How to make a concrete value sudoku with 7 numbers?

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How to make a concrete value sudoku with 7 numbers?

Postby Balu_AU » Mon Feb 01, 2016 10:33 pm

Hi my friends, i am a rokkie in this brain game - for my friends I wanna make a sudoku with special results. I wanna make classic, hard puzzled sudoku with 81 fields, and in concrete fields must me this numbers - C2=1, D3=6, E4=3, F3=1, F5=2, G2=9 and last H1=4. Do you have any program or solution, which can with this concrete numbers in fields set others 74 fields for playable sudoku, in ideal make two different versions of this? Thank you very much for link, name of program or some help - in builders is sayd "its not enough to made a sudoku or this sudoku have a more than one solutions. Thank you in advance for help :)
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Re: How to make a concrete value sudoku with 7 numbers?

Postby Leren » Tue Feb 02, 2016 12:27 am

I'm not an expert in this field but I think that the minimum number of clues for a Sudoku to have a unique solution is 16 or 17. With only 7 clues your puzzle would have a huge number of solutions.

Here is a link to a Sudoku solver site where you can enter clues manually and get a solution count. I tried your 7 clue puzzle, but the site would not allow me to enter less than 17 clues.

http://www.sudokuwiki.org/sudoku.htm

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Re: How to make a concrete value sudoku with 7 numbers?

Postby champagne » Tue Feb 02, 2016 3:03 am

.......4.
..1...9.8
.9.6.1.7.
..9.3.8..
...9.2...
..7.8.6..
.8.7.5.9.
6.2...1..
.3.......

one example using a pattern with both diagonals symmetry

I'll look to see if I have a solution with symmetry of given

EDIT to produce that one,
I first extended the request to the shown pattern
Then, I run the scan of the pattern with some given clues

with just that pattern, you surely have millions of solutions
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Re: How to make a concrete value sudoku with 7 numbers?

Postby coloin » Thu Mar 10, 2016 8:43 pm

here is a valid one ...
Code: Select all
+---+---+---+
|...|..7|.4.|
|..1|...|9..|
|.2.|6.1|...|
+---+---+---+
|..7|.3.|8..|
|...|4.2|...|
|4.5|.1.|..2|
+---+---+---+
|.7.|3..|5..|
|8..|...|.69|
|...|..5|.2.|
+---+---+---+

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Re: How to make a concrete value sudoku with 7 numbers?

Postby m_b_metcalf » Fri Mar 11, 2016 8:50 am

Here are a few more, with rotational symmetry and 'newspaper hard' (but not otherwise minimal). It's possible to generate them by the thousands, but I think that suffices.

Code: Select all
 . 3 . . . . . 4 .
 . . 1 2 5 . 9 . .
 . . . 6 . 1 . . .
 . 2 . . 3 6 5 . .
 . 7 8 5 . 2 4 1 .
 . . 3 4 1 . . 8 .
 . . . 9 . 5 . . .
 . . 7 . 6 4 8 . .
 . 1 . . . . . 5 .   ED=4.2/1.2/1.2


Code: Select all
23..8..4...1...9.....6.1...1...3...7.739.256.9...6...2...5.4.....8...7...9..2..51 
.3.7.914..61...9.8...6.1.......3.....789.251.....1.......3.5...5.3...82..921.8.5.
.3.....4...12..97....6.1...1...3....9.84.26.3....7...2...3.4....97..54...5.....2. 
.3.....4.461...9.8...6.1....2..37.....71.26.....56..1....9.8...9.4...827.7.....9. 
.3.7...4...1...9.....641...12..34.8..948.261..7.16..92...316.....3...8...1...8.2. 
23.78..4...12..97....6.1.......3..6.9.38.27.1.5..9.......3.8....14..63...7..14.82 
.3.....4...1...97.7..6.1.......36..95..8.2..48..19.......5.8..1.12...5...5.....9.


And these are minimal, non-symmetric, 'newspaper hard':
Code: Select all
.3...9.4...1...97...96.1......53....5..4.2..1..3.....2.5..2..8..4.9.5.....7......
.3.....46..1.5.9.....6.12....4.3..8.8..4.2..........2..1...68..3....8.6..9.1..... 
.3.7...4.4.1.5.9.....6.12.512..38...5..1.2...................8...2...6...439..7..
.3...9.46..1...9..7..6.1..5....3....59.8.2...84.....2....5............87....1..9.


Regards,

Mike Metcalf

Edit: Method.

1. Use the 7 clues as a 'puzzle' that is 'solved'. Retain 1 solution in 10,000 of the first 700,00 solutions.

2. Use each full grid to generate one puzzle using a top-down elimination from which the 7 clues are excluded.

3. Select the nicest.
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