| View previous topic :: View next topic |
| Author |
Message |
| puzzler111
| | Joined: 28 Feb 2007 | | Posts: 5 | | : | |
Items |
|
 Posted: Wed Feb 28, 2007 3:00 pm Post subject: Need help solving this |
 |
|
*-----------*
|.13|46.|52.|
|.94|352|.61|
|526|.17|3.4|
|---+---+---|
|185|..6|24.|
|..2|.41|..5|
|.47|2.5|.16|
|---+---+---|
|459|1..|6..|
|..1|5..|4..|
|.78|6.4|15.|
*-----------*
The eight of the (8,9) 2 possibilities in the bottom left of box 2 has three strong links and the eight of the (7,8) possible in r2,c1 has 2 strong links can i do something with these? I am just learning the advanced techniques and i am not sure if eitherof these can form nice loops or anything else? |
|
| Back to top |
|
 |
| daj95376
| | Joined: 05 Feb 2006 | | Posts: 349 | | : | |
Items |
|
| Posted: Wed Feb 28, 2007 5:45 pm Post subject: |
|
|
I don't see anything you can do with the links you mentioned ... but there are others who are a lot better than I who may see something. Assuming that you already performed all of the Locked Candidate eliminations, then you are facing Swordfish eliminations as the next logical step. I'll let you have the satisfaction of finding it for yourself. It'll mean more that way. Post again if you can't find it.
| Code: | *-----------*
|.13|46.|52.|
|.94|352|.61|
|526|.17|3.4|
|---+---+---|
|185|..6|24.|
|..2|.41|..5|
|.47|2.5|.16|
|---+---+---|
|459|1..|6..|
|..1|5..|4..|
|.78|6.4|15.|
*-----------*
|
| Code: | *--------------------------------------------------------------------*
| 78 1 3 | 4 6 89 | 5 2 789 |
| 78 9 4 | 3 5 2 | 78 6 1 |
| 5 2 6 | 89 1 7 | 3 89 4 |
|----------------------+----------------------+----------------------|
| 1 8 5 | 79 39 6 | 2 4 37 |
| 369 36 2 | 78 4 1 | 789 378 5 |
| 39 4 7 | 2 38 5 | 89 1 6 |
|----------------------+----------------------+----------------------|
| 4 5 9 | 1 278 38 | 6 378 2378 |
| 236 36 1 | 5 2789 389 | 4 3789 23789 |
| 23 7 8 | 6 29 4 | 1 5 239 |
*--------------------------------------------------------------------*
|
|
|
| Back to top |
|
|
| puzzler111
| | Joined: 28 Feb 2007 | | Posts: 5 | | : | |
Items |
|
| Posted: Wed Feb 28, 2007 8:13 pm Post subject: |
|
|
| Could you show me how to solve it because I think when I see the solution to one swordfish puzzle, I might learn how to look for them better. |
|
| Back to top |
|
|
| daj95376
| | Joined: 05 Feb 2006 | | Posts: 349 | | : | |
Items |
|
| Posted: Thu Mar 01, 2007 12:48 am Post subject: |
|
|
| Code: | # basic 222 Swordfish r469/c159 in <3>
*--------------------------------------------------------------------*
| 78 1 3 | 4 6 89 | 5 2 789 |
| 78 9 4 | 3 5 2 | 78 6 1 |
| 5 2 6 | 89 1 7 | 3 89 4 |
|----------------------+----------------------+----------------------|
| 1 8 5 | 79 *39 6 | 2 4 *37 |
| 69-3 36 2 | 78 4 1 | 789 378 5 |
|*39 4 7 | 2 *38 5 | 89 1 6 |
|----------------------+----------------------+----------------------|
| 4 5 9 | 1 278 38 | 6 378 278-3 |
| 26-3 36 1 | 5 2789 389 | 4 3789 2789-3 |
|*23 7 8 | 6 29 4 | 1 5 *239 |
*--------------------------------------------------------------------*
|
For more information on Sudoku. I suggest you go to www.sudopedia.org . |
|
| Back to top |
|
|
| puzzler111
| | Joined: 28 Feb 2007 | | Posts: 5 | | : | |
Items |
|
| Posted: Thu Mar 01, 2007 11:37 am Post subject: |
|
|
| Thanks alot. I understand it now. Wherever you put a 3 in that pattern, it will always cancel out those threes you've indicated. I guess I don't need to know the names of all the fish as long as I know the method for seeing one myself. |
|
| Back to top |
|
|
| Steve
| | Joined: 12 Apr 2006 | | Posts: 12 | | : | |
Items |
|
| Posted: Thu Mar 01, 2007 2:15 pm Post subject: |
|
|
Puzzler,
You may wish to consider whether to look for swordfish at all. They are rare and tedious to find. I think most practical solvers come to identify vaguely fish like shapes which may suggest a chain.
Conjugates are a different kettle of fish:
| Code: |
*-----------*
|.13|46.|52.|
|.94|352|.61|
|526|.17|3.4|
|---+---+---|
|185|..6|24.|
|..2|.41|..5|
|.47|2.5|.16|
|---+---+---|
|459|1..|6..|
|..1|5..|4..|
|.78|6.4|15.|
*-----------*
|
Here there are only two places for 9 in rows 1 and 9. What’s more, they share column 9. As this column cannot contain two 9s, you are faced with a fork in the logic: either r1c6 or r9c5 contains 9. Whichever applies, 9 cannot be placed in r8c6 … leaving only one cell for it in the sixth column and solving the puzzle.
Bear in mind that that this simple argument is not confined to individual cells. Here, for example, it would work just as well if r9c4 had also been open to 9. It is so fundamental that the patterns it can form have lots of names.
Steve |
|
| Back to top |
|
|
| north55
| | Joined: 02 Dec 2006 | | Posts: 43 | | : | |
Items |
|
| Posted: Tue Mar 06, 2007 5:32 am Post subject: |
|
|
| Code: | *--------------------------------------------------------------------*
| 78 1 3 | 4 6 89 | 5 2 789 |
| 78 9 4 | 3 5 2 | 78 6 1 |
| 5 2 6 | 89 1 7 | 3 89 4 |
|----------------------+----------------------+----------------------|
| 1 8 5 | 79 39 6 | 2 4 37 |
| 369 36 2 | 78 4 1 | 789 378 5 |
| 39 4 7 | 2 38 5 | 89 1 6 |
|----------------------+----------------------+----------------------|
| 4 5 9 | 1 278 38 | 6 378 2378 |
| 236 36 1 | 5 2789 389 | 4 3789 23789 |
| 23 7 8 | 6 29 4 | 1 5 239 |
*--------------------------------------------------------------------* |
There are 4 patterns here that are "easy" to spot and 3 of them, alone,
reduce the puzzle to easy.
The Unique Rectangle in columns 1 and 2 is very easy to spot and does some
of the same eliminations the swordfish does, just not the important ones,
on this occasion.
| Code: | | 78 1 3
| 78 9 4
| 5 2 6
|----------------------
| 1 8 5
| 69-3 *36 2
| 39 4 7
|----------------------
| 4 5 9
| 26-3 *36 1
| 23 7 8 |
A hinge, more commonly called an Empty Rectangle, makes the same elimination
that a skyscraper (I'll show it next) does and leaves the puzzle harmless.
| Code: | *--------------------------------------------------------------------*
| 78 1 3 | 4 6 *89 | 5 2 789 |
| 78 9 4 | 3 5 2 | 78 6 1 |
| 5 2 6 |*89 1 7 | 3 #89 4 |
|----------------------+----------------------+----------------------|
| 1 8 5 | 79 39 6 | 2 4 37 |
| 369 36 2 | 78 4 1 | 789 378 5 |
| 39 4 7 | 2 38 5 | 89 1 6 |
|----------------------+----------------------+----------------------|
| 4 5 9 | 1 278 38 | 6 378 2378 |
| 236 36 1 | 5 2789 38-9 | 4 #3789 23789 |
| 23 7 8 | 6 29 4 | 1 5 239 |
*--------------------------------------------------------------------* |
There is a skyscraper, which is one of the 3 forms of Turbot Fish, that
makes the same elimination just shown.
| Code: | *--------------------------------------------------------------------*
| 78 1 3 | 4 6 *89 | 5 2 *789 |
| 78 9 4 | 3 5 2 | 78 6 1 |
| 5 2 6 | 89 1 7 | 3 89 4 |
|----------------------+----------------------+----------------------|
| 1 8 5 | 79 39 6 | 2 4 37 |
| 369 36 2 | 78 4 1 | 789 378 5 |
| 39 4 7 | 2 38 5 | 89 1 6 |
|----------------------+----------------------+----------------------|
| 4 5 9 | 1 278 38 | 6 378 2378 |
| 236 36 1 | 5 2789 38-9 | 4 3789 23789 |
| 23 7 8 | 6 *29 4 | 1 5 *239 |
*--------------------------------------------------------------------* |
The swordfish was shown well already. There are usually many ways to
solve a puzzle, if I do the same one twice, on paper, I will likely chose
different routes.
I agree that swordfish are fairly rare. |
|
| Back to top |
|
|
| puzzler111
| | Joined: 28 Feb 2007 | | Posts: 5 | | : | |
Items |
|
| Posted: Tue Mar 06, 2007 1:40 pm Post subject: |
|
|
Thanks, you've shown what to do really clearly. Is it easiest to look for fish by seeing if 2 squares where one of which has to be true can eleiminate another one, or do you look for the fish patterns you know of? Which is the easier way?
I'm probably being really stupid, but with the rectangle I understan that all the squares cannot be 3 or 6 because it would give a non-unique solution, but how do you know you can eliminate the threes? |
|
| Back to top |
|
|
| north55
| | Joined: 02 Dec 2006 | | Posts: 43 | | : | |
Items |
|
| Posted: Wed Mar 07, 2007 4:01 am Post subject: |
|
|
| puzzler111 wrote: | | Thanks, you've shown what to do really clearly. Is it easiest to look for fish by seeing if 2 squares where one of which has to be true can eleiminate another one, or do you look for the fish patterns you know of? Which is the easier way? |
I look for patterns I know. X-wing and skyscraper are similar, you are likely to find one when you are looking for the other.
| Quote: | | I'm probably being really stupid, but with the rectangle I understan that all the squares cannot be 3 or 6 because it would give a non-unique solution, but how do you know you can eliminate the threes? |
| Code: |
| 78 1 3
| 78 9 4
| 5 2 6
|----------------------
| 1 8 5
| 69-3 *36 2
| 39 4 7
|----------------------
| 4 5 9
| 26-3 *36 1
| 23 7 8 |
The first column has no 6s except in the pattern. If either was a three the other would have to be a 6 and the deadly pattern is possible. Therefore neither may be a three. |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in
Log in to check your private messages
