Sudoku 676358 - very hard

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Sudoku 676358 - very hard

Postby NoClue » Thu Jun 09, 2011 7:24 pm

Hi, all,

that extremely easy puzzle I couldn´t solve :

Code: Select all
+-----+-----+-----+
|4 . .|. 1 . |. . 8|
|. . 6|. . .|4 . 3|
|. 9 .|8 . 4|. . .|
+-----+-----+-----+
|. . 7|. . .|. . 6|
|8 . .|7 . 6|. . 5|
|9 . .|. . .|8 . .|
+-----+-----+-----+
|. . .|3 . 9|. 2 .|
|6 . 4|. . .|7 . .|
|3 . .|. 2 .|. . 4|
+-----+-----+-----+


This Sudoku has 26 given numbers

Too less hidden singles I found, as you can see as followed:

Code: Select all
+-----------+----------------+-----------+
|4.. 7. 235.|259.. 1... 235..|29.. 6.. 8.|
|125 8. 6...|259.. 7... 25...|4... 159 3.|
|125 9. 1235|8.... 6... 4....|12.. 157 27|
+-----------+----------------+-----------+
|125 34 7...|12459 3589 12358|1239 149 6.|
|8.. 34 12..|7.... 39.. 6....|1239 149 5.|
|9.. 6. 125.|1245. 35.. 1235.|8... 147 27|
+-----------+----------------+-----------+
|7.. 5. 8...|3.... 4... 9....|6... 2.. 1.|
|6.. 2. 4...|15... 58.. 158..|7... 3.. 9.|
|3.. 1. 9...|6.... 2... 7....|5... 8.. 4.|
+-----------+----------------+-----------+


I only found 21 hidden singles, so I had to pencilmark 34 (!!!) cells.

Any help is appreciated.
NoClue
 
Posts: 48
Joined: 01 April 2011

Re: Sudoku 676358 - very hard

Postby daj95376 » Thu Jun 09, 2011 8:34 pm

First, you missed these basic moves. However, the remaining solution is not trivial.

Code: Select all
         Hidden Single                   =  3    r1c6,r3c3
         Hidden Single                   =  3    r6c5
         Naked  Single                   =  9    r5c5

   c1b1  Locked Candidate 1              <> 1    r4c1
daj95376
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Re: Sudoku 676358 - very hard

Postby NoClue » Fri Jun 10, 2011 4:08 pm

Hi, daj95376,

I can´t explain and understand, how you found the hidden singles in r1c6, r3c3 and r6c5. Locked candidate 1 is it equal to "Pointing Pairs"?

Greetings
No Clue
NoClue
 
Posts: 48
Joined: 01 April 2011

Re: Sudoku 676358 - very hard

Postby JeJ » Fri Jun 10, 2011 7:35 pm

Hidden Single = 3 at r1c6 and r3c3 come from having put 6 at r3c5 which you had already done.

3 at r3c3 leaves "3" as a hidden single at r6c5 which in turn leaves 9 as a naked single at r5c5
JeJ
 
Posts: 76
Joined: 06 January 2011

Re: Sudoku 676358 - very hard

Postby NoClue » Fri Jun 10, 2011 9:12 pm

Hi, JeJ,

I didn´t understand the messages you wrote about the hidden singles. I couldn´t spot any hidden singles more than the ones I could find out in the 2nd version of the Sudoku (the sudoku with the pencilmarks)

Thanks in advance
NoClue
 
Posts: 48
Joined: 01 April 2011

Re: Sudoku 676358 - very hard

Postby JeJ » Sat Jun 11, 2011 12:58 am

Sorry sometimes explaining it is not so easy.

Go back to your candidates, check box 2. "3" is a hidden single on r1c6.

Check row 3, "3" is a hidden single on r3c3.

Those two placements, leave "3" as a hidden single at r6c5 which in turn leaves 9 as a naked single at r5c5
JeJ
 
Posts: 76
Joined: 06 January 2011

Re: Sudoku 676358 - very hard

Postby NoClue » Sat Jun 11, 2011 6:45 am

Hi, JeJ,

yesterday I checked my Sudoku again - the hidden singles in r1c6 and r3c3 I found with your help.

Thanks
NoClue
 
Posts: 48
Joined: 01 April 2011


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