The Sudoku Swordfish: An X Wing Variant with a 3x3 Rectangle
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- Опубликовано: 15 июл 2024
- Lesson #11: The Swordfish pattern will sometimes appear in a medium to advance level sudoku puzzle. You can usually spot it at the early stages of solving a sudoku puzzle. Please review the x wing pattern first before moving on to the swordfish. The x wing is a 2x2 rectangle, the swordfish is a 3x3 rectangle. Both have the same logic, if one cell is true, then the others in the same row or column cannot be true, and if you follow the logic around the rectangle you can then eliminate all the other same candidates in the row or column. The concept is a little more complicated than the x wing, but the logic is the same. You might want to watch this lesson more than once ;)
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I've been trying to wrap my head around identifying swordfish and this helps so much!
Your ability to explain solutions is excellent. Love your diagramming help in understanding the logic. Keep the video's coming
brilliant, now to actually spot them myself is the next challenge
Now i understood...hope am able to find it in a puzzle ❤ thanks for making it so easy to grasp🌻
I was stuck with a difficult sudokou and I watched your video to learn some new cool technique... I was able to find the pattern and applied it and it seems it worked! :D thank you!
Nice explanation of the swordfish. A fun but tough puzzle to solve using this strategy is Tatooine Sunset by Philip Newman. I needed multiple Swordfishes, X-Wings, and even Jellyfish (4x4) to solve it. Thanks for sharing.
Thanks for sharing that, I will definitely check that one out!
But I still don’t understand why the 6’s in column 9 aren’t included in the pattern
I had to really study this, but I realized that columns 2, 6, and 7 are lined up with where a 6 can go. Columns 6 & 7 only have two spots where the 6 can go and column 2 has 3 which line up perfectly with 6 & 7 making the only columns necessary to use this technique. Column 9 is irrelevant in this case since it has 3 sixes and only 2 line up with the ones in columns 2, 6, and 7.
Thank you very much, you're explanation was amazingly simple and straight to the point. Good job!
Thanks PapaBear!
Very good explanation. The best I have seen. The other videos are unclear or boring. Congratulations. Best wishes from Mallorca.
Super good explanation. Thank you.
Excellent explanation
Great video thanks! 😃
Here is the real problem. At position 3:30 in your video, how do you identify that it is a swordfish? What tells you at this point to consider swordfish rather than the hidden single (7) in row 6 col 3?
Nice explanation.
Nice strategy for solving extreme levels of sudoku
There is still something I'm missing. And columns 1 and 9 there also 6 is that matchup. So I still don't understand I'm a newbie LOL
Good video. Thanks.
*_thank you for reminding me of how x.wing 3x3 works. I hope the loop will see you instructing on "Medusa" and "hidden group in the loop" how correctly_*
There is a lot to absorb here, so I plan to watch the video many more times, but I have been very eager to learn this pattern, so thank you very much. What I am a little confused about is you mentioned working on this in the beginning or middle of a puzzle, but I thought we did not look at all possible candidates and start eliminating them until we were pretty far along in solving the puzzle, using only Snyder notation in the earlier stages. I hope we can watch you use this pattern as we follow along when you solve your next puzzle. Thank you for all you do for us newbies 🙂
Thanks Andrea for the question! On harder Sudoku puzzles the Snyder notation doesn't get you far enough, so you need to start looking for logic elsewhere. Towards the end of a puzzle too many of the cells are already filled in to be able to see the swordfish, so it becomes more obvious in the earlier stages. If you don't use Snyder notation but rather start filling in all the candidates then you'll see this earlier on. Otherwise you might catch it at the middle stages when you are stuck. Keep enjoying the mental journey, its very satisfying to solve harder and harder puzzles!
@@LearnSomethingNewEveryDay Yes, it is satisfying - and in some strange way I don't completely understand, I also find it relaxing. On the other hand, many days I am so frustrated with myself and convinced I have no talent for this - and I just want to quit. But I never do 🤔🥴
@@Tee-Catin Don’t quit. You can do it! Some of these more advanced strategies take a little time to internalize and apply correctly.
@@Tee-Catin Quitters never win, and winners never quit.....right? You are a winner!
Let me just add that on very difficult puzzles, when you can't fill in any numbers right away, you are forced to start writing in the candidates (or using the auto candidate mode) because there is nothing you can place. Once you write in those candidates you will see patterns, x wing 2x2 or swordfish 3x3, or jellyfish etc. and that will allow you to start eliminating candidates and begin placing those first numbers. Other than that the only other way to solve those very difficult puzzles is to "bifurcate" or guess, and then run through the logic until you see it doesn't work, then you know your guess was wrong. These strategies are useful for killer sudoku when logic fails, or if you are in a timed competition and need to start getting some numbers fast. Hope that helps!
thank you for the video but how can you decide which rectangle to choose? i see other options of rectangles for the same number. for ex in your video:4:01 , why did you decide columns 2-6-7? there are others "6" in column 5...so how can i choose the right rectangle?
first part makes sense, second part, not. It looks like picking 3 numbers instead of 2 in a column, which feels random and counter-intuitive on what was initially taught. Sorry, i still don't get it.
not sure why she didn't mention but u can have at most 3 numbers sometimes, same rules still apply
Can options be part of the same 3x3 square?
so is it true to say no matter the type of swordfish (as long as its 3x3), we can eliminate the same number across the 3 rows AND 3 columns outside of the rectangle? in your examples you only eliminate either across the rows or down the columns, not both.
Ok this has been the best explanation I've come across so far. But I'm embarrassed to say I still don't fully understand how to spot it. In the last example, why didn't we chose the 1st column candidates? The rows seemed to match up...? What am I not getting here?
I think the six in A1 disqualifies that column as it doesn't match up with any other
@@soteri787what about C1, F1 and G1?
This is immaterial using Snyder notation.
How can I know which one is true and which one is false?
Gawd, I'll never be an advanced soduku solver because I don't like to write the little numbers inside the cells. After some of this the puzzle just gets too messy and I give up on it. I do the write the possible numbers off the puzzle by the rows and columns. This seems to work for me to solve alot of the harder puzzles.
I suggest using a phone app to play sodoku instead of traditional pen and paper. much cleaner and will instantly let you know if you made a mistake, instead of having to find out way later on and being extremely disappointed.
@@mitchellwinters6198 thanks Mitchell. Any app u could recommend?
i dont understand how your notes were made (swordfish 1 ex.) They seem incomplete to me and once the remaining fours are filled the pattern you describe cannot be found anymore
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I don't get what you are calling a 2x2 or a 3x3. What you show has larger rectangles every time!
Its about the number of corners... not the size of the rectangle... misleading way of describing it, but the XWing has 2 rows/columns and the Swordfish has 3
Hard to find these patterns. Expert level sudoku is killing me.
I understand the technique but I don't understand the logic behind it.
How did you choose the number.
I understand when you said, if there's a six here then there's not a six here. But why those exact spots?
What if the six is not in neither of those stops.
In the last explanation there's a six in e3, how are you 100% that one cant have a six?
Plese Explain jelly fish sudoku
2:55 I don't understand. Why 4 in A8 must be true? Why not in A7 or A9? How do we choose those numbers?
And I would never put 4 in A4 just because it is obvious that 4 in row C can be only in C4 or C6 hence 4 cannot be in A4.
I can simply put fours in
C6, A7, D8, G9, F4, E2, J3
Yo