The New Sudoku Players' Forum

[Sixteen]

Hi, I'm new, and I have a question about Sudoku.
I know that the least numbers needed to have one solution is 17, but what is the least amount of numbers to have 2 solutions? Or the most numbers to have 2 solutions?

[JPF]

Hi Sixteen, welcome to the forum.
There is no certainty about 17, just a conjecture.
See here for the answers :

16 clues :

Code: Select all

 5 . 2 | . . . | 4 . .
 . . . | 7 1 . | . . 3
 . . . | . . . | . . .
-------+-------+-------
 . . . | . . 4 | 6 . .
 . 7 . | 2 . . | . . .
 . 1 . | . . . | . . .
-------+-------+-------
 6 . . | . . 2 | . . .
 . . . | . 3 . | . 1 .
 4 . . | . . . | . . .


77 clues :

Code: Select all

 1 5 9 | 2 8 6 | 4 7 3
 2 3 7 | 1 5 4 | 8 9 6
 4 8 6 | 3 9 7 | 5 2 1
-------+-------+-------
 9 1 2 | 8 4 3 | 7 6 5
 3 4 5 | . . 9 | 1 8 2
 6 7 8 | 5 2 1 | 3 4 9
-------+-------+-------
 8 6 1 | 4 3 2 | 9 5 7
 5 9 3 | . . 8 | 2 1 4
 7 2 4 | 9 1 5 | 6 3 8


These 2 puzzles have 2 solutions.

JPF

[ab]

please let us know if you find a 15 clue puzzle with just two solutions. You could then add one clue and have a 16 clue valid puzzle