## Stuck yet again on a very hard

Advanced methods and approaches for solving Sudoku puzzles

### Stuck yet again on a very hard

Stuck again. Started with this:

*3* *** *4*
**6 *8* 1**
*** 659 ***

*75 *** 49*
*** 9*2 ***
*12 *** 37*

*** 817 ***
**4 *6* 7**
*2* *** *8*
and have managed to get as far as this:

*3* 721 *4*
**6 *8* 1**
*** 659 ***

*75 13* 492
*** 972 ***
912 54* 37*

*** 817 **4
**4 26* 7**
*2* *9* *8*
I have used x-wings in 9s and 6s and candidates in blank squares as follows:

r1c1 =58 r1c3=89 r1c7=5689 r1c9=568
r2c1-257 r2c2=59 r2c4=34 r2c6=34 r2c8=25 r2c9=579
r3c1=12478 r3c2=48 r3c3=178 r3c7=28 r3c8=23 r3c9=378
r4c1=68 r4c6=68
r5c1=348 r5c2=468 r5c3=38 r5c7=58 r5c8=156 r5c9=158
r6c6=68 r6c9=68
r7c1=35 r7c2=56 r7c3=39 r7c7=259 r7c8=2356
r8c1=1358 r8c2=589 r8c6=35 r8c8=135 r8c9=1359
r9c1=13567 r9c3=137 r9c4=34 r9c6=345 r9c7=56 r9c9=1356
I have probably missed something again but would appreciate any advice
Roger Scriven

Posts: 15
Joined: 12 May 2005

### Re: Stuck yet again on a very hard

Roger Scriven wrote:Stuck again. Started with this:

*3* *** *4*
**6 *8* 1**
*** 659 ***

*75 *** 49*
*** 9*2 ***
*12 *** 37*

*** 817 ***
**4 *6* 7**
*2* *** *8*
and have managed to get as far as this:

*3* 721 *4*
**6 *8* 1**
*** 659 ***

*75 13* 492
*** 972 ***
912 54* 37*

*** 817 **4
**4 26* 7**
*2* *9* *8*
I have used x-wings in 9s and 6s and candidates in blank squares as follows:

r1c1 =58 r1c3=89 r1c7=5689 r1c9=568
r2c1-257 r2c2=59 r2c4=34 r2c6=34 r2c8=25 r2c9=579
r3c1=12478 r3c2=48 r3c3=178 r3c7=28 r3c8=23 r3c9=378
r4c1=68 r4c6=68
r5c1=348 r5c2=468 r5c3=38 r5c7=58 r5c8=156 r5c9=158
r6c6=68 r6c9=68
r7c1=35 r7c2=56 r7c3=39 r7c7=259 r7c8=2356
r8c1=1358 r8c2=589 r8c6=35 r8c8=135 r8c9=1359
r9c1=13567 r9c3=137 r9c4=34 r9c6=345 r9c7=56 r9c9=1356
I have probably missed something again but would appreciate any advice
tso

Posts: 798
Joined: 22 June 2005

Look at the triple 589 in block 1.
Last edited by simes on Sun Dec 11, 2011 9:25 am, edited 1 time in total.
simes

Posts: 324
Joined: 11 March 2005
Location: UK

For simes dont quite see this.
Roger Scriven

Posts: 15
Joined: 12 May 2005

Roger Scriven wrote:For tso Your comments not showing.

He highlighted the important cells for you.
angusj

Posts: 306
Joined: 12 June 2005

got it Thanks. too busy looking for chains and fish to see the obvious.
Roger Scriven

Posts: 15
Joined: 12 May 2005

Was this really a very hard? Took well under 10 minutes (from the starting point) with no "pencil marks".

No X-wings needed - the whole thing can be done with simple candidate removal.
whohe

Posts: 32
Joined: 28 May 2005