SudokuSolver Forum

A forum for Sudoku enthusiasts to share puzzles, techniques and software
It is currently Thu Mar 28, 2024 8:02 pm

All times are UTC




Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: Need help.
PostPosted: Tue Feb 10, 2009 8:14 pm 
Offline
Grand Master
Grand Master
User avatar

Joined: Mon Apr 21, 2008 10:32 am
Posts: 868
I need help with the following puzzle:

Image

006000207000070050002500004005040001900306005400010300500002400060090000103000900



Using only Basic Techniques (N/H-Subsets and Intersections) I can solve this puzzle as far as follows:
Image
Code:
+----------------------+----------------------+----------------------+
| 38     5      6      | 14     38     14     | 2      9      7      |
| 38     14     14     | 2      7      9      | 6      5      38     |
| 7      9      2      | 5      6      38     | 1      38     4      |
+----------------------+----------------------+----------------------+
| 6      3      5      | 9      4      78     | 78     2      1      |
| 9      178    178    | 3      2      6      | 78     4      5      |
| 4      2      78     | 78     1      5      | 3      6      9      |
+----------------------+----------------------+----------------------+
| 5      78     9      | 178    38     2      | 4      1378   6      |
| 2      6      478    | 1478   9      13478  | 5      1378   38     |
| 1      478    3      | 6      5      478    | 9      78     2      |
+----------------------+----------------------+----------------------+

To complete the puzzle I need two Advanced Techniques plus Basic Techniques.
Almost any combination of two Advanced Techniques cracks the puzzle.
Here are a couple of possibilities:
Hidden Text:
Image



Image

What I am trying to figure out is if it is possible to solve this puzzle using a single Advanced Technique only, plus Basic Techniques.
My analysis (which could be flawed) concludes that to solve the puzzle using a single Advanced Technique only, this technique must determine the solution for one of the eight green coloured cells, which all takes either the digit 7 or 8 as its solution.

Any bright ideas?

_________________
Quis custodiet ipsos custodes?
Normal: [D  Y-m-d,  G:i]     PM->email: [D, d M Y H:i:s]


Top
 Profile  
Reply with quote  
 Post subject: Re: Need help.
PostPosted: Fri Feb 13, 2009 8:25 pm 
Offline
Grand Master
Grand Master
User avatar

Joined: Tue Aug 05, 2008 11:43 am
Posts: 251
I couldn't find the desired step.

Børge,
The Players' forum has many players who solve even the impossible ones manually. I'm sure you'll find your answer there.

tarek


Top
 Profile  
Reply with quote  
 Post subject: Re: Need help.
PostPosted: Fri Sep 03, 2010 1:16 am 
Offline
Regular
Regular

Joined: Tue Jun 16, 2009 1:35 pm
Posts: 6
..6...2.7....7..5...25....4..5.4...19..3.6..54...1.3..5....24...6..9....1.3...9..

after applying singles
Code:
38 ```5 ```6 | 1489 38 13489 | `2 ``389 ``7
38 1489 1489 | ```2 `7 13489 | `6 ````5 389
`7 ``89 ```2 | ```5 `6 ``389 | `1 ``389 ``4
-------------+---------------+--------------
`6 ```3 ```5 | `789 `4 ``789 | 78 ````2 ``1
`9 `178 `178 | ```3 `2 ````6 | 78 ````4 ``5
`4 ```2 ``78 | `789 `1 ````5 | `3 `6789 689
-------------+---------------+--------------
`5 `789 `789 | 1678 38 ````2 | `4 13678 368
`2 ```6 `478 | 1478 `9 13478 | `5 `1378 `38
`1 `478 ```3 | 4678 `5 ``478 | `9 ``678 ``2


naked pair r1.15 {38}.468// in row 1, col's 1 and 5 the naked pair {38} preempts the same candidates from r1c4, r1c6 and r1c8

assert singles again

Code:
38 ```5 ```6 | ``14 38 ```14 | `2 ```9 `7
38 1489 1489 | ```2 `7 13489 | `6 ```5 38
`7 ``89 ```2 | ```5 `6 ``389 | `1 ``38 `4
-------------+---------------+------------
`6 ```3 ```5 | ```9 `4 ```78 | 78 ```2 `1
`9 `178 `178 | ```3 `2 ````6 | 78 ```4 `5
`4 ```2 ``78 | ``78 `1 ````5 | `3 ```6 `9
-------------+---------------+------------
`5 `789 `789 | `178 38 ````2 | `4 1378 `6
`2 ```6 `478 | 1478 `9 13478 | `5 1378 38
`1 `478 ```3 | ```6 `5 ``478 | `9 ``78 `2


naked pair r2.19 {38}.236
naked pair b1.14 {38}.8 // the positions 1 and 4 of box 1 have a naked {38}, preempting it from box 1 position 8

assert singles

Code:
38 ``5 ``6 | ``14 38 ```14 | `2 ```9 `7
38 `14 `14 | ```2 `7 ````9 | `6 ```5 38
`7 ``9 ``2 | ```5 `6 ```38 | `1 ``38 `4
-----------+---------------+------------
`6 ``3 ``5 | ```9 `4 ```78 | 78 ```2 `1
`9 178 178 | ```3 `2 ````6 | 78 ```4 `5
`4 ``2 `78 | ``78 `1 ````5 | `3 ```6 `9
-----------+---------------+------------
`5 `78 ``9 | `178 38 ````2 | `4 1378 `6
`2 ``6 478 | 1478 `9 13478 | `5 1378 38
`1 478 ``3 | ```6 `5 ``478 | `9 ``78 `2

ff {3} r1c5 % r37 > c8 // this is a sashimi fish fin, {3} cannot be in r1c5 because then rows three and seven would only have candidate {3}'s in column eight alone.

assert singles

Code:
3 ``5 ``6 | `14 8 `14 | `2 9 7
8 `14 `14 | ``2 7 ``9 | `6 5 3
7 ``9 ``2 | ``5 6 ``3 | `1 8 4
----------+-----------+--------
6 ``3 ``5 | ``9 4 `78 | 78 2 1
9 178 178 | ``3 2 ``6 | 78 4 5
4 ``2 `78 | `78 1 ``5 | `3 6 9
----------+-----------+--------
5 `78 ``9 | `78 3 ``2 | `4 1 6
2 ``6 `47 | 147 9 147 | `5 3 8
1 `48 ``3 | ``6 5 `48 | `9 7 2

naked pair c4.67 {78}.8
house innersection claim b7 {8} c2.5 // box 7 claims the {8} out of column 2 position 5 (r5c2)
ff {7} r5c2 % r67 > c4 // sashimi fish fin r5c2 cannot be {7} because rows 6 and 7 then only have candidate {7} in column 4 alone

Code:
3 `5 ``6 | 14 8 `14 | `2 9 7
8 14 `14 | `2 7 ``9 | `6 5 3
7 `9 ``2 | `5 6 ``3 | `1 8 4
---------+----------+--------
6 `3 ``5 | `9 4 `78 | 78 2 1
9 `1 178 | `3 2 ``6 | 78 4 5
4 `2 `78 | 78 1 ``5 | `3 6 9
---------+----------+--------
5 78 ``9 | 78 3 ``2 | `4 1 6
2 `6 `47 | 14 9 147 | `5 3 8
1 48 ``3 | `6 5 `48 | `9 7 2

naked singles from here to the end.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group