| View previous topic :: View next topic |
| Author |
Message |
Ajò Dimonios
Joined: 01 May 2017
Posts: 339
Location: Sassari Italy
|
 Posted: Sat Mar 23, 2019 10:30 pm Post subject: c.v.fr. 24/03/2019 |
 |
|
Hi everyone
| Code: |
+-------+-------+-------+
| . 1 . | . 7 3 | 4 . . |
| . 7 . | . . . | . . . |
| . . 2 | 8 1 . | 7 . 3 |
+-------+-------+-------+
| 7 . . | . 8 . | 1 . . |
| . 2 . | . . . | . 7 . |
| . . 1 | . 4 . | . . 2 |
+-------+-------+-------+
| 8 . 4 | . 5 1 | 6 . . |
| . . . | . . . | . 4 . |
| . . 3 | 4 6 . | . 8 . |
+-------+-------+-------+
|
Play this puzzle online at the Daily Sudoku site
apparently easy but not so.
Ciao a Tutti
Paolo |
|
| Back to top |
|
 |
immpy
Joined: 06 May 2017
Posts: 571
|
| Posted: Mon Mar 25, 2019 2:01 am Post subject: |
|
|
Another BRUTAL puzzle, Paolo. You may consider me thoroughly STUMPED!
cheers...immp |
|
| Back to top |
|
|
Ajò Dimonios
Joined: 01 May 2017
Posts: 339
Location: Sassari Italy
|
| Posted: Wed Mar 27, 2019 10:32 am Post subject: |
|
|
Hi everyone.
After basics
| Code: |
+------------+-------------+----------------+
| 569 1 5689 | 2569 7 3 | 4 2569 5689 |
| 3 7 5689 | 2569 29 4 | 2589 1 5689 |
| 569 4 2 | 8 1 569 | 7 569 3 |
+------------+-------------+----------------+
| 7 3 569 | 569 8 2 | 1 569 4 |
| 4 2 569 | 1 3 569 | 589 7 5689 |
| 569 8 1 | 7 4 569 | 359 3569 2 |
+------------+-------------+----------------+
| 8 9 4 | 23 5 1 | 6 23 7 |
| 12 6 7 | 239 29 8 | 235 4 15 |
| 12 5 3 | 4 6 7 | 29 8 19 |
+------------+-------------+----------------+
|
Play this puzzle online at the Daily Sudoku site
Five step after basics.
This scheme is a classic example that can be solved using the technique “Naked Sets” http://www.philsfolly.net.au/naked_help.htm.
It can be used in line 3 or 4. In these sets there are three cells that have 569 as candidates. The possible combinations that solve the pattern are 6 but 5 lead to a contradiction while the last leads to the solution using only the technique of basis. I report the conclusions of the combinations that lead to contradiction for the case of line 3.
R3C1=5, R3C6=6 e R3C8=9
R9C7=Ø
| Code: |
+--------+----------+----------+
| 9 1 8 | 25 7 3 | 4 6 5 |
| 3 7 6 | 59 9 4 | 2 1 58 |
| 5 4 2 | 8 1 6 | 7 9 3 |
+--------+----------+----------+
| 7 3 9 | 6 8 2 | 1 5 4 |
| 4 2 5 | 1 3 9 | 8 7 6 |
| 6 8 1 | 7 4 5 | 9 3 2 |
+--------+----------+----------+
| 8 9 4 | 23 5 1 | 6 2 7 |
| 12 6 7 | 239 29 8 | 35 4 159 |
| 12 5 3 | 4 6 7 | . 8 19 |
+--------+----------+----------+
|
Play this puzzle online at the Daily Sudoku site
R3C1=5, R3C6=9 e R3C8=6
R5C3=Ø
| Code: |
+---------+--------+------------+
| 6 1 89 | 5 7 3 | 4 29 589 |
| 3 7 89 | 6 2 4 | 589 1 589 |
| 5 4 2 | 8 1 9 | 7 6 3 |
+---------+--------+------------+
| 7 3 6 | 9 8 2 | 1 5 4 |
| 4 2 . | 1 3 5 | 89 7 6 |
| 9 8 1 | 7 4 6 | 3 3 2 |
+---------+--------+------------+
| 8 9 4 | 23 5 1 | 6 23 7 |
| 12 6 7 | 23 9 8 | 235 4 15 |
| 12 5 3 | 4 6 7 | 29 8 19 |
+---------+--------+------------+
|
Play this puzzle online at the Daily Sudoku site
R3C1=6, R3C6=5 e R3C8=9
R9C7=Ø
| Code: |
+--------+----------+----------+
| 9 1 8 | 26 7 3 | 4 5 6 |
| 3 7 5 | 69 9 4 | 2 1 68 |
| 6 4 2 | 8 1 5 | 7 9 3 |
+--------+----------+----------+
| 7 3 9 | 5 8 2 | 1 6 4 |
| 4 2 6 | 1 3 9 | 58 7 58 |
| 5 8 1 | 7 4 6 | 9 3 2 |
+--------+----------+----------+
| 8 9 4 | 23 5 1 | 6 2 7 |
| 12 6 7 | 239 29 8 | 35 4 159 |
| 12 5 3 | 4 6 7 | . 8 19 |
+--------+----------+----------+
|
Play this puzzle online at the Daily Sudoku site.
R3C1=6, R3C6=9 e R3C8=5
R5C9=Ø
| Code: |
+--------+-------+---------+
| 5 1 8 | 6 7 3 | 4 9 8 |
| 3 7 9 | 5 2 4 | 8 1 6 |
| 6 4 2 | 8 1 9 | 7 5 3 |
+--------+-------+---------+
| 7 3 5 | 9 8 2 | 1 6 4 |
| 4 2 6 | 1 3 5 | 9 7 . |
| 9 8 1 | 7 4 6 | 5 3 2 |
+--------+-------+---------+
| 8 9 4 | 2 5 1 | 6 3 7 |
| 12 6 7 | 3 9 8 | 25 4 15 |
| 12 5 3 | 4 6 7 | 2 8 19 |
+--------+-------+---------+
|
Play this puzzle online at the Daily Sudoku site
R3C1=9, R3C6=5 e R3C8=6
R6C7=Ø
| Code: |
+---------+----------+-------------+
| 6 1 58 | 29 7 3 | 4 25 589 |
| 3 7 58 | 6 29 4 | 2589 1 589 |
| 9 4 2 | 8 1 5 | 7 6 3 |
+---------+----------+-------------+
| 7 3 6 | 5 8 2 | 1 9 4 |
| 4 2 . | 1 3 9 | 58 7 6 |
| 5 8 1 | 7 4 6 | . 3 2 |
+---------+----------+-------------+
| 8 9 4 | 23 5 1 | 6 2 7 |
| 12 6 7 | 239 29 8 | 2359 4 159 |
| 12 5 3 | 4 6 7 | 29 8 19 |
+---------+----------+-------------+
|
Play this puzzle online at the Daily Sudoku site
R3C1=9, R3C6=6 e R3C8=5=>solution.
Ciao a Tutti
Paolo |
|
| Back to top |
|
|
immpy
Joined: 06 May 2017
Posts: 571
|
| Posted: Wed Mar 27, 2019 12:36 pm Post subject: |
|
|
Naked sets, eh? OK, I see the logic. Of course, someone might call this guessing (not myself).
My program WAS able to whittle this puzzle down to a point where one could use the Finned XY-Wing as a means to a solution, which is another technique that gets categorized as "guessing" by some. The pertinent cell was r8c7 with the "fin" of 3 either being true or false. The "fin" in this case proved true with no contradictions, so r8c7=3.
The fin was in the pivot cell of a 235 XY-Wing. 35 was located at r6c7 and 23 was located at r7c8. Thus cell r8c7 is either <> 3 (=25!) or the fin of 3 is true for this cell.
cheers...imp
Still a damn tough puzzle which I could not solve without help. |
|
| Back to top |
|
|
Ajò Dimonios
Joined: 01 May 2017
Posts: 339
Location: Sassari Italy
|
| Posted: Wed Mar 27, 2019 1:21 pm Post subject: |
|
|
Hi Immpy,
Immpy Wrote:
| Code: | Naked sets, eh? OK, I see the logic. Of course, someone might call this guessing (not myself).
My program WAS able to whittle this puzzle down to a point where one could use the Finned XY-Wing as a means to a solution, which is another technique that gets categorized as "guessing" by some. The pertinent cell was r8c7 with the "fin" of 3 either being true or false. The "fin" in this case proved true with no contradictions, so r8c7=3.
The fin was in the pivot cell of a 235 XY-Wing. 35 was located at r6c7 and 23 was located at r7c8. Thus cell r8c7 is either <> 3 (=25!) or the fin of 3 is true for this cell. |
Frankly, I think the term "guess" should only be used in cases where the solution is found without demonstrating its uniqueness. In this case all Backdoors (R1C4 = 2, R1C8 = 6, R2C5 = 9, R2C7 = 2, R6C7 = 5, R7C8 = 3, R7C4 = 3, R7C8 = 2, R8C5 = 2 and R8C7 = 3) and all resolutions in which obviously a priori techniques of uniqueness are used (uniqueness1-2-3-4-5-6,Hidden rectangle e avoidable rectangle 1-2).In practice I think that useful techniques should only be based on logics that demonstrate a contradiction.
Ciao a Tutti
Paolo |
|
| Back to top |
|
|
immpy
Joined: 06 May 2017
Posts: 571
|
| Posted: Thu Mar 28, 2019 12:22 pm Post subject: |
|
|
I agree wholeheartedly, my friend...just relating the sentiment I often encounter when I use the Finned XY-Wing to solve on occasion. Maybe Naked Sets will be more accepted by our solving peers.
cheers...immp |
|
| Back to top |
|
|
Ajò Dimonios
Joined: 01 May 2017
Posts: 339
Location: Sassari Italy
|
| Posted: Thu Mar 28, 2019 1:29 pm Post subject: |
|
|
Hi Immpy,
Immpy Wrote:
| Code: | | I agree wholeheartedly, my friend...just relating the sentiment I often encounter when I use the Finned XY-Wing to solve on occasion. Maybe Naked Sets will be more accepted by our solving peers |
The difference between the two methods is this: finxyWind allows you to find a solution to the scheme, identifying a backdoor R8C7 = 3, but it does not allow you to demonstrate its uniqueness, which is generally the most difficult operation, in this case it takes 5 step to do it. I believe that a complete resolution must also contain this passage.
Ciao a Tutti
Paolo |
|
| Back to top |
|
|
|
|
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 vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
