## It had to happen!

Advanced methods and approaches for solving Sudoku puzzles

### It had to happen!

There I was, cruising the Vhards like an expert, thinking I knew it all! Then this Vhard from the program hit me . I managed to get as far as :-

**7 359 ***
*56 72* 394
**9 **4 527

9** 482 7**
*** 9*7 4**
*74 *35 2*9

*93 2** ***
712 596 843
*** **3 9**

Then I could not see my way forward from there. Perhaps the bottle of wine was to blame, but to be honest I was lost before I even started on the wine!!

I must be missing something, but what??

Any assistance gratefully received
White Knight

Posts: 17
Joined: 26 May 2005

problem for white knight

the sollution:

2 4 7 - 3 5 9 - 1 6 8
1 5 6 - 7 2 8 - 3 9 4
3 8 9 - 6 1 4 - 5 2 7

9 3 1 - 4 8 2 - 7 5 6
5 2 8 - 9 6 7 - 4 3 1
6 7 4 - 1 3 5 - 2 8 9

8 9 3 - 2 4 1 - 6 7 5
7 1 2 - 5 9 6 - 8 4 3
4 6 5 - 8 7 3 - 9 1 2

Guest

I dubbed this puzzle in and found that after finding the candidates for the first three rows it was pretty straightforward completing row 2. I'm nowhere near expert so I'm pretty sure you'll find a clear head and a re-check of your candidates will un-stick you.
joolslee

Posts: 29
Joined: 05 May 2005

Manolito, my above answer assumes that White Knight is looking for a nudge to help him complete the puzzle himself rather than a complete solution. This was certainly the case for me when I was stuck and asked for help on here.
joolslee

Posts: 29
Joined: 05 May 2005

Hi Joolslee

My candiates for the first 3 rows are as follows:-

[24 ][24][] [ ][ ][ ] [16][168][168]
[18 ][ ][] [ ][ ][18] [ ][ ][ ]
[138][38 ][] [168][16][] [ ][ ][ ]

Lots of triplets and pairs but I can't see any way to get to a row 2 resolution from here with the techniques that I am familiar with. Can you let me in on the secret please?
White Knight

Posts: 17
Joined: 26 May 2005

Well I hope my logic holds up ... but when I got to that point I figured that with only four empty cells in row 3, the candidates would have to be 2 x 2 pairs so I deleted the obvious and that enabled me to complete row 2. Does that make sense? You've got me doubting myself now lol. Where's Animator when you need him
Guest

Posts: 312
Joined: 25 November 2005

Probaly taking a well deserved bank holiday break!!

Yes, looking at it as pairs in row three certainly gets the right result, but is it for the right reason I ask myself?? My understanding of the logic of pairs is that if the cells of the pair are "contaminated" with (an)other candidate(s), then these contaminates can be deleted, as long as the members of the pair do not appear outside the two pair cells.

Bingo, you are dead right, I have looked at it again, and the 168 16 pair meet the above criteria! I was not looking clearly enough, and concentrating in the 138 38 supposed pairing in that row, which obviously does not qualify as a pair as it stands, as there is another candidate 8 in the row. Woolly thinking strikes again! many thank for your help. I'm off for a very long weekend now to give my brain time to recover, and I am determined not to look at another Su Doku until I get back!

Have a good weekend
White Knight

Posts: 17
Joined: 26 May 2005

### Re: It had to happen!

White Knight wrote:I must be missing something, but what??

There is atleast one thing you are missing: number 2 in box 9.

Other then that, there are two X-wings, one with the number 1, and one with the number 8. I suggest you see where those take you.
Animator

Posts: 469
Joined: 08 April 2005