Usually sudokus reach a "solved" point when you can fill in the rest of the numbers with classic sudoku rules, you'll notice this if you've solved a lot of sudokus
What about solving it from memory instead of putting in "pencil marks"??? More of a challenge. I know I feel better when I solve all my puzzles without pencil marks.
@@sltga1254 There is plenty of memory training out there, so entirely possible, and with a little work shouldn't seem any harder than marking them down.
@ronald seawell , I usually open my eyes for half a second to remember the puzzle, then close my eyes and solve it. When I'm done, I scream the solution and my mom comes running into my room in the basement and checks if I was right. She usually misses the first 4 or 5 digits, but that doesn't matter, because I have yet to make a mistake.
For sudoku players wanting to learn about X-wing technique/strategy, I am providing time stamps. It basically begins at: 5:32 (column 2) 6:22 (column 7) 6:51 (X-wing explanation) This is good and very simple explanation of the X-wing technique/strategy for solving more difficult sudoku puzzles. It would be nice if these timestamps were provided in description or a marked comments etc. I'm going through all vids myself trying to learn and understand all advanced techniques/strategies without falling asleep anf being bored to death.
Been doing sudoku for a decade, and I had read explanations of y-wing an x-wing and seen them in-game, but it never ever clicked what to do with them. Today I learned X-wing and why it's important. Thanks for that. :)
Same here too. I was doing very well till i started on the *very hard* ones. I would solve almost 80% and then was stumped. In frustration i would abandon them, hoping to start over again later. But every time i would reach the same dead end. I realised that all the plain tricks of logic i had developed myself had missed some vital aspect. One of them is the X-wing which i have never heard of before. Thanks to Mark & Simon i have now learned it now. I think it is one barrier broken . I will go back to the hard ones and try to crack them and then return for the W, Y, Zs etc 😀😀
@@shanthasathyanarayana1113 I think the video does that quite well. once you have found the rectangle such that a particular number must occupy any two of its four corners, you know that number cannot be located anywhere else along the lines of that rectangle, including an extension to the edge of the puzzle. What I would like to know is how he decided that eight was the likely number to form the x-wing. All he said in the video was that it would not be a one or a seven.
@@AlDunbar What is important here is that he looks to see where does the 8 go in columns 2 and 7. These are the only places for the 8's. So then he gets the X-wing pattern. Beautiful!
This was the first video I ever watched of yours. I was having trouble on a sudoku and literally searched "sudoku tricks" Then you changed my life. I've been rewatching from your start and I love how far you've come...granted the new videos are way more polished but I love the old ones too! Keep going guys! You are my daily unwind!
There is so much to learn from this channel, so many techniques to discover, and they made videos on all of them. X-Wing, Y-wing, Swordfish, Forcing Chains, Unique Rectangle, and many more. Have fun!
For anyone else who is new here--isn't it amazing how far the channel has come in such a short time? Like going back and binging all these videos... you really see how much they glew up. Not just in quality of video but behind the scenes as well. So cool to see!
Thanks so much. I had a puzzle I could not resolve without brute force (guessing...). Even with the answer I could not figure out how to get there without 'guessing' and I hate guessing. I have been looking at it on and off for literally a few years. I watched your magic rectangle and applied it to the puzzle to eliminate one number possibility. Still could not resolve. Then I watched this video and because of the magic rectangle elimination I had a beautiful X wing. (I still didn't believe it so I tried the number in the bad spots in the rows and it became obvious why the X wing works). I cannot tell you how satisfying it is to have a puzzle poke fun at you for years and finally come up with a logical resolve.
I need to remember it's about focusing on the columns separately to the rest of the puzzle. And that you won't really stumble upon an X-Wing, you have to be looking out for it. Thank you for this!
Thank you very much for this. I was already doing the pencil mark pairs, but what I learned was to spot the X wing BEFORE the puzzle got congested. Thank you for sharing your outstanding techniques. Your voice and style are very suited for a teacher, a damn good one.
This was a sick puzzle! There is actually a second X-wing of eights one square down and to the right from the first one. I've never seen adjacent X-wings like that before, super cool!
!! THANK you for explaining how X-wing works. I have been struggling to grasp it, so many people just say use it but never explained it. I love how you explain each thing with examples.!!
Was reading a book two days ago while UA-cam was on, one of your videos popped up and I've been going non-stop since! Thanks for making me give it a try and finding a new great hobby!
I sometimes use an advanced option of this: if an action would lead to two overlapping x-wings, it would cause the puzzle to be unsolvable so the original action is impossible
If by two overlapping x-wings you mean with two different numbers but in the same 4 squares, then it's solvable if there are more than just basic sudoku rules, otherwise you are correct. It doesn't absolutely prove without a doubt that your action is impossible however, it proves that either the action is wrong or the puzzle has multiple solutions. You're putting a lot of faith in the fact that it has only one solution, without logically proving that it does.
@@avicennitegh1377 as far as I know, and it's not alot, if you have 16 or more numbers in the beginning the puzzle has a solution, any puzzle who gives out less than 16 numbers has multiple
I've totally done the X-Wing before without really knowing what I was doing. Basically instead of putting pencil marks box-by-box, you get stuck and start pencil marking by columns and rows. You're bound to find an X-Wing by doing that, but it of course should be the first choice.
This was really helpful content. I downloaded your app after never doing sudoku because you made it seem fun. The first several puzzles I felt like a dunce because I'd seen your more monstrous solves but it was taking hours for me to do the simple puzzles. I'm hoping content like this, which is more applicable to me, will help me get faster.
I been doing expert level sudoku for years and have heard of this trick. But nothing ever explained it well enough for me to understand. Just that 3min section was HUGE. This will easily take 10% off my solve times...
I never understood what to look for with others explaining, but starting with a blank puzzle and finding it naturally while being walked through what you’re thinking was very helpful
Thank You. I have read several descriptions in books about x-wing but could not figure out what the point was until you so very clearly made it as plain as the nose on … my face. And I used today for first time to solve the NYT hard puzzle.
I am happy to inform you that I tried this out the moment I saw it, and I actually found an X-wing in the puzzle I tried solving, and it helped me get through it!
I have a book of "diabolical" sudoku puzzles from the mid 2000s by Wayne Gould. I hear the x-wing was the hardest thing out there back then, so if I learn how to spot and make use of it, this is going to be really useful.
This is the most console demonstration I’ve seen yet. Thank you! I’ve become quite addicted to sudoku in the last few months and have definitely been struggling with the harder puzzles. 🙏
X-wing is a perfect example of quantum wave function collapse; when one of two entangled superposition particles (or sudoku numbers) is observed (or confirmed) the position of the other is automatically known.
I am working on your Classic Sudoku bundle #32 - spotting the X Wing - which I worked out after the HINT and doing the puzzle several more times. The HINT helps with spotting the X wing and is great. The second part states that after completing the X wing r2c6 resolves IMMEDIATELY to 1. I have stared at this for sometime and cannot resolve the 1 - this early in the puzzle that is! What I am missing? A side note I am struggling with your puzzles, but learning a lot. I went to another puzzle locale and I am completing their EXPERT puzzles. I do not mind learning at all.
I'd heard you mentioning x-wings a number of times, but I never really understood what they were -- until a few days ago. I took a very long time to solve that puzzle, but I did notice fairly early on a couple of 23 pairs, accompanied by a pair of threes on the right and a pair of twos on the left. They were all at the top and bottom of the board. I figured that twos and threes were barred from the respective pair of columns. Then when you did the puzzle, you spotted the same 2s and 3s, and called them x-wings. So I finally got the tactic.
Immediately after getting the first 8 X-wing, there's an opportunity to identify a second 8 X-wing offset one square right and one square down. The instant any one of these squares is filled in, you can deduce all four of the 8s in one go.
I tried to learn X-wings from written instructions, and it was always too confusing. Now that I see it so simply put I realise it's something I was already using!
Was in the middle of a solve as i was watching this, immediately noticed not one but 2 x wings in my puzzle. Wonderful tip thanks for the excellent explanation
There is a simple trick for solving x-wing that also works for swordfish and jellyfish. If you list row-by-row all the columns occupied by a number, you then look for "self-contained" groups of two, three or (rarely)4. These can then be eliminated a candidates from all the other rows.
Just cracked my "first" puzzle addopting your technique. I think it took a bit longer first, while trying to identify the pencil-downs and x-wings, but once I got that part figured out, it was quite a straight forward Nd smoot run. Thank you so much for the vid and explanation. 👏🏻👏🏻👏🏻☺️☺️☺️
Knowing in advance there was an X-Wing to be found must have helped in speeding the solution. Rather like being given a chess position and asked to find the nice snappy finish - knowing for sure there's something "on" is in itself a help; not at all like encountering that position over the board in a game.
Been stalling and kind of stopped doing sudoku because I promised I would learn x wing first, and I could only find reading material about it, come to find out the guy I regularly watched and motived me to keep going had a video on it, who knew! Also pretty simple to follow along,been procrastinating to keep playing for something simple lol.
How did you determine (at 4:12), in the upper left 9x9 square, that the 5 went where it did. You put it in the far left column...how did you eliminate the possibility that it could have been placed in the far right column of that square?
I cheered when I saw your positions of the "pencil marks" as it is something I invented myself (with DOTS) after learning Sudoku in 2006 from my then partner... She used to put messy groups of numbers in the tops of every square and I am a LOGIC person (tech and digital electronics nut and certificate holder) and I thought there's no way to see what's there at a mere glance without a lot of re-reading. SO I developed the DOT system in the exact positions your little numbers reside.... maybe I stole it from the universal mind OR I put it there, but I never saw it until years later I spotted someone doing the exact same thing (and I had told not a soul except my ex! and she thought I was an idiot...) When I asked what he was doing being curious where he would have gotten my idea from, he said he was doing what I had devised. He was from the Salvation Army sitting collecting for the charity and so I said to him "I invented that and it is proof we are all connected in our minds through God" and he didn't look like he believed I'd done it. Anyway thanks for this "X" thingy, looks interesting and another solving tool for the diabolicals I couldn't solve in the past (I photograph them and leave them in the computer for later, throwing the physical one away for now.) I'm sure there's a mathematical principle somewhere in these things and I love math ;) Cheers brother, will sub!
I started solving sudoku puzzles a little over a year ago to keep my 70+ yo mind sharp and over the course of time I have developed my own techniques for solving them. It has gotten to the point where I find only expert level puzzles challenging and I can solve them in around 15 minutes or so. I start by looking at exclusion cells. Next I look for pairs and that's when numbers start to drop out. That usually leads to more exclusions. Every action is done in numerical order. Since I hardly think about my method while solving, my description of it is rather simplistic. When it comes down to it sudoku is actually a sorting problem. Btw, I have yet to get a puzzle I couldn't solve.
Not sure why this video was randomly recommended to me, but in one of my sudoku books, there is one solitary puzzle that stumped me for a couple months. I narrowed it down to two possible solutions and couldn't find the next move. I'm not a true expert by any means, but it's the only sudoku puzzle so far I've conceded to. I should go back and see if this would've made the difference.
Nice and cozy puzzle.. Made notation free in 12m45s. The X Wing of 8s needs to be spotted, but it is well telegraphed in this puzzle. Once you have the X Wing and accordingly place an 8 in r7c5, the puzzle crumbles and it is clear sailing to the end.
2:18 I just did my first Sudoku on a computer program set to hard (not extreme). I put marks EVERYWHERE, sometimes even 5 in one box to keep track and it took me an hour and a half to solve. I guess there is an easier way to do it 😂.
Not sure if you still play or not, but a very helpful piece of advice I heard was that the more difficult is, the less a brute force method will work. Brute force being pencil marks everywhere. It only complicates things further
5:57 earlier you said that you use Snyder (edge) markings when you know that the unknown number is within a 3x3 cell. So why do you use that notation here too? (In regards to what you describe at 1:42).
I notice that stuff all the time. I just bypass and continue solving the puzzle. My personal faves are the puzzles with 2 or more solutions. I’ve only ever found 1 but it’s intriguing none the less.
Thanks! Glad I watched this... will save me time on my solving. I use the pencil marks as well but use the top of the cell for 3x3 and the bottom of the cell for 1x9 I use pencil and paper or my Remarkable notepad with a pdf. something about interacting with the puzzle directly is more satisfying for me.
Gregory Dalton I always work in pen and try to incorporate my inchoate markings into my big numbers. It’s very satisfying to finish a puzzle with few extraneous marks.
@@hammockmonk actually I use a fine pen as well rarely a pencil and occasionally can morph a little number successfully into a big one. My daughter does them without any marks! A good challenge to see how far you can go.
@@mfsolutions rather than small numbers I just place a dot in one of the nine areas inside the square. Makes it fairly easy to incorporate into the big number later. Then I try to make the big number a perfect duplicate of the printed ones. Cheers!
Really nice! Previous explanations I've seen implied that spotting an x-wing somehow told me how to fill in those squares, but now it's clear that it's about those other squares in those rows and columns.
I am impressed with myself! I came up with, what I call either-or, two possiblities pencil marks in 9 blocks very early, and some had to teach the champion... But I had never noticed the X-Wing story for use early in the puzzle. Powerful stuff!
good stuff. definitely a new solving technique for me. i never heard of such a thing and u probably muddle thru the puzzles i do solve. thanks for this great video.
Once you spotted the xwing, you could have filled in the rest of the pencil markings for the 8s. This would have saved some time when you solved the 9s as the xwing would have instantly resolved (I don't know if that's the right term).
there was a second x-wing, with the 2s in rows 4 &5. At that point the puzzle was solvable by more elementary means, but given the theme it would have been nice to point it out.
Because of the 8 in column 9, row 6, there cannot be another 8 in that box. That eliminates the open boxes in the center of column 7. Now there are only 3 open boxes left, the ones in rows 1, 3, and 8. Row 3 also has an 8 in column 4, so the only possible positions for an 8 in column 6 are rows 1 and 8.
I am on the verge of understanding the X-wing. I am presuming that once the numerical value is identified for the X-wing, it is a process of elimination and deduction to determine which pair of squares is correct?? and then eleminiate the supected values form the rows and Columns? or can you do that before you get to assigning squares for the numbers?
We could, but here specifically pencil marks were not bound to squares but to columns instead, that’s why Simon coloured them green. Could we place 8 in column 3 or 8? Probably yes. But it doesn’t have anything to do with X-wing.
I would like it if you were to do a more thorough explanation of the 'standard notation' pencil marks. I taught myself how to do sudoku & have always put in every number possible into a given cell when I put in pencil marks. Every time I've tried your method, I have either borked the puzzle up or found myself reverted back to how I've always done it. =( I really want to improve my solving technique, but am having this hangup. (I do most non-diabolical puzzles without any pencil marks on the paper - only in my head - but the harder puzzles really do require scribbles to solve.) Also, ran into a REALLY hard puzzle the other day... I'll try to find it and forward it over to you. Interested in seeing what you can do with it.
I think the idea is that if you're putting more than 2 numbers in as a placeholder, it's not a useful clue. And to try and find clues that can be gained with less notation. Reducing clutter and making useful thinks more immediately apparent
You only put the pencil marks in if there are exactly two squares within a (3x3) block that can contain a certain number. However, an individual square could have lots of pencil marks. For example, a single square could have a 2, 3 and 4 pencilled in to it, but there would only be 2 2s, 2 3s and 2 4s pencilled into that block. Say you then discovered that that square was the 4. Then since that was one of two places the 2 could be, the 2 must be in the other. Similarly, since you rubbed out the 3 pencil mark, the 3 must be in the other marked square.
For example, say you have a 3x3 block which I'll label like this. (I missed I so it doesn't get confused with a 1). A. B. C. D. E. F. G. H. J. Suppose you know that 2 must be in A or E. You also know 3 is in B or E, and 4 is in E or F. You might pencil mark the grid like this: 2. 3. C. D. 234. 4. G. H. J. Then you find a 4 somewhere else in the third column. That means the 4 must be in E. But since you're rubbing out marks for 2 and 3, you can now place them. Does that make sense?
I love it when he says "And now this puzzle is complete" but it's like 20% done
Agus Jauregui lmao
Usually sudokus reach a "solved" point when you can fill in the rest of the numbers with classic sudoku rules, you'll notice this if you've solved a lot of sudokus
I tried it. And the naked singles sprang up like mushrooms.
I played bridge with someone, after the bidding, and one or two tricks played, would write down the score. And he was always right.
He's ultimate big brain
Most important thing I learned: put pencil marks where there are ONLY 2 possibilities.
What about solving it from memory instead of putting in "pencil marks"???
More of a challenge. I know I feel better when I solve all my puzzles without pencil marks.
Sportsquirrel, generally yes, but not there are times 3 can help.
@@sltga1254 There is plenty of memory training out there, so entirely possible, and with a little work shouldn't seem any harder than marking them down.
@@sltga1254 Memorize this ua-cam.com/video/eBs5N99m1aA/v-deo.html :)
@ronald seawell , I usually open my eyes for half a second to remember the puzzle, then close my eyes and solve it. When I'm done, I scream the solution and my mom comes running into my room in the basement and checks if I was right. She usually misses the first 4 or 5 digits, but that doesn't matter, because I have yet to make a mistake.
For sudoku players wanting to learn about X-wing technique/strategy, I am providing time stamps. It basically begins at:
5:32 (column 2)
6:22 (column 7)
6:51 (X-wing explanation)
This is good and very simple explanation of the X-wing technique/strategy for solving more difficult sudoku puzzles.
It would be nice if these timestamps were provided in description or a marked comments etc. I'm going through all vids myself trying to learn and understand all advanced techniques/strategies without falling asleep anf being bored to death.
Thank you
You are a blessing
Thank you
Thank you so much!!😃
Been doing sudoku for a decade, and I had read explanations of y-wing an x-wing and seen them in-game, but it never ever clicked what to do with them. Today I learned X-wing and why it's important. Thanks for that. :)
Still could not learn
Same here too. I was doing very well till i started on the *very hard* ones. I would solve almost 80% and then was stumped. In frustration i would abandon them, hoping to start over again later. But every time i would reach the same dead end.
I realised that all the plain tricks of logic i had developed myself had missed some vital aspect.
One of them is the X-wing which i have never heard of before.
Thanks to Mark & Simon i have now learned it now. I think it is one barrier broken . I will go back to the hard ones and try to crack them and then return for the W, Y, Zs etc 😀😀
@@krish6729 is it possible to explain x wing in simple way
@@shanthasathyanarayana1113 I think the video does that quite well. once you have found the rectangle such that a particular number must occupy any two of its four corners, you know that number cannot be located anywhere else along the lines of that rectangle, including an extension to the edge of the puzzle.
What I would like to know is how he decided that eight was the likely number to form the x-wing. All he said in the video was that it would not be a one or a seven.
@@AlDunbar What is important here is that he looks to see where does the 8 go in columns 2 and 7. These are the only places for the 8's. So then he gets the X-wing pattern. Beautiful!
The X-wing is EXACTLY what I have been looking for for YEARS!
I KNEW there was a way to improve! WOOOONNNNDERFUL and THANX! ;O)
On the same boat. Now that we know the X -trick we will tackle the very tough ones and, hopefully, catch up with
Mark & Simon.😆
Spotting the X-wing means solving several other bits before using the X-wing numbers. I finally understand that.
This was the first video I ever watched of yours. I was having trouble on a sudoku and literally searched "sudoku tricks" Then you changed my life. I've been rewatching from your start and I love how far you've come...granted the new videos are way more polished but I love the old ones too! Keep going guys! You are my daily unwind!
There is so much to learn from this channel, so many techniques to discover, and they made videos on all of them.
X-Wing, Y-wing, Swordfish, Forcing Chains, Unique Rectangle, and many more. Have fun!
For anyone else who is new here--isn't it amazing how far the channel has come in such a short time? Like going back and binging all these videos... you really see how much they glew up. Not just in quality of video but behind the scenes as well. So cool to see!
Thanks so much. I had a puzzle I could not resolve without brute force (guessing...). Even with the answer I could not figure out how to get there without 'guessing' and I hate guessing. I have been looking at it on and off for literally a few years. I watched your magic rectangle and applied it to the puzzle to eliminate one number possibility. Still could not resolve. Then I watched this video and because of the magic rectangle elimination I had a beautiful X wing. (I still didn't believe it so I tried the number in the bad spots in the rows and it became obvious why the X wing works). I cannot tell you how satisfying it is to have a puzzle poke fun at you for years and finally come up with a logical resolve.
I need to remember it's about focusing on the columns separately to the rest of the puzzle. And that you won't really stumble upon an X-Wing, you have to be looking out for it. Thank you for this!
Thank you very much for this. I was already doing the pencil mark pairs, but what I learned was to spot the X wing BEFORE the puzzle got congested. Thank you for sharing your outstanding techniques. Your voice and style are very suited for a teacher, a damn good one.
This was a sick puzzle! There is actually a second X-wing of eights one square down and to the right from the first one. I've never seen adjacent X-wings like that before, super cool!
!! THANK you for explaining how X-wing works. I have been struggling to grasp it, so many people just say use it but never explained it. I love how you explain each thing with examples.!!
The 1-6s is a mini X-wing att he lower right corner at 14 mins in.
Thanks for this technique. I've smelled it, but never formalized it. Very helpful!
the 2 digit x wings are all over the place. he was looking for a single digit x wing.
Now Im going to be looking for the X-Wing every time I play. Thank you for this!
15:15 shows another X-wing pattern on the 2's in R4&R5, deciding the 2 in C1. Just a little Easter egg
Thanks! Just learning about x wings and a 2nd example helped.
yes, but the 8s came out earlier than the 2s
Good eye mate.
That took me a couple of minutes to identify even with your explanation. I will really struggle on a normal game.
So, even though there are 3 possibilities of placing a 2 in row 5, the x wing is still applicable?
Was reading a book two days ago while UA-cam was on, one of your videos popped up and I've been going non-stop since! Thanks for making me give it a try and finding a new great hobby!
I sometimes use an advanced option of this: if an action would lead to two overlapping x-wings, it would cause the puzzle to be unsolvable so the original action is impossible
If by two overlapping x-wings you mean with two different numbers but in the same 4 squares, then it's solvable if there are more than just basic sudoku rules, otherwise you are correct. It doesn't absolutely prove without a doubt that your action is impossible however, it proves that either the action is wrong or the puzzle has multiple solutions. You're putting a lot of faith in the fact that it has only one solution, without logically proving that it does.
@@Zombie-lx3sh Interesting - I'd always assumed there was only one correct solution in the puzzle.
@@avicennitegh1377 Traditionally, "valid" sudokus only have one possible solutions. Otherwise it's just a broken puzzle.
@@avicennitegh1377 as far as I know, and it's not alot, if you have 16 or more numbers in the beginning the puzzle has a solution, any puzzle who gives out less than 16 numbers has multiple
@@GtotheK Thanks so much
This just showed up in my recommendations today. Amazing how far the channel has come in a year!
I've totally done the X-Wing before without really knowing what I was doing. Basically instead of putting pencil marks box-by-box, you get stuck and start pencil marking by columns and rows. You're bound to find an X-Wing by doing that, but it of course should be the first choice.
This was really helpful content. I downloaded your app after never doing sudoku because you made it seem fun. The first several puzzles I felt like a dunce because I'd seen your more monstrous solves but it was taking hours for me to do the simple puzzles. I'm hoping content like this, which is more applicable to me, will help me get faster.
Thank you I could never get how it worked just reading the description online. This clicked so easily!
I been doing expert level sudoku for years and have heard of this trick. But nothing ever explained it well enough for me to understand. Just that 3min section was HUGE. This will easily take 10% off my solve times...
i’ve been using this trick for ages, good to know it has a name!!
I never understood what to look for with others explaining, but starting with a blank puzzle and finding it naturally while being walked through what you’re thinking was very helpful
This is the best explanation of how to find and use the x-wing. It has always seemed complicated when others have tried to explain it. Thank you!!!
This is a great example of an x-wing, I might finally understand
5:05 These aren't the droids you're looking for 😂
Thank You. I have read several descriptions in books about x-wing but could not figure out what the point was until you so very clearly made it as plain as the nose on … my face. And I used today for first time to solve the NYT hard puzzle.
Finally I feel like I get what the X-wing is about, thanks!
I think this is the technique I've needed for all the puzzles I've been getting stuck on. Thanks!
I am happy to inform you that I tried this out the moment I saw it, and I actually found an X-wing in the puzzle I tried solving, and it helped me get through it!
Thank you for opening my eyes. I wonder how many puzzles I was stumped with could have been solved with x-wing.
A good one to spot an x-wing without having too many pencil marks.
Very helpful and makes my journey to solving puzzles faster
It has shades of The Hunt, Sudoku. First there is stalking the prey, and then the chase to fill in the numbers once its tricks have been grasped!
I have a book of "diabolical" sudoku puzzles from the mid 2000s by Wayne Gould. I hear the x-wing was the hardest thing out there back then, so if I learn how to spot and make use of it, this is going to be really useful.
This is the most console demonstration I’ve seen yet. Thank you! I’ve become quite addicted to sudoku in the last few months and have definitely been struggling with the harder puzzles. 🙏
Absolutely awesome explanation thankyou. My solving skills have improved so much since I found your channel! Great work thankyou! 😁
This has been giving me brain ache for a while. Thanks to your lesson I now understand X Wing
X-wing is a perfect example of quantum wave function collapse; when one of two entangled superposition particles (or sudoku numbers) is observed (or confirmed) the position of the other is automatically known.
Thank you so much!Very helpful...finally got the concept!
Excellent explanation of X-wing, thanks.
I am working on your Classic Sudoku bundle #32 - spotting the X Wing - which I worked out after the HINT and doing the puzzle several more times. The HINT helps with spotting the X wing and is great. The second part states that after completing the X wing r2c6 resolves IMMEDIATELY to 1. I have stared at this for sometime and cannot resolve the 1 - this early in the puzzle that is! What I am missing?
A side note I am struggling with your puzzles, but learning a lot. I went to another puzzle locale and I am completing their EXPERT puzzles. I do not mind learning at all.
I'd heard you mentioning x-wings a number of times, but I never really understood what they were -- until a few days ago. I took a very long time to solve that puzzle, but I did notice fairly early on a couple of 23 pairs, accompanied by a pair of threes on the right and a pair of twos on the left. They were all at the top and bottom of the board. I figured that twos and threes were barred from the respective pair of columns. Then when you did the puzzle, you spotted the same 2s and 3s, and called them x-wings.
So I finally got the tactic.
Immediately after getting the first 8 X-wing, there's an opportunity to identify a second 8 X-wing offset one square right and one square down. The instant any one of these squares is filled in, you can deduce all four of the 8s in one go.
Right - I saw that one too, but the first one is key. :).
i only spoted the one in rows 2 and 9
Thank you for an excellent explanation of the X-Wing. Best I have come across!
I tried to learn X-wings from written instructions, and it was always too confusing. Now that I see it so simply put I realise it's something I was already using!
Was in the middle of a solve as i was watching this, immediately noticed not one but 2 x wings in my puzzle. Wonderful tip thanks for the excellent explanation
There is a simple trick for solving x-wing that also works for swordfish and jellyfish. If you list row-by-row all the columns occupied by a number, you then look for "self-contained" groups of two, three or (rarely)4. These can then be eliminated a candidates from all the other rows.
Never have used X-wing. Thank you much. I understand it and will use it to make the most difficult puzzles easier.
Just cracked my "first" puzzle addopting your technique. I think it took a bit longer first, while trying to identify the pencil-downs and x-wings, but once I got that part figured out, it was quite a straight forward Nd smoot run. Thank you so much for the vid and explanation. 👏🏻👏🏻👏🏻☺️☺️☺️
Thanks. Thoroughly enjoyed it. I've wanted to understand the X-Wing, and now I finally do.
Thanks for explaining that. I have been trying to figure out how it works and this was really clear. Looking forward to better results.
Knowing in advance there was an X-Wing to be found must have helped in speeding the solution. Rather like being given a chess position and asked to find the nice snappy finish - knowing for sure there's something "on" is in itself a help; not at all like encountering that position over the board in a game.
True, but now I'll always be looking for an x-wing somewhere.
I am finally able to solve expert level puzzles many times in a row after watching your videos.
Been stalling and kind of stopped doing sudoku because I promised I would learn x wing first, and I could only find reading material about it, come to find out the guy I regularly watched and motived me to keep going had a video on it, who knew!
Also pretty simple to follow along,been procrastinating to keep playing for something simple lol.
Very helpful - thanks!
I'm supposed to be studying for finals, yet here I am learning how to master sudoku because that's more important
I love how British this is.
Thank you, really enjoying this explanations.
Good job. This was a new solving technique for me at least. Gonna give it a try in the future Sudoku puzzles I face.
within a year, the software used to solve it has improved a lot and that let viewers the opportunity to try it by ourselves
How did you determine (at 4:12), in the upper left 9x9 square, that the 5 went where it did. You put it in the far left column...how did you eliminate the possibility that it could have been placed in the far right column of that square?
The middle left 3x3 had to have the 5 on the right because of the 2-4 pair on the left.
Thank you. I understand it now. Bought a book but it's going in the bin after watching this.
I cheered when I saw your positions of the "pencil marks" as it is something I invented myself (with DOTS) after learning Sudoku in 2006 from my then partner... She used to put messy groups of numbers in the tops of every square and I am a LOGIC person (tech and digital electronics nut and certificate holder) and I thought there's no way to see what's there at a mere glance without a lot of re-reading. SO I developed the DOT system in the exact positions your little numbers reside.... maybe I stole it from the universal mind OR I put it there, but I never saw it until years later I spotted someone doing the exact same thing (and I had told not a soul except my ex! and she thought I was an idiot...) When I asked what he was doing being curious where he would have gotten my idea from, he said he was doing what I had devised. He was from the Salvation Army sitting collecting for the charity and so I said to him "I invented that and it is proof we are all connected in our minds through God" and he didn't look like he believed I'd done it. Anyway thanks for this "X" thingy, looks interesting and another solving tool for the diabolicals I couldn't solve in the past (I photograph them and leave them in the computer for later, throwing the physical one away for now.) I'm sure there's a mathematical principle somewhere in these things and I love math ;) Cheers brother, will sub!
I started solving sudoku puzzles a little over a year ago to keep my 70+ yo mind sharp and over the course of time I have developed my own techniques for solving them. It has gotten to the point where I find only expert level puzzles challenging and I can solve them in around 15 minutes or so. I start by looking at exclusion cells. Next I look for pairs and that's when numbers start to drop out. That usually leads to more exclusions. Every action is done in numerical order. Since I hardly think about my method while solving, my description of it is rather simplistic. When it comes down to it sudoku is actually a sorting problem. Btw, I have yet to get a puzzle I couldn't solve.
Not sure why this video was randomly recommended to me, but in one of my sudoku books, there is one solitary puzzle that stumped me for a couple months. I narrowed it down to two possible solutions and couldn't find the next move.
I'm not a true expert by any means, but it's the only sudoku puzzle so far I've conceded to. I should go back and see if this would've made the difference.
Nice and cozy puzzle.. Made notation free in 12m45s. The X Wing of 8s needs to be spotted, but it is well telegraphed in this puzzle. Once you have the X Wing and accordingly place an 8 in r7c5, the puzzle crumbles and it is clear sailing to the end.
terrific video. Now I finely got it! Actually there is another X-wing too with 8, row 3 and row 8.
2:18 I just did my first Sudoku on a computer program set to hard (not extreme). I put marks EVERYWHERE, sometimes even 5 in one box to keep track and it took me an hour and a half to solve. I guess there is an easier way to do it 😂.
Rauschka I am with you!🤣😂😅
Not sure if you still play or not, but a very helpful piece of advice I heard was that the more difficult is, the less a brute force method will work. Brute force being pencil marks everywhere. It only complicates things further
Thank you! I’m not great at these, but I’m obsessed.
5:57 earlier you said that you use Snyder (edge) markings when you know that the unknown number is within a 3x3 cell. So why do you use that notation here too? (In regards to what you describe at 1:42).
I notice that stuff all the time. I just bypass and continue solving the puzzle. My personal faves are the puzzles with 2 or more solutions. I’ve only ever found 1 but it’s intriguing none the less.
By definition, if there is more than 1 solution, it is not a Sudoku.
lovely technique. Thank you
A better microphone would be a huge quality boost for the videos or less echo somehow
I don't think it's echo that's the problem, there seems to be some compression artifact happening.
@@Gennys He's in a small, sparse room. I bet a few sound foam blocks on that sloped ceiling would help.
I think it sounds unique and cool. It's partially robotic, and helps the nerdy intellectual appeal.
Given what this video is, it's not a big deal. I can hear and understand him just fine.
I heard absolutely fine, not sure what the issue is?
Thank you! That opens new horizons. Happy New Year!
This is absolutely fantastic, keep up the amazing work with this channel
Thanks! Glad I watched this... will save me time on my solving. I use the pencil marks as well but use the top of the cell for 3x3 and the bottom of the cell for 1x9 I use pencil and paper or my Remarkable notepad with a pdf. something about interacting with the puzzle directly is more satisfying for me.
Gregory Dalton I always work in pen and try to incorporate my inchoate markings into my big numbers. It’s very satisfying to finish a puzzle with few extraneous marks.
@@hammockmonk actually I use a fine pen as well rarely a pencil and occasionally can morph a little number successfully into a big one. My daughter does them without any marks! A good challenge to see how far you can go.
@@mfsolutions rather than small numbers I just place a dot in one of the nine areas inside the square. Makes it fairly easy to incorporate into the big number later. Then I try to make the big number a perfect duplicate of the printed ones. Cheers!
@@hammockmonk so how do you distinguish
whether it is referring to the block or the row or do you not make notes about the row binaries
Really nice! Previous explanations I've seen implied that spotting an x-wing somehow told me how to fill in those squares, but now it's clear that it's about those other squares in those rows and columns.
I am impressed with myself! I came up with, what I call either-or, two possiblities pencil marks in 9 blocks very early, and some had to teach the champion... But I had never noticed the X-Wing story for use early in the puzzle. Powerful stuff!
what program are you using to solve the sudoku? I would like to download it if possible. thanks.
The app used in this video is Duncan's SuDoku Solver
Thanks for the video, I'm new to Sudoku, and fine your videos helpful
Very knowledgeable & interesting
thank you so much, im getting into sodoku for the first time since high school and it just much fun competing with myself hehe
brilliant, can't wait to practise
To ask a very stupid question, what software are you using to work these puzzles?
good stuff. definitely a new solving technique for me. i never heard of such a thing and u probably muddle thru the puzzles i do solve. thanks for this great video.
Once you spotted the xwing, you could have filled in the rest of the pencil markings for the 8s. This would have saved some time when you solved the 9s as the xwing would have instantly resolved (I don't know if that's the right term).
Indeed these would form another xwing, which means as soon as you got any of these squares, you can resolve the entire lot!
Great explanation on X-wing. Thank you!!!
there was a second x-wing, with the 2s in rows 4 &5. At that point the puzzle was solvable by more elementary means, but given the theme it would have been nice to point it out.
This is very helpful! Thank you.
Cool! I hadn't thought of this technique.
Thank you
What a throwback 😊
I do not understand how you eliminate the 8's that can go in column 8 for number 8 in the X-wing. Please explain :)
Did you watch the video?
Because of the 8 in column 9, row 6, there cannot be another 8 in that box. That eliminates the open boxes in the center of column 7. Now there are only 3 open boxes left, the ones in rows 1, 3, and 8. Row 3 also has an 8 in column 4, so the only possible positions for an 8 in column 6 are rows 1 and 8.
I am on the verge of understanding the X-wing. I am presuming that once the numerical value is identified for the X-wing, it is a process of elimination and deduction to determine which pair of squares is correct?? and then eleminiate the supected values form the rows and Columns? or can you do that before you get to assigning squares for the numbers?
why can we not have 8s in column 3 or column 8 in the top and bottom boxes when making the x wing for 8?
We could, but here specifically pencil marks were not bound to squares but to columns instead, that’s why Simon coloured them green.
Could we place 8 in column 3 or 8? Probably yes. But it doesn’t have anything to do with X-wing.
Very well explained, thank you!
My aim is to put no marks, only certainties. Many thanks for this extra string to the solving bow!
I would like it if you were to do a more thorough explanation of the 'standard notation' pencil marks. I taught myself how to do sudoku & have always put in every number possible into a given cell when I put in pencil marks. Every time I've tried your method, I have either borked the puzzle up or found myself reverted back to how I've always done it. =( I really want to improve my solving technique, but am having this hangup. (I do most non-diabolical puzzles without any pencil marks on the paper - only in my head - but the harder puzzles really do require scribbles to solve.)
Also, ran into a REALLY hard puzzle the other day... I'll try to find it and forward it over to you. Interested in seeing what you can do with it.
I think the idea is that if you're putting more than 2 numbers in as a placeholder, it's not a useful clue. And to try and find clues that can be gained with less notation. Reducing clutter and making useful thinks more immediately apparent
I do not often do these but when I do I try not to mark the grid except with the final numbers.
You only put the pencil marks in if there are exactly two squares within a (3x3) block that can contain a certain number. However, an individual square could have lots of pencil marks. For example, a single square could have a 2, 3 and 4 pencilled in to it, but there would only be 2 2s, 2 3s and 2 4s pencilled into that block. Say you then discovered that that square was the 4. Then since that was one of two places the 2 could be, the 2 must be in the other. Similarly, since you rubbed out the 3 pencil mark, the 3 must be in the other marked square.
For example, say you have a 3x3 block which I'll label like this. (I missed I so it doesn't get confused with a 1).
A. B. C.
D. E. F.
G. H. J.
Suppose you know that 2 must be in A or E. You also know 3 is in B or E, and 4 is in E or F. You might pencil mark the grid like this:
2. 3. C.
D. 234. 4.
G. H. J.
Then you find a 4 somewhere else in the third column. That means the 4 must be in E. But since you're rubbing out marks for 2 and 3, you can now place them. Does that make sense?
@@ianmoseley9910 Whenever possible, so do I. When you do an extremely difficult puzzle, it's unavoidable though.