| View previous topic :: View next topic |
| Author |
Message |
Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
|
 Posted: Sat Dec 01, 2007 8:05 pm Post subject: Many techniques |
 |
|
I needed a variety of techniques to unravel this one,
including x-wing, xy-wing, xy-wing plus coloring, xy-chain.
Anyone see a neater path?
Earl
| Code: |
+-------+-------+-------+
| . . . | . . 1 | 7 . . |
| . 9 2 | 4 . . | . 3 . |
| 4 . 1 | . . 3 | 2 9 . |
+-------+-------+-------+
| 5 . 3 | . 8 . | . 4 . |
| . . . | 5 . 4 | . . . |
| . 8 . | . 3 . | 6 . 5 |
+-------+-------+-------+
| . 1 5 | 6 . . | 4 . 3 |
| . 3 . | . . 2 | 1 5 . |
| . . 7 | 3 . . | . . . |
+-------+-------+-------+
|
Play this puzzle online at the Daily Sudoku site |
|
| Back to top |
|
 |
nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
|
| Posted: Sat Dec 01, 2007 9:59 pm Post subject: |
|
|
Medusa wrap again:
I just colored that long long chain of "8"s (only partially shown) and medusa-ed into 6.
In this position:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 3 5 6g8r | 29 29 1 | 7 6r8 4 |
| 78g 9 2 | 4 67 678 | 5 3 1 |
| 4 67 1 | 78 5 3 | 2 9 68 |
+--------------------------+--------------------------+--------------------------+
| 5 267 3 | 1 8 67 | 9 4 27 |
| 1679 267 69 | 5 2679 4 | 3 1278 278 |
| 179 8 4 | 279 3 79 | 6 127 5 |
+--------------------------+--------------------------+--------------------------+
| 28r9 1 5 | 6 79 789 | 4 27 3 |
| 69 3 689 | 789 4 2 | 1 5 679 |
| 269 4 7 | 3 1 5 | 8 2r6g 269 |
+--------------------------+--------------------------+--------------------------+ |
Look at row 7.
If red is true, then r7c1<>2 (because red 8 in r7c1)
AND
if red is true, then r7c8<>2 (because red 2 in r9c8)
Since (under this assumption that red is true) there are no "2"s left in row 7, red must be false. There are tons of cells connected to those red "8"s - the puzzle is solved. |
|
| Back to top |
|
|
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Sat Dec 01, 2007 11:34 pm Post subject: |
|
|
| Quote: | | Medusa wrap again: |
I have a lot to learn.
Keith |
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Sun Dec 02, 2007 1:30 am Post subject: |
|
|
You can get to a contradiction even faster (without using the X-Wing on <8>, which isn't necessary for nataraj's contradiction either) by noting the potential {27} UR in R45C29. If R3C2 is <6>, then R5C9 must be <8> to avoid the DP, creating a second <6> in R2 at C9. So, R3C2 is <7>.
(That's twice in as many days that I've found a DP useful in Medusa coloring!)
After setting R3C2 to <7>, there is a {17} UR in R56C18 that removes <2> from R4C9 and solves the puzzle. |
|
| 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
