## Unique-solution puzzles that cannot be solved with logic

Advanced methods and approaches for solving Sudoku puzzles
George wrote:In the above web site, it suggests that "there are examples of 17-hint uniquely completable Sudoku puzzles, but no known 16-hint examples." What that means is that 17 initial numbers are the minimum required to give a unique solution. But, have you considered what should be the minimum initial numbers given such that bifurcation (including forcing chain) is not required to solve it.

I think I've seen 17 and 18 puzzles that would be classified as "easy". I don't have time to look for them but I can give you one of the few 19-clues easy puzzles I have generated.

Code: Select all
`....3.7.5.316.....2.............5.....7.1.9.....4.............4.....782.7.6.9....`
Nick70

Posts: 156
Joined: 16 June 2005

simes wrote:It's still 17. Some (if not most) of those examples can be solved logically - even excluding forcing chain.

Simes

I am not disputing the existence of the 17s. There may even be 16s or even 15s. But, they must be at the tail end of the natural distribution. Can you send me one or two if you happen to come across them.

Cheers
George
George

Posts: 20
Joined: 20 July 2005

I can, but I got them from here.
simes

Posts: 324
Joined: 11 March 2005
Location: UK

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