The New Sudoku Players' Forum

[Duncan]

..that after a week of trying I'm giving up on this very hard puzzle and getting someone to point out the obvious thing that I can't see because I've been looking of too long.
I would like to point out in mitigation that I've done many VHs and this is by far the hardest I've come across.

Original puzzle printed from Sudoku program:

*2*|8**|***
*83|*5*|*91
***|7**|*2*
***|***|5*6
*1*|*4*|*8*
7*5|***|***
*5*|**9|***
86*|*1*|24*
***|**8|*6*

These are the number I've got so far:

*27|8**|*5*
*83|*5*|791
5**|7**|*2*
**8|***|5*6
*1*|*4*|*8*
7*5|*8*|4**
*5*|**9|***
869|*1*|24*
*7*|*28|*6*

Answers on my desk in say, 15 minutes

Duncan

[simes]

block 2: column 6 must contain 1, removing 1 from candidates for cell(s) (4,6)(6,6)
block 2: column 5 must contain 9, removing 9 from candidates for cell(s) (4,5)
block 4: row 5 must contain 6, removing 6 from candidates for cell(s) (5,4)(5,6)
block 6: column 8 must contain 1, removing 1 from candidates for cell(s) (7,8)
block 7: column 1 must contain 3, removing 3 from candidates for cell(s) (4,1)(5,1)
block 8: column 4 must contain 4, removing 4 from candidates for cell(s) (2,4)
X-Wing found for columns 6 and 9 in rows 5 and 8 for 7 - updating cell(s) (6,4)(9,7)
column 6: unique subset 12346 in cells (1,6)(2,6)(3,6)(4,6)(6,6) - updating candidates for cell(s) (5,6)(8,6)
column 9: unique subset 348 in cells (1,9)(3,9)(7,9) - updating candidates for cell(s) (5,9)(6,9)(8,9)(9,9)
(8,4) = 3 : only cell in row 8 that can contain 3
...

[lunababy_moonchild]

Don't'cha just hate when that happens? You've been staring at it for a week and you can't see the obvious move, which turns out to be staring you in the face and you know it?

It's enough to give the DT's!



Never done a VH in my life, so you're further on than me.

Luna

[Duncan]

column 6: unique subset 12346 in cells (1,6)(2,6)(3,6)(4,6)(6,6) - updating candidates for cell(s) (5,6)(8,6)

Thanks, I got all of the above apart from the quoted line, can you explain this line?
There is another x-wing on the 7s in cols 5 and 8 but that line above must be the key if I understood it.

Thanks

Duncan

p.s Ahh, I see now, I've spotted a few 3into3s but a 5into5 that's a bit harsh
Still food for thought

[Duncan]

Don't'cha just hate when that happens? You've been staring at it for a week and you can't see the obvious move, which turns out to be staring you in the face and you know it?

It's enough to give the DT's!



Never done a VH in my life, so you're further on than me.

Luna

That was NOT obvious

[lunababy_moonchild]

Sorry duncan, I was empathasing with you, because I know what it's like to stare at a puzzle and not see the obvious but I have only gotten as far a Fiendish (from the book) so am not as advanced as you are with the very hard.

The DT's (I'm given to understand!) are the delerium tremens, associated with alcohol abuse - the connection I was making was the addiction part. When you stop drinking, basically, you can't stop shaking. It's not fatal in and of itself, but it is unpleasant and very public and thus embarrassing.

Hope that clears it up!

Luna

[Animator]

column 6: unique subset 12346 in cells (1,6)(2,6)(3,6)(4,6)(6,6) - updating candidates for cell(s) (5,6)(8,6)

Thanks, I got all of the above apart from the quoted line, can you explain this line?
There is another x-wing on the 7s in cols 5 and 8 but that line above must be the key if I understood it.

No, that line is just a constation of his solver, you don't really need it.

(Update: I'm not sure if I postsed this too soon or not... I'll continue solving it and see)

This is exactly your grid, without any other things applied, which is showing the possible places for a 7.

* 2 7 | 8 * * | * 5 * |
* 8 3 | * 5 * | 7 9 1 |
5 * * | 7 * * | * 2 * |
-----------------------
* * 8 | * 7? 7? | 5 7? 6 |
* 1 * | * 4 7? | * 8 7? |
7 * 5 | * 8 * | 4 * * |
-----------------------
* 5 * | * 7? 9 | * 7? 7? |
8 6 9 | * 1 7? | 2 4 7? |
* 7 * | * 2 8 | * 6 * |

In this grid you can see two x-wings:

The one in the columns: column 5 and column 7 have only two possible cells for the number 7, and they are on the same row. This is an x-wing.

(It allows you to remove the 7 from: r4c6 and r7c8)

The one in the rows: row 4 and row 5 have only two possible cells for the number 7 and they are in exactly the same column. This too is an x-wing. It also allows the removal of the 7 from r4c6 and r7c8.

And as a side note: how do you expect and answer to your initial question? you haven't said where your desk is located! should we guess? :)

[Duncan]

Sorry duncan, I was empathasing... [snip]
Luna

No need to be sorry, I wasn't offended, I was glad that it was something hard to spot. I'd have been p***** off if I'd missed an easy trick

Duncan

[Animator]

Okey, my previous post was slightly incorrect and not really on the point... (sorry about that)...

What simes's says about column 6 is true, but there is an easier way to look at it: there are only two cells that can have a 5 or a 7...

The key to solving it is the combination of the X-wing, column 9 and column 6.

[Duncan]

In this grid you can see two x-wings:

The one in the columns: column 5 and column 7 have only two possible cells for the number 7, and they are on the same row. This is an x-wing.

(It allows you to remove the 7 from: r4c6 and r7c8)

The one in the rows: row 4 and row 5 have only two possible cells for the number 7 and they are in exactly the same column. This too is an x-wing. It also allows the removal of the 7 from r4c6 and r7c8.

And as a side note: how do you expect and answer to your initial question? you haven't said where your desk is located! should we guess?

I got the two 7 x-wings and removed the 7s as above but I'm still no nearer, I'm thinking that you'll find my desk easier than the solution

[Duncan]

Okey, my previous post was slightly incorrect and not really on the point... (sorry about that)...

What simes's says about column 6 is true, but there is an easier way to look at it: there are only two cells that can have a 5 or a 7...

The key to solving it is the combination of the X-wing, column 9 and column 6.

Yes, that's better but does it crack it?

Duncan

[Duncan]

Okey, my previous post was slightly incorrect and not really on the point... (sorry about that)...

What simes's says about column 6 is true, but there is an easier way to look at it: there are only two cells that can have a 5 or a 7...

Yes, that's better but does it crack it?

Duncan

Yes it gives me the three in r8c4

[Guest]

..that after a week of trying I'm giving up on this very hard puzzle and getting someone to point out the obvious thing that I can't see because I've been looking of too long.
I would like to point out in mitigation that I've done many VHs and this is by far the hardest I've come across.

Original puzzle printed from Sudoku program:

*2*|8**|***
*83|*5*|*91
***|7**|*2*
***|***|5*6
*1*|*4*|*8*
7*5|***|***
*5*|**9|***
86*|*1*|24*
***|**8|*6*

These are the number I've got so far:

*27|8**|*5*
*83|*5*|791
5**|7**|*2*
**8|***|5*6
*1*|*4*|*8*
7*5|*8*|4**
*5*|**9|***
869|*1*|24*
*7*|*28|*6*

Answers on my desk in say, 15 minutes

Duncan

I'll like to ask Duncan as to his thinking behind the placement of a 4 in (6,7) and a 2 in (9,5)?

I've been on this, starting from scratch, for about an hour and I cannot see how he reached his conclusions.

[Animator]

MCC, can you post your current grid? it will be easier for us to tell you what move you are missing... yes I could start from scratch too but then there is the risc that I make the same move as Duncan without thinking about it... (and thus without posting the reason why)

[su_doku]

I echo MCC having started from scratch - here's the current grid


*27|8**|*5*
*83|*5*|791
5**|7**|*2*
**8|***|5*6
*1*|*4*|*8*
7*5|*8*|***
*5*|**9|***
869|*1*|24*
*7*|**8|*6*