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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Thu Jul 10, 2008 3:48 pm Post subject: Impossible |
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Well, impossible for me. This is puzzle #92, rated Outlaw, from the gallery at Paul's Pages. I had one useless Finned X-Wing and can't even Medusa or chain it. Please, tell me there's a mechanical error, it's better for my ego. 
| Code: |
+----------------+-----------------+-----------------+
| 15 4 1578 | 1678 9 367 | 568 2 138 |
| 3 1289 1589 | 12468 12468 26 | 45689 68 7 |
| 12 12789 6 | 5 1478 237 | 489 348 1389 |
+----------------+-----------------+-----------------+
| 8 69 45 | 267 2567 1 | 3 47 29 |
| 7 1369 139 | 2368 268 4 | 29 18 5 |
| 145 13 2 | 378 578 9 | 478 1478 6 |
+----------------+-----------------+-----------------+
| 6 237 347 | 9 247 8 | 1 5 23 |
| 9 12378 1378 | 1267 1267 5 | 2678 3678 4 |
| 124 5 1478 | 12467 3 267 | 2678 9 28 |
+----------------+-----------------+-----------------+
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Play this puzzle online at the Daily Sudoku site |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Thu Jul 10, 2008 4:51 pm Post subject: Impossible |
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Simple Sudoku says "Invalid Puzzle. No solution."
Perhaps there was an error in entering the numbers.
Earl |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Jul 10, 2008 6:11 pm Post subject: |
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| Thanks Earl. I guess I'll erase everything and try it again. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Thu Jul 10, 2008 8:40 pm Post subject: |
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The problem appears to be that <6> placement in r7c1. Here is my grid after basics:
| Code: | +-------------------+-------------------+-------------------+
| 15 4 1578 | 1678 9 367 | 568 2 138 |
| 3 1289 1589 | 12468 12468 26 | 45689 468 7 |
| 12 12789 6 | 5 12478 237 | 489 348 1389 |
+-------------------+-------------------+-------------------+
| 8 69 45 | 267 2567 1 | 3 47 29 |
| 7 1369 139 | 2368 268 4 | 29 18 5 |
| 45 13 2 | 378 578 9 | 478 1478 6 |
+-------------------+-------------------+-------------------+
| 246 237 347 | 9 2467 8 | 1 5 23 |
| 9 12378 1378 | 1267 1267 5 | 2678 3678 4 |
| 1246 5 1478 | 12467 3 267 | 2678 9 28 |
+-------------------+-------------------+-------------------+ |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Thu Jul 10, 2008 10:46 pm Post subject: |
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From the above grid, Sudoku Sussser uses Trebor's Tables and generates the following output:
| Quote: | * Made progress using Trebor's Tables to find inferences about the puzzle. A total of 11223 implications about the puzzle were generated and examined in order to find these inferences - you'd run through several pencils working them out by hand!
The following verities were found (only first verity proving the assertion is shown):
R3C9<>8 (Implied by all valid values of R2C8)
R3C9<>3 (Implied by all valid values of R3C8)
R1C3<>1 (Implied by all valid values of R3C8)
R9C3<>7 (Implied by all valid values of R3C8)
R2C8<>4 (Implied by all valid values of R7C3)
R2C7<>6 (Implied by all valid values of R7C3)
R3C2<>1 (Implied by all valid values of R9C3)
R3C5<>1 (Implied by all valid values of R9C3)
R2C2<>1 (Implied by all valid values of R9C3)
R2C7<>4 (Implied by all valid values of R9C7)
The following veracities were found (may duplicate verities, above):
R1C3<>1 (Implied by at least 2 R3<>3 squares)
R1C3<>5 (Implied by all R9=2 squares)
R2C2<>1 (Implied by at least 2 R9<>1 squares)
R2C7<>4 (Implied by all R9=2 squares)
R2C7<>6 (Implied by all R7=3 squares)
R2C7<>8 (Implied by all R9=2 squares)
R2C7<>9 (Implied by all R9=2 squares)
R2C8<>4 (Implied by all R7=3 squares)
R3C2<>1 (Implied by at least 2 R9<>1 squares)
R3C2<>9 (Implied by all R9=2 squares)
R3C5<>1 (Implied by at least 2 R9<>1 squares)
R3C8<>4 (Implied by all R9=2 squares)
R3C8<>8 (Implied by all R9=2 squares)
R3C9<>3 (Implied by all R3=3 squares)
R3C9<>8 (Implied by all R3=1 squares)
R8C8<>7 (Implied by all R9=7 squares)
R9C3<>7 (Implied by at least 2 R3<>3 squares)
The following squares can have possibilities eliminated:
R1C3: remove <15> from <1578> leaving <78>.
R2C2: remove <1> from <1289> leaving <289>.
R2C8: remove <4> from <468> leaving <68>.
R3C2: remove <19> from <12789> leaving <278>.
R3C5: remove <1> from <12478> leaving <2478>.
R3C9: remove <38> from <1389> leaving <19>.
R8C8: remove <7> from <3678> leaving <368>.
R9C3: remove <7> from <1478> leaving <148>.
The following squares can be solved:
R2C7 = 5
R3C8 = 3
Tabling was terminated after 5 reductions or solves were found... |
If you work through the remaining steps, you will see the puzzle is solved.
There are puzzles that we solve for enjoyment, and:
There are puzzles used to test computer programs.
Keith |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Jul 11, 2008 12:24 pm Post subject: |
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| I just started - and I notice the 1369 quad in box 4 also takes out the 1 in R6C1. I'll get back when I have it finished. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Fri Jul 11, 2008 8:18 pm Post subject: |
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| cgordon wrote: | | I'll get back when I have it finished. |
I'll be very interested to see that. I couldn't make a dent in the thing! |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jul 11, 2008 9:12 pm Post subject: |
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| Craig likes to speak with a forked tongue. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Fri Jul 11, 2008 9:21 pm Post subject: |
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I did make a dent ...
From Asellus' position:
Extended Medusa (or rather "GEM", starting at 45 in r6c1) removed 3 and 8 from r3c9.
Medusa (GEM) again, starting at 23 in r7c9 leads to 3 cells being solved: r1c6, r3c8,r7c9 =3 (all of them are "3")
After that, skyscraper "6", coloring "7" , and another brick wall here:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 15 4 1578 | 1678 9 3 | 568 2 18 |
| 3 1289 1589 | 12468 12468 26 | 45689 468 7 |
| 12 12789 6 | 5 12478 27 | 489 3 189 |
+--------------------------+--------------------------+--------------------------+
| 8 69 45 | 267 2567 1 | 3 47 29 |
| 7 1369 139 | 2368 268 4 | 29 18 5 |
| 45 13 2 | 378 578 9 | 478 1478 6 |
+--------------------------+--------------------------+--------------------------+
| 246 27 47 | 9 2467 8 | 1 5 3 |
| 9 12378 1378 | 127 127 5 | 2678 678 4 |
| 1246 5 148 | 12467 3 267 | 278 9 28 |
+--------------------------+--------------------------+--------------------------+
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Medusa (GEM) again, starting at "45" in r4c3, solves r2c7=5,r4c3=5 and finally (I had to use an xy-chain near the end) the puzzle.
Not pretty, but still much less of trial and error than the susser methods.
And no, I did not do it by hand - I used computer help for the color marks.
"I do declare there were times when I was so lonesome
I took some comfort there
la la la ..."
Last edited by nataraj on Fri Jul 11, 2008 9:34 pm; edited 1 time in total |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Jul 11, 2008 9:27 pm Post subject: |
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Nah! I felt I had to finish – even by meaningless guessing - which is surely guaranteed to work. I guessed at the <1> in R1C1 then the <5> but got stuck on the <5> – so guessed at the next <78>. Neither of them worked.
"I'm a Loser, I'm a Loser
..And I'm not what I appear to be"
(Beatles) |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Fri Jul 11, 2008 11:28 pm Post subject: |
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I retraced nataraj's steps (using extended Medusa, not GEM) and only noted a couple of minor differences. In that first extended Medusa cluster, I was also able to eliminate <1> from r1c34, <2> from r4c5, and then <1> from r2c3. That produced a slightly different "brick wall," but wasn't otherwise helpful.
That <7> coloring is actually multi-coloring (a Turbot Fish).
nataraj doesn't mention it but the other two extended Medusa clusters produce their placements via color wraps, whereas the first cluster eliminations are all traps.
Near the end I must have selected a different XY Chain because I still had to use an XY Wing at the very end.
I guess it's sort of ironic that my recent resistance to extended Medusa kept me from trying it in this case. Anyway, nice to know that this puzzle could be vanquished! |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Jul 12, 2008 6:47 am Post subject: |
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We did it! And Asellus is right, of course, about the traps and wraps and fish...
 |
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