Need help or a clue in my super fiendish sudoku puzzle please

[LindorDoubleChoc]

Been stuck on this one for days! Has anyone got a hint they can give me? I'm going to be VV embarrassed if it turns out to be something obvious 🤣

Thank you! This is the point I missed and it enabled me to solve it without trial and error. I can rest now 😂

Done it!!!!

Thanks to boatyroo for this hint which made the rest all fall into place !

LindorDoubleChoc can I ask where you got this puzzle? I really enjoyed the difficulty level (I normally doing The Guardian expert level)

I’ve just had a quick look at the solving techniques on that website that was linked. I’ve only skimmed it, but forcing chain and nishio methods sound just like what I would consider to be “trial and error” I.e. you test one of the candidate digits by following the logic through to see if it’s a valid solution. How does that differ from trial and error? Have I missed something?

ive looked through the website and I think forced chaining is more like -

cell (1) has only two options. try option 1 and work out what happens in the rest of the grid. you get a nice solution for cell (2) somewhere else in the grid. Now try option 2 in cell(1) and work through and find the SAME solution for cell (2). So you still don't know which is the correct option for cell (1) but you now have a definite solution for cell 2.

but in the example for this suduko, you have to pick one thing for cell (1) and then work through 3 steps to get to the cell (2) solution and then do it all again. how anyone would know which cells to target for this very convoluted method is beyond me.

I have finally solved it, but had to use what I call trial and error.

I got as far as OP did, and then highlighted cells in red where only 2/3 possible answers.

I knew 5 could only go in row 1 column 9 or row 2 column 8.

I tried 5 in row 2 column 8 first and ended up going wrong, so went back and put 5 in row 1 column 9. That worked. It's not an elegant way of doing it, but sometimes it's the only way I know how to solve it.

You could just add the numbers anywhere; no one checks them ;-)

😂true!

I have done this before when I’ve got horribly stuck, I filled the squares in randomly so that I could never go back to it!

Can I just say I’ve really enjoyed this thread - OP post another one you’re stuck on.

@parietal that does sound way too complicated!

I also have to say, though, that this puzzle didn't need trial and error to be solved.

... but what's been really interesting is seeing how different people use different techniques.

Yep. Still stuck!! 🙄I'm refusing to do any sort of trial and error technique, I'll put a great big cross through the whole lot with a black sharpie before I go down that route.

@HighburyLass it's from an old Times (as in The Times newspaper) book. I've had a look and you can buy single volumes of these super fiendish ones if you're up for it.

I can't see the argument for "this helps you eliminate the 4 in row 1 column 5" in boatyroo's hint which you quoted, hence still stuck!

Why don't you post a photo of how far you've got @LindorDoubleChoc?

Not made a move since first picture 😱.

I've pencilled in all the options but no further forward. I might give this one the heave-ho.

I did post upthread some answers - but reading back you said you didn't want those.

... but here's how to get started @LindorDoubleChoc

as PP have said, start with the top left-hand square, by removing the 5s in column 2 and 3. (Because column one can only be 4, 5 or 7, therefore none of those numbers will appear elsewhere in that square.). Then remove the 7s from column 3 and column 2.

Next go to the top right-hand square, where you can see that there are triples - 356, 356, 3569, 69. You can delete the 9 from column 8, row 2 - which means that column 8 row 3 must be a 9.

Now go back to the top left-hand square. Column 2 row 3 has two possibles, 6 and 9 (as you've deleted the 7, because that has to be in column 1). But it can't be 9, because you've just put that into column 8 row 3 - therefore column 2, row 3 has to be a 6.

@peekaboopumpkin posted a clearer explanation of the solution I posted about.

I'm sorry but as pointed out before, this is not correct, you can't logically delete this 9 at this point, it's absolutely not a hidden triple:
"Next go to the top right-hand square, where you can see that there are triples - 356, 356, 3569, 69. You can delete the 9 from column 8, row 2 - which means that column 8 row 3 must be a 9."

And I do appreciate, it is a 9, but that's just luck adding it at that point.

If you want to solve it I really recommend putting your numbers in the website I posted before and it will show and explain the x-wing tip

I started to draw all this out and it seems that the best way forward is to work out the top three in column A (the first column). Possibly the only way is to draw out all the options and work from there, but at least with the only options being pairs, and solving one would give you the other two numbers, that seems the best starting point.

I have cheated and run it through a sudoku solver so it can be done. I am going to look back at the hints as I only got as far as filling in the cells mentioned.

^ The hint was to start in that part of the puzzle and eliminate all the 4s 5s and 7s from the remainder of that particular square/section.
However, it didn't explain WHY it was what it ended up being.

Once you've sorted out A1,A2 and A3 then you can solve D3, and hopefully make some progress.

Ok, after putting all possible numbers in all possible empty squares, the breakthrough was that Row 2 (from the top) column 2 and column 8 only contained 6 & 9. From there I was able to solve the whole puzzle without any guessing. (Looks like I'm agreeing with BIWI).

I think you mean row 3 not row 2 @YarkYark ?

I'm afraid I still don't see how to solve the next clue. In row 3, columns 2 and 8 are 6 or 9, and columns 1 and 4 are 4 or 7. So that's a stalemate.

I'm going to boost myself with a cup of tea and look at @boatyroo 's posts and the mysterious x-wing theory next.

I've solved it, using one hint, to ascertain one square, from the sudoku solver (as per my earlier posts)