The New Sudoku Players' Forum

[Happiehappie]

I am stuck in this puzzle on an iOS app called Sudoke ME, can anyone guide me or give me an explanation on how to find the next number? I don't need it to be solved as I still hope to complete it myself, but would really appreciate a hint as I've been stuck here for 15min without a single idea

[enxio27]

You have a locked candidate 1 in R7C56.

[Leren]

I'm not sure how you deleted 49 from r7c6, but you do have a locked pair (49) in r38c5, with eliminations in column 5 as shown in the diagram below.

Code: Select all

*-----------------------------------------*
| 3  6  1 | 458  57-49 4579 | 2  49   489 |
| 9  4  8 | 1    2     3    | 7  5    6   |
| 7  5  2 | 48  *49    6    | 1  3    489 |
|---------+-----------------+-------------|
| 14 2  5 | 9    3     8    | 46 1467 47  |
| 8  3  6 | 45   157-4 1457 | 9  14   2   |
| 14 7  9 | 2    6     14   | 5  8    3   |
|---------+-----------------+-------------|
| 2  19 3 | 6    15-49 1459 | 8  479  479 |
| 5  8  7 | 3   *49    2    | 46 469  1   |
| 6  19 4 | 7    8     19   | 3  2    5   |
*-----------------------------------------*

Leren

<edit>

OK, now I've got it, there is a UR (19) in r79c26 that removes 19 from r7c6. Correct, but I think most people would have played the 49 naked pair first.

The UR isn't actually necessary, because after the naked pair a Skyscraper in 9's (shown below and marked in cells a-b-c-d) solves the puzzle.

Code: Select all

*------------------------------------------*
| 3  6  1 | 458  57  4579 | 2   4-9   489  |
| 9  4  8 | 1    2   3    | 7   5     6    |
| 7  5  2 | 48  b49  6    | 1   3    a489  |
|---------+---------------+----------------|
| 14 2  5 | 9    3   8    | 46  1467  47   |
| 8  3  6 | 45   157 1457 | 9   14    2    |
| 14 7  9 | 2    6   14   | 5   8     3    |
|---------+---------------+----------------|
| 2  19 3 | 6    15  1459 | 8   479   47-9 |
| 5  8  7 | 3   c49  2    | 46 d469   1    |
| 6  19 4 | 7    8   19   | 3   2     5    |
*------------------------------------------*

Leren

<edit> <edit>

Just checked with Hodoku (that's a free web solver). They had the same solution as me. Apart from singles, one pointing pair, one naked pair and a Skyscraper.

Leren

[Kozo Kataya]

The puzzle is shown as below in line-format.
361...2..948123756752..613..25938...836...9.2.7926.5832.36..8..5873.2..16.478.325

Can't get how did you eliminate 4 at r1c46, r7c56 and 9 at r7c56, cells marked with*.

Code: Select all

 Your PM  cells *  without 4 
| 3   6   1 | 58* 4579 579*| 2  49   489|
| 9   4   8 | 1   2    3   | 7  5    6  |
| 7   5   2 | 48  49   6   | 1  3    489|
|-----------+--------------+------------|
| 14  2   5 | 9   3    8   | 46 1467 47 |
| 8   3   6 | 45  1457 1457| 9  147  2  |
| 14  7   9 | 2   6    14  | 5  8    3  |
|-----------+--------------+------------|
| 2   19  3 | 6   15*  15* | 8  479  479|
| 5   8   7 | 3   49   2   | 46 469  1  |
| 6   19  4 | 7   8    19  | 3  2    5  |


i think the following PM might be correct. Pls note cells* at r38c5

Code: Select all

 to be PM
| 3   6   1 | 458 4579 4579| 2  49   489|
| 9   4   8 | 1   2    3   | 7  5    6  |
| 7   5   2 | 48  49*  6   | 1  3    489|
|-----------+--------------+------------|
| 14  2   5 | 9   3    8   | 46 1467 47 |
| 8   3   6 | 45  1457 1457| 9  147  2  |
| 14  7   9 | 2   6    14  | 5  8    3  |
|-----------+--------------+------------|
| 2   19  3 | 6   1459 1459| 8  479  479|
| 5   8   7 | 3   49*  2   | 46 469  1  |
| 6   19  4 | 7   8    19  | 3  2    5  |


1st move after to-be-PM, delete 4,9 at r157c5 then:

Code: Select all

 PM after 49 pair
| 3   6   1 | 458 57*  4579| 2  49   489|
| 9   4   8 | 1   2    3   | 7  5    6  |
| 7   5   2 | 48  49   6   | 1  3    489|
|-----------+--------------+------------|
| 14  2   5 | 9   3    8   | 46 1467 47 |
| 8   3   6 | 45  157* 1457| 9  147  2  |
| 14  7   9 | 2   6    14  | 5  8    3  |
|-----------+--------------+------------|
| 2   19  3 | 6   15   1459| 8  479  479|
| 5   8   7 | 3   49   2   | 46 469  1  |
| 6   19  4 | 7   8    19  | 3  2    5  |


2nd move: note 19 at r79c26, r7c6 can't be 19 , so must be 4 or 5.
if 4r7c6, it will be fatal, hence 4r7c6>9r8c5>1r9c6 also 1r6c6.

Regards

[JasonLion-Admin]

I see a naked pair, two unique rectangles, and a skyscraper. After those it is fairly easy.

[Kozo Kataya]

The UR isn't actually necessary, because after the naked pair a Skyscraper in 9's (shown below and marked in cells a-b-c-d) solves the puzzle.

Yes and Sure, though how he presented the original PM. Want his thinking procedure.
Though, i would like to accept the other approach to solve a puzzle including UR.

To solve a particular sudoku-puzzle, there might be lots of routes, and which is the best is the concern of this forum ?

BTW: there are lots of puzzle suppliers including SUDOKU solvable with multi solutions.　Though !!!
in japanese, [SU] means in english as [number,digit,count,and etc.] and differs are recognized by different characters.
PLS imagine, a weather [raining] in spring and in autumn, is how and so differ.
also [DOKU] means as [single, alone, only and etc.], i prefer [ bachelor].

THKS so enjoyable this FORUM members, REGARDS kozo

[eleven]

Though, i would like to accept the other approach to solve a puzzle including UR.

What you described as "if 4r7c6, it will be fatal, hence 4r7c6>9r8c5>1r9c6 also 1r6c6", we call an xy-wing.
I am with you, that spotting a UR (type 1) and an xy-wing (in the near) can be easier than finding the skyscraper.