughton.co.uk/sudoku/SudokuSolver.msi
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Re: Stumped on Samurai

Postby SpAce » Sat Feb 09, 2019 3:35 am

sigsky wrote:I find determining the possibles for a common sudoku is tedious, but for a samurai it borders on torture.

enxio27 wrote:I find calculating pencil marks (possibles) to be tedious and fraught with potential mistakes, as well. That's why I have software to do it for me.

Sounds like poor technique to me, especially if you're prone to make mistakes. I'd estimate the error rate of my pencil&paper solving to be at most 5/1000, regardless of puzzle type or difficulty and whether I use pencil marks or not. It's quite fast too, relatively speaking, though it's always been a secondary goal compared to reliability (I'd really hate to restart a puzzle), good solving aids (showing all native and grouped strong links when necessary), a visually pleasing end-result (without using an eraser), and a layered structure for different levels of puzzles (to avoid hunting flies with cruise missiles).

Of course manual pencil-marking is still tedious and slow compared to using a good software solver with adequate visual aids, which is why I rarely bother nowadays. Perfecting the technique was the interesting part, but I can't think of how it could be improved any more.
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