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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Tue Jul 26, 2005 12:37 pm    Post subject:  | 
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                                here is the collection of puzzles which I found so far, which
 
require more than forced2 chains, where forced1 refers to
 
the 4*81 basic constraints. Bifurcations where one fork
 
is a forced1-chain would be considered forced2.
 
All other puzzles posted here
 
(if I found them) were solvable by considering forced2 chains
 
only, without backtracking.
 
 
 
 
....3....93..6.8..56......4..2.16...85.47....6...29..37.....21.................59
 
..26......9....4...1...9..7....46..5..4.9..8....71.3.48...31...3..98.......4...32
 
3...6...5.2.....4...7...2.....6.7...9...8...6...9.1.....2...7...4.....1.6...5...9
 
8.2.....4.9......7..5..139..8..17......5.2..1.....8.36..71.....4...7....32...5...
 
..3.5.4..7...6.....5.8...6.5....3..4.1..7..8.2..4....7.4...8.5.....4...9..6.1.2..
 
.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
 
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5.....
 
..12...6...9..8.4..5..4.9..73..8......5.3.1......6..34..3.2..9..2.8..5...9...14..
 
....7..9......8..4.42..1.7...4.....88..2.5..95.....7...7.6..13.2..8......6..3....
 
 
 
 
solver output:
 
 
1 solutions  , 1(2) guesses  , 3982 placements    time=0/91sec.
 
1 solutions  , 1(2) guesses  , 5643 placements    time=0/91sec.
 
1 solutions  , 1(2) guesses  , 4850 placements    time=0/91sec.
 
1 solutions  , 1(2) guesses  , 8098 placements    time=0/91sec.
 
1 solutions  , 1(2) guesses  , 6895 placements    time=0/91sec.
 
1 solutions  , 3(6) guesses  , 10525 placements    time=0/91sec.
 
1 solutions  , 2(4) guesses  , 5344 placements    time=5/91sec.
 
1 solutions  , 1(2) guesses  , 6097 placements    time=5/91sec.
 
1 solutions  , 1(2) guesses  , 4807 placements    time=5/91sec.
 
 
 
my other solver says:
 
 
1 solutions  242 nodes   396 node2   1203 node3   3 guesses
 
1 solutions  186 nodes   202 node2   1110 node3   1 guesses
 
1 solutions  280 nodes   364 node2   2353 node3   2 guesses
 
1 solutions  271 nodes   790 node2   2961 node3   5 guesses
 
1 solutions  405 nodes   356 node2   1623 node3   2 guesses
 
1 solutions  436 nodes   556 node2   2188 node3   3 guesses
 
1 solutions  390 nodes   602 node2   2037 node3   3 guesses
 
1 solutions  249 nodes   268 node2   1007 node3   1 guesses
 
1 solutions  244 nodes   110 node2   343 node3   1 guesses
 
 
 
it depends on the ordering of the constraints, so an equivalent
 
transformation of the sudoku gives a different result once
 
backtracking ("guesses") is involved.
 
 
 
Guenter. | 
                         
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                 |  Nick70
 
  |  | Joined: 08 Jun 2005 |  | Posts: 160 |  | :  |   |   Items |  
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                                 Posted: Tue Jul 26, 2005 2:01 pm    Post subject:  | 
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                                Are you sure you posted the right puzzles?
 
Especially the first one, which is easy.
 
 
 	  | Code: | 	 		  ....3....93..6.8..56......4..2.16...85.47....6...29..37.....21.................59
 
diff 01 [single sector candidate]
 
 
..26......9....4...1...9..7....46..5..4.9..8....71.3.48...31...3..98.......4...32
 
diff 13 [forcing chain] (chain score  505)
 
 
3...6...5.2.....4...7...2.....6.7...9...8...6...9.1.....2...7...4.....1.6...5...9
 
diff 15 [guessing] ( 1 lucky guesses to solution) (first easy iteration:  6)
 
 
8.2.....4.9......7..5..139..8..17......5.2..1.....8.36..71.....4...7....32...5...
 
diff 14 [multi forcing chain] (chain score  856) (first easy iteration:  2)
 
 
..3.5.4..7...6.....5.8...6.5....3..4.1..7..8.2..4....7.4...8.5.....4...9..6.1.2..
 
diff 15 [guessing] ( 2 lucky guesses to solution)
 
 
.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
 
diff 11 [xy-wing] (score  42, total 1, empty cells at first 27)
 
 
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5.....
 
diff 11 [xy-wing] (score  42, total 1, empty cells at first 27) (first easy iteration:  4)
 
 
..12...6...9..8.4..5..4.9..73..8......5.3.1......6..34..3.2..9..2.8..5...9...14..
 
diff 15 [guessing] ( 1 lucky guesses to solution)
 
 
....7..9......8..4.42..1.7...4.....88..2.5..95.....7...7.6..13.2..8......6..3....
 
diff 15 [guessing] ( 2 lucky guesses to solution) | 	 
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Tue Jul 26, 2005 3:05 pm    Post subject:  | 
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                                yes, I'm sure I posted the right puzzles.
 
I'm not sure how to interpret your comments.
 
Do you think I have a bug in my program ?
 
Is there a forced2-chain to solve puzzle 1 ?
 
 
I can add some clues, so this is the critical position:
 
 
... .3. ... 
 
93. .6. 8.. 
 
56. ... ..4 
 
 
3.2 .16 ... 
 
85. 473 ... 
 
6.. .29 ..3 
 
 
7.. ... 21. 
 
... ... ... 
 
... ... .59 | 
                         
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                 |  Nick70
 
  |  | Joined: 08 Jun 2005 |  | Posts: 160 |  | :  |   |   Items |  
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                                 Posted: Tue Jul 26, 2005 5:56 pm    Post subject:  | 
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                                 	  | dukuso wrote: | 	 		  | Do you think I have a bug in my program ? | 	  
 
 
Maybe, since it is missing one of the most basic logic rules.
 
 
There are many single sector candidate eliminations possible. For example:
 
 
8 is limited to column 4 in box 5
 
2 is limited to row 1 in box 1
 
5 is limited to column 4 in box 5
 
 
and so on.
 
 
Even Simple Sudoku suggest to use a naked pair before the single candidate rule, I guess this is by design but it seems a bit odd. | 
                         
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                 |  angusj Site Admin
   |  | Joined: 18 Jun 2005 |  | Posts: 406 |  | :  |   |   Items |  
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                                 Posted: Wed Jul 27, 2005 12:20 am    Post subject:  | 
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                                 	  | Nick70 wrote: | 	 		  | Even Simple Sudoku suggest to use a naked pair before the single candidate rule, I guess this is by design but it seems a bit odd. | 	  
 
Yes, it's by design because I generally find it easier to spot Naked Pairs than what you call single sector candidates (or what I've less helpfully called Eliminating Candidates). | 
                         
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Wed Jul 27, 2005 5:24 am    Post subject:  | 
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                                >dukuso wrote:
 
 >>Do you think I have a bug in my program ?
 
 >
 
 >Maybe, since it is missing one of the most basic logic rules. 
 
 
I think it works as described and this "basic" rule is missing by design.
 
This could be a weakness, I'm not sure.Maybe I can change this.
 
 
 >There are many single sector candidate eliminations possible. 
 
 >For example: 
 
 >
 
 >8 is limited to column 4 in box 5 
 
 >5 is limited to column 4 in box 5 
 
 
but which row ?
 
 
 >2 is limited to row 1 in box 1 
 
 
gives no forced placement yet
 
 
 >and so on. 
 
 >
 
 >Even Simple Sudoku suggest to use a naked pair before the 
 
 >single candidate rule, I guess this is by design but it seems 
 
 >a bit odd.
 
 
 
Can you send/post your hardest sudokus ?
 
(preferrably in one big file to sterten( at)aol.com)
 
 
 
 
 
 
-------------
 
 
I changed it now.
 
My old rule went like this:
 
 
We have the obvious 324 constraints : cell, symbol in row,
 
symbol in column, symbol in block with 81 each.
 
These make the forced(1) - placements.
 
Forced(2) includes forced(1) and bifurcation with (at least) one
 
dead end (when filling in forced(1)-placements)
 
 
Now I made it:
 
Forced(2) includes forced(1) and k-furcations with (at least) k-1
 
dead ends (when filling in forced(1)-placements)
 
 
A k-furcation is a constraint which can be met in k ways.
 
Or a binary column with sum=k in exact-cover-speak.
 
 
That means now, that I not necessarily always choose a 
 
binary column with minimum sum as is typical for exact-cover-solver.
 
This could make it slower for small n.
 
 
Now with this new forced(2)-rule, I can find no 9*9 sudoku-grid
 
which requires backtracking.
 
 
here is one 16*16 which still requires guessing:
 
 
 
BC-1--6GD-E--F----------3--FC-1BE-6-9A----8-G----5--2-------697----------B-G-C5-5-3-F-72-----1--2-A-5---4--E-8----B9-E-3FC--2D--3----65-G-9-FB---E58B--F--D--7---2D-C-8----4----A--6-----E7-----6--B--9A-D---4F---8-G--B-A4----1G-4-3--E61C----5--E----5---3--89
 
 
 
there could still be bugs in that version .... | 
                         
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Wed Jul 27, 2005 7:35 am    Post subject:  | 
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                                here is my updated list of hard 9*9 sudokus.
 
The 1st sudoku forces my new program (with the k-furkations rule)
 
to backtrack.
 
The others force my previous program (with the bifurcations rule) to backtrack.
 
 
 
 
6...4...3.1.....7...5...8.....5.2...3...9...2...1.3.....8...9...7.....5.2...3...4
 
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5.....
 
....3....93..6.8..56......4..2.16...85.47....6...29..37.....21.................59
 
....3....93..6.8..56......43.2.16...85.473...6...29..37.....21.................59
 
....7..9......8..4.42..1.7...4.....88..2.5..95.....7...7.6..13.2..8......6..3....
 
..12...6...9..8.4..5..4.9..73..8......5.3.1......6..34..3.2..9..2.8..5...9...14..
 
..26......9....4...1...9..7....46..5..4.9..8....71.3.48...31...3..98.......4...32
 
..3.5.4..7...6.....5.8...6.5....3..4.1..7..8.2..4....7.4...8.5.....4...9..6.1.2..
 
.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
 
3...6...5.2.....4...7...2.....6.7...9...8...6...9.1.....2...7...4.....1.6...5...9
 
4...1...8.5.....2...6...9.....9.2...8...5...3...1.8.....9...6...2.....5.1...7...4
 
6...7...9.1.....2...5...4.....1.2...9...8...6...6.9.....1...2...3.....4.7...5...8
 
8.2.....4.9......7..5..139..8..17......5.2..1.....8.36..71.....4...7....32...5...
 
9...7...4.1.....5...8...2.....8.9...7...4...6...2.7.....3...1...2.....8.6...9...7 | 
                         
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                 |  Nick70
 
  |  | Joined: 08 Jun 2005 |  | Posts: 160 |  | :  |   |   Items |  
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                                 Posted: Wed Jul 27, 2005 8:21 am    Post subject:  | 
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                                 	  | dukuso wrote: | 	 		  | I think it works as described and this "basic" rule is missing by design. | 	  
 
 
Well, if you are attempting to rate the difficulty of puzzles, and your program considers super-hard puzzles that everyone else considers easy, I think that is definitely a bug  
 
 
 	  | dukuso wrote: | 	 		   >8 is limited to column 4 in box 5 
 
 >5 is limited to column 4 in box 5 
 
 
but which row ? | 	  
 
 
Who knows? But the candidate can be removed from the other cells of box 5.
 
 
 	  | dukuso wrote: | 	 		  Can you send/post your hardest sudokus ?
 
(preferrably in one big file to sterten( at)aol.com) | 	  
 
 
I can just post them here.
 
Out of ~70000 puzzles I've generated so far (my generator is slower than yours, but I'm doing a complete search of puzzles with a fixed initial pattern) only ~100 require my solver to use T&E.
 
 
 	  | Code: | 	 		  31.6.......2.......5..3.89......5....8..1..7....4......47.8..3.......9.......7.62
 
31.6.......2.......5..9.86......5....6..1..9....4......94.6..7.......3.......7.12
 
31.6.......2.......6..7.59......5....9..1..7....4......78.9..4.......3.......7.12
 
31.6.......2.......6..8.37......5....3..1..6....4......75.3..9.......6.......7.42
 
31.6.......2.......7..3.89......5....8..1..7....4......97.8..3.......4.......7.62
 
31.6.......2.......8..9.76......5....6..1..9....4......98.6..1.......4.......7.82
 
31.6.......4.......7..3.95......5....6..1..3....4......98.5..6.......7.......7.42
 
31.6.......4.......9..8.15......5....2..1..3....4......86.3..7.......4.......7.92
 
31.6.......4.......9..8.57......5....3..1..8....4......87.9..3.......1.......7.62
 
31.6.......5.......2..7.84......5....7..1..2....4......46.9..8.......4.......7.12
 
31.6.......5.......2..9.56......5....6..1..8....4......38.6..9.......4.......7.12
 
31.6.......5.......8..3.47......5....2..1..3....4......37.2..1.......5.......7.62
 
31.6.......5.......8..9.75......5....3..1..6....4......58.6..3.......4.......7.12
 
31.6.......5.......9..7.18......5....8..1..7....4......76.8..9.......3.......7.12
 
31.6.......5.......9..7.82......5....8..1..7....4......74.9..3.......4.......7.12
 
31.6.......7.......9..4.28......5....8..1..3....4......45.8..9.......5.......7.62
 
31.6.......9.......7..2.48......5....2..1..6....4......56.8..9.......1.......7.32
 
32.6.......1.......9..8.74......5....7..1..3....4......85.3..6.......9.......7.12
 
32.6.......4.......5..8.17......5....7..1..9....4......37.5..4.......6.......7.82
 
32.6.......4.......7..9.81......5....9..1..3....4......15.3..9.......5.......7.62
 
32.6.......5.......6..7.41......5....7..1..6....4......18.6..7.......3.......7.52
 
32.6.......5.......6..7.49......5....7..1..6....4......98.6..7.......3.......7.52
 
32.6.......5.......6..8.71......5....8..1..3....4......16.3..8.......9.......7.62
 
32.6.......5.......7..8.16......5....8..1..9....4......67.9..8.......5.......7.32
 
32.6.......5.......7..9.18......5....9..1..6....4......36.8..9.......7.......7.12
 
32.6.......5.......9..7.16......5....7..1..9....4......68.9..7.......3.......7.52
 
32.6.......6.......4..7.81......5....9..1..7....4......85.4..9.......3.......7.42
 
32.6.......7.......1..4.59......5....9..1..7....4......78.9..4.......6.......7.82
 
32.6.......7.......1..8.37......5....7..1..2....4......86.2..9.......4.......7.12
 
32.6.......7.......1..8.56......5....3..1..8....4......85.6..1.......7.......7.52
 
32.6.......7.......1..9.58......5....9..1..2....4......48.3..9.......6.......7.12
 
32.6.......7.......4..3.18......5....6..1..3....4......38.4..6.......5.......7.92
 
32.6.......7.......4..8.59......5....3..1..7....4......98.3..1.......6.......7.42
 
32.6.......8.......6..9.71......5....9..1..3....4......85.3..9.......4.......7.62
 
32.6.......9.......1..8.45......5....8..1..2....4......75.3..8.......9.......7.62
 
32.6.......9.......6..4.58......5....8..1..2....4......17.5..3.......9.......7.62
 
32.6.......9.......6..8.57......5....8..1..2....4......37.4..1.......9.......7.62
 
32.6.......9.......8..3.67......5....6..1..3....4......17.6..9.......4.......7.82
 
34.6.......2.......6..7.18......5....7..1..6....4......85.6..7.......4.......7.32
 
34.6.......2.......6..7.81......5....7..1..6....4......15.6..7.......4.......7.32
 
34.6.......2.......6..9.17......5....3..1..8....4......98.3..6.......7.......7.42
 
34.6.......2.......6..9.83......5....8..1..7....4......75.8..1.......4.......7.62
 
34.6.......2.......7..3.51......5....3..1..7....4......28.5..6.......1.......7.32
 
34.6.......5.......2..8.53......5....9..1..7....4......78.3..1.......6.......7.42
 
34.6.......5.......7..8.53......5....8..1..9....4......38.9..7.......6.......7.42
 
34.6.......7.......2..8.57......5....7..1..2....4......36.2..1.......9.......7.82
 
34.6.......7.......2..9.57......5....7..1..2....4......68.2..1.......3.......7.92
 
35.6.......2.......6..5.48......5....3..1..6....4......18.3..5.......7.......7.92
 
35.6.......2.......9..5.48......5....6..1..9....4......18.6..5.......7.......7.32
 
35.6.......4.......1..7.29......5....7..1..3....4......68.9..1.......4.......7.52
 
35.6.......4.......1..7.29......5....7..1..3....4......68.9..7.......4.......7.52
 
35.6.......4.......2..7.89......5....7..1..2....4......36.9..1.......5.......7.82
 
35.6.......4.......8..3.57......5....3..1..8....4......16.8..3.......7.......7.42
 
35.6.......6.......1..4.29......5....7..1..2....4......48.9..6.......5.......7.12
 
35.6.......6.......1..4.98......5....2..1..7....4......48.2..6.......5.......7.12
 
35.6.......6.......9..4.17......5....7..1..2....4......48.9..6.......5.......7.12
 
35.6.......6.......9..4.17......5....7..1..8....4......48.2..6.......5.......7.12
 
35.6.......6.......9..4.17......5....7..1..9....4......48.2..6.......5.......7.12
 
35.6.......7.......1..2.89......5....6..1..2....4......94.8..5.......6.......7.32
 
35.6.......7.......1..2.94......5....3..1..8....4......48.9..1.......7.......7.32
 
35.6.......7.......1..8.34......5....2..1..8....4......46.2..1.......7.......7.52
 
35.6.......7.......9..3.18......5....6..1..9....4......18.9..6.......5.......7.32
 
35.6.......9.......6..8.71......5....8..1..3....4......16.3..7.......4.......7.82
 
37.6.......2.......1..9.85......5....9..1..3....4......35.6..9.......4.......7.82
 
37.6.......2.......6..8.14......5....2..1..3....4......85.3..6.......7.......7.92
 
37.6.......4.......1..3.62......5....2..1..3....4......65.2..8.......4.......7.12
 
37.6.......4.......5..2.61......5....2..1..3....4......18.3..7.......4.......7.92
 
37.6.......4.......5..8.19......5....9..1..3....4......85.3..7.......6.......7.42
 
37.6.......4.......9..2.41......5....2..1..9....4......18.9..6.......5.......7.32
 
37.6.......5.......2..8.69......5....6..1..8....4......98.2..6.......3.......7.12
 
37.6.......5.......6..2.19......5....2..1..6....4......38.6..1.......5.......7.32
 
37.6.......5.......8..9.42......5....2..1..5....4......46.8..9.......7.......7.82
 
37.6.......5.......9..2.48......5....2..1..9....4......16.9..7.......8.......7.32
 
37.6.......9.......2..8.16......5....9..1..8....4......58.6..9.......3.......7.42
 
37.6.......9.......2..8.65......5....6..1..8....4......98.2..4.......3.......7.12
 
37.6.......9.......6..2.18......5....2..1..9....4......16.9..7.......5.......7.42
 
37.6.......9.......8..2.46......5....3..1..8....4......45.8..1.......9.......7.32
 
38.6.......2.......7..3.51......5....9..1..6....4......18.6..3.......4.......7.92
 
38.6.......4.......1..7.52......5....7..1..9....4......58.9..7.......4.......7.52
 
38.6.......4.......1..9.72......5....3..1..6....4......98.6..3.......5.......7.42
 
38.6.......4.......2..9.15......5....7..1..6....4......98.6..7.......4.......7.32
 
38.6.......4.......6..9.17......5....9..1..3....4......16.3..9.......5.......7.82
 
38.6.......4.......6..9.17......5....9..1..6....4......17.6..9.......5.......7.82
 
38.6.......5.......1..7.89......5....9..1..7....4......76.9..8.......3.......7.12
 
38.6.......5.......6..2.71......5....2..1..8....4......16.8..7.......9.......7.42
 
38.6.......5.......9..7.42......5....2..1..9....4......48.9..1.......3.......7.62
 
38.6.......6.......2..7.41......5....9..1..7....4......48.2..5.......3.......7.92
 
38.6.......6.......9..8.75......5....4..1..3....4......35.9..8.......4.......7.62
 
38.6.......7.......5..9.86......5....6..1..9....4......94.5..1.......6.......7.32
 
38.6.......9.......4..7.12......5....7..1..8....4......15.8..9.......3.......7.42
 
39.6.......2.......1..3.87......5....3..1..6....4......64.9..3.......6.......7.52
 
39.6.......2.......1..8.75......5....7..1..8....4......38.5..7.......6.......7.92
 
39.6.......2.......4..3.85......5....6..1..9....4......15.6..3.......7.......7.82
 
39.6.......2.......5..3.18......5....3..1..6....4......85.6..1.......4.......7.32
 
39.6.......5.......6..2.81......5....2..1..3....4......17.3..4.......5.......7.62
 
39.6.......7.......6..4.82......5....8..1..6....4......46.8..1.......3.......7.92
 
39.6.......7.......6..8.52......5....2..1..6....4......85.6..1.......4.......7.32
 
39.6.......7.......6..8.52......5....2..1..6....4......85.9..1.......4.......7.32
 
39.6.......7.......6..9.12......5....2..1..6....4......85.6..9.......4.......7.32
 
31.6.......2.......5..9.78......5....9..1..6....4......75.6..3.......4.......7.92
 
31.6.......4.......5..9.28......5....7..1..3....4......38.5..9.......4.......7.62
 
31.6.......4.......7..3.95......5....6..1..3....4......98.5..1.......7.......7.42
 
31.6.......5.......9..7.18......5....8..1..7....4......76.8..1.......3.......7.92
 
31.6.......7.......9..2.85......5....3..1..9....4......84.9..1.......6.......7.32
 
31.6.......7.......9..8.52......5....2..1..9....4......35.9..1.......4.......7.62
 
32.6.......4.......6..8.17......5....7..1..8....4......85.9..1.......4.......7.52
 
32.6.......6.......1..8.95......5....9..1..2....4......58.3..1.......6.......7.42
 
32.6.......9.......8..7.15......5....7..1..3....4......15.8..7.......6.......7.82
 
34.6.......2.......6..7.89......5....7..1..6....4......95.6..7.......4.......7.32
 
34.6.......5.......8..7.12......5....7..1..3....4......16.2..4.......9.......7.82
 
35.6.......6.......7..4.98......5....2..1..7....4......48.2..6.......5.......7.12
 
37.6.......4.......1..8.52......5....2..1..8....4......47.5..9.......8.......7.62
 
37.6.......9.......8..2.71......5....2..1..8....4......16.8..7.......4.......7.32
 
38.6.......2.......9..7.41......5....7..1..9....4......45.8..3.......5.......7.82
 
38.6.......4.......2..8.45......5....9..1..6....4......15.6..9.......3.......7.82
 
38.6.......5.......9..7.61......5....2..1..7....4......67.2..8.......9.......7.32
 
38.6.......9.......2..3.51......5....3..1..6....4......17.5..8.......9.......7.32
 
39.6.......5.......2..7.46......5....7..1..9....4......86.9..4.......3.......7.12
 
39.6.......6.......4..2.81......5....7..1..2....4......85.4..7.......3.......7.42
 
39.6.......6.......4..8.52......5....2..1..9....4......18.6..4.......9.......7.32
 
39.6.......7.......1..4.28......5....8..1..9....4......46.3..1.......5.......7.62
 
32.6.......6.......4..9.53......5....3..1..7....4......98.3..1.......6.......7.42
 
32.6.......8.......6..9.17......5....9..1..3....4......85.3..9.......4.......7.62
 
37.6.......4.......1..8.52......5....2..1..8....4......47.5..3.......8.......7.62
 
37.6.......5.......1..8.46......5....6..1..8....4......28.9..7.......3.......7.52
 
38.6.......4.......1..9.37......5....9..1..8....4......35.8..6.......4.......7.12 | 	 
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Wed Jul 27, 2005 12:41 pm    Post subject:  | 
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                                thanks for the 125 !
 
Now I have 2 (42) which require backtracking with algo2 (algo1).
 
Yes, my hardness measure is not so good for humans to determine
 
how hard a problem will be for them to solve.
 
But for computers-solvers it could be useful. It's just the level of lookahead required.
 
I'm wondering which level we need for 16*16,25*25,... sudokus.
 
Well, I just tried 25*25 and it is already rather slow.
 
I didn't succeed to generate a 25*25 sudoku with my program.
 
 
 
here are the 42: (first 2 are "hardest")
 
 
38.6.......9.......2..3.51......5....3..1..6....4......17.5..8.......9.......7.32
 
6...4...3.1.....7...5...8.....5.2...3...9...2...1.3.....8...9...7.....5.2...3...4
 
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5.....
 
....3....93..6.8..56......4..2.16...85.47....6...29..37.....21.................59
 
....3....93..6.8..56......43.2.16...85.473...6...29..37.....21.................59
 
....7..9......8..4.42..1.7...4.....88..2.5..95.....7...7.6..13.2..8......6..3....
 
..12...6...9..8.4..5..4.9..73..8......5.3.1......6..34..3.2..9..2.8..5...9...14..
 
..26......9....4...1...9..7....46..5..4.9..8....71.3.48...31...3..98.......4...32
 
..3.5.4..7...6.....5.8...6.5....3..4.1..7..8.2..4....7.4...8.5.....4...9..6.1.2..
 
.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
 
3...6...5.2.....4...7...2.....6.7...9...8...6...9.1.....2...7...4.....1.6...5...9
 
4...1...8.5.....2...6...9.....9.2...8...5...3...1.8.....9...6...2.....5.1...7...4
 
6...7...9.1.....2...5...4.....1.2...9...8...6...6.9.....1...2...3.....4.7...5...8
 
8.2.....4.9......7..5..139..8..17......5.2..1.....8.36..71.....4...7....32...5...
 
9...7...4.1.....5...8...2.....8.9...7...4...6...2.7.....3...1...2.....8.6...9...7
 
31.6.......2.......5..9.86......5....6..1..9....4......94.6..7.......3.......7.12
 
31.6.......2.......6..7.59......5....9..1..7....4......78.9..4.......3.......7.12
 
31.6.......2.......6..8.37......5....3..1..6....4......75.3..9.......6.......7.42
 
31.6.......2.......7..3.89......5....8..1..7....4......97.8..3.......4.......7.62
 
31.6.......5.......2..9.56......5....6..1..8....4......38.6..9.......4.......7.12
 
31.6.......5.......8..3.47......5....2..1..3....4......37.2..1.......5.......7.62
 
31.6.......5.......9..7.82......5....8..1..7....4......74.9..3.......4.......7.12
 
32.6.......5.......6..8.71......5....8..1..3....4......16.3..8.......9.......7.62
 
32.6.......7.......1..8.37......5....7..1..2....4......86.2..9.......4.......7.12
 
34.6.......2.......6..9.83......5....8..1..7....4......75.8..1.......4.......7.62
 
34.6.......7.......2..8.57......5....7..1..2....4......36.2..1.......9.......7.82
 
37.6.......4.......1..3.62......5....2..1..3....4......65.2..8.......4.......7.12
 
37.6.......5.......2..8.69......5....6..1..8....4......98.2..6.......3.......7.12
 
37.6.......5.......6..2.19......5....2..1..6....4......38.6..1.......5.......7.32
 
38.6.......2.......7..3.51......5....9..1..6....4......18.6..3.......4.......7.92
 
38.6.......9.......4..7.12......5....7..1..8....4......15.8..9.......3.......7.42
 
39.6.......2.......1..8.75......5....7..1..8....4......38.5..7.......6.......7.92
 
39.6.......7.......6..4.82......5....8..1..6....4......46.8..1.......3.......7.92
 
39.6.......7.......6..9.12......5....2..1..6....4......85.6..9.......4.......7.32
 
32.6.......9.......8..7.15......5....7..1..3....4......15.8..7.......6.......7.82
 
34.6.......5.......8..7.12......5....7..1..3....4......16.2..4.......9.......7.82
 
37.6.......4.......1..8.52......5....2..1..8....4......47.5..9.......8.......7.62
 
37.6.......9.......8..2.71......5....2..1..8....4......16.8..7.......4.......7.32
 
38.6.......2.......9..7.41......5....7..1..9....4......45.8..3.......5.......7.82
 
38.6.......4.......2..8.45......5....9..1..6....4......15.6..9.......3.......7.82
 
39.6.......6.......4..8.52......5....2..1..9....4......18.6..4.......9.......7.32
 
37.6.......4.......1..8.52......5....2..1..8....4......47.5..3.......8.......7.62 | 
                         
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                 |  MadOverlord
 
  |  | Joined: 01 Jun 2005 |  | Posts: 80 |  | :  |  | Location: Wilmington, NC, USA |   Items |  
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                                 Posted: Tue Aug 09, 2005 12:11 pm    Post subject:  | 
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                                | 60 deduction passes in Susser, lots of Bingo. | 
                         
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                 |  Sambor
 
  |  | Joined: 07 Nov 2005 |  | Posts: 1 |  | :  |   |   Items |  
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                                 Posted: Mon Nov 07, 2005 11:26 am    Post subject:  | 
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                                 	  | tilps wrote: | 	 		  Since we're here
 
1.6.3 - current hardest
 
 
 	  | Code: | 	 		  ..3|.5.|4..
 
7..|.6.|...
 
.5.|8..|.6.
 
-----------
 
5..|..3|..4
 
.1.|.7.|.8.
 
2..|4..|..7
 
-----------
 
.4.|..8|.5.
 
...|.4.|..9
 
..6|.1.|2..
 
 | 	 
  | 	  
 
 
Hmm, I have tried this but didn't get far. So I tried to check it with various solvers, and they all claim that there is no solution. So is it correct? Is your solver doing something no one else do? Just wondering... | 
                         
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Mon Nov 07, 2005 5:33 pm    Post subject:  | 
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                                 	  | Sambor wrote: | 	 		   	  | tilps wrote: | 	 		  Since we're here
 
1.6.3 - current hardest
 
 
 	  | Code: | 	 		  ..3|.5.|4..
 
7..|.6.|...
 
.5.|8..|.6.
 
-----------
 
5..|..3|..4
 
.1.|.7.|.8.
 
2..|4..|..7
 
-----------
 
.4.|..8|.5.
 
...|.4.|..9
 
..6|.1.|2..
 
 | 	 
  | 	  
 
 
Hmm, I have tried this but didn't get far. So I tried to check it with various solvers, and they all claim that there is no solution. So is it correct? Is your solver doing something no one else do? Just wondering... | 	  
 
 
exactly one solution. You tried the wrong solvers | 
                         
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                 |  Ruud Site Admin
   |  | Joined: 17 Sep 2005 |  | Posts: 708 |  | :  |  | Location: Netherlands |   Items |  
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                                 Posted: Mon Nov 07, 2005 7:13 pm    Post subject:  | 
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                                 	  | Quote: | 	 		  | exactly one solution | 	  
 
Correct. Worthy candidate for the top871 though... | 
                         
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                 |  dukuso
 
  |  | Joined: 14 Jul 2005 |  | Posts: 424 |  | :  |  | Location: germany |   Items |  
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                                 Posted: Tue Nov 08, 2005 8:28 am    Post subject:  | 
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                                 	  | Ruud wrote: | 	 		   	  | Quote: | 	 		  | exactly one solution | 	  
 
Correct. Worthy candidate for the top871 though... | 	  
 
 
 
rating is 385,  it's #723 in top862 | 
                         
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                 |  gsf
 
  |  | Joined: 18 Aug 2005 |  | Posts: 411 |  | :  |  | Location: NJ USA |   Items |  
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                                 Posted: Tue Nov 08, 2005 12:04 pm    Post subject:  | 
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                                 	  | dukuso wrote: | 	 		  thanks for the 125 !
 
here are the 42: (first 2 are "hardest") | 	  
 
 
the 125 had some equivalent dups and these may have filtered into the 42
 
here are the first and dup occurrences, preceded by the canonical solution
 
 	  | Code: | 	 		  
 
123456789456789132789231546247318695361925478598647213674892351835164927912573864
 
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5.....
 
.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
 
123456789456789231789132465238915674574268913961374852312697548695841327847523196
 
38.6.......2.......9..7.41......5....7..1..9....4......45.8..3.......5.......7.82
 
38.6.......4.......2..8.45......5....9..1..6....4......15.6..9.......3.......7.82
 
123457689456189237789236415215764893374598162698312574567843921842971356931625748
 
31.6.......2.......5..9.86......5....6..1..9....4......94.6..7.......3.......7.12
 
31.6.......2.......6..7.59......5....9..1..7....4......78.9..4.......3.......7.12
 
123457689456189237789263154295874316314526978867391542572618493638945721941732865
 
31.6.......2.......7..3.89......5....8..1..7....4......97.8..3.......4.......7.62
 
37.6.......5.......2..8.69......5....6..1..8....4......98.2..6.......3.......7.12
 
123457689456189237789623415234716958517894326698532741371948562862375194945261873
 
32.6.......5.......6..8.71......5....8..1..3....4......16.3..8.......9.......7.62
 
37.6.......9.......8..2.71......5....2..1..8....4......16.8..7.......4.......7.32
 
123457689456189327789263145275641938638972514914538276362894751547316892891725463
 
31.6.......5.......8..3.47......5....2..1..3....4......37.2..1.......5.......7.62
 
37.6.......4.......1..3.62......5....2..1..3....4......65.2..8.......4.......7.12
 
123457689456189327789263451278635914391842576564971832612598743847316295935724168
 
39.6.......2.......1..8.75......5....7..1..8....4......38.5..7.......6.......7.92
 
39.6.......7.......6..4.82......5....8..1..6....4......46.8..1.......3.......7.92
 
123457689456189372789263154238791546574638921691542837347816295815924763962375418
 
31.6.......5.......2..9.56......5....6..1..8....4......38.6..9.......4.......7.12
 
31.6.......5.......9..7.82......5....8..1..7....4......74.9..3.......4.......7.12
 
123457689456189723789362154248916375395874261617523498532648917874291536961735842
 
....3....93..6.8..56......4..2.16...85.47....6...29..37.....21.................59
 
....3....93..6.8..56......43.2.16...85.473...6...29..37.....21.................59
 
 | 	  
 
 
also, this one (one of the dups) only needs the basic FN constraints and box claims to solve:
 
 	  | Code: | 	 		  | ....3....93..6.8..56......4..2.16...85.47...6...29..37.....21.................59 | 	 
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