A Classic Sudoku to start the Year

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Normal sudoku rules apply (Place 1-9 in each row, column and 3x3 box).
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Hi! We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships. We're also "cryptic crossword" aficionados. Mark is the twelve-time winner of The Times championship and twice Senior World Champion in Sudoku, and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.
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▶ Contents ◀
0:00 Theme Music & News around the channel
7:00 Start Of Solve - Let's Get Cracking!

[@SmartHobbies]

Fantastic puzzle and great solve by Mark. Mark, 16:50 you found a W-Wing using the 19 bivalue cells as end points that are connected by a conjugate pair of 9s.

[@Urroner]

For the New Years, I need to count my blessings. First, I am very grateful to have lived to 70 years. Back in the day, most people had bought the farm by then. Some of my sons ask me when I'm moving to a small town and buying a farm. Only if you go in on buying the farm. Second, I am very thankful for Somon and Mark. It was just right after the pandemic started. They had just started two videos a day. I had tried playing sudoku before, but filling every square with all possible numbers overwhelmed my ADHD infested brain and most of the time I love my ADHD. The first thing I learnt was Snyder's notation. That was the third best thing to happen to me when it comes sudoku. Of course, the two mostest bestest things are Simon and Mark. Their sense of humor, their good looks (I think I'm partially blind. 🤭), their poking fun of each other ( Why yes Simon, it's very approachable. The puzzle wasn't very approachable and Simon thought he was losing sanity. That was as classic video.) At first, they only did classical, then they started to do variations. I didn't want to see that crap. I wanted REAL sudoku. These variations were just too dang hard for me. Okay, I loved seeing the logic used in solving them, but there was no way I could do them...then they came out with the different sudoku apps and it was over for me. I have played each app several times and learn new things every time. I loathe the killer app and have never made it all the way through, but each time I conquer more stars before throwing up my hand and cursing whoever came up with this variant. Yep, with Simon and his guitar and Mark and his GAS, life has become so much sweeter. BTW, it took me 50 minutes to solve this puzzle, but I did it without any help from the video. Today, i am a man.

[@emilywilliams3237]

A great example of a classic that needs some expertise - thanks for sharing how to spot the technique, Mark - and a very Happy New Year to you!

[@TurquoizeGoldscraper]

I got stuck, I don't think I would have ever seen the 1-9 Mark pointed out.

[@glen4688]

Same for me. I had the solve along with him right up to that point.

[@achimsinn6189]

I also got stuck - and then used trial and failure to solve the puzzle using the 2/8 pair in the centre box. Mainly watched to find out what the "proper" solution to the puzzle is.

[@mc_davit]

After glancing at this comment in my solve i immediately thought about r3c5 after finishing every pencil mark and it helped me get a time of 10:41, so i guess this is a bit of a spoiler even if it wasn't intended 😅

[@jessevennard2640]

This was definitely a z-wing

[@alanclarke4646]

I got stuck after putting 7 digits in.

[@al129]

Not gonna lie, I need Mark's assistance at 17:08 ... despite saying anyone should be able to look ahead to see it , I certainly couldn't

[@joemucchiello4542]

Agreed. Anybody could not have spotted that.

[@Urroner]

@@joemucchiello4542 only those few who have been accepted into the "High and Illustrious Secret Cabal of Damn Hot Sudoku Nreds, Geeks, and Total Dweebs" have been been taught this modern day esoteric gnosis of knowing what to look for in advance. I've even tried to persuade them to accept me,, there are four conditions I need to fulfill. 1) The $2,000,000 non-refundable deposit/bribe; 2] be a true sesquipedalian, 3) swear the secret Oath of the Glorious M Man, OIOW, you must forever and always proclaim dear fealty to Mephistopheles, the Slayer of the minds of all those unworthy to even attempt to think about solving the least of his puzzles; and 4) Be of superior and epical and preeminent rizz of the uttermost highest achievable. The only one I can fulfill is #3. Alas, there be no hope for a sub-pariah like me. My life is an utter fail.

[@RobinBaich]

Finally, a sudoku I can complete. Happy new year!

[@Jodawo]

At 15:50 in the puzzle, Mark gets the big break-in. Without this you are destined to search forever for the solution. After this point the puzzle pretty much falls apart. If you are stuck and you've tried everything it's probably because you missed this one "easy to miss" technique.

[@joemucchiello4542]

Mark calling this "something you can find" is insane. I never would have spotted that in a million years.

[@Jodawo]

@@joemucchiello4542 Don't sell yourself short. It wouldn't take a million years... LOL

[@mudscuffer]

I solved it with related but slightly different logic. If you put a 1 in R3C5, then that leads to: - R7C5 being a 9 - R2C7 being a 1 - R8C7 being a 9 - R6C7 (the 19 pair) no longer having any valid value.

[@ryanb1174]

A nice little peaceful solve, thanks Mark

[@stevieinselby]

Mark going full Simon in eliminating 2 from r3c9 😎

[@mikedonnan6541]

😂

[@cmodzins]

Loved this puzzle. The solve speed was at a pace that I could follow.

[@piarittersporn]

Beautiful and quite approachable classic sudoku puzzle.

[@brenthooton3412]

I ended up colouring 1s and 9s... the first way worked, then I tried it the other way and it broke the puzzle, so I had my answer. But that felt like too much like bifurcation, and I knew if I watched the video Mark would have a much more elegant way of differentiating.

[@joemucchiello4542]

That is the definition of bifurcation. But I never would have solved this puzzle without Mark showing me the answer, or bifurcation.

[@unlikelyskymoo]

Just came here to say great work on countdown today, never in doubt.

[@coyote4237]

Thank you for the classic.

[@loretaruisenor988]

HAPPY NEW YEAR 🎉🎉🎉🎉

[@adamtassell2919]

11:22 for me! I usually struggle finding the sneaky tricks in classics but got this one

[@trainsinpoland]

A happy and successful New Year

[@Gonzalo_Garcia_]

7:19 for me. Nice puzzle!!

[@Svuppedasker]

I have just finished it in 8:18, without any problems along the way. No trickery, no break, no coloring, just a nice flowing solve. I am usually way behind most of you here, so now I got to see the video and spot where the hard part is 😉 EDIT: My own mistake. I mis-noted the possible positions for a 2 in box 6 early on, prematurely leading to the correct placement of it when I got the 19 pair in the same box. Dang. Now I feel robbed of a more challenging puzzle

[@samkeen]

Lovely start to the year by going back to some fundamentals

[@daniellucas5522]

I think the best way to see the break-in is to look at c8 - no matter which value you put in r4c8 there's either a 1 in r3c8 or a 9 in r7c8, forcing column 5 the same way.

[@Rach881101]

9:06 for me. Nice puzzle!

[@prunabluepepper]

Happy new year everyone 🎉

[@darkerarts]

Nice puzzle. Took me a while to figure out the final break, but was fun. Took 67 minute including cooking dinner 😁

[@joelstevens5670]

This puzzle’s break-in is a gem. For those who want to understand what is going on, see below (I’ve tried to break it down as best as I can to make it easier to grasp). If you look carefully at columns 5 and 8, you will see that 9 can go in one of two cells in each column. So if we consider the columns together, 9 is in exactly two of four cells. We also know that two of the cells are in row 8, one of which must contain a 9. Therefore, the other two cells (row 3 column 5 and row 4 column 8) must also contain exactly one 9 (this technique is a variant of what is known as a skyscraper, with the 9s in row 8 representing the bottom of two buildings and the 9s in rows 3 and 4 representing their tops of different heights). But how does this help? Well, if there is exactly one 9 in these cells and the only possibilities are 1 and 9 then there must be exactly one 1 in those same cells. This stops row 3 column 8 being a 1, allowing us to solve the puzzle. :)

[@RichSmith77]

Nicely explained. I spotted a chain that led to an impossibility, if I tried making one of those skyscraper cells (r4c8) a 9, but I felt like I lucked into finding it. I need to get better at spotting things like skyscrapers.

[@joelstevens5670]

@@RichSmith77 Thanks for the kind response. I would have to agree that skyscrapers are not easy to spot, having been bad at finding them myself until recently. My tip would be to focus on row/column sudoku and see if there is any interplay between a pair of rows or columns. Of course, it isn’t always obvious that a skyscraper is needed but if you go about it this way then it won’t vary too much from standard solving techniques like x-wings, swordfish, jellyfish, y-wings etc.

[@pedrosaraiva1411]

I was stuck in this for almost an hour , I got a lot of pairs and triples and even one quadrupule but I wasnt advancing more than that. Thanks for the nice explanation

[@joelstevens5670]

@@pedrosaraiva1411 I know the feeling (I was stuck for a while before spotting the right thing)! Glad you found it helpful.

[@IlliniRocket]

I think you meant to refer to Row 7, not Row 8 in your explanation. And I don't think it's necessarily true that the two cells (r3c5 and r4c8) contain exactly one 9; they could have both been 1 if I'm not mistaken. But that is inconsequential, as we only need one of them to be 1 in order to rule 1 out of r3c8. Skyscraper deductions are very tough for me to see, so I was very happy to find this one without help.

[@ericobarrera6580]

Happy New Year! 21:41 for me, I forgot how to do regular sudokus..

[@RhenishHelm]

10.44 for me - lovely puzzle!

[@anaayoung9142]

A good old classic! I try it and did it, this time felt like a GAS puzzle for me (usually I have problems to find the last link in the chain) 6:55 was my time. But to confess this time I found the X cell in the first cell I looked for (R7C2 for me); "place" 1 there, looked where all the 1's could be (because 1 in that row is only in C2 or C5) and then "put" 9 R7C5 and oops, could not place 9 in box 6. When I say place/put I am using colours for the number 1 (in Sven app this always help me, and sometimes, like here, help me to solve the puzzle). Maybe this is biffurcation, but if I had a great memory I could do this without using colours. Anyway the way you solve have a great logic, and it is the intended logic (I guess), so is nice to watch the solve even after I did it. At the end you were right. But I have difficult to find this logic (xy wings, and others)... 😅 Thanks for the solve!

[@srwapo]

18:22, but I was horribly stuck and looked at the video around @15:56 and saw that I had to play around with the 19 in r3c5. Did some coloring and finished it from there.

[@ServantOfSatania]

23:10 For me, found the break-in through R8C7 using the same 19 pair interaction

[@phoenixaki3458]

I'm at the point in my sudoku "career" that I can almost always get to the same point (in puzzles like this) that Mark/Simon get to before realizing the big break-in step, except I can only solve it by blindly bifurcating a bit to remove options from some cells 😅 That's how I did this one after a while of staring blankly (got it in 35:35) and I knew there'd be a more straightforward way of noticing something that Mark came through on once I watched the solution after

09:24 for me! Happy New Year!

[@davidh.4944]

42:21@#731. Once again I wasted a lot of time looking for fish patterns and such, before looking at the obvious 19 chains. As soon as I focused on the right place I was able to pick out a key elimination fairly easily. I blame a couple glasses of wine and need for sleep.

[@martinyyt]

Finished in 38:14 but, I regret to say, my path past that difficult point would be considered classic bifurcation. I tried the options for the 28 pair in the central box. I did suspect that there had to be a pretty and clever way to solve the puzzle and the video has enlightened me on that. Thank you.

[@mudscuffer]

13:55 for me, pretty happy with that!

[@Issaquatch]

23:11. No bifurcation or clues. Nice puzzle!

[@donaldsnyder1543]

12:30 for me , no help. Nice puzzle.

[@bertbergers9171]

23:08 is decent enough. had a mishap in being fast to the finish and mixing something up. Maybe i found some logic very slow, so eagerly watching Mark now.

[@MariaVlasiou]

It was fun. 13:24.

[@NicholasLayton]

I don't think it's my job to prove that theres only 1 solution, it's the setters job to produce a puzzle with 1 solution

[@RichSmith77]

Ah, see, I don't see it as a job. I see it as an enjoyable leisure pastime, one where I take pleasure in finding the logic that proves there's a unique solution. 🙂 After all, the setter and testers had to prove there was a unique solution, so it must be possible.

[@Kirbyfan87827]

Finished in 13:18. Got stuck at the same place everyone else appeared to get stuck at going by the comments, and I wouldn't have figured out where to look without the comments, either.

[@Hetpust]

Happy New Year 00:18:22 love it. Solve2027

[@lasagna312]

19:15 I'm actually kind of proud of myself for getting this one with no help

[@Aliessil]

Finished in 20:09. For some reason I tend to be slower on these difficult, basic sudoku, and do better with the more complicated rulesets 🤔

[@psiphiorg]

A fun, easier puzzle. My time for this one was 6:50, solver number 915.

[@sharath123sk]

Mark mark mark!!! I solved the sudoku in 8 mins 20 sec, atleast that’s what the timer says, but really I was stuck for atleast 30 mins without doing that beautiful deduction of what if r3c5 is 1, I didn’t do anything up until that point I just was searching sudoku in sudoku puzzle🤦🏽‍♂️🤦🏽‍♂️ so the timer was stopped for atleast 30 mins automatically because I didn’t do anything significant but when I finished I was shocked

[@dwarfigplays9806]

Nice! 25:50 for me.

[@megaminxpll]

7:08 for me, found a W-wing (as it's called) to unlock this one.

[@JohnRandomness105]

14:20 I can *almost* see it in this video's grid, but finding it in my own solve was deaf, dumb, blind luck and trial-and-error. What effect does 4 in R5C7 (with 46 penciled) have on the 19 pair in column 5? We get 9 in R8C7 and R7C5 becomes 9. We also get R79C8 = 46, R1C8 = 5, R3C8 = 1, and R3C5 = 9. That cracked the puzzle, although a 458 triple in row 3 helped later. 15:10 It's now visible once he penciled 1456 into block 3.

[@zobososhizion6478]

final solve is 00:25:23 twenty two minutes in I took at hint from 16:24

[@stupidas9466]

First time ever everything to be seen i saw, and nothing i did see wasn't there! Solved in 10:11 and i left to take a quick pee without pausing the timer as well! Sure beats my usual 50-150 minute solves😢 Btw Mark, i already named the "break in" you did around the 16-17 minute mark. I call it the "P Wing" because it occurred to me whilst my trip to the loo!

[@NelielSugiura]

Your coloured boxes made me think of a finned x-wing, but it might be a finned y-wing. Something like that. Been a while since I looked at all their names.

[@darthrainbows]

I was so proud of myself for solving this one way way way faster than Mark (6:51)... until I realized I made a logical error that happened to work out in my favor 😅. Turns out this puzzle is really easy if you pencil in R7C4,5,6 as a 128 triple, which forces R7C8 to be a 9, avoiding the most challenging part of the solve.

[@penrith50]

But R7C4,5,6 isn't a 128 triple ?

[@darthrainbows]

@@penrith50 it is a 128, but I didn't have a valid justification for penciling it in at the time I did it.

[@86larsonrd]

So...I color bifurcated. (blue is 9 and 1 is light grey, etc) and tried a bunch of ways...but I did not use the solutions from each directly. I used them to say.."OK that is not the way." Doing that lead to the 19 cycle that Mark showed, and I got it with that. Took a while, but I think it was a legit solve.

[@robertcousins2274]

13:44 for me

[@santisis]

8:21 for me.

[@KeisariCubes]

I saw a short video once again and tried it. Didn't get very far. I'm bad at seeing triples and even less quads.

[@benjaminrealy5661]

12:49. Easy start to 2024

[@RADZIO895]

22:17 for me

[@basil8940]

I put 1, 2, 9 is every row, column and box and found the puzzle has multiple solutions

[@RichSmith77]

You're supposed to put 1,2,9 in every row, column and box (along with 3,4,5,6,7,8). There is only one solution though.

[@anis786]

I looked at it a different way. If r3c5 is a 1 so is r2c7, r7c5 and r8c7 are 9's and now r6c7 has no fill

[@drengskap]

Nope, I got stuck at the 19 extended Y-wing bit and had to watch the video.

[@doncook4097]

I know most of you won’t agree with me The last couple of normal sudokus just didn’t do it for me. Variant sudokus are just more challenging and interesting.

[@boydegg]

20:26 ... with bifurcation :(

[@milkom2021]

⚠ Spoiler Alert ⚠ There's a 19 W-Wing in r3c5 and r4c8 that resolves the puzzle

[@bruceh8043]

23:31 for me and solver #2277.

[@guanyin19]

I would argue that guessing the number of a cell, then determining if that number is correct or not based on whether or not the puzzle solves or breaks is true bifurcation. The other method is nothing more than intelligence and cognition. Asking yourself if cell X can be a certain digit by deducing in a few short steps that cell Y is no longer left with any valid digits as a result of cell X is what I would call a chain of logic. There is probably even a given name for whatever previously discovered logic chain you're deducing, even if you may not know the actual name of that specific technique.

[@philswhite1]

I never really understood why a break-in like this isn't bifurcation. Just because there are only a few steps along the bifurcation path if you happen to pick the right one. Had me beaten as I can't bifurcate anyway (visually impaired, so I can only see a couple of horizontally adjacent cells at a time in the magnifier and have to memorize most of the grid). The uniqueness path on the 8 doesn't help, by the way - I went there and it gave me absolutely nothing. But it would interest me to hear whether others here regard a three or four-step lookahead as bifurcation. Merely out of interest. For myself, it's not a value judgement - it's just beyond my visual/memory capabilities.

[@joemucchiello4542]

Mark usually defines it as, if you can't do it in your head, it's bifurcation. So once you write "1" into a cell as a guess and continue solving the puzzle normally until it breaks, you've used bifurcation. But, if you do the same thing entirely in your head, writing nothing into the puzzle, you haven't used bifurcation. It's flimsy, because some solves, like this one, require some form of "look ahead" technique.

[@philswhite1]

@@joemucchiello4542 Thanks. The same applies to most colouring techniques, of course. Either way, deduction chains longer than about 2 or 3 moves are out of the question for me, so it is purely an academic exercise. But a fun puzzle when you have seen it.

[@wibblywobblyidiotvision]

That was nice, but pretty easy. it only ate up about 15 minutes of my tuesday.

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

7:50 for me.