Next move

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Next move

Postby Simple mind » Sat Jan 21, 2006 11:20 am

I'm still a beginner at this, could someone please explain what's the next move I should take? I can't seem to see an easy next move...

Code: Select all

  18    6   1278 |  3   4   5  |  127   9   12
  2     3   15   |  7   9   8  |  15    6   4
  457   47  9    |  1   6   2  |  57    3   8
 ----------------+-------------+---------------
  43    9   423  |  8   1   6  |  23    7   5
  168   5   168  |  2   3   7  |  168   4   9
  368   78  2378 |  9   5   4  |  2368  1   23
 ----------------+-------------+---------------
  7     2   6    |  4   8   9  |  13    5   13
  9     18  138  |  5   7   13 |  4     2   6
  1345  14  1345 |  6   2   13 |  9     8   7

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Postby tarek » Sat Jan 21, 2006 11:32 am

There are a few eliminations here,

Box 1 has a naked 2 so you could eliminate the other 2s from the same box (the same goes for 1 in box 6)

You have also a Box line interaction between Column 2 & box 7

However the juicy stuff is SOMETHING HIDDEN in Columns 7 & Column 1

This puzzle is on par with the SUPERIOR sudokus in the Times

Tarek
Last edited by tarek on Sat Jan 21, 2006 7:51 am, edited 3 times in total.
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Postby Carcul » Sat Jan 21, 2006 11:35 am

Hi Simple mind.

Welcome to this forum.
You have a naked pair in box 6 (cells r4c7/r6c9) which eliminates the other "2s" and "3s" from that box. You can also eliminate some "1s" from box 7 due to locked candidates in column 2.

Regards, Carcul
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Postby tarek » Sat Jan 21, 2006 11:50 am

[Deleted - Duplicate post]
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Re: Next move

Postby QBasicMac » Sat Jan 21, 2006 11:51 am

Simple mind wrote:I can't seem to see an easy next move...


You have a hard puzzle for a beginner.

Next move is to notice that all 1's in column 2 fall in box 7. That means the 1 in box 7 must be in r8c2 or r9c2. Remove pencilmark 1 from the other three cells.

Then notice 23 appears twice in box 6. So you can erase the 23 from r6c7.

Then you are dead. There are no more easy moves.

If you just want the fun of seeing the solution, you could just make a copy of your work and guess.

Mac
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Postby Simple mind » Sat Jan 21, 2006 12:02 pm

thanks all for the hints so far...i've now erased my pencil marks down to the following....

Code: Select all

  18    6   178  |  3   4   5  |  127   9   12
  2     3   15   |  7   9   8  |  15    6   4
  45    47  9    |  1   6   2  |  57    3   8
 ----------------+-------------+---------------
  43    9   423  |  8   1   6  |  23    7   5
  168   5   168  |  2   3   7  |  68    4   9
  368   78  2378 |  9   5   4  |  68    1   23
 ----------------+-------------+---------------
  7     2   6    |  4   8   9  |  13    5   13
  9     18  38   |  5   7   13 |  4     2   6
  345   14  345  |  6   2   13 |  9     8   7



Tarek, could I have some more hints on the something hidden in columns 7 and 1 please?
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Postby tarek » Sat Jan 21, 2006 12:13 pm

Simple mind wrote:
Code: Select all

  18    6   178  |  3   4   5  |  127   9   12
  2     3   15   |  7   9   8  |  15    6   4
  45    47  9    |  1   6   2  |  57    3   8
 ----------------+-------------+---------------
  43    9   423  |  8   1   6  |  23    7   5
  168   5   168  |  2   3   7  |  68    4   9
  368   78  2378 |  9   5   4  |  68    1   23
 ----------------+-------------+---------------
  7     2   6    |  4   8   9  |  13    5   13
  9     18  38   |  5   7   13 |  4     2   6
  345   14  345  |  6   2   13 |  9     8   7


Tarek, could I have some more hints on the something hidden in columns 7 and 1 please?


well for column 6 the condition will not eliminate anything now, the candidates 68 were a hidden double in column 6 (& therefore you could eliminate 23 from r6c7), choosing 23 as naked doubles from the same box will lead to the same thing.

as for column 1.........
the candidates 1,6,8 share between them 3 cells only, which means that each cell will have 1 of these candidates as an occupant eventually.

so there is no way for the candidate 3 to remain as a valid possibility in r6c1, therfore we can eliminate it safely-This is a Hidden triple
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Postby Simple mind » Sat Jan 21, 2006 1:00 pm

Thanks Tarek! finally managed to solve it now, after removing the 3 from the hidden triplet in column 1 by taking (1,6,8) as candidates, I then chose 6,8 as naked pair in row 6 to get 7 for r6c2. Just had to do some more eliminations and 1 more hidden triplet to solve the grid. Thanks!

Just out of curiousity, is there another way of solving this grid without using pencilmarks to find hidden and naked subsets? I find that when using pencilmarks it can clutter up the grid and slow you down. Is there a way to visually see the hidden and naked subsets?
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Postby tarek » Sat Jan 21, 2006 3:55 pm

I can't do that without writing some candidates down next to the grid.
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Postby QBasicMac » Sat Jan 21, 2006 4:09 pm

tarek wrote:I can't do that without writing some candidates down next to the grid.


I can't even do it when I do write candidates!:(

That triple was invisible to me.

Mac
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Next move

Postby Cec » Sun Jan 22, 2006 6:31 am

Simple mind wrote:"..Just out of curiousity, is there another way of solving this grid without using pencilmarks to find hidden and naked subsets? I find that when using pencilmarks it can clutter up the grid and slow you down. Is there a way to visually see the hidden and naked subsets?

I might be wrong but I suspect you are using a pencil to solve the puzzle directly from a newspaper or something similar and are finding it both time consuming and difficult to write all the pencilmarks (candidates) within the usually small vacant cells.

If this is the case then there are various program solvers mentioned throughout this forum and which automatically show these candidates and other features, including hints when you get stuck. This removes the "boring" part leaving you more time for the "more
interesting" part of solving the puzzle.

It's a personal choice but I like the Simple Sudoku solver which you can learn more about by clicking HERE and it's free.

Cec
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