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Feb 17 Medium??? Puzzle

 
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PeteGrant



Joined: 17 Feb 2006
Posts: 10
Location: Saranac Lake, New York

PostPosted: Fri Feb 17, 2006 2:57 am    Post subject: Feb 17 Medium??? Puzzle Reply with quote

I solve about 50% of hard puzzles and usually do medium ones in 20 minutes or less, but this one has me stumped. So far, I have

Code:

2 3 1    _ _ _    9 7 6
4 _ _    3 _ 7    _ _ _
8 7 _    2 _ _    4 _ _

3 5 _    7 _ _    _ _ _
7 8 2    _ 3 _    5 9 _
1 _ _    _ _ 2    _ 3 7

9 _ 7    _ _ 4    3 _ _
5 _ 3    8 _ 9    7 _ _
6 _ 8    _ 7 3    2 _ 9


The Draw gives a hint to place a 9 in r6c2 but I can't see the logic behind that move. Can anyone clue me in on what I'm missing?

TIA

Pete
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Last edited by PeteGrant on Thu Feb 03, 2011 10:05 am; edited 1 time in total
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geoff h



Joined: 07 Aug 2005
Posts: 58
Location: Sydney

PostPosted: Fri Feb 17, 2006 10:17 am    Post subject: Reply with quote

Hi Pete,

Your problem may be that you have not copied the puzzle correctly. Today's puzzle has a 3 in r3c9 which you do not have.

Hope this helps.

Cheers,
Geoff.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Fri Feb 17, 2006 3:50 pm    Post subject: Feb 17 Medium Puzzle Reply with quote

Pete

Geoff is right about the 3 but I am following up his note because I am not sure if this will help you very much. I think the logic behind the 9s is:

The 9 in box 2 (the upper middle box) is not in the first row so it must occupy column 5. As a result the 9 in the central box has to be placed in column 4 and the only position available in that column is r6c4.

Steve
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PostPosted: Fri Feb 17, 2006 8:39 pm    Post subject: Reply with quote

The 9 in 3:3 leaves the 9 in 6:2 your only choice.
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Fri Feb 17, 2006 9:03 pm    Post subject: Did you copy it to "Draw" correctly? Reply with quote

PeteGrant wrote:
The Draw gives a hint to place a 9 in r6c2 but I can't see the logic behind that move. Can anyone clue me in on what I'm missing?

Hi, Pete!

Are you sure you keyed it in to the Draw program correctly? The reason I'm asking is that a "9" at r6c2 is clearly impossible, from the position you entered.
Code:
2 3 1    _ _ _    9 7 6
4 _ _    3 _ 7    _ _ _
8 7 _    2 _ _    4 _ 3

3 5 _    7 _ _    _ _ _
7 8 2    _ 3 _    5 9 _
1 _ _    _ _ 2    _ 3 7

9 _ 7    _ _ 4    3 _ _
5 _ 3    8 _ 9    7 _ _
6 _ 8    _ 7 3    2 _ 9

Looking at column 4 it's clear there must be a "9" at r6c4. There's already a "9" in the bottom center 3x3 box, and there are "9"s in rows 1 & 5, so r6c4 is the only place a "9" can fit in that column. And once that "9" is entered at r6c4 the only way to fit a "9" in column 2 is at r2c2.

I think you didn't enter the puzzle into Draw correctly, or it wouldn't have given that hint. dcb
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alanr555



Joined: 01 Aug 2005
Posts: 193
Location: Bideford Devon EX39

PostPosted: Tue Feb 21, 2006 2:34 am    Post subject: Reply with quote

Code:

As a Medium puzzle, this one was solvable without any pencil
marks in the grid. However, I did find that marking "Missing"
profiles outside the grid for most of the rows and columns did
assist with the solution.

Sometimes the solution depends upon "Sole Position" or just
"Sole Candidate" and having the "Missing" profiles for each
row or column assists by not having to work out what is missing
each time that one considers a row or column.

This is useful for the technique of comparing the string of "Missing"
digits for a row with the contents of the intersecting column for
any blank cell in the row - and vice versa of course, If this reduces
the possibilities to two or three then a quick scan of the related
region will determine if a further reduction to just one value is possible.

I have no note of any reduction to congruent subsets for any row or
column and so just general logic seems to have been adequate.

Alan Rayner  BS23 2QT

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