The New Sudoku Players' Forum

by **999_Springs** » Thu Mar 22, 2007 8:14 pm

Is this puzzle minimal? If not, then which givens can be removed?

Code: Select all: .5.|76.|..9 ...|2.5|.1. 6..|...|... ---+---+--- 1..|9..|... 9..|.4.|.36 8..|...|7.1 ---+---+--- ...|..9|... .7.|...|.5. .4.|...|3..

by **ronk** » Thu Mar 22, 2007 8:40 pm

Your puzzle is minimal. (Checked using gsf's sudoku.exe)

by **wapati** » Thu Mar 22, 2007 8:53 pm

Ugly and easy. It is minimal!

by **m_b_metcalf** » Thu Mar 22, 2007 10:33 pm

wapati wrote:Ugly and easy. It is minimal!

But it's possible to shake it a bit and lose a couple of cells:

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

Regards,

Mike Metcalf

by **JPF** » Thu Mar 22, 2007 10:55 pm

999_Springs wrote:Is this puzzle minimal? If not, then which givens can be removed?
Code: Select all
.5.|76.|..9 ...|2.5|.1. 6..|...|... ---+---+--- 1..|9..|... 9..|.4.|.36 8..|...|7.1 ---+---+--- ...|..9|... .7.|...|.5. .4.|...|3..

wapati wrote:Ugly and easy. It is minimal!

change the 2 cells in box 5 :

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

SE = 8.3

JPF

by **999_Springs** » Mon Mar 26, 2007 12:34 pm

JPF wrote:

change the 2 cells in box 5 :
Code:

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

SE = 8.3

Is that puzzle minimal? I know that it is evil enough as it is, but...
Why won't "quote" pick up "code"?

by **udosuk** » Mon Mar 26, 2007 1:40 pm

999_Springs wrote:Why won't "quote" pick up "code"?

Looks like you haven't learned the proper way to use the BBCode... When you post, look at the left side of your window. That link was right under Options... :idea:

This is what you typed:

999_Springs wrote:JPF wrote:
[quote]
change the 2 cells in box 5 :
Code:

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

SE = 8.3
[/quote]

The correct way to do it is as the following:

BBCode master wrote:[quote="JPF"]
change the 2 cells in box 5 :
[code]

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

SE = 8.3
[/code][/quote]

Which will result in this effect:

JPF wrote:change the 2 cells in box 5 :
Code: Select all
. 5 . | 7 6 . | . . 9 . . . | 2 . 5 | . 1 . 6 . . | . . . | . . . -------+-------+------- 1 . . | 3 . . | . . . 9 . . | . 8 . | . 3 6 8 . . | . . . | 7 . 1 -------+-------+------- . . . | . . 9 | . . . . 7 . | . . . | . 5 . . 4 . | . . . | 3 . . SE = 8.3

by **JPF** » Mon Mar 26, 2007 2:58 pm

Thanks udosuk !

Yes, this puzzle is minimal.
It means that removing any cell C gives a puzzle with more than 1 solution.

How minimal this puzzle is ?
We can have an idea by counting the number of solutions ni when removing the cell Ci.
With the Sudoku Explainer notations we get the following results :

Code: Select all: Cell Sol. H5 12 G6 15 D2 53 D4 53 F2 54 I6 100 E1 162 E5 201 A6 217 I5 226 I1 236 A3 240 D1 250 H8 264 B1 299 H2 >400 A4 >400 A5 >400 F7 >400 B8 >400 B9 >400 G9 >400

There are 2 weak cells H5, G6 which can be removed in order to get an almost valid puzzle.

For example, if we remove H5, we get a new valid puzzle with B1=3 and D4=5 ; only 21 cells :

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

SE=7.1 ; minimal

JPF

by **gsf** » Tue Mar 27, 2007 3:00 am

here's the same info listed by grid position

Code: Select all: 12 5306 0 299 0 | 250 162 0 | 0 0 236 0 0 0 | 53 0 54 | 0 623 0 240 0 0 | 0 0 0 | 0 0 0 ---------------+---------------+--------------- 1603 0 0 | 53 0 0 | 0 0 0 1433 0 0 | 0 201 0 | 0 12 226 217 0 0 | 0 0 0 | 15 0 100 ---------------+---------------+--------------- 0 0 0 | 0 0 1072 | 0 0 0 0 3625 0 | 0 0 0 | 0 264 0 0 5306 0 | 0 0 0 | 642 0 0

The New Sudoku Players' Forum

Minimal puzzle?

Minimal puzzle?