The New Sudoku Players' Forum

[Paul]

this puzzle has given me grief. I can get so far, but to solve the puzzle i had to guess one square. I will write the original puzzle and then the point where i get stuck.. can anyone find the next move using logic not guessing.

Original puzzle. Row one 2-5------/two----7---2/three8----64--/four96-72---1/five--18-96--/six3---61-74/seven--24----7/eight5---1----/nine------2-8

this is where i get stuck. it is correct because one guess and the puzzle is easy to solve. Row one 2-5-847--/two --6-758-2/three 87-2-6415/ four 964723581 / five 751849623 / six 328561974 / seven 6-24-81-7/ eight 587-1234-/nine -----72-8

thanks for anyone who can help

[Animator]

It would be lots easier if you pasted the differents rows at different lines...

His grid:

Code: Select all

2 * 5 | * 8 4 | 7 * *
* * 6 | * 7 5 | 8 * 2
8 7 * | 2 * 6 | 4 1 5
-----------------------
9 6 4 | 7 2 3 | 5 8 1
7 5 1 | 8 4 9 | 6 2 3
3 2 8 | 5 6 1 | 9 7 4
-----------------------
6 * 2 | 4 * 8 | 1 * 7
5 8 7 | * 1 2 | 3 4 *
* * * | * * 7 | 2 * 8


Starting grid:

Code: Select all

2 * 5 | * * * | * * *
* * * | * 7 * | * * 2
8 * * | * * 6 | 4 * *
-----------------------
9 6 * | 7 2 * | * * 1
* * 1 | 8 * 9 | 6 * *
3 * * | * 6 1 | * 7 4
-----------------------
* * 2 | 4 * * | * * 7
5 * * | * 1 * | * * *
* * * | * * * | 2 * 8


[Animator]

You want to find the next move using logic? Then define what you understand under logic.

Do you consider (for example) Nishio and Forching Chains as Logic?

If you don't then there is no next logical move.
This can mean two things: a) you made an error while copying it,
b) it's not a Pappocom puzzle (meaning you posted it in the wrong section of the Forum).

[tso]

this puzzle has given me grief.

Congratulations on worst ever way to post a puzzle!

Code: Select all

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

Code: Select all

  2     139   5     | 139   8     4     | 7     369   69   
  14    1349  6     | 139   7     5     | 8     39    2     
  8     7     39    | 2     39    6     | 4     1     5     
 -------------------+-------------------+-------------------
  9     6     4     | 7     2     3     | 5     8     1     
  7     5     1     | 8     4     9     | 6     2     3     
  3     2     8     | 5     6     1     | 9     7     4     
 -------------------+-------------------+-------------------
  6    [39]   2     | 4     359   8     | 1     59    7     
  5     8     7     | 69    1     2     | 3     4     69   
  14    1349 [39]   | 369   359   7     | 2     569   8   

1) In box 7, there is a pair of [39][39]. This lets you eliminate 3 and 9 from r9c2. This is a "naked pair".

Code: Select all

  2     139   5     | 139   8     4     | 7     369   69   
  14    1349  6     | 139   7     5     | 8     39    2     
  8     7     39    | 2     39    6     | 4     1     5     
 -------------------+-------------------+-------------------
  9     6     4     | 7     2     3     | 5     8     1     
  7     5     1     | 8     4     9     | 6     2     3     
  3     2     8     | 5     6     1     | 9     7     4     
 -------------------+-------------------+-------------------
  6     39    2     | 4     359   8     | 1     59    7     
  5     8     7     | 69    1     2     | 3     4     69   
  14    14    39    | 369   359   7     | 2     569   8   

1a) OPTIONAL: r29c12 contain a UNIQUENESS rectangle. r2c2 cannot be [14] or the puzzle would have two solutions. You can therefore elminate 1 and 4 from r2c2. After this, there will be several singles availble, but you'll still have to do step 2.


2) COLOR the THREES, starting with r9c3.

Code: Select all

  2     139   5     | 139   8     4     | 7     369   69   
  14    1349  6     | 139   7     5     | 8     39    2     
  8     7    -39    | 2    +39    6     | 4     1     5     
 -------------------+-------------------+-------------------
  9     6     4     | 7     2     3     | 5     8     1     
  7     5     1     | 8     4     9     | 6     2     3     
  3     2     8     | 5     6     1     | 9     7     4     
 -------------------+-------------------+-------------------
  6    -39    2     | 4    +359   8     | 1     59    7     
  5     8     7     | 69    1     2     | 3     4     69   
  14    14   +39    | 369   359   7     | 2     569   8     

Either the plusses are all 3s or the minuses are all 3s. Since there are two plusses in column 5, they cannot be 3s:

Code: Select all

  2     139   5     | 139   8     4     | 7     369   69   
  14    1349  6     | 139   7     5     | 8     39    2     
  8     7     3     | 2     9     6     | 4     1     5     
 -------------------+-------------------+-------------------
  9     6     4     | 7     2     3     | 5     8     1     
  7     5     1     | 8     4     9     | 6     2     3     
  3     2     8     | 5     6     1     | 9     7     4     
 -------------------+-------------------+-------------------
  6     3     2     | 4     59    8     | 1     59    7     
  5     8     7     | 69    1     2     | 3     4     69   
  14    14    9     | 369   359   7     | 2     569   8     

The rest should be easy.

[tso]

Do you consider (for example) Nishio and Forching Chains as Logic?

If you don't then there is no next logical move.
This can mean two things: a) you made an error while copying it,
b) it's not a Pappocom puzzle (meaning you posted it in the wrong section of the Forum).

All this puzzle requires is simple coloring.
Manhy puzzles posted here are non-pappocom. For hints and questions about solving techniques, posts elsewhere may be overlooked.

[Animator]

Do you consider (for example) Nishio and Forching Chains as Logic?

If you don't then there is no next logical move.
This can mean two things: a) you made an error while copying it,
b) it's not a Pappocom puzzle (meaning you posted it in the wrong section of the Forum).

All this puzzle requires is simple coloring.
Manhy puzzles posted here are non-pappocom. For hints and questions about solving techniques, posts elsewhere may be overlooked.

(I never meant to imply that Nishio and/r Forching Chains are required for to solve this puzzle... I suppose a better question would have been 'what logic do you know?')

Now that I've taken a better look at the grid I'm beginning to believe more and more that it is an error while copying the grid...

Why? If you fill in: r1c4, r1c8, r1c9, r2c2, r3c3, r3c5, r7c2, r7c5, r7c8, r8c4, r8c9, r9c3, r9c4, r9c5 or r9c7 in the starting grid then you reach a solution by using only very basic logic. (Read: just looking at cells that can have only one possibilities or rows/colums where a number has only one place. (no pairs, ...)). So I would be surprised if that one really needs coloring... (unless ofcourse it was a grid designed to explain the coloring technique but then heon would/should have said so.)
(Note: that are 15 cells of a total of 21 blank cells in his intermediate-grid).