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#12
10-21-2006, 03:23 PM
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Re: Need help with a Sudoku
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[ QUOTE ] You shouldn't have to plug in a dozen numbers before finding out you've headed down the wrong trail. [/ QUOTE ] I'm not trying to be difficult here, I'm finding the philosophy of this whole thing interesting. So wouldn't this the distinction between an easy problem and a hard one? You're saying there should be no look ahead at all in Sudoku, ever? If there can be, why couldn't the amount of look ahead needed sometimes be more than you can do in your head? [/ QUOTE ] Look ahead (or forcing chains as it is called) is required for some of the tougher sudokus. There is a difference between saying "if I put a 5 here, then I would have to put a 7 here, which leads to..." and then just start filling in the numbers, and if you end up with something, that doesn't match, you can eliminate the number you started with. Your solution to this one is very nice, and definitely acceptable, and it may very well be the only way to solve it (that is to say, I haven't been able to come up with anything more obvious). 
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#13
10-21-2006, 04:27 PM
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Re: Need help with a Sudoku
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Actually, there's no reason there couldnt be a 5 in row 4 col 1, so that chain of logic fails. [/ QUOTE ] If you stick a 5 there, that leaves only 1 spot for for both the 1 and 4 in that row.
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#14
10-21-2006, 04:29 PM
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Re: Need help with a Sudoku
[ QUOTE ]
[ QUOTE ] Actually, there's no reason there couldnt be a 5 in row 4 col 1, so that chain of logic fails. [/ QUOTE ] If you stick a 5 there, that leaves only 1 spot for for both the 1 and 4 in that row. [/ QUOTE ] yep
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#16
10-21-2006, 05:14 PM
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Re: Need help with a Sudoku
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In the fifth row, 2nd and 3rd boxes you can eliminate an 8 because you have to have an 8 in the 4th row 1st 2nd or 3rd box. [/ QUOTE ] Not quite sure if what you're saying makes any sense, but you can eliminate 8 in row 6 columns 2 and 3, since the 8 in row 5 has to be in column 1, 2 or 3. I missed that. EDIT: I think maybe we're saying the same thing, I just had a little trouble understanding you.
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#18
10-21-2006, 09:03 PM
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Re: Need help with a Sudoku
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Actually, there's no reason there couldnt be a 5 in row 4 col 1, so that chain of logic fails. [/ QUOTE ] Yes, there is a reason why it can't be a 5. Look at Row 6, Column 8. That's a 1 or 4. You'll see that Row 4 Col 1 has to match whatever goes in that square.
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#19
10-21-2006, 09:17 PM
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Re: Need help with a Sudoku
[ QUOTE ]
[ QUOTE ] In the fifth row, 2nd and 3rd boxes you can eliminate an 8 because you have to have an 8 in the 4th row 1st 2nd or 3rd box. [/ QUOTE ] Not quite sure if what you're saying makes any sense, but you can eliminate 8 in row 6 columns 2 and 3, since the 8 in row 5 has to be in column 1, 2 or 3. I missed that. EDIT: I think maybe we're saying the same thing, I just had a little trouble understanding you. [/ QUOTE ]' Yea I meant the 6th row, not the 5th.
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#20
10-21-2006, 09:38 PM
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Re: Need help with a Sudoku
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Just so you know, I ran it through a solver and [mild spoiler in white] <font color="white">it said it had to guess (and there may be more than one solution) </font> [/ QUOTE ] This is a hint that the source of the puzzle is bad. Good sudokus only have one solution and no guesses should be required.
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