What is the minimum quanity of numbers a sudoku puzzle must have at start and yet still only have one solution

mockneysparra asked:

If you attempted to solve a sudoku puzzle that only had one blank square then it would be the easiest sudoku possible. On the other hand, a sudoku puzzle with 80 blank squares is almost equally as easy because there are thousands of possible solutions. There must, therefore be an optimum quantity of “starter numbers” that constitute the hardest possible sudoku puzzle by having only one possible solution and yet having the minimum of clues.

Additionally i would love to see the maths behind the answer.

Comments (3) Posted in Other - Games & Recreation

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3 Responses to 'What is the minimum quanity of numbers a sudoku puzzle must have at start and yet still only have one solution'

emma - October 27th, 2008 at 6:26 pm
hmm good question but no idea – i guess there needs to be at least one number in each square – so a minimum of 9 numbers to start?
giz - October 31st, 2008 at 12:54 am
don’t know for sure but in my book the minimum number in the hard section is 20
xwdguy - October 31st, 2008 at 11:06 am
17, possibly (but not probably) 16.