Classic Sudoku Expertise

[@dean2163]

I think one classic a week would be cool, like a throw back Thursday classic puzzle

[@malvoliosf]

Maybe two?

[@mishkac927]

One each. Mark doing the GAS puzzles makes it feel more approachable for those of us who struggle with some yet still want in on variants. I think more people in general do Classics though so might appreciate the beauty and the hints.

[@SmartHobbies]

I wholeheartedly agree. I learn so much from watching Mark and Simon solve Classics.

[@bigjoemaggie5267]

Agreed.

[@yoshisolvessudoku]

This classic was the first I had ever seen with such a perfect chain of bivalue cells. Truly an amazing construction!

[@michaelmatter1222]

If you enjoyed this one I highly recommend checking out "Continuum" by 3good5you which has a very similar vibe. (Cheers from 99%Sneaky)

[@conexant51]

Clover sets some really nice classics as well as her variant sudokus.

[@Ardalambdion]

Yes, please do one or two classical puzzles each every month. Puzzles with interesting techniques. I tend to forget all that when doing everything else on this channel.

[@michaelmatter1222]

Always fun to see classics with interesting logical geometry patterns, very nice Tyler!

[@paulcook2961]

Always happy to watch a classic video SPECIALLY if we walk through the application of a useful trick. What would be EVEN better would be a second sudoku of similar difficulty that uses the exact same trick so we can check that we understood and can apply it.

[@yagamilight08]

Yes more classic please...it for one is helpful for beginners to understand basic sudoku techniques and it also is not always straightforward so it helps practicing scanning like u did mark...i hope its also a breather for u guys from mind tuned in varient logic n more focus on these other scanning techniques

[@renauddommergue7671]

Yes more classic sudoku please .

[@kdenney66]

I did this one...I am a novice and this one made me feel extremely happy! Thanks!

[@davebreslow1956]

More classics please I do enjoy them Big fan of the channel Merry Christmas to all

[@pgowans]

Agree - one classic each week would be great

[@smahoney1212]

Yes, definitely more classics.

[@BlakeAStoffel]

I always like seeing classics. Always good to cover the basics!

[@bergnijlpaard]

I really like it when you do old school classics sudokus with x wings and y wings and jellyfish and so on. Once a week would be great.

[@brois841]

Yes, love classics, please have more. Took me just over 60 minutes to solve this one.

[@zynzane9680]

I would love to see more classics! This was really nice. I love the puzzle solver on your earlier videos, it is perfect. The one on this one is just SO BIG on my computer screen and trying to minimize it doesn't work. But grateful for your channel and help solving the puzzles. The classics are more than challenging enough for me. I had all the options filled in and got one solve and got stuck, so that is when I started watching you. I always try to solve as much as I can on my own first. I did not know how to figure out that chain but watching you do it was so cool! Thank you for all you have taught us all.

[@JohnBodoni]

+1 for classic. and many +1s to tyler for a great puzzle.

[@bertbergers9171]

26:32 couldn't see the trees through the woods from pencilmarking for a while. Then i noticed something in column9 which started giving me digits, and then it flowed to the finish. was a nice construction, not totally approachable for me, but i liked it. Thank you @Tyler Chen for the puzzle and thank you Mark for the video! Spoiler alert: i saw a bifurcation discussion elsewhere in the comments, i found the 4 in column 9 by going through the column and rows 6 and 9 and finding that logic on 2.s in box 5 and 8 make 9 impossible to place in box 8 in one way of the 4's. Since i had quite a lot of pencil marking done, i could quite easily find and check my logic in my head. So allthough one of the options just not being able to finish the puzzle, i don't consider using my brain bifurcating.

[@ttest1682]

I vote for more classics as well. I enjoy those videos a lot!

[@longwaytotipperary]

I enjoy classic sudoku’s!! Hope Mark got where he was going in time and having fun! Also looking forward to watching Simon solve the 100 snackdokus!

[@sampathkumar-ej7xl]

I only looked for Classic sudokus when I started watching the channel a few years ago but now I really prefer the others. An occassional classic is fine.

[@Kelters]

Classics are the basis for all the interesting variations. -- It is important to keep practising and enjoying the basic puzzles. Working on the various wings and chains and fish which are often needed to solve the variants is a "good thing". They would be a great weekly replacement for the now vacant GAS window. More please.

[@Gonzalo_Garcia_]

6:34 for me. I loved the trick on this one!!

[@davidh.4944]

59:36@#3816. It was relatively easy to spot the "line" of connected cells-after wasting a lot of time looking for more traditional patterns like y-wings and empty rectangles-but it took much longer to figure out how actually take advantage of it. I almost gave up at one point, but once I really got the idea, it resolved cleanly. Pretty neat, and reminiscint of some of Clover's clever classic tricks.

[@christophejefferies522]

There's a few comments saying solves required some bifurcation. I think that's missing the point of the lovely 12 23 34 ... 89 91 chain - it's either 'all high' or 'all low'. So e.g. any cell seen by the 34 and 45 cells can't contain 4. Apply that in the bottom row with 1s, and the 28 pair Mark found pops out, which causes the puzzle to collapse. Beautiful in my opinion :)

[@thejadesilly]

I always feel like I take a month of sundays to solve a classic sudoku.. but after seeing Mark get hung up where I always get hung up, I feel far less dense, though I am by no means a genius haha

[@rampantunease6517]

A part of the fun of the channel is viewing. Skill of Simon and Mark's solve, like juggling we know how it's done but their ability to do it so fast is fun to watch. Both are not tan tan fast who also has appeared on the channel and was fun to watch.

[@christianarbeiter6235]

I had a different break in. Either r9c8 is 8 OR r9c5 is 8. The latter rules out 2 from r4c4 and forces 2 in r4c8. Meaning r9c8 can never be a 2, making r9c9 a 2. Much shorter chains/less bifurcation.

[@shawnmichajluk2044]

Agree - could use more like this. Wish I could find the breakouts like Mark.

[@林老師-i5d]

Thanks for the puzzle and solving.

[@richardlyons7582]

Wow I took 19.22 for this and thought, what a unless time, then watched Marks go and he did it in 14.13 although not at full speed, did make me feel a lot happier.

[@georgeaman1938]

Thank you Tyler Chen and Mark. What a nice classic sodoku!

[@KittyXCross]

More classics, yes please!

[@erickehr4475]

9:56 for me. A very interesting chain of bivalue cells

[@SnugglesPlays]

I definitely would love to see more classics....Good to balance out the classics with the other ones, and at the moment it's not balanced at all, so yes, more classics please! 🙂

[@JohnRandomness105]

13:20 I call it a loop. I've read the term "continuous loop" and "nice continuous loop". (They've never told us what a nasty continuous loop is, but I have one idea.) Yes, I would like to see more classic Sudoku.

[@drengskap]

I solved this in 9:16 by simple elimination, no fancy chaining or looping required.

[@dariobarisic3502]

Solving a classic once in a while is a good feeling, especially if it's one like this. It also reminds me how rusty I'm with classics :D

[@cmodzins]

Was able to follow it from beginning to end!

[@jibster5903]

What a beautiful puzzle this is

[@kevinerose]

14:00 I don't know the official name to call it but I call it "finding a 2-digit cell that looks promising and see how each digit will play out", but that's just me.

[@mcleanmachut]

bifurcation

[@jadeskyewalker]

Attempted this one before watching the solve and managed it in just over 21 minutes. Not bad I was happy with that considering I don’t do sudoku’s super often anymore. I like watching hard puzzles but it’s nice to watch a good ol classic now and then too :)

[@arataya8706]

I like the classic sudokus because it gives me new techniques when I’m solving on my own.

[@SamCoca]

Yes!!!! More classics please. : )

[@conexant51]

I have to say that classic sudokus are actually quite refreshing. A few classics per week would be a welcome change of pace imho.

[@emilywilliams3237]

This was very nice, Mark. I love seeing you solve a puzzle that you enjoy, and I know you enjoy the classics. As for whether you should do more classics, I do like the classics that are complex, because the more advanced techniques are hard to spot and hard to use - for me. (And it was on time - thank you for all the effort you put into keeping us with two puzzles a day!)

[@Swynndla]

More classics please!

[@coyote4237]

Thank you for the classic.

[@fabianminimal]

Loved the puzzle, and yes, please more classic on the channel!

[@Rach881101]

17:12 for me. Nice classic sudoku!

[@jonotick]

I love that Mark also thought r5c9 was always a 4 as well! I think we both had exactly the same thought process

[@Kirbyfan87827]

Finished in 22:35. Not really happy about how the solve went, it felt like I was just bifurcating until there was a contradiction. Not sure how to feel about that. (Thanks to NelielSugiura's comment for pointing me in the right direction on what cell to start from.)

[@piarittersporn]

Pretty puzzle.

[@shahmatjf2]

Poser la question c'est y répondre! Yes, yes, more classic sudoku

[@chocolateboy300]

I finished in 17:44 minutes. This felt really hard. I was able to make my breakthrough by asking what if 9 was in r9c2. This bounces around the grid forcing 5 into r1c5. This leaves one place for 5 in row 3, in r3c8. This forces r3c9 to be a 3 and forces r6c9 to be a 2. This 2 forces a 2 into column 4 of box 5, breaking by not allowing a 2 to exist in box 8. Getting that felt like such a relief. The rest crumbled easily. Great Puzzle!

[@dwaynejuzyk2778]

love the classics

[@cramias1]

Rather than a specific cadence like "one classic a week," I would suggest simply being willing to feature classics when a good well crafted one emerges and gets a little hype behind it. I think if you're trying to stick to a specific cadence you will inevitably end up doing some that are fairly standard and not that interesting

[@christianmcneill699]

I think I'll call it a chain whiplash. That was amazing.

[@anaayoung9142]

This kind of classic is a hard one, that some times I can't find the solution alone even after spend a time on it. Because of it I discover that I am very bad at finding x-wings (is this what they are called?) and the other ones. But this time I was happy because I found the most important cell R9C9 in my case (I did similiar to Mark, but using that cell, and find the 28 pair). 😅 Thanks for the solve Mark!

[@goonjanmall]

Got lucky to spot that if R3C9=3, then R6 will have a contradiction of 2s. Was a breeze then from 8:28 onwards. PS - Solved in 16:39 - First time ever solving anything close to Mark's time. :D

[@ewetho]

Love classics

[@grenvillephillips6998]

I love a classic!

[@achad1607]

I noticed that whether r3c6 was 3 or 4, r9c5 must be a nine. Four starts the 6,7,8, and 9 chain down c5, while a 3 forces chain of twos back to r8c6, making r9c5 a 9 again.

[@SmartHobbies]

Absolutely brilliant chain. It’s an XY-Chain Nice Continuous Loop. I spotted it around the 8:00 point. Nice solve Mark. I have got to look further at this puzzle and this setter for my channel.

[@_n_d_]

18:37 for me. That was a cool break in.

[@bristolrovers27]

Definitely more classics Maybe as a GAS substitute, once or twice a week would be great

[@bogie2820]

I probably missed an announcement... why are there no more GAS puzzles?

[@bait6652]

"Y-wing hinge". I wanted to call it a fake thermo. Didnt see the forced sliding window of low digits on the right cuz didnt get the (35)in B3...but found the thermo-ish chain in C5 that turned my 4branch into dualsolve. Very nice design that makes u want to solve it again with that (35)

[@arthurcharest9061]

Classics are good!

[@Bobbottom70]

Hey Mark have you been watching the Countdown finals, maybe seeing how you would get on.

[@_-_-Sipita-_-_]

9:09 for me. that crane was funny.

[@lexyeevee]

to be clearer and sound less like bifurcating, i think the intended breakin is (spoilers obviously) an extended chain through row 9 and columns 5/9 that goes 12 - 23 - 34 - 45 - 56 - 67 - 78 - 89 - 91, and finally eliminates 1 from r9c8, which makes the rest of the puzzle trivial. the fact that it's in order like that makes it very much seem like the whole puzzle was designed to produce that pattern. plus, the title :) i don't know what the pattern is called [edit: the sudoku wiki calls it "xy-chains"], but it's exactly the same idea as a Y-wing, just extended to an arbitrary number of cells. it will always work in any chain of AB - BC - CD - DE - ..., as long as you end up with an XA pair at the other end. then A can be eliminated from every cell that sees both the AB and XA. it doesn't matter how long the chain is, how big the sudoku is, what shape the boxes are, or what the candidates for any other cells are. for a semi-intuitive explanation, consider a short sequence like AB - BC - CD - DA. you can write this as a single string by "gluing" the pairs together at their shared digits, to produce ABCDA. whatever the final sequence of digits must look like, it has to be this same sequence with one digit deleted. (this is because dual-candidate cells have one degree of freedom, and the chaining preserves that all the way along. consider: deleting C from the full sequence is equivalent to removing C as a candidate from *both* the BC and CD cells. well that immediately forces them to be B and D, respectively, which in turn resolves the rest of the chain in both directions.) so the correct solution might be ABDA or BCDA or ACDA, but since there are two A's, you can't delete *both* of them, and you'll always have at least one left at the ends. this is also true more generally, where a chain of AB - BC - CD - DE *must* have A in the first cell or E in the last (or both), but that's less immediately useful. it could interact with a variant constraint in an interesting way though

[@Nxluda]

Love this comment. The logic is great but I don't think I've grasped it 100% If I have AB-BC-CD and AB-AE-ED, any tile that sees CD and ED cannot have D in it? And is that true for sequences of any length or sequences of varying lengths as long as they originate from the same tile?

[@lexyeevee]

@@Nxluda yeah, that's functionally one chain (DC - CB - BA - AE - ED) so all the same stuff applies the explanation is in terms of the whole chain, but in practice, you can start anywhere and search in both directions until you find useful endpoints. (i suspect people tend to think of Y-wings in terms of the "hinge" cell rather than the endpoints, too.) with this particular puzzle i think i first noticed something was going on with the 34, since that's where the chain escapes column 9, and that's what makes it interesting - a chain confined entirely to one row or column isn't a chain at all, that's just a pair/triple/etc :) though the same reasoning still works!

[@Nxluda]

@@lexyeevee ah Gotcha. The starting point was off. Does it work with any two cells in the sequence. AB-BC-CD-DB-BE-EA. Could I eliminate any cells that have B and sees two cells that have B in them?

[@rmahu]

I think Y-wing is as far as you can go before you call it bifurcation. The chain requires. 1) Find the 28 pair in box 3 (nice logic) 2) Full pencil mark of box 3. (ok) 3) Full pencil mark of column 9. (maybe) 4) Full pencil mark of column 5. (really?) 5) Full pencil mark of row 9. (really?)

[@lexyeevee]

@@Nxluda only if your AB and AE also see each other - then you'd have a loop, so you could "cut" it wherever you like and treat two adjacent cells like the ends of a chain. i don't think that's very common... but it DID happen in this puzzle, since the 19 and 12 are in the same row! and you'll notice that you can for example eliminate 6, 7, and 8 from r5c5 (which sees "links" of the looped chain containing all of those digits), leaving it only with 5 and 9, and in the solved puzzle it does contain a 5. you could also eliminate 5 from r1c1 (which sees both 45 and 56) and correctly place the 5 in box 1

[@solfeinberg437]

Mark did this puzzle in about 15 minutes. I'm not sure that I ever would've realized that the value in R1C5 took a 1 out of R9C8. But it was easy to follow that logic and ther puzzle dissolved after that breakthrough. How does one look for this. I kept looking at values and hoping I could eliminate a possibility somewhere.

[@timothyrients1685]

I watch all of your classic puzzles. Not so much for the other styles.

[@chris5619]

8:59 - "AH! Look, this cell, if that's a 6, we get"...proceeds to highlight a ten cell chain..."well that's interesting". Me now thinking he somehow saw something that this was going to lead to before the chain when he explained "Ah!". In reality, it just removed an option from a 3 option cell.

[@NelielSugiura]

Only other thing I noticed when you kept going around with that 56 of the top mid is that you also had an x-wing on fives in the first and third row, so you could have placed it in row two earlier. Did not change much, so not a big deal.

[@solfeinberg437]

Box one had a 5 in row 1 or 2. Box 3 had one in row 1 or 3. What X-wing? Help me, I'm not seeing it. I'm looking at 13:06.

[@RichSmith77]

I can see if you make the '56' orange cell (r1c5) a 6, and chase the values around the chain as Mark kept doing, then you end up with 5 in r1c7. So 5 is in either c5 or c7 in row 1, and therefore not in r1c1 in box 1. That allows you to place 5 in row 2 in box 1. I don't think you could call it an ”x-wing on 5s" though.

[@brucejones533]

One classic from Simon, one from Mark each week? A bit of coaching for those of us working our way up to variant Sudoku?

[@FloydTaylor]

I didn't resolve that 28 pair in column 8. I worked out Box 5 could have a 2 in the clockwise chain but could in the anti-clockwise chain. Still ended up with the 2 in Box 5 Square 1. MORE CLASSICS LIKE THIS PLEASE

[@navster100]

I just tried the 6789 and it just worked

[@siorac1147]

I'm going against the grain here: the fewer classics the better, and none would be best.

[@enjoyalaugh133]

Wow, It took me ages today.

[@jonLough]

I'd like to add my vote to more 'classics', I think sometimes it is easy to lose sight of why people like Sudoko and while some (not all) of the variants are probably more interesting to the likes of CtC, some of them are so far removed from a classic to almost be a completely different kind of puzzle.

[@ristojokinen1258]

II found 7 to box 2 in similar way. AND IT WAS EASY after that.

[@hiawathadevries7222]

Yes, Classic Sudoku please. But also proof or explain solution methods. Like x-wing on 6/7 in three cells: fourth can't be 6 and can't be 7! Why? I agree it can't be 6/7. It is possible that it is true. But I'm not yet really convinced. Even when it would be a "hidden" (by fog of war?) but given cell?

[@hiawathadevries7222]

Ooh this is a question about uniqueness.

[@RichSmith77]

Your 6/7 example sounds like a use of uniqueness. Some people are happy to use it, but I'd only use it if the speed of getting a solution was important. I prefer to find the logic that proves the solution is unique, rather than assume it. In your example, if the fourth cell of the rectangle/x-wing was also 6 or 7, then in a classic sudoku there would never be anything to prevent you from swapping the 6s and 7s over in those four cells, so there would have to be at least two solutions. If you allow yourself to use the meta information that the puzzle will only have one unique solution, then it must be that the fourth cell isn't a 6 or 7.

[@alanclarke4646]

I got stuck with this one. I got the Five in box seven, and a two eight pair in box three, and couldn't get any further 😢

[@RGS61]

And that's why it's called "Next In Line"! Lol!

[@phandor]

Is this called a xy-chain or so?

[@RoderickEtheria]

There is an enormous chain of bivalue cells in this puzzle. I figured out a 7 in r7c5 produced 2 in both r6c6 and r6c9.

[@willfaber633]

Call it a choo choo train

[@wanderlustwarrior]

38:02 for me. Much longer than I thought it would be.

[@wanderlustwarrior]

29:34 for me this time. Still a challenge.

[@inspiringsand123]

Rules: 02:05 Let's Get Cracking: 02:34 What about this video's Top Tier Simarkisms?! Chocolate Teapot: 1x (11:46) And how about this video's Simarkisms?! Ah: 5x (03:52, 08:00, 09:00, 09:00, 12:11) Clever: 2x (07:51, 15:15) Pencil Mark/mark: 2x (02:42, 08:00) Weird: 2x (13:25, 15:07) Sorry: 1x (02:30) Lovely: 1x (16:56) Brilliant: 1x (16:54) Surely: 1x (09:18) Obviously: 1x (08:53) Most popular number(>9), digit and colour this video: Fourteen, Twenty Eight (3 mentions) One (43 mentions) Yellow (2 mentions) Antithesis Battles: Row (14) - Column (6) FAQ: Q1: You missed something! A1: That could very well be the case! Human speech can be hard to understand for computers like me! Point out the ones that I missed and maybe I'll learn! Q2: Can you do this for another channel? A2: I've been thinking about that and wrote some code to make that possible. Let me know which channel you think would be a good fit!

[@harrykeogh3994]

Prefer Variant puzzles as there are numerous Classics elsewhere but ones like this with a really neat solve path using BVCs are always welcome I do miss the GAS puzzles though :(

[@nevilleenglish]

Bremster does them now that CTC has stopped.

[@harrykeogh3994]

Thanks @@nevilleenglish

[@mudscuffer]

~25min for me. Quite tricky to find the break-in on this one.

[@robertcousins2274]

12:15 for me

[@srwapo]

Yup, I only got that 5 after 14 minutes and gave up...

[@rmahu]

I only see and a very long chain that lead to a single elimination and a puzzle that collapse into nothing. Traing to find the chain was boring. Solving after the chain was boring.

[@HotelPapa100]

Never got to the full ring of pairs. No such thing as a "hinge" in a ring. "Next in line" should have been a clue...

[@tamaspolyak5564]

17:43 Didn't break a sweat. It was straight forward deduction. No bifurcation for me.

[@bruceh8043]

12:10 for me and solver #751.

[@ericpraline1302]

Personally I would be happy never to see a classic again :)

[@Forbizz]

I think this is called an xyz chain.

[@bjornhammer5321]

I really don't get why people seem to appreciate this puzzle. When I solved it, I had to bifurcate and assumed I missed some swordfish or other complicated logic, but the solve presented here is almost the exact same bifurcation, and yet people seem to think this is compelling for some reason?

[@yash08100]

Yeah absolutely. A bit weird for this to feature on the channel.

[@Qazqi]

While Mark doesn't capture the generalized logic, this isn't bifurcation. The entire loop of pairs is all high or all low, meaning that between any two entries, you'll have a shared digit going into one of those two, eliminating that number from any cells those both see. The beautiful part is that the loop is structured to be 12 23 34 ... 89 91. This is the same consequence Mark used, but without seeing the bigger picture of it all. The key part behind this being a pattern and not bifurcation is that this works with any closed loop of pairs such that each link shares one digit.

[@rmahu]

​@@Qazqi I only see bifurcation and your coment didn't tell me way it isn't.

[@bjornhammer5321]

@@Qazqi I'm sorry, but a pair of 10-deep forcing chains predicated on seeing what happens when the (12) in the lower right corner is 1 or 2 is definitionally a bifurcation to me. I understand now that people are reading it differently because it is very intentionally set (what with the patterning), but it being a cute premise doesn't really change it for me.

[@or3213]

@@bjornhammer5321 I would define bifurcation as a "trial and error" method where you just guess a value in a certain cell without any logic involved, without knowing how it will affect the rest of the puzzle. And then you continue the solve until you either solve the puzzle, or get a contradiction, whatever happens first. In this puzzle, I also noticed the chain of 12-23-34-...-89, and after thinking about this chain I realized I could treat it like a sort of thermo with 8 cells. (If the chain starts with a 2, then it forces higher numbers all the way to the end of the chain, and if the chain ends with 8, then it forces lower numbers all the way to the start). I didn't mentally included the 19 cell in that chain as it doesn't apply to the "thermo logic". With that thermo pattern in mind, I looked at row 9, and then could think about how different values affect the chain. Therefore I personally wouldn't classify this as bifurcation, because I immediately could see how different values in the cells of row 9 affect the rest of the cells. I liked the puzzle because I was amazed with myself that I managed to find the trick in the first place. I usually don't manage to solve classic sudokus that are featured here, because the break-in is too elusive for me.