"Just" a Classic sudoku?

[@ianpearse4480]

Wow, that was nice. Thank you for sharing.

[@alessandraperna3343]

Mark, thank you so much for taking the time to solve this puzzle! I managed to crack it with the chain you spotted over the 8's. I had written down many digits with the help of some techniques mentioned in the comments below and then got stuck. I haven't seen any comments on the hidden pair (1&8) in r6 c6 and c9 (due to the 8-1 pattern over c5,c7, c8), it helped me somehow, can't recall how though right now! In any case thank you again, I am really honored and happy you found this puzzle challenging! Grazie mille! Alessandra

[@johabee]

Really enjoy the solves of these difficult ones. Forces Mark to be creative, not just apply well known patterns, and he delivers! The chains that he finds, are not that hard to understand, once he points them out of course. I couldn't solve this one, but his creativity and intuition inspires me to keep trying.

[@woodchuk1]

The “alternating inference chain” that Mark spots on the 8’s about 6 minutes in can be eliminated...but only by first finding a finned x-wing, a finned swordfish, and an example of almost locked sets (the so-called ALS-XZ rule). Brutal! For those unfamiliar with the ALS-XZ technique, it works like this. An almost locked set (ALS) is a group of N cells located in a common row, column or box that collectively contains N+1 digits. We have to find 2 different ALS somewhere in the grid that share two common candidates, and one of these two must be placed in such a way that it cannot occur in both ALS at the same time. Then, any cell outside the two ALS that can see all instances of the OTHER common candidate in both ALS cannot contain that other common candidate.

[@AFastidiousCuber]

He missed the fact that r6c5 can be a 4, but that cell can be eliminated a different way: If r6c5 is a 4, then r4c1 is a 4, and r9c2 is a 4, which eliminates all the possible positions for a 4 in box 8. Also, to anyone else trying to solve the puzzle, my advice would be to focus on this trick with the fours and focus on row 3. Once you resolve row 3 and eliminate r6c5 from being a 4, the puzzle basically collapses.

[@anattandan]

easier to find

[@alexvalache]

Paused the video to find this comment :)

[@ozertamer210]

you mean r6c2 is 4 not r6c5? Is it? I name that cell 6b by giving numbers to rows, and letter to columns. I have a full set of notation above. please look at it and comment. Thanks.

[@martinhierz6084]

There's also a skyscrape/sashimi finned x-wing/whatever you call it going on with the 4s in column 2 (row 6 and 9) and column 4 (row 4 and 9) straight from the beginning which eliminates the 4s in r6c5 as well as r4c1.

[@driesvanoosten4417]

Actually, there is another way to eliminate the 3 from r6c2, through the triple in r3.

[@prahas777]

48:14. Lots of help from Mark needed. Yipes! Thanks.

[@emilywilliams3237]

Touring older videos brought me here. Very instructive. I feel as if I could learn a lot by watching this one a few times, so I’m saving it! Thanks, Mark.

[@Moksoory1]

I'm curious to how Simon would have approached this puzzle. Not a fan of forcing chains. Maybe some hidden bent triples, empty rectangles, etc.

[@asamirid]

unbelievable analysis you did here, respect ✅✅..

[@njuham]

I've never seen Mark struggle this much, usually he just waltzes through even the trickiest ones.

[@Wecoc1]

6:16 What he found there is called an Alternating Interference Chain (AIC) 10:22 I'm not sure what's that called, it would be a case of Multi Coloring* *Edit: And looking at it again, he messed it up with that 4 in box 5 so I'm not considering it a proper step. You can get around that with a Skyscraper: A 3 in r6c2 forces a 4 in r9c2, then at c4 the 4 can only go in r4c4.

[@necaton]

isn't this some sort of bifurcating? wonder when its called logic and when its called bifurcation.

[@zelassin]

yeah he does call it that later

[@Wecoc1]

AIC is usually not considered bifurcating. Multi Coloring is closer of being bifurcation, so some consider it is.

[@breid3492]

10:21 the 4 is forced to top left of box 5 due to box 7s 4 interacting on box 8

[@ivan_osorio]

7:13 ...I really dislike when a puzzle demands this type of "logical bifurcation" (or whatever it's called) where you have to keep a guess going until it either works or breaks down. Definitely not what I'd call "beautiful" in something like this. Spent half an hour looking at it and for this to be the thing that gets me (and you) unstuck feels somewhat... underwhelming.

[@jeanbarque9918]

For me there is only one type of puzzle that can need bifurcation, its the puzzle box, where you try things, push somewhere, pull elsewere, trying things to solve it, like a rubik cube or a chonese puzzle box, btw I make lego puzzle box 🙃. In my opinion a puzzle like sudoku, pentominos, etc should be possible to solve 100% without bifurcation. Or its a bad puzzle. We should be able to solve it with logic. When I started sudoku. I started without knowing what to do, how to do and I had a thought: there must be a way to find the numbers without having to try the options. Trying every options is infinite and pointless, there must be technics to find the numbers, and I learn by myself and find all the basic technics by myself as, in my opinion 99% of people who does sudoku. At this moment, if you told me that there are sudoku where you have to try options, I would answer that the person that make those sudoku does'nt know how to create a sudoku because they don't undetstand how to solve sudoku.. A sudoku needs logic to solve, if you need bifurcation, its a bad sudoku, in my opinion.

[@Xarlus]

i dont think this is bifurcation. He was kinda lucky to spot the chain pattern but it is a known strategy for extreme sudokus called "alternating inference chains". But i can agree that it isnt that fun anymore if you have to be lucky or a computer to spot strategies. i startet the puzzle and stoped 3 hours in with no progress after finding the skyscraper on 4s to take it to sudokuwiki to get my next step. After that i stopped completly. To hard to solve ever.

[@nimbletim]

exactly this. trial and error method, no logic involved whatsoever. if he used it in one part, what stops me from using it throughout the puzzle and then i can say i "solved" it.

[@TheGerkuman]

I think people can spot this kind of thing.

[@rabidsamfan]

@@jeanbarque9918 Either/or logic is the root of nearly all the patterns you call techniques. Even an x-wing. Spotting where to apply it is the art. If Mark was guessing, he would have picked a truly random possibility, not one that lead to a deduction within a handful of moves. I think the fear of "bifurcating" ruins a lot of neat solves for people. But I took a logic course in college and we used either/or constantly in our proofs.

[@Silkeye]

A 3 in r6c2 doesn't force a 1 into r6c6, but into r4c4. With the 4 in column 2 being pushed to r9c2 it leaves no option for a 4 in column 4. Conclusion is the same, but the logic was missing.

[@fanyaugusts9760]

Sorry but Mark does't explains clearly: 10m15s "If this one is 3.."..we have three possible positions for "4" in the central block. Why the "4" has to go to r4c4, when there is an option for "4' at r6c5?

[@stevieinselby]

He got lucky. (Again. I swear if I was as lucky as Mark is I'd never need to work another day.) In actual fact, by guessing where the 3 goes, that fixes the 4 in c2 into box 7, which in turn fixes the 4 in box 8, which does in turn rule out r6c5, so it turns out that a 4 *couldn't* go there after all, but it was just good(liffe) luck that it worked out that way.

[@JosephPetersonJEEP]

@@stevieinselby To be fair, we don't get to see the puzzle if he gets unlucky.

[@voljes9007]

Actually, what he tried really works, but probably he just doesn't utter the whole logic he has in mind. In fact, "If this one is 3.." finally a 4 goes to the bottom of the column 2 which places another 4 in the box 8 which rules out your suggested option.

[@pietndala7394]

If it’s 3 in r6c2, then 4, will be in r9c2, which then restricts 4 in c4r4, which then restricts a 1 in r6c6, and the same 1 would be in r3c6 and as he would say ‘knowledge bomb’. The 1 in r3c6 results because, of the 1 in row1c2.....higher level thinking 🤔 💭 👌🏻🙌🏽

[@rickcarter7495]

I solved it but it took quite a while... I had done 3-4 weird logic paths that took 20 minutes to eliminate a few numbers from potential boxes before it got where I could fill it in. Once I got past that I was able to fill in using normal sukoku methods. Not sure what the tricks I used would be called. xy bent wing skyscraper combo? lol

[@jockeshobbymeck]

got stuck at the same place you did. but i waited for you to do a few more digits so i could finish :D really fun to see you guys solve these incredible hard pussels! good work!

[@glennmelven3414]

Mark says, "I;m not going to say sixtynine pair". as he says what he says he not going tosay.

[@mafoofoo]

I'd tell you it's a prime example of the rhetorical device of apophasis, but it's not my place to say such things.

[@ozertamer210]

KEYS for below Notation: BOXES: A, B, C, D, E, F, G, H, I ROWS: 1, 2, 3, 4, 5, 6, 7, 8, 9 COLUMNS: a, b, c, d, e, f, g, h, i CELLS: 1a, 2a .... 9h, 9i How do you read? Example first step: 1.

[@neilnolte2587]

At 5:58 the 4 can be eliminated from C1:R4 using the empty rectangle in box 7. I'm starting to spot things. :)

[@rabidsamfan]

36:24. Fairly hard, too. Now to see how Mark solves it. Smoother than me of course, but missing the 9 in the center box from 18:46 on had me shouting at the screen.

[@HolyChez]

What's interesting at 9:40 is that if you look at your loop of 4s in boxes 4, 5, 7, and 8, you can prove that the 4 in box 4 must be r6c2. First would be 4 cannot be in r4c1 by simply following the loop; it would create no place for a 4 in box 5. Second would be a 4 in r6c1 as it forces a 1 in column 1 of box 7 and a 1 in the last place available in box 5 at r6c6 thus making it impossible to put a 1 in row 3. This leaves the only available position for a 4 in box 4 to be r6c2, just a different route for the same conclusion.

[@PH34RB]

Those 2 eliminations are available right from 6:10, but they don't yield a digit right then. By way of loop, slot machine or skyscraper.

[@gposchman]

After you put a 7 in box 2 row 3 column 6, in box 8 you created a hidden single in row 8 column 6, which may have helped you move faster. Thank you for the video. Gene

[@romane1008]

I could not solve this puzzle if my life depended on it

[@ghosttwo2]

Most of the puzzles posted on this channel are 'exhibition only'. I figure 1 in 10 are actually solvable by people who haven't made a career out of it.

[@br0wnknight989]

@@ghosttwo2 I beg to differ. Most of the puzzles are solvable by the common man and the fact that they (usually) show us a logical path proves that anyone can solve them. That's the beauty of this channel.

[@Mephistahpheles]

@6:16 One (tiny) bit of slightly easier logic is the skyscraper on 4's on column 2 & 4 to eliminate the 4 from C5R6. Something similar with 3's....but using row 3 and column 9: box 3 becomes the "base of the skyscraper"...sort of. Eliminate the 3 from C1R4. Then I quit.

[@lrvogt1257]

I tend to fill in all the possibilities in columns or rows that have 3 or 4 openings. The don't always pay off right away but but thy do eventually including revealing X-wings.

[@alienrenders]

30m for me. I did some deductions on the 4's first. You can eliminate a few possibilities early on. I then guessed a 9 in r5c2. Puzzle broke open after that. I like the find on the xwing on 3's. That was very nice.

[@pallavgoyal482]

I found an incredibly elaborate pattern on 3’s, something like a swordfish, which is there since the very beginning of the puzzle. Basically, rows 2,3,6,7 and 8 can contain a 3 only in columns 1,4,5,7 and 9. Hence, because of a swordfish-type logic, rows 1 and 5 can contain 3’s in columns 2 and 8, and so we get an X-wing on 3’s immediately, which is different from the one that Mark used in his solve!

[@stewartb1234]

r6 also has a 3 in column 2 as well no? doesn't that bugger up the swordfish?

[@pallavgoyal482]

@@stewartb1234 Not sure I understand. At the beginning of the puzzle,in the 5 rows I mentioned, 3 can potentially be in any of the 5 columns I mentioned. That’s sufficient for the swordfish logic, no?

[@Coyotek4]

Today was bad for my ego. I got nowhere with the 'Simon' puzzle, and I ended up resorting to bifurcation (twice!) to finish this one. I found a solution in 21:16, but I would *not* say I solved it. EDIT: after watching the video ... yeah, no way was I finding all of *that*.

[@nimbletim]

Mark bifurcated as well so yeah.

[@philipmetcalfe4736]

@14.53..... Mark said roughly...." now that C9, R2 can not be a 3 ...or a seven so C9,R2 becomes a 59 pair".......what had illiminated the 5 from C8 R1???...There was no 5s in R1 or in Box 2. The only 5 on the board at the time was in box 1 at R3, C2???.... have I messed up or missing something.....or more likely ...got a lot to learn😊😁

[@bluerizlagirl]

This is definitely a game of indirect elimination. As well as obvious cases where a cell directly sees a digit in its row, column or 3*3 box, there are greedy combinations that swallow up digits elsewhere in the row or column further reducing the possible candidates in each square and impossible interactions between combos (_vide_ the threes). I suppose this is an exercise in minimalism, trying to give away directly as little information as possible with each digit placed!

[@jameswiebe8956]

18:54 - "Still can't solve this 1-4-9." - Uhmm, yes you can. That was the 9 you just put in box 4. However, having said that, the x-wing solve of 3's, showing that a 1 would need to be twice in column 6 was beautiful to see.

[@Fredman2410]

It seems that whenever Simon presents a difficult classic, there is a swordfish or two involved. Mark doesn't seem to spot them, but rather relies on his prodigious brain to find other complex paths. Keeping an eye on this, I found a swordfish on 3s quite quickly (R1,5,6 C1,2,8) and solved the puzzle in 20 minutes. Yay me!

[@jeanbarque9918]

I understand the swordfish, it's like a x wing, it eliminate the the other options in the rows and colomn. At the point were I am there is a 4 in r6c2. So with your swordfish the unique candidat for row 6 is in c1 because c2 and 8 are occupied. So I thought "great so the 3 in row6 goes in c1 but I asked myself "it is really impossible to put it elsewere in the row, so I tried in c7 and no problem.. So: I tried to put a 3 in r6c7 and then I put then a 3 in r1c8, then r3c1 So I have the 3 in row 1 in c8 as your swordfish bu in column 1 I put it in row 3, for the row 5 I put in column 2 and row 6 in column 7. So there is a 3 in c128 and row 156 but without making a sword fish because the 3 in row 6 is in column 7 and the 3 in c1 is in r3 In brief the 3 from c1 is not in the swordfish but in r3 and 3 from row6 is also out of the swordfish but in c7. At this point its working, in box2 row2, box8 r7c4 or r8c5 and box 9 c9. So at this point I dont see how it is a swordfish.. Then I see Mark finding a x wing WHICH makes sens. The 3s in row 3 and 6 are in column 1 and 7. Which breaks your swordfish because r1c1 becomes impossible and in row 6 the 3 can go in c7.. Then when you see that puting a 3 in r3c1 and r6c7 breaks because of the 1s in the rows. You put the 3s in r6c1 and r3c7 but no swordfish involved because there aint any because of what I said.. the 3s could go in r3c1 and r6c7 until you eleminate this option because of the 1s and then you ve got the 2 other 3s.. no swordfish..

[@timothymcdonnell1186]

I must be missing something, because there is not a swordfish on 3s that I can see in those cells. Column 1 has many more than three positions, until the X-wing Mark used, at which point it has 2 positions, only one of which is in the rows of your swordfish.

[@voljes9007]

It's simply a lie. Or stupid mistake. There's no swordfish.

[@martinhierz6084]

At around 12:00 he tries that thing with the "alternating inference chain" (or whatever thats called) with the 9 in r5c2, he should have done this with the 3 as well (which he for some reason didn't) because then you can quite easily spot that if it were a 3, there also would be a 3 in r6c7 as well as a 1 which obviously isn't possible. That forces a 9 in r5c2 and the whole sudoku falls apart quite quickly, no fancy x-wings or anything else thats difficult to spot

[@robinbaich169]

Took me 31 minutes to solve and I'm an amateur at sudoku. Has to be a fluke, but I'm quite pleased that I almost matched Mark's time with it. Almost makes me think I'm improving at the game! :)

[@zynzane9680]

Me too, solved it on my own in 27 minutes, but then I do it the amateur way.

[@robinbaich169]

@@zynzane9680 - Amateur is me all the way. And I'm fine with it. As long as I don't have to resort to "maths" - as Simon says.

[@EmperorNeel77]

You could've avoided a lot of steps if you saw that r5c2 couldn't be a 3 as it forces a 3 in r6c7, which forces a 3 in r1c8 and then there is no where to put a 3 in r3. Once you find that you can put the 9 into r5c2 and it's fairly straightforward after that.

[@dibenp]

Why not in r3c1? 🤔

[@trolleymouse]

I made one guess, got it right, and everything fell into place.

[@MariaVlasiou]

Same here. I guessed early on the 1 in box 1.

[@jonahkoehlert8747]

Finished in 14 minutes. I did use uniqueness at one point though. I typically try not to do that but it made it much simpler

[@alvaropallete]

According to sudoku wiki, this needs 3 steps of x-cycle and 3 steps of alternating inference chains. Those make it a extreme grade with an overall score of 399. So I may not be able to solve it, but I'm keen to learn about it.

[@eduellery]

What is this sudoku wiki? A solver?

[@voljes9007]

@@eduellery yep, www.sudokuwiki.org/sudoku.htm

[@xaviarthunders4894]

That took me an hour and 58 minutes :/ Well done as always, Mark!

[@zdibs]

Took me an hour... didn't get the logic all the way, so I had to test the digits in R3C1 until it worked. :( Edit: I missed the 3 X-wing @13:30 ish. Dangit. That would have helped immensely.

[@serkanergun0]

Why does 4 have to be in r4c4 at 10:03? cant it be on r6c5?

[@HolyChez]

Follow the chain of 4s that the 3 creates in a counterclockwise loop into the middle.

[@serkanergun0]

@@HolyChez oh yeah it really does, thanks

[@hartosaarinen221]

But that is not how he thought of it I think? Maybe a mistake with notation?

[@HolyChez]

@@hartosaarinen221 That's the funny part. That loop of 4s in boxes 4, 5, 7, and 8 actually makes the r6c5 4 impossible, which leaves the two 4s he was looking at in box 5. Visual mistake or a skip in logic he still got it right. xD

[@HolyChez]

@@hartosaarinen221 That logic is what I keep looking at, but I think he actually was looking at where 4 can go in rows 2 and 4.

[@_mnejing]

Ran this through the Andrew Stuart solver when I got stuck and noticed the length of this video. I think basically everyone got stuck at the same place Mark did, as that's where the logic goes straight in to Alternative Inference Chains. The solver showed using it at least 3 times, and that's just... very meh to me. I'm not necessarily against AICs, but when they're just stacked a bunch of times, it feels less like logic, and more like trial-and-error (AICs feel way too much like bifurcation to me). I appreciate that Mark can solve this without being an actual computer, but this puzzle just feels kind of mean in general. It seems less about logic, and more about how many numbers can you keep track of at once without getting completely confused, and that's just not... fun.

[@supergogeta7003]

Simon would hate this puzzle, I hope he gives this a crack

[@pietndala7394]

It’s good to realise that r9c4, r4c4 and r6c6 is a bend triple of 148...

[@roscoman1938]

I see that now but how do you use it ?

[@Kelters]

Difficult, but not impossible. I feel so pleased, not only to have finished, but also to see that Mark used almost exactly the route I used. (Including not immediately seeing the pair of 9's resolved in the middle box!) Took me 2x as long tho. I had to watch the vid to see if I had missed any easier path, but not, apparently. And, yes. The niggling frustrations of "surely it must give me more!" after each leap of logic. Thanks for this one.

[@bazdarinothebizier9085]

Queen be damned, he pulled a Goodliffe!

[@AndreAy1975]

Solved it with help from the video for the important parts.

[@jdyerjdyer]

I'm guessing I'd be accused of bifurcation (cheating), but I couldn't see the logic here. I did make it a very educated guess as I bifurcated on R1C4 as removing a 1 from that cell gives you a triple in the column. Unfortunately, doing so you quickly get to a clashing digit (I forget what it was, but I think it was in box 6.) Anyway, once a 1 is here, the puzzle isn't super easy, but it is manageable.

[@buzzly108]

Let's get cracking: 2:00

[@YossiZinger]

well I got stuck pretty fast, then to get a hint i put it in a soduko solver, and after 3 consecutive "extreme/diabolical strategies" steps, I understood this puzzle was not meant for human beings

[@coyote4237]

Thank you.

[@ArunIyerS]

This is a very hard puzzle, sudokuwiki solver grades this as an extreme grade with a score of 399.

[@nick46285]

that's why I can only put 2 numbers without a guess

[@nick46285]

3

[@loganv0410]

KZbin just ran a Rolaids commercial on me at 19:00 in this vid: Such Timing(tm)

[@evlredsun]

i could not spot that x wing on 3's, but once mark spotted it i was golden. still an embarrassing time for me though.

[@joeshonk9715]

Isn't there a second x-wing on 3's? r1 c2 and c8, r5 c2 and c8?

[@SadisticSenpai61]

I guessed once and apparently guessed correctly. Everything just flowed from there.

[@FloydTaylor]

6:16 alternating inference chain.

[@lewsouth1539]

I got stuck, so started watching the video... After Mark showed that the 3/4 in box 4 couldn't be a 3, I thought, could something like that work for the 3/9? I quickly found that the 3's would mess up the 1's--like Mark found w/ the x-wing--and didn't overlook the 9 in the middle... and it was done.

[@gengar678]

I think bifurcation is ok as long as it is done only in the head, so without marking down etc. Technically a one step bifurcation is the main way of solving any sudoku. This puzzle is ugly as nothing else btw.

[@BertBergaf]

Wondering whether I got lucky with a false deduction, but solved it in under 10 minutes without requiring very advanced techniques

[@user-yl3pp8fy9w]

10.20 Why does 4 have to be R4C4, what about R6C5?

[@jdyerjdyer]

All I can say at 22:58 is huh?! Column and Box blind, now? lol, Easy to miss. :) Do it all the time myself. :)

[@ferst262]

21:40 “I’m not gonna say a 69 pair” xD

[@LednacekZ]

this was insane

[@JimmersThomas]

I'm not a particularly good solver but I found this one relatively easy. I sometimes labour for 40 minutes over ones you describe as approachable, but somehow managed to ace this one. No idea how

[@lroke2947]

In my case it would happen when I make a mistake.

[@JimmersThomas]

@@lroke2947 Yeah I wonder if I made a mistake on this and accidentally got a number right by some fluke

[@alessiagnocchi971]

10:03 if r6c2 is 3, why does 4 have to be in r4c4 and not in r6c5?

[@serkanergun0]

I asked exactly the same question :)

[@Silkeye]

seems he got confused by his triple pencil marking on 4s in box 5

[@HonkIfYouLoveBeer]

If you work it through, it actually *forces* a 4 in r6c5 as you say.

[@HolyChez]

Follow the chain of 4s that the 3 creates in a counterclockwise loop into the middle.

[@alessiagnocchi971]

@@serkanergun0 I tried putting 3 in r6c2 and it doesn't work because then there would be no possible place for a 4 in box 8. I think it was a lucky guess

[@andrewness]

Got this in 28 minutes, but with very little elegance.

[@mikesummers-smith4091]

I managed to prove that c1r5 couldn't be a 3, then guessed once (which 3 in box 4 fixes three digits?) and got lucky.

[@bilbo206]

What is bifurcation in Sudoku and why is it frowned upon if it works? Could this be mentioned in a video please?

[@transient_]

It involves guessing. Follow a path until it proves to be wrong. Undo and follow the other path. It is accepted if the path followed doesn't take so many steps that you can't avoid taking notes to keep track.

[@stevieinselby]

As Transient says, it's just guessing. Usually when you have a cell with just two possibilities, and you can see that picking one number will have a knock-on effect on a load of other cells. So you try one, and follow through from there, which could lead to one of three outcomes: 💚 you reach a situation where the puzzle breaks - this is what you _want_ to happen, paradoxically - which proves that your stab-in-the-dark was wrong and therefore it *must* be the other number that was right, so you unwind back to that point and go with the other number. 💛 you follow through logically and complete the puzzle - this is not as good as reaching a contradiction, because you haven't proved that it is the _only_ valid solution, but it is still better than the third possibility... 🧡 you reach a point where you have exhausted the logical chains from your bifurcation and it neither reaches a contradiction nor a completed solve, so you now don't know whether your guess was right or wrong and you have to unwind it all and you're no further forwards. Serious solvers don't like to use bifurcation - although may happily resort to it in competitions where speed is of the essence, as it can be quicker than working things out logically - because the whole aim is to use logic to resolve the puzzle. Any mug chump can try sticking a number in and seeing what happens, but the elegance and skill comes in finding a logical path to a solution rather than brute force and guesswork.

[@Jazminbanana3012]

42:09 - one of the first times using bifurcation

[@kimberlypreston6204]

at around 10 minutes in when he's explaining why that can't be a 3 I am lost. I followed his logic and when he said that the 1 has to be a 4? That is where he lost me. Why does that have to be a 4. there were other options for the 4 and several other numbers that could be there. I am not done watching so maybe he explains it more in depth but I had to comment to see if anyone can explain that to me. I am generally new to difficult sudokus.

[@lroke2947]

Since my sanity is on the line, I'd like a second opinion from another qualified doctor. But honestly, I'm very impressed with the diagnosis I've just seen.

[@bluefloyd1]

is this a CG puzzle? seems like it, a program that finds hard paths with a symmetry constraint. I thought you guys didn't do those?

[@gwenting]

Taked me 30:08 minutes. The clue with the 3 and 7 but still difficult to solve

[@pauldbentley]

“Not going to say a 69-pair” 😂🤣

[@joeshonk9715]

And then a 3rd x-wing on 3s, r2 c4 and c5, r7 c4, r8 c5?

[@JalebJay]

21:40 not going to say "69" pair... too late

[@seanmcdonough2683]

Woo. I beat Mark. Of course I just went ahead and bifurcated row 3 to do it.

[@johnnymichielsen961]

Finned x-wing on 3 8:30 in C 2/8 resulting no possible 3 at C1/R5 leaving naked single 9 at C1/R5

[@johnnymichielsen961]

Sorry I am wrong, no possible 3 is correct due to finned x-wing however no naked single at C1/R5

[@greefkarga7898]

15.43

[@user-A168]

講的好

[@eternalblasphemy6526]

20:34 for me, was a fairly easy classic one.

[@jdyerjdyer]

I heard a pair was going down in box 1 at around 21:35.

[@blobdffoo819]

Solved in 28 min, not amazing time, i lost some time while not seeing some obvious things

[@markscher1968]

At 10:50 you found a problem in column 2 with the couplets (34 - row 6) and (39 - row 5) and brilliantly proved that couple 34 could not be a 3 since caused couple 39 to be a9. You then proved that it caused a contradiction in column 6 rows 3 and six to both be 1s. You the prove that couplet 34 must be a 4. What you do next was an error. You the decide that knowing the 4 is of no help. Yet if you look at the brilliant logic you went through to get the, it all presumed why the 39 couplet couldn’t be 9. Thus the rest of the cells conclusions were still valid. I.E. you proved that couplet 39 couldn’t be 9. Clearly, nothing stops you as you always find more than one way to skin a cat. Thanks for letting me hear your thinking.

[@markscher1968]

Oops. Never mind. Everything I wrote was incorrect. I am embarrassed. Please kindly disregard my earlier reply. Apologies. No mistake was made by you.😮😮😮

[@nimbletim]

if the puzzle is so hard that you need to play the guessing game in order to solve it, then don't publish it :3. we all know how to guess and how to luck-solve something. no fun there.

[@farmersix4434]

Easy. With a lot of biacheating 😅

[@robbiebaker3722]

I got it in nineteen minutes!!1

[@adrianhead6272]

Done in 15m07s.

[@adrianhead6272]

You'd have probably found that easier if you checked your own pencil marks - the 9 in box four resolves the 149 in box five instantly (you just fail to spot it)

[@user-A168]

Good

[@antebellum1776]

12:59 with two lucky bifurcations.

[@aous9679]

meh this puzzle has no logic just a trial and error

[@davidkay6655]

5th

[@MemeLord42]

Firstn’t

[@dashxdr]

Classic sudoku boring, at least do a sandwich and or killer cage

[@romane1008]

I don't think he asked for your opinion

[@michaeljarcher]

Cracking the Cryptic has 1,460 Videos to choose from, whilst having 49,543,774 views, if you like to use the search function or the excel sheet can divert you to a suitable video for your viewing pleasure. And some people may find other puzzles boring. Each to their own, but we don't put shitty comments.

[@dashxdr]

@@romane1008 Yes he did when he started making a career of youtube. Welcome to the internet.

[@dashxdr]

@Rowan Macy I work the puzzles these guys introduce (sometimes). Their appeal is the spice they add to sudoku. Plain vanilla sudoku is so 2005

[@user-sr5wx2gf4j]

I prefer when they do classics.

[@user-A168]

Good