dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

A famous 2 solution puzzle

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Other puzzles
View previous topic :: View next topic  
Author Message
ravel



Joined: 21 Apr 2006
Posts: 536
PostPosted: Sun Feb 10, 2008 4:49 pm    Post subject: A famous 2 solution puzzle Reply with quote
This is the most famous puzzle with 2 solutions. It was found by Gordon Royle in the early days of the minimal clue search and kept being the only known one with 16 clues and 2 solutions. It is clear, that it cannot be uniuue, because both 8 and 9 are missing.
Code:
 *-----------*
 |5.2|...|4..|
 |...|71.|..3|
 |...|...|...|
 |---+---+---|
 |...|..4|6..|
 |.7.|2..|...|
 |.1.|...|...|
 |---+---+---|
 |6..|..2|...|
 |...|.3.|.1.|
 |4..|...|...|
 *-----------*
This one cannot be solved easily without guessing. Basics bring you here:
Code:
 *--------------------------------------------------*
 | 5    6    2    | 3    89   89   | 4    7    1    |
 | 89   4    89   | 7    1    6    | 2    5    3    |
 | 1    3    7    | 4    2    5    | 89   89   6    |
 |----------------+----------------+----------------|
 | 3    589  589  | 1    89   4    | 6    2    7    |
 | 89   7    46   | 2    56   3    | 1    489  589  |
 | 2    1    46   | 89   56   7    | 3    489  589  |
 |----------------+----------------+----------------|
 | 6    589  1    | 589  4    2    | 7    3    89   |
 | 7    2    589  | 6    3    89   | 589  1    4    |
 | 4    589  3    | 589  7    1    | 589  6    2    |
 *--------------------------------------------------*

I solved it by trying a 5 in r4c3, which leads to an impossible 9-cell 89-cycle.
Back to top
View user's profile Send private message
storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon Feb 11, 2008 2:38 am    Post subject: Reply with quote
yikes

nothing after basics.

I guess you can't find a rating since it isn't a valid puzzle??

hmm, is there a way to find the rating for the next step??
Back to top
View user's profile Send private message
ravel



Joined: 21 Apr 2006
Posts: 536
PostPosted: Mon Feb 11, 2008 8:30 am    Post subject: Reply with quote
Dont know, which rating you want.
As you can see, it can be solved with a 9-cell contradiction chain. But this is a bad criterium, because its easy to spot.

So from my feeling i would settle it easier than an average nightmare puzzle.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Other puzzles All times are GMT
Page 1 of 1

 
Jump to:  
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