## Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzzle

Everything about Sudoku that doesn't fit in one of the other sections

### Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzzle

"Weekly Unsolveable" AS#49, here - SE10.8

002800000030060007100000040600090000050600009000057060000300100070006008400000020

Solution based on abi's deep understanding of exocets, here.

#1. ALS (124)r46c4

a. There is an exocet at the very start.

Code: Select all
+------------------------+----------------------------+------------------------+
| 579     469    2       | 8        1347     13459    | 3569     1359    1356  |
| 589     3      589(4)  | 59(124)  6        -59(124) | 589(2)   589(1)  7     |
| 1       689    56789   | 2579     237      2359     | 235689   4       2356  |
+------------------------+----------------------------+------------------------+
| 6       1248   13478   | (124)    9        12348    | 234578   13578   12345 |
| 378(2)  5      378(14) | 6        38(124)  38(124)  | 378(24)  378(1)  9     |
| 2389    12489  13489   | (124)    5        7        | 2348     6       1234  |
+------------------------+----------------------------+------------------------+
| 2589    2689   5689    | 3        2478     24589    | 1        579     456   |
| 359(2)  7      359(1)  | 59(124)  (124)    6        | 359(4)   359     8     |
| 4       1689   135689  | 1579     178      1589     | 35679    2       356   |
+------------------------+----------------------------+------------------------+

Exocet :     base 124[r4c6=r6c4]

(SF=Swordfish)

1r46c4-1r28c4.r5c56=SF(1)[r2c6=*r2c8-r5c8=*r5c3-r8c3=*r8c5]
||
2r46c4-2r28c4.r5c56=SF(2)[r2c6=*r2c7-r5c7=*r5c1-r8c1=*r8c5]
||
4r46c4-4r28c4.r5c56=SF(4)[r2c6=*r2c3-r5c3=*r5c7-r8c7=*r8c5]

=> SF(1)=SF(2)=SF(4)

or

=> [1r2c6=1r8c5]=[2r2c6=2r8c5]=[4r2c6=4r8c5]

or

=> Target : 124[r2c6=r8c5] => -58r2c6

Conclusion : r2c6 and r8c5 can only contain the digits 1, 2 and 4 => -59r2c6

b. Further analysis of the exocet.

Let us examine the implications of each possible solution of the ALS (124)r46c4 :

Code: Select all
+--------------------------+-------------------------------+--------------------------+
| 579     69(4)    2       | 8         347-1     13459     | 3569     359-1   1356    |
| 589     3        589(4)  | 59(4-12)  6         -59(12-4) | 589(2)   589(1)  7       |
| 1       689      56789   | 579-2     37-2      2359      | 35689-2  4       356(2)  |
+--------------------------+-------------------------------+--------------------------+
| 6       28(14)   3478-1  | (12-4)    9         348-12    | 34578-2  3578-1  135(24) |
| 378(2)  5        378(14) | 6         38(4-12)  38(4-12)  | 378(24)  378(1)  9       |
| 389-2   289(14)  3489-1  | (12-4)    5         7         | 348-2    6       13(24)  |
+--------------------------+-------------------------------+--------------------------+
| 589-2   2689     5689    | 3         2478      4589-2    | 1        579     56(4)   |
| 359(2)  7        359(1)  | 59(4-12)  (12-4)    6         | 359(4)   359     8       |
| 4       689(1)   35689-1 | 579-1     178       589-1     | 35679    2       356     |
+--------------------------+-------------------------------+--------------------------+

12r46c4
||
(14r46c4)
14r28c4.r5c56=[1r5c3=1r5c8-1r2c8=(1-4)r2c6=4r2c3]
4r5c56========4r5c3=4r5c7
4r8c4===============4r8c7=4r8c5
1r8c4=====================1r8c5=1r8c3
1r5c56==========================1r5c3=1r5c8
1r2c4=================================1r2c8=1r2c6
4r2c4=======================================4r2c6=4r2c3
DP(14)r46c24====================1r9c2=============4r1c2
||
(24r46c4)
24r28c4.r5c56=[2r5c7=2r5c1-2r8c1=(2-4)r8c5=4r8c7]
4r5c56========4r5c7=4r5c3
4r2c4===============4r2c3=4r2c6
2r2c4=====================2r2c6=2r2c7
2r5c4===========================2r5c7=2r5c1
2r8c4=================================2r8c1=2r8c5
4r8v4=======================================4r8c5=4r8c7
DP(24)r46c49====================2r9c7=============4r7c9

Case 1 : 12r46c4

Case 2 : 14r46c4

1r5c3=1r5c8-1r2c8=(1-4)r2c6=4r2c3 => -4r5c3, +4r5c7

=> +4r8c5, +1r8c3 (=> -1r9c2), +1r5c8, +1r2c6, +4r2c3 (=> -4r1c2)

IOW, SF(1) and SF(4) are solved, r46c2=14 => DP(14)r46c24 !

Case 3 : 24r46c4

2r5c7=2r5c1-2r8c1=(2-4)r8c5=4r8c7 => -4r5c7, +4r5c3

=> +4r2c6, +2r2c7 (=> -2r3c9), +2r5c1, +2r8c5, +4r8c7 (=> -4r7c9)

IOW, SF(2) and SF(4) are solved, r46c9=24 => DP(24)r46c49 !

Conclusions :

+NP(12)r46c4 => -12r2389c3.r45c56

SF(1) => -1r1c5.r9c4

SF(2) => -2r3c5.r7c6

Furtermore,  SF(1) and SF(2) enter into the following nice loop :

{(1-2)r2c6=2r2c7-2r5c7=2r5c1-2r8c1=(2-1)r8c5=1r8c3-1r5c3=1r5c8-1r2c8}

=> -459r2c6, -2r346c7, -2r67c1, -4r8c5, -1r469c3, -1r14c8

Note 1 : the puzzle is reduced to SE9.0.

Note 2 : AS#49 seems to be a clone of Fata Morgana. To wit the corresponding situation :

Fata Morgana : 000000003001005600090040070000009050700050008050402000080020090003500100600000000

#2.

Code: Select all
+----------------------+------------------------+-------------------------+
| 59(7)   469    2     | 8      3-7(4)  359(14) | 3569     359     356(1) |
| 589     3      4589  | 59(4)  6       (12)    | 589(2)   59(18)  7      |
| 1       689    56789 | 579    37      2359    | 35689    4       2356   |
+----------------------+------------------------+-------------------------+
| 6       1248   3478  | 12     9       348     | 34578    357(8)  12345  |
| 8(237)  5      13478 | 6      348     348     | 3478(2)  137(8)  9      |
| 89(3)   12489  3489  | 12     5       7       | (348)    6       1234   |
+----------------------+------------------------+-------------------------+
| 589     2689   5689  | 3      2478    4589    | 1        579     456    |
| 59(23)  7      1359  | 59(4)  12      6       | 359(4)   359     8      |
| 4       1689   35689 | 579    178     589     | 35679    2       356    |
+----------------------+------------------------+-------------------------+

7r1c1=7r5c1
2r5c1=2r8c1
3r5c1=3r8c1=3r6c1
2r5c1=============2r5c7
2r2c7=2r2c6
1r2c6=1r1c6
1r1c9=1r2c8
8r2c8=8r45c8
3r6c7=========================8r6c7==4r6c7
4r8c7=4r8c4
4r1c5===============================4r1c6====================4r2c4

=> 7r1c1=4r1c5 => -7r1c5

#3.

Code: Select all
+----------------------+--------------------+-------------------------+
| 7     469    2       | 8    34      13459 | 3569     359      1356  |
| 589   3      4589    | 459  6       (12)  | 589(2)   589-1    7     |
| 1     689    5689    | 579  37      2359  | 35689    4        2356  |
+----------------------+--------------------+-------------------------+
| 6     1248   348(7)  | 12   9       348   | 3458(7)  3578     12345 |
| 238   5      348(17) | 6    348     348   | 348(27)  38-7(1)  9     |
| 389   12489  3489    | 12   5       7     | 348      6        1234  |
+----------------------+--------------------+-------------------------+
| 589   2689   5689    | 3    48(27)  4589  | 1        59(7)    456   |
| 2359  7      359(1)  | 459  (12)    6     | 3459     359      8     |
| 4     1689   35689   | 579  178     589   | 3569(7)  2        356   |
+----------------------+--------------------+-------------------------+

1r5c8=1r5c3
7r5c3=7r4c3
1r8c3=======1r8c5
2r8c5=2r7c5
7r7c5=7r7c8
7r4c7=============7r9c7=7r5c7*
2r5c7=2r2c7
1r2c6=====================================2r2c6

=> *1r5c8=7r5c7 : -7r5c8; 1r5c8=1r2c6 : -1r2c8; 10 Singles

#4.

Code: Select all
+---------------------+----------------------+----------------------+
| 7    69(4)  2       | 8      (34)   3459   | 3569     359   1     |
| 589  3      89(45)  | 59(4)  6      1      | 2        589   7     |
| 1    689    689(5)  | 59(7)  -3(7)  2      | 35689    4     (356) |
+---------------------+----------------------+----------------------+
| 6    148    3478    | 12     9      348    | 34578    3578  2345  |
| 2    5      3478    | 6      348    348    | 3478     1     9     |
| 389  1489   3489    | 12     5      7      | 348      6     234   |
+---------------------+----------------------+----------------------+
| 589  2      89(56)  | 3      78(4)  589(4) | 1        579   5(46) |
| 359  7      1       | 59(4)  2      6      | 3459     359   8     |
| 4    89(6)  89(356) | 59(7)  1      589    | 59(367)  2     5(36) |
+---------------------+----------------------+----------------------+

3r1c5=4r1c5
4r1c2=4r2c3
4r2c4=======4r8c4
4r7c56=4r7c9
7r3c5==========================7r3c4
7r9c4=7r9c7
6r7c9=======6r9c7=6r9c9
6r9c23=6r7c3
3r9c7=3r9c9========3r9c4
5r2c3=================================5r7c3=5r9c4=5r3c4
3r3c9======================================6r3c9==============5r3c9

=> 3r1c5=7r3c5=3r3c9 => -3r3c5; 3 Singles, Claiming(+3r3c79) => -3r1c78

#5. Skyscraper(3C18) : 3r6c1=3r8c1-3r8c8=3r4c8 => -3r4c3.r6c79

#6.

Code: Select all
+---------------------+------------------+-------------------+
| 7    69(4)   2      | 8      34   3459 | 569     59   1    |
| 589  3       589(4) | 59(4)  6    1    | 2       589  7    |
| 1    689     5689   | 59     7    2    | 35689   4    356  |
+---------------------+------------------+-------------------+
| 6    8(14)   478    | 12     9    348  | 34578   358  2345 |
| 2    5       478    | 6      348  348  | 3478    1    9    |
| 389  89(14)  3489   | (12)   5    7    | 8-4     6    (24) |
+---------------------+------------------+-------------------+
| 589  2       5689   | 3      48   4589 | 1       7    456  |
| 359  7       1      | 59(4)  2    6    | 359(4)  359  8    |
| 4    689     35689  | 7      1    589  | 3569    2    356  |
+---------------------+------------------+-------------------+

(4=2)r6c9-(2=1)r6c4-1r6c2=(1-4)r4c2=[4r6c2=]4r1c2-4r2c3=4r2c4-4r8c4=4r8c7

=> 4r6c9=4r6c2=4r8c7 => -4r6c7; 11 Singles

#7. Skyscraper(9C48) : 9r3c4=9r8c4-9r8c8=9r1c8 => -9r1c6.r3c7; stte
JC Van Hay

Posts: 719
Joined: 22 May 2010

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

JC Van Hay wrote:Note 2 : AS#49 seems to be a clone of Fata Morgana.

This Andrew Stuart Weekly Extreme Unsolvable #49 is definitely an isomorph of tarek's Fata Morgana.
Last edited by ronk on Fri Apr 06, 2012 4:50 pm, edited 1 time in total.
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

ronk wrote:AS#49 is a morph of tarek's Fata Morgana.

Are morphs allowed to contain extra clues/givens?

Code: Select all
020400000400009200098000004000600007500010000040003800300000060000700001004008500   AS#49
020400000000009200098000004000600007500010000040003800300000060000700001004008500   FM
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

daj95376 wrote:
ronk wrote:AS#49 is a morph of tarek's Fata Morgana.

Are morphs allowed to contain extra clues/givens?

Code: Select all
020400000400009200098000004000600007500010000040003800300000060000700001004008500   AS#49
020400000000009200098000004000600007500010000040003800300000060000700001004008500   FM

I can always claim that it is a Prtially solved FM

tarek

Posts: 2897
Joined: 05 January 2006

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

daj95376 wrote:Are morphs allowed to contain extra clues/givens?

No, not normally. but Fata Morgana has been posted many times with hidden single r5c5=5 already placed. Earliest instance AFAIK is here circa Sep 2008.

This scenario points out the importance of a library of hardest puzzles being minimal. Then all minimals of an unknown can be compared to this library.
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

ronk wrote:This scenario points out the importance of a library of hardest puzzles being minimal. Then all minimals of an unknown can be compared to this library.

This reminds me of a wiki user's claim about a hardest puzzle that turned out to be an isomorph of a puzzle posted originally by ocean. MOST of the special puzzles (hardest or others) are best kept in a database for people to check against (I do that ). So in short I do agree with ronk on this. The puzzles on gsf's q1/q2 list should be the start of such a hardest puzzles list. I should be updating the (hardest sudoku thread 2) in May. That means that I will have a database of at least all puzzle posted in that thread which I can share through a link.

tarek

Posts: 2897
Joined: 05 January 2006

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

"Weekly Unsolveable" AS#50, here - SE9.0

000700086028010700000003000905000003070040050200000407000600000004000510530002000

Code: Select all
#1. r7c6.r9c4=14; +2r7c3, +2r8c9, +4r4c2, +5r7c5; +6r9c78 :=> -6r9c3
#2. {2R15} : Skyscraper(2)(r1c5=r1c7-r5c7=r5c4) :=> -2r3c4.r4c5
#3. {1N5 79C3 1R9 8R3 4N4 2C8} :=> -2r3c5

+--------------------+------------------------+--------------------+
| 134   159   13(9)  | 7       (29)     459   | 1239   8      6    |
| 346   2     8      | 459     1        4569  | 7      349    459  |
| 1467  1569  16(79) | 459(8)  69-2(8)  3     | 129    49(2)  1459 |
+--------------------+------------------------+--------------------+
| 9     4     5      | (128)   678      1678  | 1268   6(2)   3    |
| 1368  7     136    | 12389   4        1689  | 12689  5      189  |
| 2     168   136    | 13589   3689     15689 | 4      69     7    |
+--------------------+------------------------+--------------------+
| 178   189   2      | 6       5        14    | 389    3479   489  |
| 678   689   4      | 389     3789     789   | 5      1      2    |
| 5     3     (179)  | 4(1)    789      2     | 689    4679   489  |
+--------------------+------------------------+--------------------+

(2=9)r1c5-9r1c3=HP(79)r39c3-1r9c3=1r9c4-1r4c4=*SWing[8r3c5=8r3c4-(8=*2)r4c4-2r4c8=2r3c8]

=> 2r1c5=8r3c5=2r3c8 :=> -2r3c5; +2r1c5

#4. {1R49 8B64 1B4 } :=> -1r5c4

+----------------------+----------------------+----------------------+
| 134     159    139   | 7       2     459    | 139      8     6     |
| 346     2      8     | 459     1     4569   | 7        349   459   |
| 1467    1569   1679  | 4589    689   3      | 129      249   1459  |
+----------------------+----------------------+----------------------+
| 9       4      5     | 28(1)   678   678(1) | 26(18)   26    3     |
| 36(18)  7      36(1) | 2389-1  4     1689   | 1269(8)  5     19(8) |
| 2       6(18)  36(1) | 13589   3689  15689  | 4        69    7     |
+----------------------+----------------------+----------------------+
| 178     189    2     | 6       5     14     | 389      3479  489   |
| 678     689    4     | 389     3789  789    | 5        1     2     |
| 5       3      79(1) | 4(1)    789   2      | 689      4679  489   |
+----------------------+----------------------+----------------------+

1r4c46=(1-8)r4c7=8r5c79-8r5c1=(8-1)r6c2=[1r5c13=]1r6c3-1r9c3=1r9c4

=> 1r4c46=1r5c13=1r9c4 :=> -1r5c4

#5. {5C4 5R1 1R49 1C29} :=> -1r6c4

+---------------------+------------------------+----------------------+
| 134   9(15)   139   | 7         2     49(5)  | 139     8     6      |
| 346   2       8     | 49(5)     1     4569   | 7       349   459    |
| 1467  569(1)  1679  | 489(5)    689   3      | 129     249   459(1) |
+---------------------+------------------------+----------------------+
| 9     4       5     | 28(1)     678   678(1) | 268(1)  26    3      |
| 1368  7       136   | 2389      4     1689   | 12689   5     89(1)  |
| 2     68(1)   136   | 389-1(5)  3689  15689  | 4       69    7      |
+---------------------+------------------------+----------------------+
| 178   89(1)   2     | 6         5     14     | 389     3479  489    |
| 678   689     4     | 389       3789  789    | 5       1     2      |
| 5     3       79(1) | 4(1)      789   2      | 689     4679  489    |
+---------------------+------------------------+----------------------+

Kite(5)(r6c4=r23c4-r1c6=r1c2)-1r1c2=*Jellyfish(1)[r4c46=r4c7-r5c9=r3c9-r3c2=*[r6c2=]r7c2-r9c3=r9c4]

=> 5r6c4=1r4c46=1r6c2=1r9c4 :=> -1r6c4

#6. {1R69 8B46 7N1 7C8 2B6 6C8 6B4 3R5 2C4} :=> -1r4c4; 3 Singles

+----------------------+-----------------------+------------------------+
| 134     159    139   | 7       2     459     | 139      8       6     |
| 346     2      8     | 459     1     4569    | 7        349     459   |
| 1467    1569   1679  | 4589    689   3       | 129      249     1459  |
+----------------------+-----------------------+------------------------+
| 9       4      5     | 8-1(2)  678   1678    | 16(28)   (26)    3     |
| 1(368)  7      1(36) | 89(23)  4     1689    | 169(28)  5       19(8) |
| 2       (168)  3(16) | 3589    3689  5689(1) | 4        9(6)    7     |
+----------------------+-----------------------+------------------------+
| (178)   189    2     | 6       5     14      | 389      349(7)  489   |
| 678     689    4     | 389     3789  789     | 5        1       2     |
| 5       3      79(1) | 4(1)    789   2       | 689      49(67)  489   |
+----------------------+-----------------------+------------------------+

1r9c4=1r9c3
1r6c6=1r6c3=1r6c2
8r6c2=8r5c1
8r5c79=8r4c7
1r7c1=======8r7c1=======7r7c1
7r7c8=7r9c8
2r4c7============2r5c7=2r4c8
6r9c8=======6r4c8=6r6c8
6r6c2=6r5c1===============================6r6c3=6r5c3
3r5c1===================3r5c4=============3r5c3
2r4c4=====================================2r5c4

=> 1r9c4=1r6c6=2r4c4 :=> -1r4c4; +1r9c4, +4r7c6, +4r1c1

#7. {4C48 2C8 4N4 8R3 9N35} :=> -59r9c8; stte

+------------------+----------------------+----------------------+
| 4     159   139  | 7       2      59    | 139    8        6    |
| 36    2     8    | 59(4)   1      569   | 7      39(4)    459  |
| 167   1569  1679 | 59(48)  69(8)  3     | 129    9(24)    1459 |
+------------------+----------------------+----------------------+
| 9     4     5    | (28)    678    1678  | 1268   6(2)     3    |
| 1368  7     136  | 2389    4      1689  | 12689  5        189  |
| 2     168   136  | 3589    3689   15689 | 4      69       7    |
+------------------+----------------------+----------------------+
| 178   189   2    | 6       5      4     | 389    379      89   |
| 678   689   4    | 389     3789   789   | 5      1        2    |
| 5     3     (79) | 1       (789)  2     | 689    6-79(4)  489  |
+------------------+----------------------+----------------------+

4r9c8=[4r3c4=4r2c4-4r2c8=*(4-2)r3c8=2r4c8-(2=8)r4c4]-8r3c4=8r3c5-(8=79)r9c35

=> 4r9c8=79r9c35 :=> -79r9c8; stte
JC Van Hay

Posts: 719
Joined: 22 May 2010

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

tarek wrote:
ronk wrote:This scenario points out the importance of a library of hardest puzzles being minimal. Then all minimals of an unknown can be compared to this library.

This reminds me of a wiki user's claim about a hardest puzzle that turned out to be an isomorph of a puzzle posted originally by ocean. MOST of the special puzzles (hardest or others) are best kept in a database for people to check against (I do that ). So in short I do agree with ronk on this. The puzzles on gsf's q1/q2 list should be the start of such a hardest puzzles list. I should be updating the (hardest sudoku thread 2) in May. That means that I will have a database of at least all puzzle posted in that thread which I can share through a link.

It seems that you did not look at that thread for a while

champagne
champagne
2017 Supporter

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Location: France Brittany

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

"Weekly Unsolveable" AS#56, here - SE9.0

805000006010000002026010500060401000008000700000508060002040130500000080900000207

Hidden Text: Show
Code: Select all
#1. After LC and LS :

+---------------------+----------------------+---------------------+
| 8      347(9)  5    | 2379   23(9)  23479  | 349     1      6    |
| 347    1       3479 | 36789  5-8    345679 | 349(8)  479    2    |
| 347    2       6    | 3789   1      3479   | 5       479    348  |
+---------------------+----------------------+---------------------+
| 237    6       379  | 4      237    1      | 3(89)   2(59)  358  |
| 1234   5       8    | 239    6      239    | 7       24     134  |
| 12347  347(9)  3479 | 5      237    8      | 34(9)   6      134  |
+---------------------+----------------------+---------------------+
| 6      78      2    | 78(9)  4      7(59)  | 1       3      (59) |
| 5      347     1347 | 12379  23(9)  2379   | 6       8      49   |
| 9      348     134  | 1368   (58)   356    | 2       4(5)   7    |
+---------------------+----------------------+---------------------+

Chain[8] : {59R7 5C8 8C7 9C25 9N5 9B6} :=> -8r2c5

8r2c7=(8-9)r4c7=*[5r9c8=(5-9)r4c8=*9r6c7-9r6c2=9r1c2-9r1c5=9r8c5-9r7c46=(9-5)r7c9=5r7c6]-(5=8)r9c5

=> 8r2c7=8r9c5 :=> -8r2c5; 3 Singles, 1 LC

#2. AIC[5] : 8r2c4=8r2c7-8r4c7=(8-5)r4c9=5r4c8-5r9c8=(5-6)r9c6=6r2c6

=> 8r2c4=6r2c6 :=> -6r2c4; 4 Singles

#3. AIC[5] : 2r1c4=2r5c4-2r5c8=(2-5)r4c8=5r4c9-(5=9)r7c9-(9=7)r7c4

=> 2r1c4=7r7c4 :=> -7r1c4

#4.

+------------------------+-------------------+----------------------+
| 8      3-47(9)  5      | 239   239   23479 | 49(3)   1      6     |
| 37(4)  1        37(49) | 3789  5     6     | 9(348)  79(4)  2     |
| (347)  2        6      | 3789  1     3479  | 5       479    4(38) |
+------------------------+-------------------+----------------------+
| 237    6        379    | 4     2379  1     | 389     259    358   |
| 1234   5        8      | 239   6     239   | 7       249    (134) |
| 12347  347(9)   379(4) | 5     2379  8     | (349)   6      (134) |
+------------------------+-------------------+----------------------+
| 6      8        2      | 79    4     579   | 1       3      59    |
| 5      34(7)    3(47)  | 1     239   239   | 6       8      9(4)  |
| 9      34       1      | 6     8     35    | 2       5(4)   7     |
+------------------------+-------------------+----------------------+

Chain[12] : {4R2 7R8 4C3 9C2 3N1 6N7 56N9 9B1 38B3 4B9} :=> -47r1c2

9r1c2=9r6c2
9r6c7=3r6c7
3r5c9=1r5c9=4r5c9
3r6c9=1r6c9=4r6c9
4r8c9=4r9c8
3r12c7==================3r3c9
8r3c9=8r2c7
9r1c2===========================================9r2c3
4r2c8=======4r2c7=4r2c3=4r2c1*
7r3c1===============================3r3c1=============4r3c1**
||
4r6c7
4r6c3=4r2c3=4r8c3
4r9c8=4r8c9
4r5c9=============1r5c9=3r5c9
4r6c9=============1r6c9=3r6c9
9r1c2=====================================9r2c3
4r2c7=4r2c8===================4r2c3=4r2c1*
4r6c3=========================4r2c3=======4r8c3
7r8c2=================================================7r8c3**

* 9r1c2=4r2c13      :=> -4r1c2
** 9r1c2=7r3c1=7r8c2 :=> -7r1c2

4 Singles, 1 NP, 1 LC

#5. AIC[4] : 9r8c5=9r1c5-(9=3)r1c2-3r9c2=(3-5)r9c6=5r7c6

=> 9r8c5=3r9c6 :=> -3r8c5
=> 9r8c5=5r7c6 :=> -9r7c6

Singles only to the end.
JC Van Hay

Posts: 719
Joined: 22 May 2010

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

I wasn't aware this was an isomoph of a previously published puzzle. But it's also not surprising that the occasional puzzle will be an isomoph of a known one - all the ones I publish are outputs of the creation software I've developed. It's in my job queue to get the canonical form stuff completed for easy comparison to the hard lists. I'm interested that #49 has extra clues which I'll look at.
Andrew Stuart

Posts: 1
Joined: 23 September 2012

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

Hi Andrew,

I agree that there is a possibility of generating isomorphs with these qualities, However, unless a tedious neighbourhood search was done around carefully generated hard puzzle seeds (which is how the original was discovered) then I would say that the chances are slim. You can track the development of the Hardest Sudokus through the 2 dedicated threads to get a feel of how a tedious & laborious process it was to stumble upon these special puzzles. The puzzle in questions -although not the current hardest- has been influential at the time in developing new rating/solving and analysis systems of these beasts.

tarek

tarek

Posts: 2897
Joined: 05 January 2006

### Re: Andrew Stuart - Weekly Extreme 'Unsolveable' Sudoku Puzz

tarek wrote: The puzzle in questions -although not the current hardest- has been influential at the time in developing new rating/solving and analysis systems of these beasts.

It has clearly been the puzzle where the exocet pattern has been shown, but moreover, this has been the start for an active search on complex logics leading to the discovery of huge rank 0 logic SLG's (although that one have none) , so I would say that is has been with Easter Monster a key puzzle for that development.

champagne
champagne
2017 Supporter

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Location: France Brittany