dailysudoku.com

[daykart]

After getting assistance with some of my earlier posts, many of you have helped me get through the last 4 very hard puzzles all by myself.
Therefore, I decided to try something harder.
The folowing puzzle comes off of a NY Times Su Doku site.

I am not interested in the answer...but there are some big holes in my logic, and I need aid with that. I have looked for "hidden pairs", single number is a row or column, and everything else that I know of. If I did not make a silly omission, then there is a lot more to Su Doku than I am aware of.

Enlighten me, please.


_ _ _ _ _ _ _ 1 8
_ _ 8 4 9 1 _ 2 _
_ _ 1 _ 3 8 _ _ _

_ 4 _ _ _ _ 8 _ 2
6 3 _ _ _ _ 7 4 1
8 _ 7 _ _ 4 _ 9 _

_ _ _ 6 4 _ 5 _ _
_ 9 _ _ 2 _ 1 _ _
_ _ _ _ _ 3 2 _ _

r1c1 2,3,4,5,7,9 c2 2,5,7,9 c3 2,3,4,5,9 c4 2,5,7 c5 1,5,6 c6 2,5,6,7
c7 4,9

r2c1 3,5,7 c2 5,6,7 c6 3,6 c8 3,5,6,7

r3c1 2,4,5,7,9 c2 2,5,6,7 c4 2,5,7 c7 4,9 c8 5,6,7 c9 5,6,7

r4c1 1,5,9 c5 5,9 c4 1,3,5,7,9 c5 1,5,6,7 c6 5,6,7,9 c8 3,5,6

r5c3 2,5,9 c4 2,5,8,9 c5 5,8 c6 2,5,9

r6c2 1,2,5 c4 1,2,3,5 c5 1,5,6 c7 3,6 c9 3,5,6

r7c1 1,2,3,7 c2 1,2,7,8 c3 2,3 c6 7,9 c8 3,7,8 c9 3,7,9

r8c1 3,4,5,7 c3 3,4,5,6 c4 5,7,8 c6 5,7 c8 3,6,7,8 c9 3,4,6,7

r9c1 4,5,7 c2 5,6,7,8 c3 4,5,6 c4 1,5,7,8,9 c5 1,5,7,8 c8 6,7,8
c9 4,6,7,9

Thanks for any explanations you can offer.

[David Bryant]

This one's not really so bad, Daykart. At least, it's fairly easy to get started.

1. There's a pair {3, 6} in column 6, r2 & r6.
2. Eliminating 3 & 6 in col 6 reveals {4, 9} pair in col 6, r1 & r3.
3. Eliminating 4 & 9 in top right 3x3 box (at r3c9) reveals naked quad {2, 5, 6, 7} in row 3, and also second piece of hidden pair {4, 9} -- pair at r1c3 & r6c3.
4. The same naked quad {2, 5, 6, 7} appears in row 1. Elimination reveals triplet {3, 4, 9} in r1c1, r1c3, & r1c6.

5. Now we have a value -- r7c1 = 2 (unique in column)
6. r7c3 = 3 (sole candidate)
7. Pair {7, 9} revealed in row 7, at r7c6 & r7c9. This leads to
8. r7c8 = 8
9. r7c2 = 1

and you can make good progress from there. dcb

[David Bryant]

Hi, Daykart! It's me again.

After I posted the brief explanation of how to place the first few digits in this puzzle, I continued working on it, and arrived at a contradiction (two occurences of "6" in row 9, the way I went at it). So I tried again, with the same result.

So then I got suspicious and fed the puzzle to an automated solver, which informed me that there are no valid solutions to the puzzle you posted.

Either you transcribed it incorrectly, or it was a bum puzzle to start with! dcb