| View previous topic :: View next topic |
| Author |
Message |
nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
|
 Posted: Mon Sep 10, 2007 9:58 am Post subject: sept 10 vh |
 |
|
I found today's rather interesting in that I needed both alternating inference chains and xy-wing techniques to solve.
At some point, this is the situation in '3's, marked are strong links (rows, cols, boxes with exactly 2 occurrences) and the remaining cells with '3'.
| Code: |
+·····+·····+·····+
·*---*· · ·
· |· · ·
· |· · ·
· |· · ·
· |· · ·
+····|+·····+·····+
·*-----* · ·
· |· \ · ·
· |· \ · ·
· |· \ · ·
·o * *· *· ·
+··|··+····|+·····+
· | · *-----*·
· | · · |·
·*-----* · |·
· \| · · |·
· * ·o · *·
+·····+·····+·····+
|
The candidate '3' can be removed from r1c1 and r6c1(41=44-66=76-84=81),
r6c3 (continue ...81-92=62), and r9c4(92=62-66=76).
A few steps later, an xy-wing leaves naked '7' in r1c1 and the puzzle collapses.
very nice |
|
| Back to top |
|
 |
sdq_pete
Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL
|
| Posted: Mon Sep 10, 2007 11:53 am Post subject: |
|
|
| Code: |
+---------------+----------------+----------------+
| 3567 9 3578 | 468 14568 14 | 5678 568 2 |
| 1 78 2 | 9 568 68 | 3 4 5678 |
| 56 4 58 | 2 3 7 | 1568 1568 9 |
+---------------+----------------+----------------+
| 39 1 4 | 36 7 5 | 2 689 68 |
| 2 6 57 | 48 48 9 | 57 3 1 |
| 3579 378 3578 | 1 2 36 | 4 569 567 |
+---------------+----------------+----------------+
| 4 2 1 | 5 9 368 | 68 7 368 |
| 37 5 6 | 37 18 2 | 9 18 4 |
| 8 37 9 | 3467 1468 14 | 156 2 356 |
+---------------+----------------+----------------+
|
Play this puzzle online at the Daily Sudoku site
Interesting pattern, though I did it simply with 2 (rather easily spotted) XY wings (pivots R3C3 and then R6C6)
Peter |
|
| Back to top |
|
|
nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
|
| Posted: Mon Sep 10, 2007 2:38 pm Post subject: |
|
|
thx, Peter 
I usually try the coloring approach first to reduce the number of candidates in the cells (also to double-check for hidden singles etc.), and only then look for xy- and w-wings.
Seeing how easy it was with xy-wing, maybe I'll re-evaluate my search pattern... |
|
| Back to top |
|
|
Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
|
| Posted: Mon Sep 10, 2007 6:19 pm Post subject: |
|
|
There is also a one step move present that collapses the puzzle completely.
A 6-cell xy-chain starting with <8> in R2C6
[68][87][73][37][73][36], which erases both <6>'s in R1C4 and R6C6
| Code: |
+---------------+----------------+----------------+
| 3567 9 3578 |4-68 14568 14 | 5678 568 2 |
| 1 B78 2 | 9 568 A68 | 3 4 5678 |
| 56 4 58 | 2 3 7 | 1568 1568 9 |
+---------------+----------------+----------------+
| 39 1 4 |F36 7 5 | 2 689 68 |
| 2 6 57 | 48 48 9 | 57 3 1 |
| 3579 378 3578 | 1 2 3-6 | 4 569 567 |
+---------------+----------------+----------------+
| 4 2 1 | 5 9 368 | 68 7 368 |
|D37 5 6 |E37 18 2 | 9 18 4 |
| 8 C37 9 | 3467 146 14 | 156 2 356 |
+---------------+----------------+----------------+
|
|
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Mon Sep 10, 2007 11:04 pm Post subject: |
|
|
nataraj,
In your 3-grid, there is an X-Wing in R48 that eliminates R16C1 and R9C4 directly and R6C3 indirectly. The "color wings" work, but the fish is more direct. |
|
| Back to top |
|
|
nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
|
| Posted: Tue Sep 11, 2007 11:48 am Post subject: |
|
|
indeed. x-wing. how straightforward.  |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
