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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Tue Apr 18, 2006 4:56 pm Post subject: Stuck on a toughie |
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I always have second thoughts about requesting help on these because of the possibility that I've made an error along the way and people work on something that's invalid to start with.
This is the strangest one I've encountered, because I've had an X-Wing, two swordfish, a block interaction, a forcing chain and unique X-Wing and still have hardly made a dent. Following my grid is the original.
| Code: | ----------------------------------------------------------
|9 4 8 |2 36 37 |5 1 367 |
|2 135 1367 |178 9 1357 |467 348 3678 |
|356 13 1367 |4 13568 137 |9 2 3678 |
----------------------------------------------------------
|58 89 2 |189 1348 6 |14 7 1359 |
|1 589 346 |789 348 3479 |46 3459 2 |
|36 7 346 |5 1234 12349 |8 349 1369 |
----------------------------------------------------------
|47 2 9 |3 145 8 |17 6 157 |
|38 138 13 |6 7 59 |2 59 4 |
|47 6 5 |19 124 1249 |3 89 1789 |
---------------------------------------------------------- |
| Code: | --8---51-
2---9----
---4--9--
--2--6-7-
1-------2
-7-5--8--
--9--8---
----7---4
-65---3-- |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Apr 18, 2006 5:15 pm Post subject: Bad news |
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Marty, the original code is a valid puzzle.
The grid you posted is not - it has no solutions.
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Wed Apr 19, 2006 12:24 am Post subject: |
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Marty,
From your starting grid, without chains, I get to here:
| Code: |
+-------------------+-------------------+-------------------+
| 9 4 8 | 237 236 237 | 5 1 367 |
| 2 135 1367 | 1378 9 1357 | 467 348 3678 |
| 356 13 1367 | 4 13568 137 | 9 2 3678 |
+-------------------+-------------------+-------------------+
| 58 89 2 | 1389 1348 6 | 14 7 1359 |
| 1 589 346 | 3789 348 3479 | 46 3459 2 |
| 36 7 346 | 5 1234 12349 | 8 349 1369 |
+-------------------+-------------------+-------------------+
| 47 12 9 | 13 1345 8 | 127 6 157 |
| 38 1238 13 | 6 7 59 | 12 59 4 |
| 47 6 5 | 129 124 1249 | 3 89 1789 |
+-------------------+-------------------+-------------------+
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And, I can tell you that R1C4 is NOT <2>. So far as I can see, your other values are correct.
Keith |
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David Bryant
Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado
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| Posted: Wed Apr 19, 2006 12:46 pm Post subject: r2c4 is not "3" |
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I agree with you, Keith, with one tiny exception. The "3" at r2c4 can be eliminated by a simple argument.
-- If r2c8 = 3 then clearly r2c4 <> 3.
-- If the "3" in box 3 lies in column 9 then r4c9 <> 3, and that leaves an X-Wing on "3" in rows 4 & 7, again implying that r2c4 <> 3.
I spent a little while looking for double-implication chains at this spot, without any success so far. This one is very difficult. dcb |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Apr 19, 2006 4:40 pm Post subject: |
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| Quote: | | The grid you posted is not - it has no solutions. |
I must have known something when I talked about error possibilities in my post. I had been reluctant to erase everything and start over because I had put so much work into it, but I'll do just that now that I know for sure I've made errors.
Thanks to both of you. |
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Guest
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| Posted: Thu Apr 20, 2006 9:50 pm Post subject: |
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Uh, good luck, Marty,
this is a challenge, cant see a nice solution. |
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ravel
Guest
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| Posted: Thu Apr 20, 2006 9:51 pm Post subject: |
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you know it was me  |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 21, 2006 1:20 am Post subject: |
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| ravel wrote: | | you know it was me |
Yup, sure did. You remind me of myself on another forum. I was an active poster as a Guest for two years before I registered. Don't ask why, I have no idea. 
OK, here we go again for the second and LAST time. After the erasure and restart, I've only been able to solve eight cells. My deep apologies if this has an error like the first grid I posted.
| Code: | ----------------------------------------------------------
|9 4 8 |237 236 237 |5 1 367 |
|2 135 1367 |1378 9 1357 |467 348 3678 |
|356 13 1367 |4 13568 137 |9 2 3678 |
----------------------------------------------------------
|58 89 2 |1389 1348 6 |14 7 1359 |
|1 589 346 |3789 348 3479 |46 3459 2 |
|36 7 346 |5 1234 12349 |8 349 1369 |
----------------------------------------------------------
|4 2 9 |13 135 8 |17 6 157 |
|38 138 13 |6 7 59 |2 59 4 |
|7 6 5 |129 124 124 |3 89 189 |
---------------------------------------------------------- |
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ravel
Guest
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| Posted: Fri Apr 21, 2006 8:29 am Post subject: |
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| The grid is ok, but I still only see a brute force method: There are only 2 ways to place the 5's, so one wrong 5 immediately leads to 5 others. But unfortuneately i dont get earlier, but later a contradiction ;( |
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