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More UR goodies?

 
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garytorborg



Joined: 19 Jan 2011
Posts: 28

PostPosted: Wed Mar 23, 2011 9:43 pm    Post subject: More UR goodies? Reply with quote

Hmmm. I'm stuck in a puzzle that I suspect has some more of those hidden URs like the last one. Can anyone help?

Code:

+--------------+--------------+---------------+
| 89   89  5   | 167 167  2   | 3    146 467  |
| 3    4   167 | 8   167  9   | 17   5   2    |
| 2    17  167 | 3   5    4   | 8    9   67   |
+--------------+--------------+---------------+
| 79   5   8   | 47  479  3   | 6    2   1    |
| 19   6   3   | 2   8    15  | 4    7   59   |
| 4    179 2   | 167 1679 156 | 59   8   3    |
+--------------+--------------+---------------+
| 158  2   9   | 146 3    7   | 15   146 4568 |
| 6    3   17  | 5   124  8   | 1279 14  479  |
| 1578 178 4   | 9   126  16  | 1257 3   5678 |
+--------------+--------------+---------------+

Play this puzzle online at the Daily Sudoku site

All those "167s" have to mean something...
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keith



Joined: 19 Sep 2005
Posts: 3341
Location: near Detroit, Michigan, USA

PostPosted: Wed Mar 23, 2011 10:50 pm    Post subject: Reply with quote

Look at R3. You can eliminate 1 in R2C3.

Otherwise, I don't see anything.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Mar 24, 2011 12:22 am    Post subject: Re: More UR goodies? Reply with quote

garytorborg wrote:
Hmmm. I'm stuck in a puzzle that I suspect has some more of those hidden URs like the last one. Can anyone help?

Code:

+--------------+--------------+---------------+
| 89   89  5   | 167 167  2   | 3    146 467  |
| 3    4   167 | 8   167  9   | 17   5   2    |
| 2    17  167 | 3   5    4   | 8    9   67   |
+--------------+--------------+---------------+
| 79   5   8   | 47  479  3   | 6    2   1    |
| 19   6   3   | 2   8    15  | 4    7   59   |
| 4    179 2   | 167 1679 156 | 59   8   3    |
+--------------+--------------+---------------+
| 158  2   9   | 146 3    7   | 15   146 4568 |
| 6    3   17  | 5   124  8   | 1279 14  479  |
| 1578 178 4   | 9   126  16  | 1257 3   5678 |
+--------------+--------------+---------------+

Play this puzzle online at the Daily Sudoku site

All those "167s" have to mean something...

You can play with the potential 58 UR in boxes 79. R79c1 must be 1 or 7. This pseudo cell combines with r8c3 to force r9c2<>17. R79c9 must be 4,6 or7. This combines with r13c9 to form a 467 pseudo cell, forcing r8c9<>47. Under both scenarios, r1c12=89 and r9c2=8, bringing us here, where I still don't see anything.

Code:

+-------------+--------------+--------------+
| 8   9   5   | 167 167  2   | 3    146 467 |
| 3   4   167 | 8   167  9   | 17   5   2   |
| 2   17  167 | 3   5    4   | 8    9   67  |
+-------------+--------------+--------------+
| 79  5   8   | 47  479  3   | 6    2   1   |
| 19  6   3   | 2   8    15  | 4    7   59  |
| 4   179 2   | 167 1679 156 | 59   8   3   |
+-------------+--------------+--------------+
| 15  2   9   | 46  3    7   | 15   46  8   |
| 6   3   17  | 5   124  8   | 1279 14  479 |
| 157 8   4   | 9   126  16  | 1257 3   567 |
+-------------+--------------+--------------+

Play this puzzle online at the Daily Sudoku site
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keith



Joined: 19 Sep 2005
Posts: 3341
Location: near Detroit, Michigan, USA

PostPosted: Thu Mar 24, 2011 1:39 am    Post subject: Reply with quote

Marty, R6C2 is not 9. Also, look at R3. R2C3 is not 1.Which gets us here:
Code:
+----------------+----------------+----------------+
| 8    9    5    | 167  167  2    | 3    146  467  |
| 3    4    6-7  | 8    167  9    | 17#  5    2    |
| 2    17   167  | 3    5    4    | 8    9    67   |
+----------------+----------------+----------------+
| 79   5    8    | 47   479  3    | 6    2    1    |
| 19   6    3    | 2    8    15   | 4    7    59   |
| 4    17   2    | 167  1679 156  | 59   8    3    |
+----------------+----------------+----------------+
| 15@  2    9    | 46   3    7    | 15@  46   8    |
| 6    3    17#  | 5    124  8    | 1279 14   479  |
| 157  8    4    | 9    126  16   | 1257 3    567  |
+----------------+----------------+----------------+

The W-wing solves it.

Keith
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Thu Mar 24, 2011 7:56 am    Post subject: Reply with quote

Forgoing DPs, I used the otherwise useless 15 W-Wing in r5c6|r7c7 with transports:
(1)r5c6-(1=6)r9c6 and (1)r7c7-ALS[(1)r78c8=(6)r7c8]; r9c9<>6

(Alternately, that second transport can be a short XY-Chain via box 3 to <6> in r3c9.)

After simplification (no <6> in r7c4), repeat with different transports:
(1)r5c6-(1=9)r5c1 and (1)r7c7-(1=4)r7c4-(4=7)r4c4-(7=9)r4c1; r1c1<>9

That solves the puzzle.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Fri Mar 25, 2011 2:04 am    Post subject: Reply with quote

Okay, since Ted doesn't seem interested, here's a UR step that helps:

Code:
 <58> UR r79c19 w/external SIS r1c1=8 and/or r5c9=5

 (8=9)r1c1 - (9=1)r5c1 - (1=5)r5c6 - UR[(5)r5c9 = (8)r1c1]  =>  r1c1=8
 +--------------------------------------------------------------+
 | #89    89    5     |  167   167   2     |  3     146   467   |
 |  3     4     167   |  8     167   9     |  17    5     2     |
 |  2     17    167   |  3     5     4     |  8     9     67    |
 |--------------------+--------------------+--------------------|
 |  79    5     8     |  47    479   3     |  6     2     1     |
 |  19    6     3     |  2     8     15    |  4     7    #59    |
 |  4     179   2     |  167   1679  156   |  59    8     3     |
 |--------------------+--------------------+--------------------|
 | *58+1  2     9     |  146   3     7     |  15    146  *58+46 |
 |  6     3     17    |  5     124   8     |  1279  14    479   |
 | *58+17 178   4     |  9     126   16    |  1257  3    *58+67 |
 +--------------------------------------------------------------+
 # 69 eliminations remain

 r7      Naked  Pair                     <> 15   r7c48

 r3  b1  Locked Candidate 2              <> 1    r2c3

   c2348 Jellyfish (2222)                <> 1    r1c5,r6c56,r8c57   -or-
 r2579   Jellyfish (2224)                <> 1    r1c5,r6c56,r8c57

 r9  b8  Locked Candidate 1              <> 1    r9c17

Code:
 +-----------------------------------------------------+
 |  8    9    5    |  167  67   2    |  3    146  467  |
 |  3    4    67   |  8    167  9    |  17   5    2    |
 |  2    17   167  |  3    5    4    |  8    9    67   |
 |-----------------+-----------------+-----------------|
 |  79   5    8    |  47   479  3    |  6    2    1    |
 |  19   6    3    |  2    8    15   |  4    7    59   |
 |  4    17   2    |  167  679  56   |  59   8    3    |
 |-----------------+-----------------+-----------------|
 |  15   2    9    |  46   3    7    |  15   46   8    |
 |  6    3    17   |  5    24   8    |  279  14   479  |
 |  57   8    4    |  9    126  16   |  257  3    567  |
 +-----------------------------------------------------+
 # 48 eliminations remain

W-Wing: (7=1)r2c7 - r1c8 = r8c8 - (1=7)r8c3  =>  r2c3,r8c7<>7   -or-
W-Wing: (7=1)r2c7 - r7c7 = r7c1 - (1=7)r8c3  =>  r2c3,r8c7<>7   -or-
W-Wing: (7=1)r2c7 - r7c7 = r8c8 - (1=7)r8c3  =>  r2c3,r8c7<>7

-or-

XY-Chain: (7=1)r2c7 =5r7c7 =1r7c1 =7r8c3     =>  r2c3,r8c7<>7
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ronk



Joined: 07 May 2006
Posts: 398

PostPosted: Fri Mar 25, 2011 10:27 am    Post subject: Reply with quote

daj95376 wrote:
... here's a UR step that helps:

Code:
 <58> UR r79c19 w/external SIS r1c1=8 and/or r5c9=5

 (8=9)r1c1 - (9=1)r5c1 - (1=5)r5c6 - UR[(5)r5c9 = (8)r1c1]  =>  r1c1=8

There seems to be a growing tendency to write expressions that result in placements, and I don't understand why. Isn't r1c1<>9 the underlying move here, a move which would still be true even if r1c1 had three or more candidates?

(9)r5c1 = (9)r5c9 - UR[(5)r5c9 = (8)r1c1] => r1c1<>9
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Fri Mar 25, 2011 5:43 pm    Post subject: Reply with quote

ronk wrote:
There seems to be a growing tendency to write expressions that result in placements, and I don't understand why. Isn't r1c1<>9 the underlying move here, ...?

Yes, you caught me making the same mistake that I dislike seeing others make. My only excuse is that I was tired from spending the whole day moving furniture so the cleaning lady could get to places that haven't seen sunlight in years. Today, I finish move it all back. Oh Joy!!!
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.

PostPosted: Fri Mar 25, 2011 6:19 pm    Post subject: Reply with quote

For those who don't see the distinction, using a UR to set one cell doesn't always get all the eliminations. If you use the UR to remove all the candidates indicated you may well shorten your solving path. Geez, I'm agreeing with ronk! Shocked
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Sat Mar 26, 2011 12:49 pm    Post subject: Reply with quote

Another perspective of dealing with AURs, is that of using various combinations of strong inferences; each set has the potential of providing different deletions.

Ted
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Sat Mar 26, 2011 2:30 pm    Post subject: Reply with quote

Been away for a while and just had the opportunity to review the details of these earlier posts. The one by Danny using an external strong inference set was short and effective; what more could you want. However, I really liked the technique used by Marty; I think it generally had less probability of success but he made it happen!

The great flexibility offered by ADPs is a major attraction to me.

Ted
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