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Puzzle 11/03/24: ~ Difficult++

 
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Thu Mar 24, 2011 8:03 pm    Post subject: Puzzle 11/03/24: ~ Difficult++ Reply with quote

Code:
 +-----------------------+
 | 5 7 . | . 2 . | . 1 9 |
 | 4 1 . | . . 8 | . . 5 |
 | . . 2 | . . 1 | . . . |
 |-------+-------+-------|
 | . . . | . 9 6 | . . . |
 | 1 . . | 2 7 . | . . . |
 | . 6 9 | 8 . 3 | . 2 . |
 |-------+-------+-------|
 | . . . | . . . | 9 . . |
 | 3 . . | . . 9 | . . 1 |
 | 8 9 . | . . . | . 4 . |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Thu Mar 24, 2011 10:51 pm    Post subject: Reply with quote

Ouch! 3s seems to be the key...
Quote:
als(3458=2)r7c2589 - als(2=36)r9c59 ; r9c7<>3
grouped-kite(3) r3, c7 ; r5c2<>3
xy-chain ; (3=8)r3c2 - (8=4)r5c2 - (4=5)r7c2 - (5=1)r9c3 - (1=5)r9c4 - (5=6)r8c4 - (6=3)r1c4 ; r1c3<>3
colouring(3) ... ; r5c9<>3, r4c3<>3
xy-wing(48-5)r5c2 ; r4c2<>5, r89c3<>5
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JC Van Hay



Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

PostPosted: Fri Mar 25, 2011 9:51 pm    Post subject: Reply with quote

A possible shortest path on the 3s :
Quote:
4 SIS X Chain on 3 : B1 B3 C4 C8 : 3r12c3=3r4c8 => r4c3<>3
6 "native" SIS AIC : 4R5 (45)R7C2 5R9 (56)R8C4 6C5 3R2 : 4r5c3=3r2c3 => r5c3<>3; LC(3)C2; 2 singles
5 "native" SIS AIC : 7R8 4R8 8C5 8C9 6R5 : 7r8c7=6r5c7 => r8c7<>6
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Sat Mar 26, 2011 12:07 am    Post subject: Reply with quote

I generated a new batch of puzzles where many turned out to be more difficult than posted in awhile. This was the first.

Code:
 r79c34  <15> UR Type 4.2243             <> 5    r7c34

 +-----------------------------------------------------+
 |  5    7    368  |  36   2    4    |  38   1    9    |
 |  4    1    36   |  9    36   8    |  2    7    5    |
 |  9    38   2    |  7    5    1    |  4    368  368  |
 |-----------------+-----------------+-----------------|
 |  2    358  358  |  4    9    6    |  1    38   7    |
 |  1    348  348  |  2    7    5    |  368  9    368  |
 |  7    6    9    |  8    1    3    |  5    2    4    |
 |-----------------+-----------------+-----------------|
 |  6    45   147  |  13   48   27   |  9    358  238  |
 |  3    2    457  |  56   48   9    |  678  568  1    |
 |  8    9    15   |  15   36   27   |  367  4    236  |
 +-----------------------------------------------------+
 # 50 eliminations remain

AIC: (3)r9c5 = (3-1)r7c4 = (1-7)r7c3 = r8c3 - r8c7 = (7)r9c7  =>  r9c7<>3

 r3c7    2-String Kite (grouped)         <> 3    r5c2

XY-Loop: (3=6)r1c4 =5r8c4 =1r9c4 =5r9c3 =4r7c2 =8r5c2 =3r3c2 =6r2c3 =3r2c5 - loop
          =>  r1c3<>3; r8c3<>5; r4c2<>8

 r14c3   Skyscraper                      <> 8    r3c8,r5c7

XY-Chain: (8=3)r4c8 =5r4c2 =4r7c2 =8r5c2  =>  r4c3,r5c9<>8

 r1c8    2-String Kite                   <> 3    r7c4
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JC Van Hay



Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

PostPosted: Sat Mar 26, 2011 7:53 am    Post subject: Reply with quote

Reviewing previous path, the following is even shorter, with the same eliminations ...
Code:
4 SIS t-Chain on 3 : r12c3=r3c2-r3c8*9=r1c7-r1c4=r7c4-[r7c8 AND r3c8*]=r4c8 => r4c3<>3
5 "native" SIS AIC with AHS : 4r5c3=47r78c3-1r7c3=(1-3)r7c4=3r9c5-3r2c5=3r2c3 =>  r5c3<>3; LC(3)C2; 2 singles
4 "native" SIS ALS XZ-Rule : (65=8)r8c48-(8=36)r4c8,r5c7 => r8c7<>6
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