FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in          Games  Calendar Log in to check your private messages    Minimum clues for a samurai?          Sudoku Programmers Forum Index -> Exotic sudoku View previous topic :: View next topic   Author Message garthd Joined: 29 Apr 2006 Posts: 32 : Items Posted: Tue Feb 23, 2010 11:25 am    Post subject: Minimum clues for a samurai? It appears that the minimum number of clues for a standard 9x9 sudoku that still results in a single valid solution is 17 clues (on the assumption that no one has - as yet - found a valid 16 clue puzzle with a single solution). Does anyone have views on the minimum number of clues for a samurai puzzle? Back to top m_b_metcalf Joined: 13 Mar 2006 Posts: 210 : Location: Berlin Items Posted: Tue Feb 23, 2010 2:00 pm    Post subject: Re: Minimum clues for a samurai? garthd wrote: It appears that the minimum number of clues for a standard 9x9 sudoku that still results in a single valid solution is 17 clues (on the assumption that no one has - as yet - found a valid 16 clue puzzle with a single solution). Does anyone have views on the minimum number of clues for a samurai puzzle? Since this discussion I haven't really thought about it. Regards, Mike Metcalf P.S. Upon reflection, I suppose that one could imagine 4 outside puzzles each with 16 clues and a central one with 5. P.P.S. I now see that the puzzle I posted there with only 5 clues in the central box is not minimal. Here is a minimal version: Code:  . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . 1 . . . . . . 1 . . . 8 4  . . . 1 2 3 4 . 5 . . . . . 9 . . . 2 . .  . 1 . . . 5 . . 7 . . . . . 5 . . 2 . . 9  . . . . . . . 2 . . . . . . 7 . . . . 4 .  . . 8 . 7 4 3 . 6 . . . . 3 . . . 4 5 . 2  . 3 . . 4 8 . . . . . . . . . . . 6 . . .  . 4 . 6 . 7 . . . . . . . . . . 2 3 . 7 5  9 . 1 . . . . . . . . . . . . 8 . 5 1 . .  . . . . . . . . . 3 7 . . . . . . . . . .  . . . . . . . . . . . 6 . . . . . . . . .  . . . . . . . . . . 2 4 . . . . . . . . .  . . . . . . . . . . . . . . . 1 . . 7 . 9  . 5 . . . 7 . . . . . . . . . 2 8 . . 5 .  . 8 9 1 4 . . . . . . . . . . . . . . . 3  . 1 . . . 6 . 9 . . . . 1 . . . 4 6 . . 7  . . . 7 9 . . 3 . . . . . . . . . . . . .  . . . . . . . . . . . . . 8 9 3 1 . . . 4  . . 1 8 6 . . . . . . . . 4 . . 5 3 . . .  . . 3 . 2 4 8 5 . . . . . 9 3 . . 4 . . 2  . . . . . . 2 . . . . . . . . . . . . . . Code: .................1...1234.5.1...5..7.......2...8.743.6.3..48....4.6.7...9.1...... ............1...84..9...2....5..2..9..7....4..3...45.2.....6.......23.75...8.51.. ..............................37.........6.......24.............................. ..........5...7....8914.....1...6.9....79..3............186......3.2485.......2.. ...1..7.9...28..5.........31...46..7..........8931...4.4..53....93..4..2......... Back to top m_b_metcalf Joined: 13 Mar 2006 Posts: 210 : Location: Berlin Items Posted: Wed Feb 24, 2010 10:31 am    Post subject: Re: Minimum clues for a samurai? garthd wrote: It appears that the minimum number of clues for a standard 9x9 sudoku that still results in a single valid solution is 17 clues (on the assumption that no one has - as yet - found a valid 16 clue puzzle with a single solution). Does anyone have views on the minimum number of clues for a samurai puzzle? Just for fun, I made a stab at a small number of clues. The result is 4 x 14 + 20 (=76). It's based on a 17-clue puzzle from Gordon Royle's collection and is rotationally symmetric. Regards, Mike Metcalf Code:  . 2 . . . . . . . . . . . . . . . . . 8 .  . 8 1 . . . . . . . . . . . . . . . 7 2 .  . . . 4 . . 5 . . . . . . . 3 . . 9 . . .  . . . 9 . . . . . . . . . . . . . 6 . . .  . . . . . . . 2 8 . . . 2 8 . . . . . . .  7 . . 5 . 6 . . . . . . . . . 4 . 3 . . 5  5 . . . . . . . . 8 . 2 . . . . . . . . 3  3 . . . . . . . . 5 . 1 . . . . . . . . 6  . . . . 1 . . . . . 9 4 . . . . 7 . . . .  . . . . . . 4 . . . . . . 3 5 . . . . . .  . . . . . . . . 6 . . . 1 . . . . . . . .  . . . . . . 1 3 . . . . . . 7 . . . . . .  . . . . 2 . . . . 9 1 . . . . . 1 . . . .  8 . . . . . . . . 2 . 3 . . . . . . . . 3  1 . . . . . . . . 4 . 8 . . . . . . . . 5  3 . . 1 . 5 . . . . . . . . . 6 . 5 . . 7  . . . . . . . 4 9 . . . 8 2 . . . . . . .  . . . 8 . . . . . . . . . . . . . 9 . . .  . . . 6 . . 1 . . . . . . . 5 . . 4 . . .  . 9 2 . . . . . . . . . . . . . . . 1 8 .  . 4 . . . . . . . . . . . . . . . . . 2 . Code: .2........81.........4..5.....9............287..5.6...5........3............1....  tl .......8.......72...3..9........6...28..........4.3..5........3........6....7....  tr ...8.2......5.1.......94...4......35..6...1..13......7...91.......2.3......4.8...  m ....2....8........1........3..1.5..........49...8........6..1...92.......4.......  bl ....1............3........5...6.5..782............9.....5..4.........18........2.  br Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         Sudoku Programmers Forum Index -> Exotic sudoku All times are GMT Page 1 of 1   Jump to: Select a forum Sudoku----------------Solving sudokuSetting sudokuProgramming sudokuThe mathematics of sudokuExotic sudoku Library----------------PuzzlesSoftwareSudoku elsewhere Not sudoku----------------Random thoughtsForum feedback  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum   Powered by phpBB © 2001, 2005 phpBB Group Igloo Theme Version 1.0 :: Created By: Andrew Charron