| View previous topic :: View next topic |
| Author |
Message |
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
 Posted: Thu Nov 22, 2007 12:42 am Post subject: A Super Hard |
 |
|
You all might enjoy this one from Menneske:
| Code: | Puzzle: M4934597sh(15)
+-------+-------+-------+
| . 8 . | . 6 9 | . 2 . |
| . 6 7 | . . . | 8 5 . |
| . . 2 | 8 . . | 3 . . |
+-------+-------+-------+
| . . . | . 1 . | . . . |
| . . . | 7 3 6 | . . . |
| 9 . . | . 8 . | . . 7 |
+-------+-------+-------+
| . . 9 | . . 1 | 5 . . |
| . 4 5 | . . . | 6 7 . |
| . 7 . | 5 4 . | . 3 . |
+-------+-------+-------+
|
Keith |
|
| Back to top |
|
 |
Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
|
| Posted: Thu Nov 22, 2007 2:06 am Post subject: |
|
|
Not familiar with Menneske, but this one proceeded along pretty smoothly. Three moves did it for me.
XY-Wing with coloring
XYZ-Wing
XY-Wing with coloring |
|
| Back to top |
|
|
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Thu Nov 22, 2007 3:03 am Post subject: |
|
|
Marty,
I did the XYZ-wing and a couple of uniqueness things. I ended by finding an XY-wing 13-23-12 in C3R8. Then, coloring on <1> extended it to solve R8C1 as <8>.
Here is the Menneske site.
http://www.menneske.no/sudoku/eng/
The "Very Hard" puzzles seem to have a lot of remote pairs and X-wings. I am finding that the "Super Hard" puzzles with ratings of about 15 are just my speed.
Happy Thanksgiving!
Keith |
|
| Back to top |
|
|
Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
|
| Posted: Thu Nov 22, 2007 3:16 am Post subject: Super Hard |
|
|
A three step xy-chain eliminates 1 from R1C3 and the rest is singles.
Earl
PS I am not familiar with "xy-wing with coloring." |
|
| Back to top |
|
|
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Thu Nov 22, 2007 3:43 am Post subject: Re: Super Hard |
|
|
| Earl wrote: |
PS I am not familiar with "xy-wing with coloring." |
Which is why I posted the puzzle! The basics get you to here:
| Code: | +----------------+----------------+----------------+
| 5 8 13 | 13 6 9 | 7 2 4 |
| 13 6 7 | 134 2 34 | 8 5 9 |
| 4 9 2 | 8 5 7 | 3 1 6 |
+----------------+----------------+----------------+
| 7 25 6 | 9 1 245 | 24 8 3 |
| 28 12 48 | 7 3 6 | 124 9 5 |
| 9 1235 34 | 24 8 245 | 124 6 7 |
+----------------+----------------+----------------+
| 238 23 9 | 6 7 1 | 5 4 28 |
| 128 4 5 | 23 9 238 | 6 7 128 |
| 6 7 18 | 5 4 28 | 9 3 128 |
+----------------+----------------+----------------+
|
There are two overlapping XYZ-wings with pivots in R78C1. They take out <2> in R8C1 and <8> in R7C1. The result is:
| Code: | +----------------+----------------+----------------+
| 5 8 13A | 13@a 6 9 | 7 2 4 |
| 13a 6 7 | 134 2 34 | 8 5 9 |
| 4 9 2 | 8 5 7 | 3 1 6 |
+----------------+----------------+----------------+
| 7 25 6 | 9 1 245 | 24 8 3 |
| 28 12 48 | 7 3 6 | 124 9 5 |
| 9 1235 34 | 24 8 245 | 124 6 7 |
+----------------+----------------+----------------+
| 23 23 9 | 6 7 1 | 5 4 8 |
| 18 4 5 | 23@ 9 238 | 6 7 12@ |
| 6 7 18 | 5 4 28 | 9 3 12 |
+----------------+----------------+----------------+
|
Note the seemingly useless XY-wing labelled @. Note also the coloring on <1>, aAa, that says R1C4 and R3C1 have the same value.
The XY-wing says that any cell which sees both R8C9 and R1C4 cannot be <1>. There are no such cells. But, coloring extends this to R8C9 and R3C1, solving R8C1 as <8>. And, solving the puzzle.
Pretty cool, I think!
Keith |
|
| 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
