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cavalier
Joined: 20 Jul 2006
Posts: 7
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 Posted: Mon Jul 31, 2006 10:42 am Post subject: help with 7-22 Sudoku |
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In the following grid, I can get "6" in R4C9. but no idea why the hint give "9" in R6C9. I will appreciated if any one can advise. Tks!
4xx|216|39x
12x|439|xx8
396|587|124
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xxx|x2x|73x
xx2|37x|4xx
713|x64|2xx
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x3x|7x8|x12
2x1|6x3|xxx
x5x|1x2|xx3 |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Jul 31, 2006 11:38 am Post subject: |
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In box 6 the 9 must be in column 9, therefore r8c9 cannot be 9.
Then there is a hidden pair 16 in r45c9 (16 in rows 1,6 and 8). |
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cavalier
Joined: 20 Jul 2006
Posts: 7
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| Posted: Thu Aug 03, 2006 7:10 am Post subject: hint explanation for Aug 3 puzzle |
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First,many tks for Ravel's help, your answer is simple and easy to understand!
As per this puzzle, in my way, I got 4 in R3C5 and 1 in R1C6 sequently,then finish it. But no idea how the hint gives 9 in R9C4.
Can anyone advise it?
5xx|7xx|x42
xx2|5xx|xx8
xx6|2xx|5x9
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x19|37x|82x
7xx|x8x|193
xxx|xx9|76x
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xxx|xx7|2x6
8xx|xx4|9x7
x37|xxx|4x1 |
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Chuck B
Joined: 24 Jun 2006
Posts: 24
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| Posted: Thu Aug 03, 2006 9:45 am Post subject: |
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It takes two steps. Consider the candidate list at this point: | Code: | *--------------------------------------------------------------------*
| 5 89 138 | 7 #1369 1368 | 36 4 2 |
| 1349 479 2 | 5 #13469 136 | 36 137 8 |
| 134 478 6 | 2 134 138 | 5 137 9 |
|----------------------+----------------------+----------------------|
| 46 1 9 | 3 7 56 | 8 2 45 |
| 7 2456 45 | 46 8 256 | 1 9 3 |
| 234 2458 3458 | 14 1245 9 | 7 6 45 |
|----------------------+----------------------+----------------------|
|*149 *459 *145 | 189 x1359 7 | 2 358 6 |
| 8 256 *15 | 16 12356 4 | 9 35 7 |
|x269 3 7 |>689< x2569 2568 | 4 58 1 |
*--------------------------------------------------------------------*
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First, block 2's '9' must be in r1c5 or r2c5, so r9c5 cannot hold a 9. (nor can r7c5, but that doesn't affect the hint)
Second, there is a 'naked quad' in block 7, in the cells marked with '*'. The digits {1, 4, 5, 9} have to occupy the *'d cells, so r9c1 cannot hold a 9.
This leaves r9c4 as the only cell in r9 that can hold a 9.
-cb |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Thu Aug 03, 2006 3:33 pm Post subject: |
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| As always, the naked quad has a hidden counterpart, in this case a hidden pair 26 in r8c2 and r9c1, which can be spotted (without candidates/pencilmarks), because you have 2 and 6 both in column 3 and in row 7. |
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Chuck B
Joined: 24 Jun 2006
Posts: 24
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| Posted: Thu Aug 03, 2006 5:05 pm Post subject: |
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| ravel wrote: | | ...which can be spotted (without candidates/pencilmarks), because you have 2 and 6 both in column 3 and in row 7. |
Thanks for that insight, ravel - very helpful & motivating!
Some of us aging boomers really do need the mental exercise, so I'll have to give that minimal pencil mark approach a go. Now back to the 'easy' archives...  |
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cavalier
Joined: 20 Jul 2006
Posts: 7
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| Posted: Fri Aug 04, 2006 12:30 am Post subject: Tks Chuck B and Ravel! |
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Tks to both of you! I learned a lot from your help.
By the way, what does the "boomer" mean here? new comer or green hand?
P.S.: I am in China. |
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Chuck B
Joined: 24 Jun 2006
Posts: 24
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| Posted: Fri Aug 04, 2006 1:44 am Post subject: Re: Tks Chuck B and Ravel! |
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| cavalier wrote: | Tks to both of you! I learned a lot from your help.
By the way, what does the "boomer" mean here? new comer or green hand?
P.S.: I am in China. |
Hi, cavalier!
The term 'boomer' is short for 'baby boomer'. It's an American slang name for my generation, who were born in the 'baby boom' that followed our soldiers' homecoming after World War II. As you might surmise, many of us are starting to show our age - e.g., I'm older than the PRC! 
Cheers!
-cb |
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cavalier
Joined: 20 Jul 2006
Posts: 7
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| Posted: Fri Aug 04, 2006 3:01 am Post subject: Tks Chuck! |
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Hi Chuck,
Tks for your explanation!
Bill Clinton may be the most famous boomer in China. But seems he likes physical exercise than mental, hehe.
You are older than PRC, but never to be older than China,haha.
Best
Cavalier |
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