The New Sudoku Players' Forum

[jamesmcskeane]

Hi,
I am doing a study into the game of Sudoku, i see that some puzzle's can be simple while others hard, the hard ones normally find the form of 50 50s where you get to a point where there can be two possible solutions to a square, but what is normally the case, there is only really one there other will just take you down the wrong path!

My query is this, at what point is their only one possible solution? Can any give me a puzzle with a large amount of numbers and still have two possible solutions?

[CathyW]

If you have a valid sudoku puzzle there will only ever be one solution, it's just a question of working it out using the various techniques available.

If a puzzle has more than one solution it is generally considered to be invalid. Sorry I don't have an example to post but I expect someone else will.

[PaulIQ164]

Theoretically, a puzzle could have as many as 77 clues and still have two solutions. Here's an example:

Code: Select all

864¦732¦159
137¦659¦284
529¦148¦637
---+---+---
275¦816¦943
398¦42 ¦ 61
641¦39 ¦ 28
---+---+---
953¦274¦816
716¦583¦492
482¦961¦375

Obviously this is a pretty stupid puzzle, but it goes to show that there's no particular relation between number of clues and he uniqueness or otherwise of the solution.