5 out of 5 star on difficulty

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5 out of 5 star on difficulty

Postby radioman » Sat Jan 07, 2006 7:27 am

x 8 6 + x x 5 + 7 4 x
x x 4 + 8 x x + x 3 x
2 3 x + x x 4 + 9 8 x
+++++++++ ++++++
7 6 3 + x x x + 8 x 4
8 4 9 + x 6 x + 1 7 x
5 2 1 + 4 x x + 3 6 9
+++++++++ ++++++
x x 2 + 9 x x + x 1 3
x 1 x + x x x + 4 9 8
x 9 8 + 1 x x + x x 7


Hopefully someone can help me get the first box figured out and why logically it has to be. The bolded numbers are clues and the other numbers are the ones i figured out. Relatively new to Sudoku's here so hopefully this post doesnt confuse anyone. Thanks again.

P.S. This publication (Argus Leader - US - SD) just started to put Sudokus in as of Jan 2nd. But nowhere can I find that it is Copyrighted by Pappocom
radioman
 
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Postby Shazbot » Sat Jan 07, 2006 7:40 am

without knowing what eliminations you've already made, I'll start from the full set of candidates from the above grid:
Code: Select all
 *--------------------------------------------------------*
 | 19   8    6    | 23     1239   5      | 7    4    12   |
 | 19   57   4    | 8      1279   12679  | 256  3    1256 |
 | 2    3    57   | 67     17     4      | 9    8    156  |
 |----------------+----------------------+----------------|
 | 7    6    3    | 25     1259   129    | 8    25   4    |
 | 8    4    9    | 235    6      23     | 1    7    25   |
 | 5    2    1    | 4      78     78     | 3    6    9    |
 |----------------+----------------------+----------------|
 | 46   57   2    | 9      4578   678    | 56   1    3    |
 | 36   1    57   | 23567  2357   2367   | 4    9    8    |
 | 346  9    8    | 1      2345   236    | 256  25   7    |
 *--------------------------------------------------------*

  • locked candidates (2s) in box 9 (only one row where 2s can go in that box, so 2s in that row in other boxes can be removed)
  • naked pair (2/5) in row 4 (two cells can only contain the same two numbers - 2 and 5, so one must contain 2, and the other must contain 5 - these numbers can be removed from all other cells in that row)
  • naked triple (2/3/5) in column 4 (three cells can only contain the same three numbers [rows 1, 4 and 5], so one must contain 2, another 3 and the other 5 - these numbers can be removed from all other cells in that column [r8c4])
  • locked candidates (6s) in column 9 (can only go in box 3, so other cells in box 3 not in that column can have 6s removed)
  • hidden pairs (1/9) in column 6 (only 2 cells that can contain either 1 or 9, so one must have 1 and the other must have 9 - all other candidates in those two cells can be removed)
  • naked pair (1/9) again in row 2
  • hidden single (6) in row 2 (only one place for the 6 to go) which leads to another hidden single (6) in row 3
This gives your next placement - a 7 in r8c4, which will lead to placement of a 7 in box 7 and then in box 1. Then just follow the naked singles (only one number that can go in a cell) and you'll finish off that first box and the rest of the puzzle.
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Postby radioman » Sat Jan 07, 2006 8:49 am

I must have made a mistake somewhere on my calculations:( , becuase I still cannot find a solution, maybe you should just solve this puzzle Shazbot by using the bolded numbers only, i know that they are right.
radioman
 
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Postby Shazbot » Sat Jan 07, 2006 9:39 am

I used all your numbers in the grid and was able to solve the puzzle. Can you show what stage you're up to, with the placed numbers AND your candidates? (See the layout above) - then someone can point you in the right direction.
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Postby radioman » Sat Jan 07, 2006 10:24 am

I started over, got to the point where i was at before, and only had to use your "hidden pairs (1/9) in column 6 (only 2 cells that can contain either 1 or 9, so one must have 1 and the other must have 9 - all other candidates in those two cells can be removed)" to finish the puzzle. I had worked on this puzzle for about 6 hours total in the day before I came on here and asked so my brain has been pretty shot. Thanks for your help. I can sleep in peace tonight:D
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Postby tarek » Sat Jan 07, 2006 2:30 pm

My solver spots the doubles after box-line eliminations, This is an obvious case where you can spot doubles first (if you want to).

This is how it goes:
After obvious single eliminations, you have to do a couple of box-line eliminations, then a hidden double then again a box-line elimination then another hidden double. It should be straight forward from then....

Code: Select all
*-----------------------------------------------------------------*
| 19     8      6     | 23     1239   5     | 7      4      12    |
| 19     57     4     | 8      1279   12679 | 256    3      1256  |
| 2      3      57    | 67     17     4     | 9      8      156   |
|---------------------+---------------------+---------------------|
| 7      6      3     | 25     1259   129   | 8      25     4     |
| 8      4      9     | 235    6      23    | 1      7      25    |
| 5      2      1     | 4      78     78    | 3      6      9     |
|---------------------+---------------------+---------------------|
| 46     57     2     | 9      4578   678   | 56     1      3     |
| 36     1      57    | 23567  2357   2367  | 4      9      8     |
| 346    9      8     | 1      2345   236   | 256    25     7     |
*-----------------------------------------------------------------*
Eliminating 6 From r2c7 (Box-line interaction)
*-----------------------------------------------------------------*
| 19     8      6     | 23     1239   5     | 7      4      12    |
| 19     57     4     | 8      1279   12679 | 25     3      1256  |
| 2      3      57    | 67     17     4     | 9      8      156   |
|---------------------+---------------------+---------------------|
| 7      6      3     | 25     1259   129   | 8      25     4     |
| 8      4      9     | 235    6      23    | 1      7      25    |
| 5      2      1     | 4      78     78    | 3      6      9     |
|---------------------+---------------------+---------------------|
| 46     57     2     | 9      4578   678   | 56     1      3     |
| 36     1      57    | 23567  2357   2367  | 4      9      8     |
| 346    9      8     | 1      2345   236   | 256    25     7     |
*-----------------------------------------------------------------*
Eliminating 2 From r9c5 (Box-line interaction)
Eliminating 2 From r9c6 (Box-line interaction)
*-----------------------------------------------------------------*
| 19     8      6     | 23     1239   5     | 7      4      12    |
| 19     57     4     | 8      1279   12679 | 25     3      1256  |
| 2      3      57    | 67     17     4     | 9      8      156   |
|---------------------+---------------------+---------------------|
| 7      6      3     | 25     1259   129   | 8      25     4     |
| 8      4      9     | 235    6      23    | 1      7      25    |
| 5      2      1     | 4      78     78    | 3      6      9     |
|---------------------+---------------------+---------------------|
| 46     57     2     | 9      4578   678   | 56     1      3     |
| 36     1      57    | 23567  2357   2367  | 4      9      8     |
| 346    9      8     | 1      345    36    | 256    25     7     |
*-----------------------------------------------------------------*
r8c4 Must only have 67 as valid Candidates (Hidden Double)
*-----------------------------------------------------------------*
| 19     8      6     | 23     1239   5     | 7      4      12    |
| 19     57     4     | 8      1279   12679 | 25     3      1256  |
| 2      3      57    | 67     17     4     | 9      8      156   |
|---------------------+---------------------+---------------------|
| 7      6      3     | 25     1259   129   | 8      25     4     |
| 8      4      9     | 235    6      23    | 1      7      25    |
| 5      2      1     | 4      78     78    | 3      6      9     |
|---------------------+---------------------+---------------------|
| 46     57     2     | 9      4578   678   | 56     1      3     |
| 36     1      57    | 67     2357   2367  | 4      9      8     |
| 346    9      8     | 1      345    36    | 256    25     7     |
*-----------------------------------------------------------------*
Eliminating 5 From r4c5 (Box-line interaction)
*-----------------------------------------------------------------*
| 19     8      6     | 23     1239   5     | 7      4      12    |
| 19     57     4     | 8      1279   12679 | 25     3      1256  |
| 2      3      57    | 67     17     4     | 9      8      156   |
|---------------------+---------------------+---------------------|
| 7      6      3     | 25     129    129   | 8      25     4     |
| 8      4      9     | 235    6      23    | 1      7      25    |
| 5      2      1     | 4      78     78    | 3      6      9     |
|---------------------+---------------------+---------------------|
| 46     57     2     | 9      4578   678   | 56     1      3     |
| 36     1      57    | 67     2357   2367  | 4      9      8     |
| 346    9      8     | 1      345    36    | 256    25     7     |
*-----------------------------------------------------------------*
r2c6 Must only have 19 as valid Candidates (Hidden Double)
r4c6 Must only have 19 as valid Candidates (Hidden Double)
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