The New Sudoku Players' Forum

[Mathimagics]

I would appreciate it if someone could help me identify the minimum clue counts for these two cases (standard Sudoku):

Code: Select all


A:
516783924
834295617
927164538
763851492
285349761
491672385
358426179
642917853
179538246

B:
586192347
741863925
923475618
819526473
634781259
257349861
372618594
495237186
168954732


I make it 21 in each case, but my method is rather crude, I'm hoping that somebody has better software for doing reduction testing.

[Afmob]

So far, I've found a valid 19 clue puzzle for each grid.

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586...........39...2.....1....52...3.....1.....7...8.....6.8......2.....1.....73.
5...8...4.........92..6..3......1.9..85.4.7.............8.2.......9...53.7.......


I've used the subset method described in this thread to get a rough overview on the distribution of the minimal puzzles (with regards to clue count) where I found 19 clue puzzles for grid B and 20 clue puzzles for grid A. Afterwards, I tried to hit the UA (unavoidable sets) of grid A with 19 clues and found a valid puzzle. I don't know whether they also have a valid 18 clue puzzles because I haven't found one so far. I would guess that grid B is more likely to have one.

Edit: Both grids have no valid 18 clue puzzle. Therefore 19 is indeed the minimum clue count.

[Mathimagics]

Thank you!

These are the orthogonal pair of grids that are the solution to the puzzle here, where the minimum clue count is now down to 23.