Challenging sudoku

Post the puzzle or solving technique that's causing you trouble and someone will help

Challenging sudoku

Postby Amonra » Mon Jun 18, 2018 9:29 pm

Hi fellow sudoku folks,

I have been struggling this sudoku. I’d appreciate your tips on what to do or look for next.

.5.947...
2.6351...
...628...
395762148
..84935..
462815937
...53....
...28.3.1
...179.8.

Thank you!
Amonra
 
Posts: 6
Joined: 10 November 2015

Re: Challenging sudoku

Postby ArkieTech » Tue Jun 19, 2018 1:22 am

Look at 9's in first block
dan
User avatar
ArkieTech
 
Posts: 2978
Joined: 29 May 2006
Location: NW Arkansas USA

Re: Challenging sudoku

Postby Leren » Tue Jun 19, 2018 3:24 am

Code: Select all
*-----------*
|.5.|947|...|
|2.6|351|...|
|...|628|...|
|---+---+---|
|395|762|148|
|..8|493|5..|
|462|815|937|
|---+---+---|
|...|53.|...|
|...|28.|3.1|
|...|179|.8.|
*-----------*

What the previous reply was hinting at was a pointing pair of 9's in Box 1, as shown in the following diagram (cells marked *).

Code: Select all
*--------------------------------------------------------------------------------*
| 18      5       13       | 9       4       7        | 268     126     236      |
| 2       478     6        | 3       5       1        | 478     79      49       |
|*179     1347   *13479    | 6       2       8        | 47      157-9   345-9    |
|--------------------------+--------------------------+--------------------------|
| 3       9       5        | 7       6       2        | 1       4       8        |
| 17      17      8        | 4       9       3        | 5       26      26       |
| 4       6       2        | 8       1       5        | 9       3       7        |
|--------------------------+--------------------------+--------------------------|
| 16789   12478   1479     | 5       3       46       | 2467    2679    2469     |
| 5679    47      479      | 2       8       46       | 3       5679    1        |
| 56      234     34       | 1       7       9        | 246     8       2456     |
*--------------------------------------------------------------------------------*

That eliminates some 9's in Box 3 as shown. Also there is a naked triple 479 in Box 3, as shown in the following diagram (cells marked *).

Code: Select all
*--------------------------------------------------------------------------------*
| 18      5       13       | 9       4       7        | 268     126     236      |
| 2       478     6        | 3       5       1        | 8-47   *79     *49       |
| 179     1347    13479    | 6       2       8        |*47      15-7    35-4     |
|--------------------------+--------------------------+--------------------------|
| 3       9       5        | 7       6       2        | 1       4       8        |
| 17      17      8        | 4       9       3        | 5       26      26       |
| 4       6       2        | 8       1       5        | 9       3       7        |
|--------------------------+--------------------------+--------------------------|
| 16789   12478   1479     | 5       3       46       | 2467    2679    2469     |
| 5679    47      479      | 2       8       46       | 3       5679    1        |
| 56      234     34       | 1       7       9        | 246     8       2456     |
*--------------------------------------------------------------------------------*

After the eliminations in Box 3 the puzzle solves with singles. I haven't checked whether the naked triple alone would solve the puzzle but it would be normal practice to take all available intersection moves before looking for something else.

Leren
Last edited by Leren on Tue Jun 19, 2018 10:05 am, edited 2 times in total.
Leren
 
Posts: 3315
Joined: 03 June 2012

Postby Pat » Tue Jun 19, 2018 7:30 am

see box 3,
cells marked "_"
naked triple ={4,7,9}

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


( or hidden quint {1,2,3,5,6} )
User avatar
Pat
 
Posts: 3653
Joined: 18 July 2005


Return to Help with puzzles and solving techniques