Х-wing - an Advanced Sudoku technique

In this video you'll learn how to use the Х-wing strategy in a Sudoku game!
"Х-wing" is an advanced Sudoku technique, which is based on two parallel rows or columns. You can ignore the 3x3 blocks as they aren't involved in this strategy.
This is a rather difficult Sudoku strategy. But knowing tricks such as Х-wing will help you solve Sudoku much faster.
Watch the video, train your brain and have fun!
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[@genevievearchbaker8604]

For those who dont understand why these rows were picked: its because these 2 rows both only have 2 spots where one can put a 4. These 4 spots where you can put a 4 form a rectangle. It doesn't matter whether its a row or column, the important part is that both rows/columns only have 2 spots where a particular number fits. You cant use a row and a column though, its either 2 rows or 2 columns. Some rows I see mentioned here in the comments: - row 1 can have a 4 literally anywhere - row 2 can have a 4 literally anywhere like row 1 - row 6 has 4 spots where a 4 can go. Yes 2 of them make a cross with row 3, but there are more spots available in row 6 Edit: I think its important to note that, this is a technique for advanced sudoku for a reason. It requires a lot of practice and skill, as well as some insight that you can only get by doing hundreds if not thousands of puzzles. I'm doing 12 star sudoku and it took me a moment to figure it out, so dont worry if you don't get it right away ❤

[@lynettecannon8136]

Thank you for taking the time to explain without being condescending!

[@genevievearchbaker8604]

@@lynettecannon8136 it's my pleasure 🙂

[@Jugdjay]

If I got that right, Rows 3 & 5 are chosen because those two rows only have two cells where they could be placed. The other rows containing 4's have more than two possible cells.

[@DavidLGood]

Thanks for that -- it was a sticking point for me, but you've clarified it.

[@Shuyin781]

Thanks for the clarification! I was wondering why these specific 4's were chosen for the X-wing

[@genevievearchbaker8604]

I saw this technique as a picture in my sudoku book, I thought that might be the logic indeed but wanted to check

[@TheGrimravager]

this applies for all rows that have 7 out of 9 numbers filled. And can be used to cross out the given number in the corresponding columns. we can use rotational symmetry here to show that this also holds for all columns that have 7 out of 9 numbers filled, crossing out the given number in the corresponding rows

[@stephanijeopdevelt5600]

It is soooo frustrating. People complaining about the missing explanation, as to why those rows have been chosen in the forst place, and you don’t care to update your tutorials! Why even upload any (or keep them up), when not useful at all?

[@doomnotron]

100% agree

[@davedune3121]

from @Jugdjay Rows 3 & 5 are chosen because those two rows only have two cells where they could be placed. The other rows containing 4's have more than two possible cells.

[@rilesw7576]

It's fairly easy to follow lol

[@stephanijeopdevelt5600]

@@rilesw7576 Thank you for sharing your experience. I‘m very proud of you! - I think you are aware that the fact, that some might find this video easy to follow, doesn’t take away from the experience of others not to being able to fully grasp the information. In case you are not aware, for people struggling it’s not helpful when others share their success in a manner, that it can be understood like „Lol, are you stupid?! I don’t have any problems whatsoever!“ - I personally assumed, you just felt happy about being able to understand, and that’s why I chose to congratulate you. But felt the need to point out, how your answer could have been perceived.

[@martins8786]

Thats exactly my question. Why are those 2 rows chosen? Why rows 3&5? Why not 1&5, 1&6, 2&5, or 2& 6? Does it work with columns? Then the same question would apply when looking at columns. Also, do each if the cells have to be in a seprate section? Would it work if say it was row 1&3, or like 5&6?

[@davedune3121]

from @Jugdjay Rows 3 & 5 are chosen because those two rows only have two cells where they could be placed. The other rows containing 4's have more than two possible cells.

[@leakpham2309]

The question is not accurate, each box containing the number 4 selected in X-wing can only fill in 2 numbers, which causes confusion for the other boxes.

[@hernandayolearyallda]

Can we get explanation of how the rows are chose, does it always work, the exceptions? I tried it and it didn't work. Like why 4 blocks across and 3 blocks vertical, why not extend it all the way to the top?

[@Wedders]

I'm going to abbreviate the 4s they've chosen as Top/Bottom/Left/Right. TL and TL are the only possible 4s in their horizontal row. Same for BL and BR. This means there are only 2 possible scenarios - either TL must be a 4 or TR is. Scenario 1: If TL is a 4, the other 4s vertically above it can be eliminated. Scenario 2: If TR is a 4, then we know BR cannot be a 4, in which case we know BL must be a 4. If BL is a 4, it also eliminates the same 4s above TL as in Scenario 1, because we have this convenient square shape. Since these are the only two possible scenarios, we know those other 4s can be eliminated either way, even if we don't know which of these scenarios is true.

[@lorenzo_dininno]

You have to choose two rows or columns in wich there are only 2 possible blocks for a certain number (in this case 4) and they form a square. Then, if it was two rows you look at the columns, if it was two columns you look at the rows

[@Meisterling]

Is it rare to get a situation where this applies? I almost never need or get to use this.

[@davidlarroya]

i never use it and im top 1% 😅

[@genevievearchbaker8604]

Im not sure its rare, I only just now learned about the X and Y wings, but I think it takes practice and experience to find these situations. Its probably only useful in the really difficult puzzles, like 10 or 12 stars

[@marcogonzalez8360]

You missed to delete 4-notes on the same block of the cells involved in the X-wing cross

[@nice-pants-dude]

You cannot delete the 4 from the remaining cells in this instance, because here the X spans across four blocks and you don’t yet know which pair of blocks actually contains the 4’s (i.e. NW-SE or SW-NE) You would be right to do this however if the X spanned only across 2 blocks.

[@kaneshoots]

Just tried this method on my notepad, unfortunately didn't work, why row 3 and 5, and not 3 and 6, there's also 4's in row 6. Also creates a cross

[@Adasko91]

Why you choose 3 and 5 rows? Why not maybe 2 and 6? There are notes "4" too and then we will delete different notes.

[@luckymustard]

Because row 2 has five instances of "4" in it, and row 6 has four instances of "4" in it. When looking for an x-wing that might be in any sudoku puzzle, but not always will you find it happening in any given puzzle, you need to look for any 2 rows or any 2 columns that have the same digit ONLY twice in a rectangular distribution. I say rectangular because if they are skewed a little, then the x-wing won't necessarily work quite as well, if at all. And I say ONLY twice, or better yet twice and only twice, no more, no less, as having only 1 instance means you've solved that cell.

[@lorenzo_dininno]

These rows/columns that we choose have to have only 2 options each, in this case 3 and 5 have each one two possible blocks for the number 4 and they are alligned in a square shape

[@stephanijeopdevelt5600]

@@lorenzo_dininnoThe upper cell on the right of the chosen ones contain three notes. So your attempt to explain, why these cells have been chosen (each have two notes, 4 being one of them in all) seems to not be true. What am I missing?

[@doomnotron]

​@@stephanijeopdevelt5600 i need clarification as well

[@BushcraftingBogan]

Forgive me for this but Im a super newb. What is a "note"? Is it just a number? A number with a specific meaning?

[@BlackPixel1]

a "note" is every number you write in "Pencil" in a small digit before you write the actual solve in that spot

[@manson24]

Why, what is the logic here? I don't want to understand

[@genevievearchbaker8604]

If you dont WANT to understand, why ask? Unless that's a typo or translation error, then I said nothing 😊

[@GreenOrochi89]

Are there mistakes that I need to be aware of? I confidently cross off the remaining notes in the column but the answer I get was incorrect.

[@TheFenwick85]

Le tuto fais a moitié... Vous oubliez la moitié de comment ca doit etre utiliser... C est comme si au premie on t apprend a appuyer sur m embrayage mais on te dit pas pourquoi ni de passer la vitesse...