Hardest Sudoku I've ever seen

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[bojtun]

I'm not very good at these - I always try them on a computer, without writing down dual/triple possibilities (which is probably why I'm not good at these) - but I actually did it on paper ... answer sent.

Got stuck in one spot for a few minutes.

[durron597]

[ QUOTE ]
I'm not very good at these - I always try them on a computer, without writing down dual/triple possibilities (which is probably why I'm not good at these) - but I actually did it on paper ... answer sent.

Got stuck in one spot for a few minutes.

[/ QUOTE ]

your answer is correct

it definitely does require guessing, you said so yourself... this is probably the puzzle that requires guessing the earliest i've ever seen

[Stephen H]

This puzzle does not require guessing. A few applications of X-wing, Y-wing, and simple coloring can resolve this - I tossed it into a Sudoku Solver and it didn't even get to the uglier solving methods like Finned X-wing and MultiColoring etc, and it certainly didn't get into the "Trial and Error" (or guessing) methods.

[durron597]

[ QUOTE ]
This puzzle does not require guessing. A few applications of X-wing, Y-wing, and simple coloring can resolve this - I tossed it into a Sudoku Solver and it didn't even get to the uglier solving methods like Finned X-wing and MultiColoring etc, and it certainly didn't get into the "Trial and Error" (or guessing) methods.

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sudokusolver.co.uk definitely got into guessing

[Stephen H]

www.scanraid.com/sudoku.htm did not - that's my solver of choice when playing with soduku solvers.

[Nicholasp27]

so far i haven't done any guessing; i'll let u know if i had to when finished

[kokiri]

doesn't colouring imply guessing?

i mean that i would only use a colour change if i'm stuck, but have a cell that is either 5 or 9. Then i try 5 in another colour until i hit a contradiction and, if so, switch back to 9. I view that as guessing.

Playing around with this one, it occurred to me that this sort of guessing/scenario testing, is probably much quicker than my usual technique. Usually I go in a cycle that runs:

1) do all the obvious deductions
2) do some less obvious ones
3) get stuck and hunt around for a new complicated deduction.

Where step 3) is way the slowest. By replacing 3) with 'choose a 50% shot and see if it leads to a contradiction', as long as you have an audit trail, the slowest part of the techniques is removed, at the expense of potentially being wrong.

i hate these things with a passion.

[Stephen H]

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doesn't colouring imply guessing?

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That's a long discussion but I can see the complaint. I turned off coloring as an option and it solved it just using Xwing and Ywing deductions on top of the basic stuff.

Having to do multiple Xwings to solve a Sudoku is pretty obnoxious and easy to miss so I would definately classify this as a darn hard Sudoku.