| View previous topic :: View next topic |
| Author |
Message |
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
 Posted: Sat Jul 28, 2007 9:50 am Post subject: DB Saturday Puzzle: July 28, 2007 |
 |
|
Seems to me, this one requires a chain ...
| Code: | Puzzle: DB072807 ******
+-------+-------+-------+
| . . 8 | . . . | 7 . . |
| . . . | 7 . 3 | . 2 5 |
| . . 7 | . 4 . | 1 9 . |
+-------+-------+-------+
| . . . | . 9 . | . . 7 |
| . 9 1 | . . . | 5 4 . |
| 3 . . | . 8 . | . . . |
+-------+-------+-------+
| . 4 2 | . 3 . | 9 . . |
| 7 1 . | 2 . 9 | . . . |
| . . 9 | . . . | 2 . . |
+-------+-------+-------+ |
Keith |
|
| Back to top |
|
 |
Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
|
| Posted: Sat Jul 28, 2007 5:52 pm Post subject: DB July 28 |
|
|
Basic technique got me here:
| Code: |
+---------+------------+-----------+
| 1 35 8 | 9 2 56 | 7 36 4 |
| 9 6 4 | 7 1 3 | 8 2 5 |
| 2 35 7 | 68 4 58 | 1 9 36 |
+---------+------------+-----------+
| 4 2 6 | 5 9 1 | 3 8 7 |
| 8 9 1 | 3 67 67 | 5 4 2 |
| 3 7 5 | 4 8 2 | 6 1 9 |
+---------+------------+-----------+
| 56 4 2 | 68 3 578 | 9 57 1 |
| 7 1 3 | 2 56 9 | 4 56 8 |
| 56 8 9 | 1 567 4 | 2 3567 36 |
+---------+------------+-----------+
|
Play this puzzle online at the Daily Sudoku site
Then I had to color 6's from R9C9 to R9C1 to eliminate some from R9; then a W-wing took care of the 7 in R9C8 and rest was a cake walk.
Perhaps there is a more direct solution.
Earl |
|
| Back to top |
|
|
jLo
Joined: 30 Apr 2007
Posts: 55
|
| Posted: Sat Jul 28, 2007 6:29 pm Post subject: Re: DB July 28 |
|
|
| Earl wrote: | Basic technique got me here:
| Code: |
+---------+------------+-----------+
| 1 35 8 | 9 2 56 | 7 36 4 |
| 9 6 4 | 7 1 3 | 8 2 5 |
| 2 35 7 | 68 4 58 | 1 9 36 |
+---------+------------+-----------+
| 4 2 6 | 5 9 1 | 3 8 7 |
| 8 9 1 | 3 67 67 | 5 4 2 |
| 3 7 5 | 4 8 2 | 6 1 9 |
+---------+------------+-----------+
| 56 4 2 | 68 3 578 | 9 57 1 |
| 7 1 3 | 2 56 9 | 4 56 8 |
| 56 8 9 | 1 567 4 | 2 3567 36 |
+---------+------------+-----------+
|
Play this puzzle online at the Daily Sudoku site
Then I had to color 6's from R9C9 to R9C1 to eliminate some from R9; then a W-wing took care of the 7 in R9C8 and rest was a cake walk.
Perhaps there is a more direct solution.
Earl |
You can eliminate the <5> from R7C6 because the <5> for column 8 must be
either R8C5 or R9C5. This opens up a W-wing on <56>s and solves R9C9
and reduces the puzzle to singles. |
|
| Back to top |
|
|
Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
|
| Posted: Sat Jul 28, 2007 8:49 pm Post subject: |
|
|
I solved it with five moves:
1) Eliminated a candidate to break up a potential deadly pattern in a rectangle
2) W-Wing
3) Type 4 rectangle
4) Skyscraper
5) W-Wing finishes it off
I make moves when I see them, so I don't know if every one of my moves was necessary.
I had a lot of fun with this one. |
|
| Back to top |
|
|
Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
|
| Posted: Sat Jul 28, 2007 10:32 pm Post subject: DB 28 JULY |
|
|
It took me four steps to solve this one
1. XY-chain length 5
2. XY-chain length 4
3. Swordfish
4. XY-chain length 4 |
|
| Back to top |
|
|
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Sun Jul 29, 2007 12:47 am Post subject: |
|
|
In the position posted by Earl, there is a swordfish on <6> in R158.
Keith |
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Mon Jul 30, 2007 8:19 pm Post subject: |
|
|
Just got around to this puzzle...
I couldn't get to Earl's basic position. I needed a W-Wing on 16 in R79. That got me here:
| Code: | +------------+---------------+-------------+
| 1 35 8 | 9 2 56 | 7 D36 4 |
| 9 6 4 | 7 1 3 | 8 2 5 |
| 2 35 7 |B68 4 5-68 | 1 9 C36 |
+------------+---------------+-------------+
| 4 2 6 | 5 9 1 | 3 8 7 |
| 8 9 1 | 3 67 67 | 5 4 2 |
| 3 7 5 | 4 8 2 | 6 1 9 |
+------------+---------------+-------------+
| 56 4 2 |A68 3 -678 | 9 5-67 1 |
| 7 1 3 | 2 F56 9 | 4 E56 8 |
| 56 8 9 | 1 5-67 4 | 2 35-67 36 |
+------------+---------------+-------------+ |
Next, there is a nice XY Loop (XY Chain that closes on itself to form a loop) which I have marked A through F. This produces all of the <6> eliminations shown.
After that, it is just a BUG+1. Done in 3 steps! |
|
| Back to top |
|
|
Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
|
| Posted: Tue Jul 31, 2007 12:24 am Post subject: XY-loop |
|
|
Asellus,
I've encountered these endless XY-chains several times in puzzles.
But didn't know how to make the eliminations. So the eliminations you made on <6>, are they resulting from the strong links [AF], [BC], and [DE] in the loop, or maybe something else? |
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Tue Jul 31, 2007 6:01 pm Post subject: |
|
|
Johan,
Yes, it is the strong links you mention that cause the eliminations.
It is important to point out that the links in an open XY Chain are not strong links. It is only when the chain forms a closed XY Loop that strong links are formed along the chain.
In an open chain, one or both of the pincer ends may contain the shared digit. This is the basis of the eliminations from the "buddies" of the pincers. However, if the pincer ends share a common house, then the relationship becomes an either/or "strong link" and an XY Loop is formed. In such a Loop, all of the sequential links along the Loop chain are strong links and can, potentially, perform eliminations.
XY Loops are common, though often they are just circulations around related locked sets where all the eliminations have already been exploited. However, sometimes one turns up as in this puzzle where new eliminations can be exploited. |
|
| Back to top |
|
|
Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
|
| Posted: Tue Jul 31, 2007 6:32 pm Post subject: |
|
|
Asellus,
Thanks for the useful info. |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
