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July16 very hard

 
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oaxen



Joined: 10 Jul 2006
Posts: 96

PostPosted: Sun Jul 16, 2006 2:03 pm    Post subject: July16 very hard Reply with quote

I gave up. After receiving the following pattern I had to ask for a hint. Gives me 5 in c3r5. I suppose because the program will eliminate the other possibility, 7, in the same cell, but why? Am I blind now again?


3798xx5x2
x2xxx7x38
816253479
xx2x1x84x
x8xxxxx2x
x3xx829xx
7x153928x
2534x8x9x
xx8x2x35x

Lars (oaxen)
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sun Jul 16, 2006 3:24 pm    Post subject: Reply with quote

Code:
 *--------------------------------------------------------------------*
 | 3      7      9      | 8      46     146    | 5      16     2      |
 | 45     2      45     | 169    469    7      | 16     3      8      |
 | 8      1      6      | 2      5      3      | 4      7      9      |
 |----------------------+----------------------+----------------------|
 | 569    69     2      | 3679   1      56     | 8      4      3567   |
 | 14569  8     >457<   | 3679   4679*# 456#   | 167*   2      13567  |
 | 1456   3      457    | 67     8      2      | 9      16     1567   |
 |----------------------+----------------------+----------------------|
 | 7      46     1      | 5      3      9      | 2      8      46     |
 | 2      5      3      | 4      67*    8      | 167*   9      167    |
 | 469    469    8      | 167    2      16     | 3      5      1467   |
 *--------------------------------------------------------------------*

The candidates for R5C3 are 4, 5 and 7.

One of the cells R5C5 and R5C6 (marked with #, above) must hold block 5's '4', which eliminates 4 as a candidate for R5C3.

There is an X-wing in '7' at R58C57 (marked with '*', above), which eliminates '7' as a candidate from all other cells in rows 5 and 8 - in particular, for R5C3.

5 is the only candidate left in R5C3.

Cheers!
- cb
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David



Joined: 02 Jun 2006
Posts: 58
Location: Bedford, UK

PostPosted: Sun Jul 16, 2006 4:01 pm    Post subject: Reply with quote

There is an X wing on 7's at r4c49 and r9c49. This allows reduction of cell at r6c4 to a 6, and the rest of the puzzle falls out.
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TexCat



Joined: 07 Jul 2006
Posts: 31

PostPosted: Sun Jul 16, 2006 4:03 pm    Post subject: Reply with quote

Code:

-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  -  -  | -  -  -  |

-  -  -  |  7* -  -  | -  -  7  |
-  -  7  |  7  7  -  | 7* -  7  |
-  -  7* |  7  -  -  | -  -  7  |

-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  7* -  | 7  -  7  |
-  -  -  |  7  -  -  | -  -  7* |
============================
-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  -  -  | -  -  -  |

-  -  -  |  7  -  -  | -  -  7* |
-  -  7  |  7  7* -  | 7  -  7  |
-  -  7* |  7  -  -  | -  -  7  |

-  -  -  |  -  -  -  | -  -  -  |
-  -  -  |  -  7  -  | 7* -  7  |
-  -  -  |  7* -  -  | -  -  7  |

I gave up and used trial and error on the 7's in column 7. First I assumed that row 5 was 7, then that row 8 was a 7. In both cases, R6C3 had to be a 7. I filled the 7 in there and everything else was pie. I never can find the xy-wings, but if I suspect that's what is needed, sometimes trial and error on just 1 number will work for me.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jul 16, 2006 5:26 pm    Post subject: Reply with quote

Another way of looking at it:
Code:

 *-----------*
 |.79|...|5..|
 |...|..7|..8|
 |...|25.|4.9|
 |---+---+---|
 |..2|.1.|.4.|
 |.8.|...|.2.|
 |.3.|.8.|9..|
 |---+---+---|
 |7.1|.39|...|
 |2..|4..|...|
 |..8|...|35.|
 *-----------*
 *--------------------------------------------------------------------*
 | 34     7      9      | 8      46     146    | 5      136    2      |
 | 345    2      45     | 169    469    7      | 16     136    8      |
 | 8      1      6      | 2      5      3      | 4      7      9      |
 |----------------------+----------------------+----------------------|
 | 569    69     2      |(37)    1      56     | 8      4     (37)    |
 | 156    8      57     | 3679   4679   456    | 167    2      13567  |
 | 1456   3     (457)   |(67)    8      2      | 9      16    (1567)  |
 |----------------------+----------------------+----------------------|
 | 7      46     1      | 5      3      9      | 2      8      46     |
 | 2      5      3      | 4      67     8      | 167    9      167    |
 | 69     49     8      |(167)   2      16     | 3      5     (47)    |
 *--------------------------------------------------------------------*

Marked cells form a swordfish (degenerate, I think, because one column contains only one cell) which makes the same key exclusion as the one x-wing (leaves r5c3 as a naked single).
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oaxen



Joined: 10 Jul 2006
Posts: 96

PostPosted: Mon Jul 17, 2006 7:20 am    Post subject: Reply with quote

Thank you Chuck B. I missed your X-wing
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