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competition puzzles

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sun Feb 17, 2008 8:35 pm    Post subject: competition puzzles Reply with quote
might as well bundle them in one post.

weekly extreme #73...
http://www.sudoku.org.uk/PrintWeeklySudoku.asp?number=73

Code:
5..|.4.|...
..3|...|62.
...|..9|..4
---+---+---
..6|..7|2..
81.|...|.43
..9|1..|...
---+---+---
7..|5..|...
.92|...|8..
...|.3.|..6   SE 8.4


friday diabolical #950
http://www.sudoku.org.uk/DailySudoku.asp?day=15/02/2008

Code:
..7|.4.|.2.
6.2|8..|...
1..|.9.|..6
---+---+---
.2.|1..|.58
...|.7.|...
86.|..9|.7.
---+---+---
3..|.2.|..9
...|..5|4.7
.4.|.1.|2..  SE 6.7


Sunday Diabolical # 952
http://www.sudoku.org.uk/DailySudoku.asp?day=17/02/2008
Code:
42.|5..|.1.
...|.31|...
.19|.7.|.5.
---+---+---
8..|294|...
...|...|...
...|783|..5
---+---+---
.5.|.4.|73.
...|82.|...
.9.|..6|.48  SE 7.1


the extreme puzzle is a little beyond me yet, but the two diabolicals are a bit tricky but fun all the same.
---

in the second diabolical, if you don't like xy-chains then you might have a hard time finding a solution path. and the grid after basics contains an ER but the x-wing does more damage on 6.

after the x-wing on 6, there is a two step medusa solution. a trap first that opens up a wrap
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ravel



Joined: 21 Apr 2006
Posts: 536
PostPosted: Mon Feb 18, 2008 11:37 am    Post subject: Re: competition puzzles Reply with quote
storm_norm wrote:
in the second diabolical, if you don't like xy-chains then you might have a hard time finding a solution path.
Not too hard:
Code:
 *------------------------------------------------*
 | 4    2    37    | 5  6  8  | 39    1    379    |
 | 5    8   #67    | 9  3  1  | 246   26-7 247    |
 |A36   1    9     | 4  7  2  | 8     5    36     |
 |-----------------+----------+-------------------|
 | 8    367  5     | 2  9  4  | 136  #67   137    |
 | 239  347  234   | 6  1  5  | 2349  8    23479  |
 | 129  46   1246  | 7  8  3  | 2469  269  5      |
 |-----------------+----------+-------------------|
 |B26   5    8     | 1  4  9  | 7     3   A26     |
 | 13   346  1346  | 8  2  7  | 5    B69   19     |
 | 7    9    12    | 3  5  6  | 12    4    8      |
 *------------------------------------------------*

There is an "extended" w-wing 67 connected by 2 strong links for 6 (either r3c1 or r8c8 must be 6) => r2c8<>7
A "normal" w-wing finishes it off.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon Feb 18, 2008 8:11 pm    Post subject: Reply with quote
Ravel,
very nice. w-wings still don't come naturally for me.
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
PostPosted: Tue Feb 19, 2008 3:00 am    Post subject: Reply with quote
That Extreme was really tough! It has some interesting techniques present right at the beginning, however.

The grid after basics:
Code:

+--------------+-------------------+-------------------+
| 5    267  18 | 23678  4      136 | 1379  13789  1789 |
| 9    4    3  | 78     157    15  | 6     2      1578 |
| 26   267  18 | 23678  12567  9   | 1357  13578  4    |
+--------------+-------------------+-------------------+
| 34   5    6  | 34     89     7   | 2     189    189  |
| 8    1    7  | 269    2569   56  | 59    4      3    |
| 234  23   9  | 1      58     34  | 57    6      578  |
+--------------+-------------------+-------------------+
| 7    36   4  | 5      169    8   | 139   139    2    |
| 36   9    2  | 467    167    146 | 8     1357   157  |
| 1    8    5  | 79     3      2   | 4     79     6    |
+--------------+-------------------+-------------------+

Here are those interesting initial steps:

(1) a Finned Swordfish on <3> in r348 that removes <3> from r1c8;
(2) a Sashimi Swordfish on <8> in r123 that removes <8> from r1c9;
(3) a Kite on <6> pivoting in b7 that removes <6> from r3c5; and
(4) a Finned Jellyfish in c1456 that removes <6> from r8c4.

You don't find a Finned Jellyfish every day! (They're probably there, but you don't need to use them.)

The grid now, with extended Medusa:
Code:

+----------------+---------------------+-------------------+
| 5     267   18 | 2g-3678 4     -13r6 | 1379  1789   179  |
| 9     4     3  | 78g     157    1g5  | 6     2      1578 |
| 2G6R  267   18 | 23678   1257   9    | 1357  13578  4    |
+----------------+---------------------+-------------------+
| 34r   5     6  | 3r4     89g    7    | 2     189    189  |
| 8     1     7  | 26g9    2g569  5g6  | 59g   4      3    |
| 2R34  2G3R  9  | 1       58g    34r  | 5g7   6      57g8 |
+----------------+---------------------+-------------------+
| 7     3G6R  4  | 5       16G9   8    | 1g39  139g   2    |
| 3R6G  9     2  | 4r7     1g67   146  | 8     13G57  15g7 |
| 1     8     5  | 79g     3      2    | 4     7g9    6    |
+----------------+---------------------+-------------------+

(I tried strict Medusa multi-coloring, without "extensions," but got nowhere.) There are some eliminations in r1. Continuing:
Code:

+-----------------+---------------------+-------------------+
| 5      2-67  18 | 2g678   4      3r6g | 1379  1789   179  |
| 9      4     3  | 78g     157    1g5  | 6     2      1578 |
| 2G6R   267   18 | 23g-678 1257   9    | 1357  13578  4    |
+-----------------+---------------------+-------------------+
| 34r    5     6  | 3r4     89g    7    | 2     189    189  |
| 8      1     7  | 26g9    2g569  5g6  | 59g   4      3    |
| 2R-34  2G3R  9  | 1       58g    3g4r | 5g7   6      57g8 |
+-----------------+---------------------+-------------------+
| 7      3G6R  4  | 5       16G9   8    | 1g39  139g   2    |
| 3R6G   9     2  | 4r7g    1g67   14g6 | 8     13G57  15g7 |
| 1      8     5  | 79g     3      2    | 4     7g9    6    |
+-----------------+---------------------+-------------------+

The <6> eliminations in b12 and the elimination of <3> in r6c1 lead to color promotion, and there are more extensions:
Code:

+----------------+---------------------+---------------------+
| 5     27    18 | 2g6R78  4      3R6G | 13G79  1789   179   |
| 9     4     3  | 78g     157g   1g5  | 6      2     #15g78 |
| 2G6R  26G7  18 | 23G78   125g7  9    | 1357g  13578  4     |
+----------------+---------------------+---------------------+
| 3G4R  5     6  | 3R4G    89g    7    | 2      189    189   |
| 8     1     7  | 26G9    2g569  5g6  | 59g    4      3     |
| 2R4G  2G3R  9  | 1       58g    3G4R | 5g7    6      57g8  |
+----------------+---------------------+---------------------+
| 7     3G6R  4  | 5       16G9   8    | 1g39   139g   2     |
| 3R6G  9     2  | 4R7G    1g67   14G6 | 8      13G57 #15g7  |
| 1     8     5  | 79g     3      2    | 4      7g9    6     |
+----------------+---------------------+---------------------+

We now find two green <5>s in c9. So, all red values are true. This gets us here:
Code:

+--------+----------------+----------------+
| 5 2 18 | 6    4      3  | 179  1789  179 |
| 9 4 3  | 78   157    15 | 6    2     158 |
| 6 7 18 | 28   125    9  | 135  1358  4   |
+--------+----------------+----------------+
| 4 5 6  | 3   A89     7  | 2    189   189 |
| 8 1 7  | 29   2-569 C56 | 59   4     3   |
| 2 3 9  | 1   B58     4  | 57   6     578 |
+--------+----------------+----------------+
| 7 6 4  | 5   E19     8  | 139  139   2   |
| 3 9 2  | 4   -167   D16 | 8    157   157 |
| 1 8 5  | 79   3      2  | 4    79    6   |
+--------+----------------+----------------+

There is a 5-cell XY Loop that makes 2 eliminations. And, there is another XY Loop:
Code:

+--------+----------------+----------------+
| 5 2 18 | 6    4      3  | 179  1789  179 |
| 9 4 3  |I78   157    15 | 6    2     158 |
| 6 7 18 |H28   125    9  | 135  1358  4   |
+--------+----------------+----------------+
| 4 5 6  | 3   F89     7  | 2    189   189 |
| 8 1 7  |G29   26-9  D56 | 59   4     3   |
| 2 3 9  | 1   E58     4  | 57   6     578 |
+--------+----------------+----------------+
| 7 6 4  | 5   B19     8  | 139  139   2   |
| 3 9 2  | 4    67    C16 | 8    157   157 |
| 1 8 5  |A79   3      2  | 4    79    6   |
+--------+----------------+----------------+

This opens up a Skyscraper on <9> in r59. Then, an XY Wing removes <1> from r7c8. Then, back to Medusa:
Code:

+--------+------------------+-------------------+
| 5 2 18 | 6     4     3    | 179R  178   179G  |
| 9 4 3  | 7G8R -157R  1G5R | 6     2     1-58G |
| 6 7 18 | 2R8G  12G-5 9    | 13R5  13G58 4     |
+--------+------------------+-------------------+
| 4 5 6  | 3     8R9G  7    | 2     18    1-89R |
| 8 1 7  | 2G9R  2R6G  5G6R | 5R9G  4     3     |
| 2 3 9  | 1     5R8G  4    | 57    6     578R  |
+--------+------------------+-------------------+
| 7 6 4  | 5     1G9R  8    | 1R3G  3R9G  2     |
| 3 9 2  | 4     6R7G  1R6G | 8     157   157   |
| 1 8 5  | 7R9G  3     2    | 4     7G9R  6     |
+--------+------------------+-------------------+

And:
Code:

+--------+------------------+-------------------+
| 5 2 18 | 6     4     3    | 179R  178  -179G  |
| 9 4 3  | 7G8R  5G7R  1G5R | 6     2     1R8G  |
| 6 7 18 | 2R8G  1R2G  9    | 13R5 -13G58 4     |
+--------+------------------+-------------------+
| 4 5 6  | 3     8R9G  7    | 2     1R8G  1G9R  |
| 8 1 7  | 2G9R  2R6G  5G6R | 5R9G  4     3     |
| 2 3 9  | 1     5R8G  4    | 57    6     578R  |
+--------+------------------+-------------------+
| 7 6 4  | 5     1G9R  8    | 1R3G  3R9G  2     |
| 3 9 2  | 4     6R7G  1R6G | 8     157  -157   |
| 1 8 5  | 7R9G  3     2    | 4     7G9R  6     |
+--------+------------------+-------------------+

And:
Code:

+--------+------------------+-------------------+
| 5 2 18 | 6     4     3    | 179R -178   7R9G  |
| 9 4 3  | 7G8R  5G7R  1G5R | 6     2     1R8G  |
| 6 7 18 | 2R8G  1R2G  9    | 13R5  3G58  4     |
+--------+------------------+-------------------+
| 4 5 6  | 3     8R9G  7    | 2     1R8G  1G9R  |
| 8 1 7  | 2G9R  2R6G  5G6R | 5R9G  4     3     |
| 2 3 9  | 1     5R8G  4    | 57    6     578R  |
+--------+------------------+-------------------+
| 7 6 4  | 5     1G9R  8    | 1R3G  3R9G  2     |
| 3 9 2  | 4     6R7G  1R6G | 8     1G57  5-7   |
| 1 8 5  | 7R9G  3     2    | 4     7G9R  6     |
+--------+------------------+-------------------+

And the puzzle is solved.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Tue Feb 19, 2008 3:43 am    Post subject: Reply with quote
Asellus,

excellent!

these extreme competition puzzles, IMHO, are a nasty bunch of puzzles. at least with the nightmares you know what you are getting into each day.
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