Washington Post 7/14 hard

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Washington Post 7/14 hard

Postby wcm » Sat Jul 21, 2007 2:44 pm

I am looking for clues to break this puzzle.

32*/76*/981
6*7/3**/245
9**/***/637
*7*/**6/51*
159/472/368
*6*/5**/47*
7*6/***/*93
59*/6*3/724
*32/**7/*56
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Postby udosuk » Sat Jul 21, 2007 3:35 pm

Focus on c5 (the middle column). 3 digits can only appear in 3 cells. And one of these 3 cells cannot hold 2 of these digits, so must hold the remaining digit.

This technique is what we call a hidden triple or hidden trio. Alternatively, if you write out all the candidates for each cell you'll spot a naked quad on the same column.:idea:
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Postby re'born » Sat Jul 21, 2007 9:49 pm

Or you could spot the obvious:D ALS elimination:
Code: Select all
 *--------------------------------------------------------------------*
 | 3      2      45     | 7      6      45     | 9      8      1      |
 | 6      18     7      | 3      189A   189    | 2      4      5      |
 | 9      148    1458   | 128    12458  1458   | 6      3      7      |
 |----------------------+----------------------+----------------------|
 | 248B   7      348    | 89B    389B   6      | 5      1      29B    |
 | 1      5      9      | 4      7      2      | 3      6      8      |
 | 28     6      38     | 5      1389A  189    | 4      7      29     |
 |----------------------+----------------------+----------------------|
 | 7      148    6      | 128    12458  1458   | 18     9      3      |
 | 5      9      18     | 6      18A    3      | 7      2      4      |
 | 48-    3      2      | 189    1489A  7      | 18     5      6      |
 *--------------------------------------------------------------------*

A={1,3,4,8,9} on r2689c5
B={2,3,4,8,9} on r4c1459
x=3
z=4
=>r9c1<>4.


...or maybe the naked quad is easier.
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re: Washington Post 2007.Jul.14

Postby Pat » Sun Jul 22, 2007 1:16 pm

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


udosuk wrote:Focus on c5.
3 digits can only appear in 3 cells.
And one of these 3 cells cannot hold 2 of these digits,
so must hold the remaining digit.

This technique is what we call a hidden triple or hidden trio.



it's a "hidden" duo --
    c5 {2,5} can only be at r3,r7
    (this solves the 4 for that column)
the Pappocom Hard puzzles will only rarely require a trio

~ Pat
User avatar
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Postby udosuk » Sun Jul 22, 2007 1:20 pm

Pat, you're absolutely right.:)

I was just trying to pretend like I'm a non-pencilmark solver and show the compliment move of the naked quad. Guess I really do suck at that.

Forget it, I'll go back to pencilmark solving mode and let you experts handle these requests.:)
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