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 🤣

Can you share a pic with options noted?

If nothing comes of that (usually I have made a tiny error or missed something), then I do a little trial and error using the bottom corner of each cell. Usually it goes impossible within a few number placings and gets me started.

If you’re doing advanced techniques like x wing and y wing, you need to write the notes down to spot them.

I like to think I'm pretty good at these, faster than 99% at extreme level my app flatters me but I can't solve this one.

5 below the 9 in the bottom left block.

How are you getting on with it @LindorDoubleChoc?

Thanks everyone for trying to help me

Morning BIWI! It was frying my poor old brain last night so I left it and made dinner and watched Black Doves instead.

I'm going to revisit today after work. In particular I'm intrigued by this contribution:

Rows 5 and 9 both have 4 in only either column 3 or 5, so 4s can't appear in those columns in any other row.

I'm not sure what it means but will tackle it later and report back.

I don't think that will really help!

If you put all the possible numbers in, you'll see that there's a triple in the top, right-hand corner.

This might help you:

I think I've got the solution but only by trial and error. Shall I post it?

I finally completed it too. I filled in all the options and did trial and error. Firstly I used 5 in top left cell and it went wrong. Then I used 4 in it and was able to complete the whole puzzle.

I don't know if there is another method other than trial and error when you get to this point!

@LindorDoubleChoc appreciate that clue may seem complicated but it was the only way I could get a logical next step forward rather than a guess or trial and error.
So this should help if you are wanting to know how to logically work it out. I've only seen answers with no indication how it was confirmed in other clues.

From BIWIs example image with the filled in notes:

1. Knowing that column 1 in the first block must be 4, 5 and 7 (unknown order yet), you can eliminate those from the other cells in that block
2. You then know that for row 3 column 2 and 8 are either 6 or 9, which allows you to eliminate 6 from row 3 column 4.
3. You then know in column 4, row 3 and 8 are either 4 or 7 so you can eliminate 4 and 7 from other rows in that column.
4. This uses the x-wing strategy and it's the clue given previously:

" Rows 5 and 9 both have 4 in only either column 3 or 5, so 4s can't appear in those columns in any other row." This helps you eliminate the 4 in row 1 column 5. This then leaves row 3 column 4 as the only 4 in that box, giving you that number and helping you continue on.

Thanks all! I'm at work but will look properly this evening. I think I don't know what the x-wing strategy is @boatyroo - will see if I can work it out from your latest post.

I promise to report back.

Think I'm convinced that top right is 5,but I need to check again!

If you fill in all the possible numbers, as I have in the photo up thread, there's no need for trial and error. It's logical working out.

@LindorDoubleChoc as PP have said, start with the top left-hand square, by removing the 5s in column 2 and 3. 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.

Sorry @LindorDoubleChoc just spotted that I made an error in the photo where I've filled in possible numbers. C4/R3 can't have a 2 as a possible, as there's already one in that row, at C9/R3. Apologies

@BIWI

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.

I don't see how this follows? Why can you delete the 9 from C8R2?

Because c7/r1, c9/r1 and c8/r2 have to be either 3, 5 or 6. Therefore the only place left for a 9 is c8/r3.

No, C8R2 can also be a 9.
And C8R3 can be a 6. So you don't have a triple, it's a quadruple. It's only a triple if you make it so by randomly deleting the 9 for no logical reason.

No, it's a hidden triple.

Why can't C7R1 and C9R1 be 3 and 5, and the other two squares be 6 and 9 in any order? Without using trial and error.

Hidden triples only occur when those 3 numbers are in no other squares. The 6 is also in C8R3 so it isn't a triple.

"Hidden triples" applies when three cells in a row, column, or 3x3 block contain the same three Notes. These three cells also contain other candidates, which may be removed from them.

From sudoku.com

I think you have interpreted this incorrectly.

A hidden triple is when you have the same three digits (or a subset of them) as candidates in exactly three cells within the same row, column, or block.

The three numbers in the triple cannot occur in any of the other squares. It has to be the only three squares where those three numbers can go. in this case, that isn't true. The 6 can also go in another square.

I think the OP and some other solvers may benefit from studying examples of all the solving techniques on the many sudoku helper websites.
Trial and error will never be needed to find a solution, they can all be solved using logic and method.

Unless it's a bad puzzle, which does happen sometimes.