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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Sat Jun 25, 2011 9:25 pm Post subject: Puzzle 11/06/25: ~ XY |
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| Code: | +-----------------------+
| 7 9 . | . . . | . . . |
| 8 . . | 3 . 5 | . . . |
| . . 1 | 6 7 . | . 4 . |
|-------+-------+-------|
| . 6 7 | 9 1 . | 4 8 . |
| . . 9 | 2 . 4 | . . . |
| . 8 . | . 5 6 | . . . |
|-------+-------+-------|
| . . . | 8 . . | 9 . 7 |
| . . 8 | 5 . . | . 6 4 |
| . . . | . . . | 8 5 2 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Jun 26, 2011 12:32 pm Post subject: |
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An uncomplicated one stepper...............
| Quote: | | anp(29=3)r28c5-r8c7=r7c8-(3=2)r1c8; r1c5<>2=4 |
Ted |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Jun 26, 2011 1:37 pm Post subject: |
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Here is a loop that makes 11 deletions but does not solve the puzzle.
| Code: | *--------------------------------------------------------------------*
| 7 9 256 |e14 d24 128 | 2356 c23 368 |
| 8 4 26 | 3 29 5 | 1267 1279 169 |
| 35 235 1 | 6 7 89 | 25 4 89 |
|----------------------+----------------------+----------------------|
| 2 6 7 | 9 1 3 | 4 8 5 |
| 135 135 9 | 2 8 4 | 1367 137 136 |
| 134 8 34 | 7 5 6 | 123 1239 139 |
|----------------------+----------------------+----------------------|
| 46 a1235 25 | 8 46 12 | 9 b13 7 |
| 139 1237 8 | 5 239 1279 | 13 6 4 |
| 13469 137 g34 |f14 3469 179 | 8 5 2 |
*--------------------------------------------------------------------* |
(3)r7c2=(3)r7c8-(3=2)r1c8-(2=4)r1c5-r1c4=r9c4-(4=3)r9c3-Loop; r56c8<>3, r1c367<>2, r9c15<>4, r89c12<>3
Sometimes it pays to be lucky............
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Jun 26, 2011 4:00 pm Post subject: |
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| I managed to stagger to the finish line with seven steps. Couple of XY-Wings, a DP and two Finned X-Wings. Then a key step was a Fin Transport (r2c5<>4) which opened up a short XY-Chain (r1c5, r2c78<>2). |
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PIsaacson
Joined: 13 Jun 2011
Posts: 11
Location: Campbell, CA
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| Posted: Sun Jun 26, 2011 10:31 pm Post subject: |
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After basics and an XY-Wing 123 pivot at r7c8 + r1c8 & r7c6 => r1c6 <> 2 I arrived at:
| Code: | *--------------------------------------------------------------------*
| 7 9 256 | 14 4-2 18 | 2356 *23 368 |
| 8 4 26 | 3 *29 5 | 167-2 179-2 169 |
| 35 235 1 | 6 7 89 | 25 4 89 |
|----------------------+----------------------+----------------------|
| 2 6 7 | 9 1 3 | 4 8 5 |
| 135 135 9 | 2 8 4 | 1367 137 136 |
| 134 8 34 | 7 5 6 | 123 1239 139 |
|----------------------+----------------------+----------------------|
| 46 1235 25 | 8 46 12 | 9 *13 7 |
| 139 27 8 | 5 *39 27 |*13 6 4 |
| 13469 137 34 | 14 3469 179 | 8 5 2 |
*--------------------------------------------------------------------* |
This first struck me as a DB with the stem cells bi-local 3 in box 9 tied to ALS r28c5 and ALS r1c8 with the common end-point 2s producing the 3 eliminations indicated. Then I looked at it again and thought it looked more like an ALS-XY Wing with ALSs r28c5 -3- r8c7 -1- r17c8 (other combinations are possible). But upon further examination, it looked like a simple XY-chain starting from either end r2c5 or r1c8, but again providing the same 3 eliminations. Regardless of POV, it's singles from there on.
Cheers,
Paul
That which we call a rose, by any other name... |
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dejsmith
Joined: 23 Oct 2005
Posts: 42
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| Posted: Sun Jun 26, 2011 11:12 pm Post subject: |
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I started with the same XY Wing as Paul; but, of course, my XY Chain was less efficient & lots longer! From Paul's grid, starting at r8c5: 93-31-13-32-24-41-18-89; r2c5<>9. I spend lots of time looking for those type chains when I cannot solve puzzles otherwise.
Dave |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Jun 27, 2011 1:17 pm Post subject: |
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Hi Paul, nice to have you joining our "Dailysudoku" activities.
I have been looking at "almost" conditions recently and noticed that your five cell pattern immediately after basic is an "almost xy-chain" with fin (2)r8c5. This pattern only deletes r1c5<>2 but completes the puzzle in one step.
Ted |
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PIsaacson
Joined: 13 Jun 2011
Posts: 11
Location: Campbell, CA
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| Posted: Mon Jun 27, 2011 5:35 pm Post subject: |
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Ted,
Nice! If I reproduced this correctly, the following PM appears fairly early in basics prior to any XY wing or coloring etc.: | Code: | *--------------------------------------------------------------------*
| 7 9 256 | 14 4-2 128 | 2356 b23 368 |
| 8 4 26 | 3 a29 5 | 1267 1279 169 |
| 35 235 1 | 6 7 289 | 235 4 389 |
|----------------------+----------------------+----------------------|
| 2 6 7 | 9 1 3 | 4 8 5 |
| 135 135 9 | 2 8 4 | 1367 137 136 |
| 134 8 34 | 7 5 6 | 123 1239 139 |
|----------------------+----------------------+----------------------|
| 13456 1235 25 | 8 2346 12 | 9 *13 7 |
| 139 1237 8 | 5 a239 1279 |*13 6 4 |
| 13469 137 34 | 14 3469 179 | 8 5 2 |
*--------------------------------------------------------------------*
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The 5 cells still define either a DB or an XY-Wing, but this time the mutual peers of both ALSs on the candidate 2 are restricted to the single r1c5 <> 2 elimination.
Denis Berthier would call this pattern an nrczt whip using 2r1c5 as the z-target start point. Prior to his implementation of the full nrczt logic, I think he would have called it an XY(z) chain. A very abridged version of his logic would be to consider a chain of logic starting from some z-target truth, and then extending the chain via AIC steps, but with the truths being applied as the chain is developed so that "promotions" (converting weak links to stong links) and "collisions" (impossible grid positions) are detected and applied on the fly. This is easy to emulate using SS by turning off "Block Invalid Moves" and then setting the truths. Allan Barker's XSudo allows you to easily enter nrczt chains as well.
Cheers,
Paul |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Jun 27, 2011 5:47 pm Post subject: |
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Or simply:
| Code: | (2=3)r1c8 - (3=1)r7c8 - (1=3)r8c7 - (3=29)r82c5 => r1c5<>2
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Jun 27, 2011 7:58 pm Post subject: |
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| daj95376 wrote: | Or simply:
| Code: | (2=3)r1c8 - (3=1)r7c8 - (1=3)r8c7 - (3=29)r82c5 => r1c5<>2
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... which is the reverse of my original post. It is wonderful how AICs work that way.
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Jun 27, 2011 9:39 pm Post subject: |
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| tlanglet wrote: | ... which is the reverse of my original post. It is wonderful how AICs work that way.
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Well, now I'm completely disheveled. I'd forgotten your original (whitened-out) solution, and thought you were commenting on a "new" observation related to Paul's post. Oh Well !!!
Regards, Danny |
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