My Devil's Puzzle Book

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My Devil's Puzzle Book

Postby mollwollfumble » Wed Apr 09, 2014 11:30 pm

Attached is a link to "The Devil's Puzzle Book" that I created containing "ambiguous and nearly impossible puzzles".
http://freepages.misc.rootsweb.ancestry.com/~hallsofjamaica/The%20devils%20puzzle%20book.pdf

This puzzle book contains four Sudokus, three of which have been deliberately designed to defeat Sudoku-solving computer programs. Have fun, and don't give up too soon. (I could give you a hint to make the solution of all three much easier, but I won't).
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Re: My Devil's Puzzle Book

Postby enxio27 » Fri Apr 11, 2014 4:11 pm

Your first and last sudoku grids are invalid puzzles. I'm not going to waste my time on the other two.
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Re: My Devil's Puzzle Book

Postby m_b_metcalf » Fri Apr 11, 2014 4:40 pm

enxio27 wrote:Your first and last sudoku grids are invalid puzzles. I'm not going to waste my time on the other two.

In particular:
Code: Select all
Puzzle 5
 . . . . . . . . .
 3 . . . 9 1 4 . 6
 . . 7 3 . 4 2 . 5
 . 9 . 4 . 5 6 . 7
 7 4 . . 8 . . 5 1
 5 . 1 9 . 7 . 3 .
 2 . 5 7 . 9 1 . .
 1 . 6 2 3 . . . 8
 . . . . . . . . .
No. of givens =  35

brute found 0 solution(s) in    0.00 seconds.

Code: Select all

Puzzle 17
 . . . . . . . . 1
 . . . . . . . 4 8
 . . 7 . . 3 . . .
 . 6 . . 8 . . . .
 . . 2 . . . 7 . .
 . . . . 7 . . 9 .
 . . . 5 . . 6 . .
 4 8 . . . . . . .
 1 . . . . . . . .
No. of givens =  16

brute found 110552 solution(s) in    1.01 seconds. Last was:
  8  2  3  4  5  6  9  7  1
  6  5  1  7  9  2  3  4  8
  9  4  7  8  1  3  2  6  5
  7  6  4  2  8  9  1  5  3
  5  9  2  3  4  1  7  8  6
  3  1  8  6  7  5  4  9  2
  2  7  9  5  3  8  6  1  4
  4  8  6  1  2  7  5  3  9
  1  3  5  9  6  4  8  2  7

Common clues (18):
  .  .  .  .  .  .  .  7  1
  .  .  .  .  .  .  .  4  8
  .  .  7  .  .  3  .  .  .
  7  6  .  .  8  .  .  .  .
  .  .  2  .  .  .  7  .  .
  .  .  .  .  7  .  .  9  .
  .  .  .  5  .  .  6  .  .
  4  8  .  .  .  .  .  .  .
  1  .  .  .  .  .  .  .  .


Puzzle 17 has too few clues to be valid, and interpreted as an X-sudoku has no solution.

Mike Metcalf
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Re: My Devil's Puzzle Book

Postby tarek » Fri Apr 11, 2014 8:12 pm

Blow your trumpet until you fall on it .....

There is a good reason why these puzzles defeated logical sudoku solvers :lol: :lol:

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Re: My Devil's Puzzle Book

Postby m_b_metcalf » Sat Apr 12, 2014 8:25 am

tarek wrote:Blow your trumpet until you fall on it .....

There is a good reason why these puzzles defeated logical sudoku solvers :lol: :lol:

Tarek

Quite! Of course, the puzzle with 17 clues can simply be checked against Gordon's data base, which I'm too lazy to do. At least the 18-clue puzzle represents a valid pattern:
Code: Select all
 1 . 2 . . . 3 . .
 . . . 4 . 5 . . .
 6 . . . . . . . .
 . 4 . . . . . 7 5
 2 . . . 3 . . . .
 . . . 8 . . . 9 .
 . 9 . 5 . . . . 7
 . . . . 2 . . 6 .
 . . . . . . . . .

and I suspect the particular value distribution he sets has been plucked from a data base.

Regards,

Mike
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Re: My Devil's Puzzle Book

Postby daj95376 » Sat Apr 12, 2014 6:30 pm

Puzzle 5: (first Sudoku)

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

r8c6 is void of candidates because it sees all nine values for clues/givens.

If you remove clues/givens r2c6=1 and r8c1=1, then you have a valid puzzle that solves with Naked Singles.
Subsequent reductions in clues/givens are still possible.

If you remove clue/given r3c6=4, then you have a valid puzzle that solves with Naked Singles.
Subsequent reductions in clues/givens are still possible.

If you remove clue/given r7c6=9, then you have a valid puzzle that solves with Naked Singles.
Subsequent reductions in clues/givens are still possible.

Note: all three solutions are different. FWIW, all three solutions have these cells in common.

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




Yuck !!!
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Re: My Devil's Puzzle Book

Postby blue » Sat Apr 12, 2014 8:57 pm

There's a "telling" answers section.
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Re: My Devil's Puzzle Book

Postby daj95376 » Sun Apr 13, 2014 3:47 am

blue wrote:There's a "telling" answers section.

His answers section contains two solutions:

(1) He appears to have moved r7c6=9 to r8c6=9 for his first solution.
(2) He appears to have moved r3c6=4 to r8c6=4 for his second solution.


I found three solutions.

Code: Select all
# daj derived puzzle 1:  remove r2c6=1 and r8c1=1 from givens  =>  r8c6=1

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

Code: Select all
# daj derived puzzle 2:  remove r3c6=4 from givens  =>  r8c6=4

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

Notice potential <49> UR [r78c68] prevented by clue/given r7c6=9

Code: Select all
# daj derived puzzle 3:  remove r7c6=9 from givens  =>  r8c6=9

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

Notice potential <46> UR [r37c56] prevented by clue/given r3c6=4
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Postby Pat » Wed Apr 16, 2014 7:23 am

daj95376 wrote:
His answers section contains two solutions:

(1) He appears to have moved r7c6=9 to r8c6=9 for his first solution.
(2) He appears to have moved r3c6=4 to r8c6=4 for his second solution.


some ingenious players have developed this method of
"solving" by moving the givens.

    the rule against moving (or changing) the given cells
    is often un-stated.
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