Stuck - first post for me on this forum

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Stuck - first post for me on this forum

Postby kcbear » Mon Feb 04, 2008 2:07 am

Can someone tell me how to get past this point?
i have got to this point and my friend has also independantly got to this point too so i think the numbers are correct

thanks in advance

Code:

*-----------*
|.2.|3.1|.7.|
|1.7|28.|5..|
|8..|...|.12|
|---+---+---|
|..1|975|3..|
|.7.|..8|.51|
|5.8|1.2|7..|
|---+---+---|
|41.|593|..7|
|.89|.2.|1.5|
|75.|816|.9.|
*-----------*
kcbear
 
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Re: Stuck - first post for me on this forum

Postby Cec » Mon Feb 04, 2008 10:39 am

Hi kcbear and welcome to the forum,

Firstly, your puzzle will look better and will show the following "pencilmarks" grid if you paste the puzzle between the two code buttons as described here . Also, knowing the forum's recommended Terminology should make it easier for you to understand explanations.

Code: Select all
 *-----------*
 |.2.|3.1|.7.|
 |1.7|28.|5..|
 |8..|...|.12|
 |---+---+---|
 |..1|975|3..|
 |.7.|..8|.51|
 |5.8|1.2|7..|
 |---+---+---|
 |41.|593|..7|
 |.89|.2.|1.5|
 |75.|816|.9.|
 *-----------*

 *-----------------------------------------------------------*
 | 69    2     456   | 3     456   1     | 4689  7     4689  |
 | 1     3469  7     | 2     8     49    | 5     346   3469  |
 | 8     3469  3456  | 467   456   479   | 469   1     2     |
 |-------------------+-------------------+-------------------|
 | 26    46    1     | 9     7     5     | 3     2468  468   |
 | 2369  7     2346  | 46    346   8     | 2469  5     1     |
 | 5     3469  8     | 1     346   2     | 7     46    469   |
 |-------------------+-------------------+-------------------|
 | 4     1     26    | 5     9     3     | 268   268   7     |
 | 36    8     9     | 47    2     47    | 1     346   5     |
 | 7     5     23    | 8     1     6     | 24    9     34    |
 *-----------------------------------------------------------*


About ten different "moves" are required to solve this puzzle.

As you have asked "how to get past this point?", the first move is:

(a) The above "Pencilmark" grid shows "Naked Pairs" [4,7] in row 8 (r8). This allows the remaining candidate 4 to be excluded from cell row 8 column 8 (r8c8).

If you are still stuck then you can peep at the following additional hints:)

(b) In Box 3 (Boxes are the 3X3 grids), candidates [3,4] are "Locked" in r2 of this Box which allows these candidates to be excluded from r2c2.

(c) After the above eliminations Naked Pairs [6,9] in Box 1. Therefore exclude other 6's and/or 9's from r1c3, r3c2 and r3c3.

(d) In Box 7, candidate 2's are "Locked" in c3. Exclude candidate 2 from r5c3.

(e) "NakedTriple" [3,4,6] in r5. Exclude other [3,4,6] in this row.

(f) Hidden single [3] in r8c1 leading to numerous "Naked and Hidden Singles" such as in r8c8 and r9c3.

(g) In Box 3, candidate [6] is "Locked" in c7. Exclude [6's] from c9Box3.

(h) Hidden Single [6] in Box1 (r2c2) followed by singles falling out everywhere to solve the puzzle.

Cec
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Postby Pat » Mon Feb 04, 2008 12:36 pm

Cec wrote:
Code: Select all
 *-----------*
 |.2.|3.1|.7.|
 |1.7|28.|5..|
 |8..|...|.12|
 |---+---+---|
 |..1|975|3..|
 |.7.|..8|.51|
 |5.8|1.2|7..|
 |---+---+---|
 |41.|593|..7|
 |.89|.2.|1.5|
 |75.|816|.9.|
 *-----------*



(b) In Box 3, candidates [3,4] are "Locked" in r2 of this Box which allows these candidates to be excluded from r2c2


    no, in box 3 the 4 can be outside row 2
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Postby Pat » Mon Feb 04, 2008 12:47 pm

kcbear wrote:Can someone tell me how to get past this point?

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




hi kcbear,

in box 7, the 2 must be in column 3 --
exclude 2 elsewhere in that column
( i.e. at r5c3 )

    this creates a "hidden" duo {2,9} in row 5,
    and now you can make some progress with "singles"
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first post for me on this forum

Postby Cec » Mon Feb 04, 2008 2:17 pm

Pat wrote:
Cec wrote:(b) In Box 3, candidates [3,4] are "Locked" in r2 of this Box which allows these candidates to be excluded from r2c2


    no, in box 3 the 4 can be outside row 2


"Oops! my mistake! Well spotted Pat which of course means that only candidate 3 could be excluded from r2c2. Also, your solution was a lot simpler than my "journey" to solve this puzzle.

Cec
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Postby I Am Bruce » Mon Feb 04, 2008 8:20 pm

I just discovered this forum and tried solving the puzzle. I then saw the help provided and could not understand why the "4" was a part of the "naked pair." I'm glad to see it wasn't (and that I wasn't crazy). In any event, I worked through the puzzle and eliminated most of the singles. I'm now stuck. Any thoughts?

Code: Select all
*-----------------------------------------------------------*
 | 69    2     45    | 3     456   1     | 689   7     4689  |
 | 1     469   7     | 2     8     49    | 5     3     469   |
 | 8     3469  345   | 467   456   479   | 69    1     2     |
 |-------------------+-------------------+-------------------|
 | 26    46    1     | 9     7     5     | 3     28    68    |
 | 29    7     34    | 46    346   8     | 29    5     1     |
 | 5     369   8     | 1     36    2     | 7     4     69    |
 |-------------------+-------------------+-------------------|
 | 4     1     6     | 5     9     3     | 28    28    7     |
 | 3     8     9     | 47    2     47    | 1     6     5     |
 | 7     5     2     | 8     1     6     | 4     9     3     |
 *-----------------------------------------------------------*
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Posts: 11
Joined: 04 February 2008

Postby ArkieTech » Mon Feb 04, 2008 9:13 pm

I am Bruce said
I'm now stuck. Any thoughts?


Place a 4 in row 4.

dan
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Postby I Am Bruce » Mon Feb 04, 2008 9:32 pm

Groan. How did I miss something that easy? I was looking for something more complicated. Thanks.
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Postby kcbear » Mon Feb 04, 2008 11:02 pm

Thanks for all your help people. I have only been doing sudoku for 3 weeks and as stated this is my first forum so most of what you said is going over my head a little.

I tried going to the 'terminology' link but it 404 errored. Can someone help me find this terminology page so i can find out what a naked single, locked etc means?
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Posts: 3
Joined: 03 February 2008

first post for me on this forum

Postby Cec » Mon Feb 04, 2008 11:43 pm

kcbear wrote:"...I tried going to the 'terminology' link but it 404 errored. Can someone help me find this terminology page so i can find out what a naked single, locked etc means?"


Hi again kcbear. The following links provide explanations of terminology and basic solving techniques, including naked singles, locked candidates, etc.
http://forum.enjoysudoku.com/viewtopic.php?p=28298#p28298
http://www.angusj.com/sudoku/hints.php

My apologies for previously misleading you on using an out of date Terminology link.

Edited by Cec (10am) re outdated Terminology link


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first post for me on this forum

Postby Cec » Tue Feb 05, 2008 12:49 am

I Am Bruce wrote:"I just discovered this forum and tried solving the puzzle. I then saw the help provided and could not understand why the "4" was a part of the "naked pair." I'm glad to see it wasn't (and that I wasn't crazy)..."

Hi I am Bruce,

I'd just like to clarify that my error excluding candidate 4 in row2 occurred from my incorrect application of "Locked Candidates" in Box3 where only candidate 3 was able to be excluded from row2 outside this Box.

However, my exclusion of candidate 4 in row 8 (see item (a) above) was correct due to the Naked Pair [47] in this row. This comes about because candidates 4 and 7 can only be placed either in cells r8c4 or r8c6 which means candidate 4 can be safely excluded from cell r8c8.

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Postby kcbear » Tue Feb 05, 2008 1:10 am

Thanks Cec,

thats what i needed. there is a bit of information there so i will go away and absorb and apply and get back to it then.
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