View unanswered posts | View active topics It is currently Mon Jun 25, 2018 3:41 pm ← Back to the Calcudoku puzzle page

 Page 1 of 1 [ 6 posts ]
 Print view Previous topic | Next topic
multiple solutions to 1-Oct-14, 4x4 Difficult?
Author Message

Posted on: Wed Oct 01, 2014 2:31 am

Posts: 1
Joined: Sun Mar 04, 2012 5:11 am
multiple solutions to 1-Oct-14, 4x4 Difficult?
It appears to me that there are multiple solutions to the 4x4 difficult puzzle today.

Here is what I have so far:

It appears to me that the first row can be either 3412 or 4312 equally correctly.

Posted on: Wed Oct 01, 2014 2:56 am

Posts: 2
Joined: Fri Aug 22, 2014 4:11 am
Re: multiple solutions to 1-Oct-14, 4x4 Difficult?
I found a similar problem:

4 3 1 2
3 4 2 1
2 1 4 3
1 2 3 4

and

4 3 1 2
3 4 2 1
1 2 4 3
2 1 3 4

are both equally valid solutions, yet both are being rejected as "incorrect" when submitted.

3 4 1 2
4 2 3 1
2 1 4 3
1 3 2 4

is being accepted as the solution, but it's nowhere near being the only one.

Posted on: Wed Oct 01, 2014 4:12 am

Posts: 193
Joined: Tue May 24, 2011 4:55 pm
Re: multiple solutions to 1-Oct-14, 4x4 Difficult?
Apart from four correct solutions with this arrangement of numbers in the right half of the puzzle:

x x 1 2
x x 2 1
x x 4 3
x x 3 4

there is also this (fifth) correct solution:

3 4 1 2
4 2 3 1
2 1 4 3
1 3 2 4

On my system (latest Firefox version on Windows Vista SP2) all five solutions are accepted as correct when submitted.

Posted on: Wed Oct 01, 2014 9:16 am

Posts: 108
Joined: Wed May 11, 2011 6:44 pm
Re: multiple solutions to 1-Oct-14, 4x4 Difficult?
Thanks for letting me know. I'm as far as having figured out that this is a bug
introduced in a more recent version of my solver

I ran an old version of the solver (from July 2010 (!)) on this puzzle, and it found
all five solutions.

Edit: found the bug, a fix for a problem which caused it to not be able to solve puzzles
larger than 15x15 (which I needed for the new book, which has one 17x17 puzzle) introduced
a new bug for puzzles with cages larger than 5 cells

Challenge to you all: how to modify the current puzzle so only this solution:
Code:
3  4  1  2
4  2  3  1
2  1  4  3
1  3  2  4

is valid??

Edit #2: I changed the puzzle a bit so the above is a single valid solution.

Patrick

Posted on: Wed Oct 01, 2014 10:30 am

Posts: 713
Joined: Fri May 13, 2011 6:51 pm
Re: multiple solutions to 1-Oct-14, 4x4 Difficult?
calcpnm wrote:
... I'm as far as having figured out that this is a bug
introduced in a more recent version of my solver

I ran an old version of the solver (from July 2010 (!)) on this puzzle, and it found
all five solutions.
...

Patrick

It was one possibility among 5, but I was so unlucky that only when I entered the fifth I got the 2 points .

I was really surprised since it was the first time (IIRC) that I was seeing a violation of the "dogma" of the unicity, and thinking what would have happened in case of a 9x9, ... . I supposed most players were going to feel the same and find the solution given as correct by the program in a couple of minutes (the other four times the full grid was green but the program insisted in an "incorrect solution") and I was waiting until 24.00 CET today to talk about this bug (this time only 2 points, anyway ).

Posted on: Wed Oct 01, 2014 10:44 am

Posts: 2313
Joined: Thu May 12, 2011 11:58 pm
Re: multiple solutions to 1-Oct-14, 4x4 Difficult?
clm wrote:
I supposed most players were going to feel the same and find the solution given as correct by the program in a couple of minutes

Yes, and every time this happens (a validated solution is submitted but rejected by the server) I get
a warning message, to alert me of a potential bug.

So this morning I had 400+ emails in my inbox

Edit: and after exhaustively testing all October puzzles, I found that I have to replace five more 4x4 difficult puzzles
(which had 3 or 5 solutions)

Display posts from previous:  Sort by
 Page 1 of 1 [ 6 posts ]

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

Search for:
 Jump to:  Select a forum ------------------ English    Announcements    Calcudoku General    Other number stuff    Solving strategies and tips    Specific puzzles / your own puzzles    Timed Puzzles    Bugs and errors    Killer Sudoku    Sudoku Nederlands    Aankondigingen    Calcudoku Algemeen    Oplostips en strategieën Italiano    Calcudoku Generale    Strategie e consigli per risolvere Español    Avisos    Calcudoku - General    Estrategias de solución y aspectos relevantes
All forum contents © Patrick Min, and by the post authors.

Forum software phpBB © 2000, 2002, 2005, 2007 phpBB Group.
Designed by STSoftware.