The New Sudoku Players' Forum

[m_b_metcalf]

Here is a 17-clue standard puzzle:

Code: Select all

 . . . . 1 2 3 . .
 . . 4 . 3 . . 5 .
 . . . . 6 . . . .
 . . . 7 . . . . 1
 8 . 5 9 . . . . .
 . . . . . . . . 6
 . . . 3 . . . 4 .
 2 6 . . . . . . .
 . . . . . . . . .   ED=1.5/1.5/1.5


However, its solution grid is that of an x-sudoku, thus allowing a clue to be removed when solving as an x-sudoku:

Code: Select all

 . . . . 1 2 . . .
 . . 4 . . . . 5 .
 . . . . 6 . . . .
 . . . 7 . . . . 1
 8 . 5 9 . . . . .
 . . . . . . . . 6
 . . . 3 . . . 4 .
 2 6 . . . . . . .
 . . . . . . . . .   ED=2.9/1.2/1.2


Here's a short list of some more:

Code: Select all

17 clues:
....123....4.3..5.....6.......7....18.59.............6...3...4.26................   ED=1.5/1.5/1.5   
.1....2.3...45.............6......5..7...3....5............2...4...6..8...3....41   ED=1.7/1.2/1.2   
..1.......2.....3....4..56..4........6.7..........38.18...91..........4.....2....   ED=2.0/1.2/1.2   
1.......2..34........5.......1...3.674...............88...2........1..4..5...9...   ED=2.6/1.2/1.2   
..1..2......3........4..56.........6.7.....4...2.51....6..7.....4............81..   ED=6.6/1.2/1.2   
....1....2...3..........4.53..26.....5......7.........4.....63......52...8.7.....   ED=6.7/1.2/1.2   
.1...2.......3...45......1..64...........72..83.......1..4.9..........6.......3..   ED=7.1/1.5/1.5   


and their reduced variations (in order):

Code: Select all

x-sudoku versions (15 or 16 clues):
....12.....4....5.....6.......7....18.59.............6...3...4.26................   2.9/1.2/1.2      15 clues           
.1....2.....45.............6......5..7...3....5............2...4...6..8...3....41   4.1/1.2/1.2                 
..1..................4..56..4........6.7..........38.18...91..........4.....2....   8.1/1.2/1.2      15 clues           
........2..34........5.......1...3.674...............88...2........1..4..5...9...   2.9/1.2/1.2                 
..1..2......3...........56.........6.7.....4...2.51....6..7.....4............81..   2.9/1.2/1.2                 
....1....2...3............53..26.....5......7.........4.....63......52...8.7.....   7.8/1.2/1.2                 
.1...........3...45......1..64...........72..83.......1..4.9..........6.......3..   2.0/1.5/1.5   

two with only 15 clues. What's the lowest number of clues that such a puzzle may have?

Regards,

Mike

[m_b_metcalf]

Code: Select all

.1.............74..5.9............3..9....81.6...24......1..5....4..3...2........   
.1.............7...5.9............3..9....81.....24......1..5....4..3............  14 clues     

[Hajime]

On Ruud's Website via here there is a list of SudokuX with 12 clues.
The first 12 clue SudokuX is
000000000000000000000000000000000000000000001002340000050006000000720060804000005
Question is: Is this is extendable to 17 clues and no X ? Or 1 of the other 500.000+ ?

[m_b_metcalf]

On Ruud's Website via here there is a list of SudokuX with 12 clues.
The first 12 clue SudokuX is
000000000000000000000000000000000000000000001002340000050006000000720060804000005
Question is: Is this is extendable to 17 clues and no X ? Or 1 of the other 500.000+ ?

or, solve the 500,000 puzzles, remove the isomorph solution grids, look for 17s. I pass.

Mike