New to Sudoku

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New to Sudoku

Postby bandahanson » Mon Jan 21, 2013 7:19 pm

New to Sudoku. Paper prints progressively harder one till 8 stars at end of week. I want to know if the one I am working on can be done without guessing and if so can someone give me a hint on solution

9 4 3 (8,7) (1,8,7) 6 (1,8) 2 5
1 8 5 3 2 4 9 7 6
7 2 6 (5,8) (1,5,8,9) (1,8,9 ) (1,4,8) (1,4) 3
(2,4,8) 5 (1,2,7,8,9) (1,2,4,6,7,8) (1,6,7,8,9) (1,2,8,9) 3 (1,4) (2,7,9)
3 6 (1,2,7,8,9) (2,4,7,8) (1,7,8,9) (1,2,8,9) (1,4) 5 (2,7,9)
(2,4) (1,9) (1,2,7,9) (2,4,5,7) (1,5,7) 3 6 8 (2,7,9)
5 (1,9) (1,9) (2,6,8) (6,8) (2,8) 7 3 4
6 7 4 1 3 5 2 9 8
(2,8) 3 (2,8) 9 4 7 5 6 1


in case I have totally confused everyone the original puzzle was
9 x x x x 6 x 2 x
x x 5 x 2 4 x x 6
7 x 6 x x x x x x
x 5 x x x x 3 x x
3 6 x x x x x 5 2
x x 2 x x x x 8 x
x x x x x x 7 x 4
6 x x 8 3 x 2 x x
x 3 x 9 x x x x 1
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Re: New to Sudoku

Postby JasonLion » Mon Jan 21, 2013 9:10 pm

Yes, it can certainly be done without guessing, assuming your original puzzle version is correct. I would do it with singles plus a locked candidate and a naked pair.

You appear to have already made some mistakes in the partially completed version, as R1C9 is not 5 in the solution, and there are several more similar issues in row 8.

In R5C9 you show 2 as a clue, yet you have pencil marks in the partially complete version. This got me to wondering if you wrote down the original puzzle correctly. If not, most of what I said above could be false.
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Re: New to Sudoku

Postby ArkieTech » Mon Jan 21, 2013 9:18 pm

I had trouble with your grids.
I assume you are at this position.
Code: Select all
 *-----------------------------------------------------------*
 | 9     4     3     | 157   157   6     | 15    2     8     |
 | 1     8     5     | 3     2     4     | 9     7     6     |
 | 7     2     6     | 15    1589  1589  | 145   14    3     |
 |-------------------+-------------------+-------------------|
 | 8     5     19    | 1246  169   129   | 3     14    7     |
 | 3     6     19    | 147   1789  189   | 14    5     2     |
 | 4     7     2     | 15    15    3     | 6     8     9     |
 |-------------------+-------------------+-------------------|
 | 25    9     8     | 1256  156   125   | 7     3     4     |
 | 6     1     4     | 8     3     7     | 2     9     5     |
 | 25    3     7     | 9     4     25    | 8     6     1     |
 *-----------------------------------------------------------*

There are two cells in row 6 that need either a 1 or a 5. This is called a pair. Since the pair is entirely in block 5 all the other 1's in that block can be removed as the 1 must be in row 6.
Now look in column 4. Do you see another pair? With this pair you can remove the other 1's in column 4.

Your grid should now look like this

Code: Select all
 
 *-----------------------------------------------------------*
 | 9     4     3     | 7     157   6     | 15    2     8     |
 | 1     8     5     | 3     2     4     | 9     7     6     |
 | 7     2     6     | 15    1589  1589  | 145   14    3     |
 |-------------------+-------------------+-------------------|
 | 8     5     19    | 246   69    29    | 3     14    7     |
 | 3     6     19    | 47    789   89    | 14    5     2     |
 | 4     7     2     | 15    15    3     | 6     8     9     |
 |-------------------+-------------------+-------------------|
 | 25    9     8     | 26    156   125   | 7     3     4     |
 | 6     1     4     | 8     3     7     | 2     9     5     |
 | 25    3     7     | 9     4     25    | 8     6     1     |
 *-----------------------------------------------------------*


This should leave singles to the end of the puzzle.

Guessing is not allowed. :D
dan
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Postby Pat » Thu Jan 24, 2013 9:08 am

bandahanson wrote:
the original puzzle was

Code: Select all

 9 . . | . . 6 | . 2 .
 . . 5 | . 2 4 | . . 6
 7 . 6 | . . . | . . .
-------+-------+------
 . 5 . | . . . | 3 . .
 3 6 . | . . . | . 5 2
 . . 2 | . . . | . 8 .
-------+-------+------
 . . . | . . . | 7 . 4
 6 . . | 8 3 . | 2 . .
 . 3 . | 9 . . | . . 1


"singles" gets us to 55 —

Code: Select all

 9 4 3 | . . 6 | . 2 8
 1 8 5 | 3 2 4 | 9 7 6
 7 2 6 | . . . | . . 3
-------+-------+------
 8 5 . | _ . . | 3 . 7
 3 6 . | . . . | . 5 2
 4 7 2 | . . 3 | 6 8 9
-------+-------+------
 . 9 8 | _ . . | 7 3 4
 6 1 4 | 8 3 7 | 2 9 5
 . 3 7 | 9 4 . | 8 6 1



in column 4,
the {2,6} have only 2 cells available
( "hidden" duo ) — marked "_"

this solves the 4 for row 4

no need to list the possibilities in each cell
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