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PostPosted: Mon Aug 04, 2008 4:03 pm 
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This is puzzle # 288086 from menneske.no. He lists it as "Very Hard". SadMan Sudoku rates it as "Diabolical". Sudocue says it's unsolvable (with ALL solving routines turned on in the default order). Is it?

Code:

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



000006850064080100080300000800097500090000070005420009450002080700050690000700000


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PostPosted: Mon Aug 04, 2008 4:21 pm 
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Posts: 102
Location: Belgium
JSudoku wrote:
The grid is solved!
Techniques used:
36 Naked Singles
17 Hidden Singles
3 Hidden Pairs
4 Intersections
1 X-Wing
1 Skyscrapers
1 Two String Kites
1 Empty Rectangles
2 XY-Wings
1 XYZ-Wings
5 XY-Chains up to 5 links
1 Grouped Turbot Chains with 5 links


Sudoku Explainer wrote:
Analysis results
Difficulty rating: 7.3
This Sudoku can be solved using the following logical methods:
51 x Hidden Single
1 x Direct Hidden Pair
4 x Pointing
1 x X-Wing
3 x Hidden Pair
1 x XYZ-Wing
3 x Turbot Fish
7 x Forcing Chain

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"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes.


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PostPosted: Mon Aug 04, 2008 11:34 pm 
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enxio It is necessary to activate Medusa/ALS to solve this in Sudocue, these are not amongst the Default settings.

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PostPosted: Tue Aug 05, 2008 2:32 am 
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Glyn wrote:
enxio It is necessary to activate Medusa/ALS to solve this in Sudocue, these are not amongst the Default settings.

Oh, I have ALL of the solving techniques turned on. It's the solving ORDER that I haven't changed from the default.

It puzzles and frustrates me that Sudocue is declaring some puzzles unsolvable/invalid that other software doesn't seem to have a problem with. I guess it wouldn't matter much except that I depend on Sudocue to rate the puzzles. I haven't found anything else that will give as "precise" a rating AND that will rate a batch of puzzles at once.


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PostPosted: Wed Jun 17, 2009 12:27 am 
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.....685..64.8.1.7.8.3..9..843.975...9....478.754283.945...278.7..85.69...87..2.5

Code:
`1239 1237 `12379 | `129 `147 ````6 | ``8 ```5 `2347
`2359 ```6 `````4 | `259 ```8 ```59 | ``1 ``23 ``237
`1259 ```8 ``1279 | ```3 `147 `1459 | 249 `246 `2467
------------------+-----------------+----------------
````8 1234 ``1236 | ``16 ```9 ````7 | ``5 1246 `1246
`1236 ```9 ``1236 | 1568 `136 `1358 | `24 ```7 12468
```16 ``17 `````5 | ```4 ```2 ```18 | ``3 ``16 ````9
------------------+-----------------+----------------
````4 ```5 ``1369 | `169 `136 ````2 | ``7 ```8 ```13
````7 `123 ``1238 | ``18 ```5 `1348 | ``6 ```9 `1234
12369 `123 123689 | ```7 1346 13489 | `24 1234 12345


single niches: _[4]_ <cb> r4c2 _[5]_ <rcb> r9c9 _[7]_ <r> r2c9 <rb> r6c2 _[8]_ <cb> r5c9 <r> r6c6 _[9]_ <cb> r3c7
single niches: _[3]_ <r> r4c3 _[4]_ <rb> r5c7 _[8]_ <cb> r8c4 <r> r9c3

Code:
1239 123 1279 | 129 `147 ```6 | 8 ``5 234
2359 ``6 ```4 | 259 ```8 ``59 | 1 `23 ``7
`125 ``8 `127 | ``3 `147 `145 | 9 246 246
--------------+---------------+-----------
```8 ``4 ```3 | `16 ```9 ```7 | 5 126 126
`126 ``9 `126 | 156 `136 `135 | 4 ``7 ``8
``16 ``7 ```5 | ``4 ```2 ```8 | 3 `16 ``9
--------------+---------------+-----------
```4 ``5 `169 | 169 `136 ```2 | 7 ``8 `13
```7 123 ``12 | ``8 ```5 `134 | 6 ``9 134
1369 `13 ```8 | ``7 1346 1349 | 2 134 ``5


trios: [ 123 ] <b> _b7p568_ b7p37

b7 is the 7th box, where the boxes are numbered typewriter fashion
1 2 3
4 5 6
7 8 9
p568 are the fifth, sixth, and eighth positions in the box again in the same typewriter coordinates.

rb bc claims: [3] _r89c2_ <bc> r1c2

fish fins: [ !=4 ] <r18> _r3c6_ _r9c5_
r3c6 and r9c5 cannot have a 4 as a candidate, because that would case r1 and r8 to both have to have 4 as a candidate in only column 8.

Code:
1239 `12 1279 | 129 147 ```6 | 8 ``5 234
2359 ``6 ```4 | 259 ``8 ``59 | 1 `23 ``7
`125 ``8 `127 | ``3 147 ``15 | 9 246 246
--------------+--------------+-----------
```8 ``4 ```3 | `16 ``9 ```7 | 5 126 126
`126 ``9 `126 | 156 136 `135 | 4 ``7 ``8
``16 ``7 ```5 | ``4 ``2 ```8 | 3 `16 ``9
--------------+--------------+-----------
```4 ``5 ``69 | 169 136 ```2 | 7 ``8 `13
```7 123 ``12 | ``8 ``5 `134 | 6 ``9 134
``69 `13 ```8 | ``7 136 1349 | 2 134 ``5


trios: [ 136 ] <c> _r579c5_ r13c5

Now bringing out the big guns.

als xz: _12_ r1c2 =2= r3c16 [ !=1 ] r3c3
_12_ r1c2 =1= r3c3589 [ !=2 ] r3c1
_127_ r1c234 =7= r3c136 [ !=2 ] r1c1

the two sets r1c2 and r3c16 have a 1 and 2 in common, and if 2 is in one of them, 2 cannot be in the other. the 1 in r3c3 touches the all the 1's in both sets, so r3c3 cannot be a 1 as it would cause both sets not to have a 1. Both sets are of the type that if two candidates are not in the sets, one of the cells in the two set would have to be blank.

Code:
`139 `12 1279 | 129 `47 ```6 | 8 ``5 234
2359 ``6 ```4 | 259 ``8 ``59 | 1 `23 ``7
``15 ``8 ``27 | ``3 `47 ``15 | 9 246 246
--------------+--------------+-----------
```8 ``4 ```3 | `16 ``9 ```7 | 5 126 126
`126 ``9 `126 | 156 136 `135 | 4 ``7 ``8
``16 ``7 ```5 | ``4 ``2 ```8 | 3 `16 ``9
--------------+--------------+-----------
```4 ``5 ``69 | 169 136 ```2 | 7 ``8 `13
```7 123 ``12 | ``8 ``5 `134 | 6 ``9 134
``69 `13 ```8 | ``7 136 1349 | 2 134 ``5


nice loop
=3= r2c8 -2- r3c8 -6- r3c9 =6= r4c9 -6- r6c8 =6= r6c1 -6- r5c3 =6= r7c3 =9= r7c4 -9- r1c4 -1- r3c6 =1= r3c1 =5= r2c1 =3= r1c1 -3- r1c9 =3=

proves r2c8 != 2

RC XWing: _[_-9]_r1c34_r7c34_<r>_ r2c4 also _[_-9]_r29c1_r29c6_<c>_ r2c4

als xz: _149_ r1c249 =9= b8p1268 [ !=4 ] r8c9
_1269_ r1358c3 =9= r1245c4 [ !=6 ] r5c5

pairs: [ 13 ] <c> _r78c9_ r4c9
rb bc claims: [6] _r45c4_ <bc> r7c4
fish fins: [ !=1 ] <r146> _r3c1_ [ !=1 ] <r346> _r1c4_ _r5c6_

Code:
``3 `12 1279 | `29 `47 `6 | 8 ``5 `24
`29 ``6 ```4 | `25 ``8 59 | 1 ``3 ``7
``5 ``8 ``27 | ``3 `47 `1 | 9 `26 246
-------------+------------+-----------
``8 ``4 ```3 | `16 ``9 `7 | 5 126 `26
126 ``9 `126 | 156 `13 35 | 4 ``7 ``8
`16 ``7 ```5 | ``4 ``2 `8 | 3 `16 ``9
-------------+------------+-----------
``4 ``5 ``69 | `19 136 `2 | 7 ``8 `13
``7 123 ``12 | ``8 ``5 `4 | 6 ``9 `13
`69 `13 ```8 | ``7 136 39 | 2 ``4 ``5


rb bc claims: [1] _r56c1_ <cb> r5c3
als xz: _19_ r7c4 =9= r9c26 [ !=1 ] r9c5
_13_ r7c9 =1= b8p19 [ !=3 ] r7c5
_26_ r4c9 =6= r147c4 [ !=2 ] r1c9
_19_ r1c24 =1= r9c26 [ !=9 ] r2c6 r7c4
_19_ r9c26 =1= b1p24 [ !=9 ] r9c1
_126_ b4p67 =1= r36c8 [ !=2 ] r3c3
_16_ r58c3 =1= r9c126 [ !=6 ] r5c1 r6c1 r7c3

Code:
Sudoku box
`3 `12 1279 | `29 47 `6 | 8 ``5 ``4
29 ``6 ```4 | `25 `8 `5 | 1 ``3 ``7
`5 ``8 ```7 | ``3 47 `1 | 9 `26 246
------------+-----------+-----------
`8 ``4 ```3 | `16 `9 `7 | 5 126 `26
12 ``9 ``26 | 156 13 35 | 4 ``7 ``8
`1 ``7 ```5 | ``4 `2 `8 | 3 `16 ``9
------------+-----------+-----------
`4 ``5 ```9 | ``1 16 `2 | 7 ``8 `13
`7 123 ``12 | ``8 `5 `4 | 6 ``9 `13
`6 `13 ```8 | ``7 36 39 | 2 ``4 ``5


now singles solve


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