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daily telegraph 12/21

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Dec 22, 2007 10:20 pm    Post subject: daily telegraph 12/21 Reply with quote

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



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Sat Dec 22, 2007 10:33 pm    Post subject: Reply with quote

Very nice puzzle, i needed four advanced steps to finish this one, the sequence of the steps to collapsing point :

1. ER <3> in Box 1, eliminates <3> in R4C1, it results in a [259] naked triple in C1

2. x-wing <3> in R35C19

3. 9-cell xy-chain with pincer cells in R5C9 and R2C4, takes out <1> in R5C4

4. xy-wing [14-13-34] with pivot in R5C9, eliminates <4> in R4C5

The grid after basics :
Code:

+--------------------------+--------------------------+--------------------------+
| 8         7         2    | 3         9         56   | 1         56        4    |
| 4         9         36   | 12        56        12   | 7         356       8    |
| 36        1         5    | 4         8         7    | 9         2         36   |
+--------------------------+--------------------------+--------------------------+
| 359       345       1    | 6         47        8    | 2         34        79   |
| 236       2346      7    | 12        124       9    | 5         8         13   |
| 29        24        8    | 5         1247      3    | 6         14        79   |
+--------------------------+--------------------------+--------------------------+
| 25        8         9    | 7         25        4    | 3         16        16   |
| 7         236       36   | 8         126       12   | 4         9         5    |
| 1         56        4    | 9         3         56   | 8         7         2    |
+--------------------------+--------------------------+--------------------------+     
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Asellus



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

PostPosted: Sun Dec 23, 2007 5:09 am    Post subject: Reply with quote

After Johan's first two steps, there is a shortcut:
Code:
+-----------+--------------+----------+
| 8  7   2  | 3   9     56 | 1 56  4  |
| 4  9   36 |@12  56   @12 | 7 356 8  |
| 36 1   5  | 4   8     7  | 9 2   36 |
+-----------+--------------+----------+
| 59 345 1  | 6   47    8  | 2 34  79 |
| 36 246 7  |@12 @124   9  | 5 8   13 |
| 29 24  8  | 5   1247  3  | 6 14  79 |
+-----------+--------------+----------+
| 25 8   9  | 7   25    4  | 3 16  16 |
| 7  236 36 | 8  @126  @12 | 4 9   5  |
| 1  56  4  | 9   3     56 | 8 7   2  |
+-----------+--------------+----------+

It is based on the 6-cell {12} Deadly Pattern in the middle tower, marked @. r5c5 must be <4> and/or r8c5 must be <6>. But, if r8c5 is <6>, then r8c3 is <3>, r4c2 is <3> and r4c8 is <4>. So, r5c5 and/or r4c8 is <4> and r4c5 cannot be <4>. This solves the puzzle.

For those who are interested in AICs, note that the DP creates a strong inferential link between that <4> and <6>. Then, we have:
(4)r4c5-(4)r5c5=(6)r8c5-(6=3)r8c3-(3)r8c2=(3)r4c2-(3=4)r4c8-(4)r4c5; r4c5<>4
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