- Code: Select all
`1) ...5..7...2..6..4...6..1..39..2..4...3.....1...7..3..81..7..6...5..4..7...9..8...`

2) .....1....1..2..3.4..5..1....6..7..3.8..3..1.2..9..4....9.....2.7..8..6.8..3..5..

3) ..1.....2.3..4....5..6..3....7..8..1.6..1..3.1..9..8....5..9..4.8..5..7.2..1..9..

4) 7.....4...2..7..8...3..8..9...5..3...6..2..9...1..7..6...3..9...3..4..6...9..1..5

#1) is the "12 step" 144: tso #7/31

#2) is Ocean's 11 step 165: Ocean #1/3

#3) is Ocean's 11 step 167: Ocean #3/3

#4) is the 10 step top1465 #77 "the toughest known"

Just for comparision purposes, here are ratings of these four puzzles from other sources:

Suexrat9 (gives slightly different ratings each time it's run):

http://magictour.free.fr/sudoku.htm1) 694

2) 964

3)1043

4) 867

Into Sudoku 1.83:

http://www.intosudoku.com/1) 11922

2) 21007

3) 24832

4) 12465

SudoCue 1.3.0.0:

http://www.sudocue.net/1) Total score: 21638, solving rounds: 106

2) Total score: 32027, solving rounds: 122

3) Total score: 14370, solving rounds: 82

4) Total score: 13047, solving rounds: 86

Sudoku Explainer 1.1:

http://diuf.unifr.ch/people/juillera/Sudoku/Sudoku.html1) 9.4 (out of 10)

2) 9.5

3) 9.9 (!)

4) 9.8

[edit]

Susser 2.5.4 does not solve any of these at default settings.

http://www.madoverlord.com/projects/sudoku.t1) Does not complete, solving only a single cell.

2) Does not complete, solving only a single cell.

3) Does not complete, solving only two cells.

4) Does not complete, solving only a single cell.

Adding "aggressive forces" and pins solves 1, 2 and 4, but NOT 3. Adding "sets and intersections" finally solves #3.

(As to why earlier versions of Susser might solve a puzzle when a newer version won't, my guess is that as he added more capabilities, the new version's defaut settings probably did not include the same heuristcs options as the old one.)

What other software will give numerical ratings similar to these?

My search found that the fewer clues a diagonal pattern had, the higher percentage of harder puzzles there were at various levels -- but at the same time, it was several times more difficult to find a puzzle with each fewer clue. I'd assume that the 18 cell diagonal patterns with 2 clues per row, column and box hide the hardest possible puzzles -- but they may be *very* hard to find with out smarter searches or by direct construction as they may be extremely rare -- the toughest 27's will be astronomically more common.

(Do some of the 17's fit the diagonal pattern and if so, could *they* be the toughest? This should be an easy enough test since there already is a large database.)

Viggo's comments on this subject earier in this thread seem logical to me.