The New Sudoku Players' Forum

[m_b_metcalf]

i bought the Independent today. It's not my usual paper. This was their quick sudoku on page 2:

Code: Select all

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


edit: to make matters worse it's a prize sudoku!

Then I claim the prize:

Code: Select all

Common clues (37):
 . . . 3 9 5 6 8 7
 . 3 . . . 7 . 1 2
 . 6 . . 2 . . . 4
 . 8 3 . 7 2 . 6 .
 4 . 9 5 . . . 7 .
 . 7 6 . . . . . .
 6 9 1 2 5 3 7 4 8
 3 5 . . 8 . . . .
 . . . . 1 . . . .

Regards,

Mike Metcalf

[udosuk]

i bought the Independent today. It's not my usual paper. This was their quick sudoku on page 2:

Code: Select all

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


edit: to make matters worse it's a prize sudoku!

Ah, the editor of that paper is my friend. She told me that there is a secret constraint in that puzzle which makes the solution unique. There should be 9 cells (including the centre cell) forming the shape of an "X" with no repeated digits. So be quick to work out the answer to claim your prize!

Okay, so I made that all up. But a keen sudoku player should always be looking for simple extra constraints to turn a bad puzzle into a good one!

[Luke]

Finally noticed your Editor's Teaser. Sorry, it takes me a week to do anything spontaneously....
Just so I'm on the same page as your "friend," I ask for some clarification, as opposed to a hint.

- A "constraint" in this case means adding new givens .
- an "X" is symmetrical, naturally.
- an "X" is not a "cross shape."
- the "center cell" refers to the center cell of the puzzle, as opposed to the center of the "X."
- the "X' shape itself contains the digits 1 through 9.
- You did not pay off the editor to reveal the secret.

Thank you.

[tarek]

A constraint is a RULE. The rules of sudoku can be broken into smaller constraints based on Rows, Columns & boxes

A constaraint here is a set of cells that should eventually house different symbols (digits).

Now, you need to find a 9 celled x shaped constraint

udosuk knows so much about fairy chess. That allows him to see bizarre shaped constraints easily even without the editor declaring them

My solution:
214395687938647512765128394583972461429561873176834259691253748357489126842716935
tarek

[Luke]

With the prize safely in your possession I've lost my motivation. (Not to mention the fact that I happened to see your original unedited post with the reveal in plain sight! )

[tarek]

(Not to mention the fact that I happened to see your original unedited post with the reveal in plain sight! )

That post had so many mistakes ... therefore I edited it ... The sudoku-X has 2 constraints (9x2 cells) forming 2 intersecting diagonals (X) of 17 cells.

This one however has only 9 cells in 1 constraint (I'm not sure what the variant is called)

[udosuk]

Well done tarek!

Luke451, don't lose your motivation! My friend the editor is so generous that she's offering a special bonus prize on the same puzzle.

There should be 9 cells (NOT including the centre cell) forming the shape of an "X" with no repeated digits.

This should enable you to find another unique solution.

Quick! Grab the prize before tarek does!

[StrmCkr]

Now, you need to find a 9 celled x shaped constraint

18 cells... not 9.
but.
there is an overlap in the center digit.

thus 17 diffrent ones.

[coloin]

I believe this is an example of a "9" clue "X" - but it does include the centre cell.....

Code: Select all

+---+---+---+
|...|...|...|
|...|...|...|
|..5|...|3..|
+---+---+---+
|...|9.2|...|
|...|.6.|...|
|...|8.4|...|
+---+---+---+
|..1|...|7..|
|...|...|...|
|...|...|...|
+---+---+---+

tarek's solution does include 9 different clues in these positions.....which do solve the puzzle...so he gets the initial "prize".

So, in which case the x might be in one of the other 16 [not 24] positions.

C

[udosuk]

tarek's solution does include 9 different clues in these positions.....which do solve the puzzle...so he gets the initial "prize".

So, in which case the x might be in one of the other 16 [not 24] positions.

Yes, and you're now on track to earn the "bonus prize"!

[Pat]

3 "puzzles" from Intel [ PDF, pages 20-25 ]

-- see discussion

[tarek]

Ken Ken 1258 (The Times 12.02.11): labelled as difficult, the printed puzzle is actually the solution. No much fun there and is a waste of printing space

[Pat]

sudokurush.com/challenge/

more than one answer ( discussion )

[Smythe Dakota]

How about Kakuros of Shame?

This site boasts 2 new puzzles every day. The offerings for July 26, 2011 are typical. The beginners puzzle (4x4) has two solutions. The standard puzzle (9x9) has four singularities, one near each corner, essentially dividing the puzzle into five smaller puzzles (one in each corner and one in the middle). Each of the five pieces has multiple solutions, for a total of at least 32 overall. I suspect it's more like several hundred, as I soon grew weary of looking for still more solutions.

Bill Smythe

[Smythe Dakota]

Here's another one. I suspect that a huge percentage of the puzzles on this site have multiple solutions.

For example, in Printable Puzzles, Volume 007, number 013, in the upper right corner there are two 3-digit horizontal words, one directly beneath the other, each summing to 8. What am I missing? As soon as one solution is found, another can be generated just by switching the contents of these two words.

I don't have sophisticated software for checking uniqueness, but this one sticks out like a sore thumb. But just about all the puzzles on this site have that defective (non-uniqueness) "feel", in that there never seems to be anywhere to get started.

Bill Smythe