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The minimum easiest puzzles

 
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JPF

Joined: 05 Dec 2005
Posts: 29
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Location: Paris

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PostPosted: Sat Feb 18, 2006 12:45 am    Post subject: The minimum easiest puzzles Reply with quote

I'm interested in the easy puzzles.
Obviously, easiest are the full grids ! (81 clues, 0 holes).

Now, let's agree that the easiest puzzles are those which can been solved by only using the F constraint (Forced cell : only one value possible).

Let's call such puzzles : F-puzzles

Question : what is the minimum F-puzzle (with the minimum number of clues)

My own record is 22 :
Code:

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


My Generator is rather slow and I'm sure that one can do much better.


BTW, I didn't find any F-puzzle in the Gordon's 17-clues list.
http://www.csse.uwa.edu.au/~gordon/sudokumin.php

JPF
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Ruud
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Joined: 17 Sep 2005
Posts: 708
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Location: Netherlands

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PostPosted: Sat Feb 18, 2006 3:46 am    Post subject: Reply with quote

JPF wrote:
Now, let's agree that the easiest puzzles are those which can been solved by only using the F constraint (Forced cell : only one value possible).

Many would not agree with you on this premise. I certainly don't. The N-constraint is easier to solve than the F-constraint, which requires pencilmarks.

JPF wrote:
BTW, I didn't find any F-puzzle in the Gordon's 17-clues list.

Maybe not, but there are several that only require N-constraints.

Ruud.
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Finlip

Joined: 03 Aug 2006
Posts: 2
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Location: Kathmandu, Nepal

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PostPosted: Fri Aug 04, 2006 1:33 pm    Post subject: Reply with quote

If you have a computer program with automatically generated pencil marks, forced cells are easiest. Yes it is more difficult for the naked eye to spot than are a few others.
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anttiahola

Joined: 29 Jul 2006
Posts: 14
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PostPosted: Fri Aug 25, 2006 7:22 pm    Post subject: Reply with quote

Hmm, they seem to be quite rare. My generator had to make 100 000 random boards in order to output these two:

Code:

-----------------
initialValues: 21
6.8|..7|.5.
...|9..|.6.
..5|..4|...
---+---+---
4..|...|...
.9.|...|...
...|.7.|..3
---+---+---
.1.|...|.39
...|.8.|..1
...|.56|7.2

-----------------
initialValues: 21
6..|9.3|...
..9|8..|...
.7.|...|45.
---+---+---
12.|.6.|...
.5.|...|.7.
..6|3..|...
---+---+---
...|69.|...
..8|...|.4.
2..|.1.|...
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