How do Grandmasters Solve Sudoku so fast?

Try this classic puzzle from the 2017 World Sudoku Grand Prix final (probably by Tom Collyer) here: cracking-the-cryptic.web.app/...
Miracle Sudoku is OUT on Android, Steam and App Store.
Steam: store.steampowered.com/app/13...
App Store: apps.apple.com/us/app/id15273...
Android: play.google.com/store/apps/de...
▶ CTC FAN DISCORD SERVER◀
/ discord
▶ OUR PATREON PAGE - JOIN THE COMMUNITY AND TRY OUR NEW PUZZLE HUNT◀
/ crackingthecryptic
▶ OUR SECOND SUDOKU PUZZLE HUNT - OUT NOW!◀
/ our-new-sudoku-38675803
▶SUPPORT US + ACCESS EXCLUSIVE "CRACKING THE CRYPTIC" PUZZLES/VIDEOS◀
Patreon: / crackingthecryptic
▶ OUR BACK CATALOGUE - ALL CATEGORISED WITH LINKS!◀
tinyurl.com/CTCCatalogue
▶ OUR NEW THERMO SUDOKU APP IS OUT!◀
AppStore: apps.apple.com/us/app/thermo-...
Android: play.google.com/store/apps/de...
Steam: store.steampowered.com/app/13...
▶ NEW CRACKING THE CRYPTIC MERCHANDISE◀
teespring.com/stores/cracking...
▶ THE FIRST SUDOKU PUZZLE HUNT BY BEN NEEDHAM◀
/ 36694746
▶ TRY OUR CHESS SUDOKU APP◀
AppStore: apps.apple.com/us/app/chess-s...
Steam: store.steampowered.com/app/12...
Android: play.google.com/store/apps/de...
▶TRY OUR CLASSIC SUDOKU APP◀
AppStore: apps.apple.com/us/app/classic...
Steam: store.steampowered.com/app/11...
Android: play.google.com/store/apps/de...
▶TRY OUR SANDWICH SUDOKU APP◀
AppStore: apps.apple.com/us/app/sandwic...
Steam: store.steampowered.com/app/11...
Android: play.google.com/store/apps/de...
▶SEND US PUZZLES TO SOLVE/CONTACT US◀
[e-mail]
▶FOLLOW US◀
Twitter: #crypticcracking
@crypticcracking
Instagram (for how to solve daily clues from The Times): crackingthe...
▶SOFTWARE◀
Play the puzzle in the video by clicking the link under the video (above). We are building a website which will allow you to enter your own sudoku puzzles into the software and this is coming soon!
▶Logo Design◀
Melvyn Mainini
▶Opening Credits Design◀
Joel Blundell
▶ABOUT US◀
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 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.
Thank you for watching!
Simon and Mark

[@quadmasterXLII]

1:37:11, so I may not be the smartest person in this comments section but so far I'm at least the most stubborn.

[@chibinecco1981]

There's a streamer I follow who recently started playing Celeste, which tracks how many times you die on your way up the mountain, and he's been ADAMANT about being proud of his high death counts for this very reason. "You did it in only 30 deaths your first try? that's great, means you're naturally very good at the game. But it took YOU six-HUNDRED deaths to do that same level? that took determination and grit to keep TRYING even though it was clearly VERY hard." Anyone can do something easy. It takes real fortitude to do something hard.

[@patricepederson9211]

I spent over two hours! Never figured out the 3/6 situation. :( Need to look into the sashimi x wing trick mentioned below because I hate guessing!

[@pls5201]

Finally got it on the 6th try.

[@jimjimellell]

I will spend 4 or more hours, then go to bed and resume the next day if I have to, but those are the most fun when you finish!

[@hepenypacker]

Love the comments in this thread. I thought I was the only one that meandered through these puzzles

[@serleth]

"Honestly, what's the point of spotting this stuff." Would love more speedsolving videos if only to elicit more snark from Mr. Goodliffe.

[@dancicio6499]

100% agreed. Speedsolving is awesome to watch regardless, but those moments make it even better.

[@alternativeglasto]

Mark, thank you so much for responding to the requests to show how fast you can solve, it is very much appreciated.(I tried and was nowhere near your time, obviously!). One of the wonderful things about this channel is your interactions with your subscribers, and for that we are eternally grateful.

[@MisterNohbdy]

Are you referring to this video? This definitely isn't how fast Mark can actually solve, because he's explaining things as he goes. He's shown how fast he can solve in the past, which is probably why he doesn't bother answering the requests anymore: the videos are still up if you just search through the archive. kzbin.info/www/bejne/p3y9eGqsfcalpqM ; kzbin.info/www/bejne/emnRdnSBgr6Lf5I ; kzbin.info/www/bejne/oqC7no18ZpuUosU

[@AFastidiousCuber]

1 minute 58 second for a classic sudoku? If I knew the finished solution ahead of time and were just writing in the digits I still think I'd struggle to beat that time. Is there footage available of Seungjae Kwak solving a classic Sudoku?

[@MisterNohbdy]

Hard to know without seeing the difficulty level. That wouldn't be an unusual time for something like www.websudoku.com/?level=1 , for example.

[@81Cells]

Level 1 puzzles on this website take under a minute to solve for a top player. The competition puzzle was easy, but not THAT easy. If you want to try it, it is freely available to print: gp.worldpuzzle.org/sites/default/files/Puzzles/2017/2017_SudokuPlayoffs_CB.pdf

[@miniaturecolossus5242]

I guess at the top levels even how fast you fill in the numbers starts to matter.

[@81Cells]

Yes and no. It does make a difference on easier puzzles, but it is negligible on hard ones; and since we have to solve a number of hard puzzles over the course of a competition, and these hard puzzles are the ones that bring the most points, it is not that much of an issue overall. That being said, it can matter even on tough puzzles, for example if you are near the end, left with only easy digits to write, but the round is ending in twenty seconds.

[@MattiaBiggMattGentile]

@@81Cells well that took me 10 minutes, I guess I'm kinda slow

[@dashxdr]

"Does that not get anyting done? Honestly, what's the point of spotting this stuff," Laughed out loud when I heard that.

[@dianahelin9357]

Finally a puzzle I have a decent shot at! I understand the rules, for a start...

[@Ruddigore]

A great solve. How some of the finalists managed to complete this in under four minutes just baffles me.

[@lhvinny]

One of the other commentors mentions a strategy based upon pattern work, not logic, that likely helped a lot with the quicker times.

[@joelmartin2549]

I thought he was going to answer that question, no such luck.

[@livedandletdie]

They are absolutely astonishingly good at them, that's why. And unlike me they're probably good at finding naked singles... I can hardly find myself in the shower...

[@timparenti]

The coloring contradiction Mark discovered at 11:40-12:22 was the key missing bit for me. Managed before and after that without much difficulty, albeit not nearly as efficiently. ;)

[@JohnRandomness105]

I am not good at spotting such contradictions. But I evaded that problem somehow. (I deleted the browser tab, so I can't go back and see what happened in my puzzle.)

[@dsquirrel]

A static (non-bifurcating) way to see the 3s logic at 11:39 is to note that 3 has only two slots in row 3, and that choosing one forces 3 into r8c4 while the other requires a 3 in r9c7. Both of these see r8c8 which therefore must be 9, and from this it follows that r8c2 is 6 and r8c4 is 3, joining up with mark’s further logic.

[@MrCharlieArgo]

Beautiful! I think it's even a little simpler than you said, and one can jump right to eliminating the 3 is r9c5 based on the threes in row 3, but even still... Beautiful! I love when some finds an elegant solution!

[@dsquirrel]

@@MrCharlieArgo Good point! For those who might like to see that worked out: r8c4 and r9c7 both see r9c5, so once you have a 3 in at least one of those two cells (as in my original comment) you can't have a 3 in r9c5, which places a 3 in r8c4. (No need to take a detour via r8c8, in other words.)

[@MrCharlieArgo]

@@dsquirrel Thanks for figuring it out!

[@coyote4237]

Thanks, Mark. That was a fun watch.

[@EugeneChangEC]

It'd be interesting to see how Mark and Simon solves with pencil and paper (as a one off). I'd like to see their marking/erasing techniques.

[@majascha3414]

I got stuck on the part that's solved with the 3/6 pair but otherwise it wasn't that bad... I guess it really does come down to a single number that unravels everything sometime...

[@MattiaBiggMattGentile]

i feel that's the limit of classic sudoku sometimes. Either it's a beautiful x-wing or some hidden triple, or some trial and error checking some possibilities for one single number, which I hate :D

[@GRALISTAIR]

Indeed

[@patricepederson9211]

Agreed! I spent forever on this puzzle before watching the video, and was so disappointed that it was just a dumb trial and error solution. I wish there was a better way!

[@dooby78]

@@patricepederson9211 I solved it by spotting a skyscraper pattern on the 3s in rows 3 and 8, which resolves r9c5 as a 6.

[@nomathdork6643]

I saw it as an empty rectangle on box 9. But absolutely, that was the key.

[@81Cells]

I was going to suggest studying the XV from the same year in a future video, until I reached the point where Mark talks about it. It was a great puzzle made by Arvid Baars, and it caused a bit of a tremor back then indeed. A couple remarks: - the classic studied here was indeed designed by Tom Collyer; - 2017 did not have that many specialists of classic sudoku competing in the playoff, so the times probably could have been even more impressive; several of the players who qualified for it did not take part, and among them were in particular Jakub Ondroušek, Jan Mrozowski and Shiyu Chen, all three extremely good at classic sudoku.

[@argh01hass]

Did you also use a logic chain (is that the right name?) from the 36 in box 8 to crack it? And what flagged that particular cell as a good candidate for starting one? I'm loathe to just blast away with sequences of logic at random but decent solvers seem to know where they should apply them, and use the technique somewhat efficiently.

[@Samish30]

28:02 I got stuck like everyone but eventually found an empty rectangle (thanks Simon for this technique even though it’s sometimes hard to spot) enabling to erase a 3 option in box 9

[@ry1295]

Nice solve and it’s amazing how fast they can solve them

[@achimsinn7782]

I solved it the same way... but I took like 27 minutes because I was reluctant to try out possiblities and tries all kinds of other ways before that. I also tried out with the 6 which leads to a more complicated string of logic untill it ends up not working out. Is there any way of telling when other logic will fail and when to try out stuff or to tell which number one should pick for trying out to make it easier?

[@Sktx_]

9:00 for me, yay ! highlighting initial candidate cells for 7s, 3s and 6s and later spotting a pair of X-wings (6 and 1) in rows 1-2-3 helped a lot.

[@chocolatecake50000]

that was intense, great solving.

[@hariman7727]

22:16 That's pretty quick for me, though this one didn't require much in the way of special techniques. Just a quick elimination process that tests your ability to see what's eliminated where.

[@lathspell87]

Is there a way to take sudoku puzzles from other places and put them into your app? Your app is by far my favorite.

[@fakename3724]

17:39. I'm happy with that. I used the same logic with the threes to crack the puzzle, it just took me longer to find it.

[@edensaquaponics1941]

28:54 was my time, but it took me a while to discover a slightly different piece of logic than Mark. R8c4 is 3 or 6, but both values rule out a 9 in r2c2, creating a 36 pair in r2, placing a 9 in r2c4. I think I then had to find a similar piece of logic elsewhere to finish.

[@evan-moore22]

This is the first classic puzzle I've tried with you all. I got 1:04:00! This beat me the whole way, but I still beat it! Edit: I did not spot that 3/6 logic. I slogged through with triples and an X-wing

[@BryanLeeWilliams]

I didn't finish without watching the video. I Did find an empty rectangle that eliminated a candidate that didn't help. I also found a y wing that eliminated a candidate that didn't help. I basically was at where you were at 12:00 a little before 10 minutes, and then didn't add another digit until you showed me there was something up with the 36. So I paused immediately. Figured out what the 36 did, and finished the puzzle in a couple of minutes. That was a really good spot of that 36.

[@sebrofniloc]

Thanks for that puzzle. Got stuck at more or less the point where Mark pulls the 3s trick out of the bag. Could have spent hours looking for that, I suspect. With that hint taken the rest falls into place easily. Every day's a school day!

[@atriyakoller136]

20 m 41 seconds. And one of the first puzzles I've been able to solve on the channel 😁 That naked single 4 in r7c1 took me dopo long to spot

[@youtubeonly439]

10:04. No idea how I did that. I've been struggling with far easier ones and this one just worked out somehow.

[@br0wnknight989]

I took 4 days to solve Mark's Japanese Sums puzzle and I got completely beaten by this Classic Sudoku.

[@wmiltti]

Solved it in a couple of seconds over 7 minutes - found the 5-8 pair in box 7 early on which made life relatively easy.

[@johnblazer7661]

HOW did you decide to pick threes??? First try!

[@williammoore7268]

Good question, especially, as you note, on the first try. I suppose, considering it was a 3/6 pair, it had to be one or the other - something I call a binary situation, where there are only two possible outcomes. That type of situation is the best to start a guess (coloring, chaining, etc.) with. Then because the 3's were heavily pencil marked, I am guessing that's probably what drew him to it. Of course, the 6's were also heavily pencil marked, and I have to wonder how well it would have worked if he had concentrated on them instead.

[@r0bw00d]

I don't know how he decided on 3s, either, but I do know that, when I was working the puzzle, I found an empty rectangle for 3 in Box Nine that I used to find the arrangements.

[@hariman7727]

A couple hours, but some of that was distraction from other things. The 3s are what tripped me up. I spotted similar patterns on 5s and 6s, but I missed it on 3s.

[@georgesthibaudeau1533]

Fun puzzle, relatively easy. Done without pencil marking in 11 minutes. Useful to see from the very start in block 7 that you have the oblique 58 and 69 pairs placing the 4 in r7c1. The 58 pair gets quickly disambiguated because in block 4, there is already a 5 and the chain forces the 8 to be in r6c3. With this, the rest of the puzzle goes rather smoothly.

[@shuichiakai6765]

Finished in 21:13. I was so happy for a minute there. thought I was faster than most of the experts. It turns out I didn't understand the time labels 😂😭

[@wossaaaat]

I think that 3's pattern is called a 'skyscraper'? Although, the app I originally learnt on called it a 'finned x-wing' if I remember rightly. Like an offset x-wing in rows 3 and 8 interacting with R9C5. If R8C4 is a 3, then R9C5 isn't (because same box), but if R9C5 *isn't* a 3, then the 3 in R8 would have to be in C8, which would mean R3C8 *couldn't* be a 3, and the only other place for a 3 in R3 would C5, and so R9C5 again couldn't be a 3 (because same column). In other words, wherever the 3 is in R8, R9C5 can never be a 3. You can also look at it going the other way round, where wherever the 3 is in R3, it could never be in C4. And it only took me about half an hour to spot.............. ugh.

[@neokart2660]

A non-bifurcating way at 11:40 : Skyscraper of 3 on rows 3 and 8, so there must be a 3 on r3c5 or r8c4, both cells see r9c5, which can no longer be 3, so: r9c5=6.

[@Sorata77]

35:08 for me and that's actually one of my best times yet since I started doing these a couple months back (thanks lockdown).

[@davidh.4944]

Just under 27 minutes here. The key for me was spotting that the 3s formed an empty rectangle in B3 > R8 > R3C8, which in turn fixed the 3 into R3C5. Much cleaner than the bifurcation Mark used.

[@ramprakashkrishnan6651]

12 mins for me... Side note : any F.R.I.E.N.D.S. fans out there, go to 06:25 for a small chuckle 😅

[@thomasr6735]

Ramprakash Krishnan My thought exactly. Mark impersonating Monica 😄

[@neville83]

7 7 7 7!! I did not like your comment because it has 7 likes exactly.

[@JM-gg8ct]

Top notch comment. Probably one of my favorite scenes in the show.

[@neville83]

Mark mentioned this comment in yesterday's video haha

[@ramprakashkrishnan6651]

@@neville83 Really?! Can you point out the video title and time? I couldn't find when...

[@megacalorie]

I placed 3 in r3c5 using skyscraper of 3s (rows 3 and 7). After that, the puzzle went really easy. Took me only 45 minutes. :D

[@L7A1B93]

22min with one eye on the telly (Sherlock Holmes) Fun Soduko. Thanks

[@seeker606]

9:33! Very pleased with that time!

[@Answerisequal42]

yeah ruling out that 3 was really the hard part. Finding that one was the most difgicult oart ubtil i progressed.

[@laurencegoldman4639]

Great show. As an untalented newbie, I must say, at the start, I would say biggest separator was that you had that breakthrough idea. And once you saw it, you flew thru it. Whereas I would still slog thru, maybe not even realizing I cracked it, but certainly taking tons of time to unwind it after cracking. Good to see you find that unlock.

[@davidgustavsson4000]

You are really good at spotting naked singles. It seems like you are not listing the numbers in order, do you have some other order, or a trick when you're checking?

[@futuristic2930]

Is there any way to reset my progress on the Classic Sudoku app on steam?

[@jnam23]

Finished in 8:33. Fastest one I've solved from these guys so far. In fact, I usually take >1 hour.

[@wanderlustwarrior]

After about 20 minutes, I figured out most of the puzzle, but after 18 more minutes of trying varying possibilities, I just watched to see what one thing I was missing. Turns out I was focusing on the right cell (r9c5), but I was looking at the wrong possibilities, focusing on where the 6 would make effects. took me 40:48 with the asterisk of needing one clue (so I didn't solve it on my own at all). I'd like to figure out how you spot that stuff by finding the right number to test earlier.

[@hansdietrich1496]

same here

[@jrbr549]

I never would have thought to use the 3's that early the way he did.

[@henrym5034]

35:37, after a finned x-wing the puzzle cracked open. I had to use finned swordfish at one point - not sure if it can be solved by simpler means though.

[@rickwoods5274]

42:38 ... Several "advanced" techniques in a row yielded nothing, and then eventually I just filled out every candidate in every box and started really looking hard. Got a sashimi X-wing on 3s that opened it all the way up.

[@1fosters]

The 3s were an empty rectangle from box 9. Rows 3 and 9, columns 5 and 8 always putting the 3 on box 2 no matter where is was in box 9. That and the 58 pair in box 7 helped solve it for me.

[@bysan89]

This was the answer I was looking for, thank you.

[@CilantroGamer]

Out of my own curiosity, I ran this through a solver, and if I'm understanding everything correctly it took more or less the exact same path - it used simple coloring to get the 3s.

[@ThatGuy-dj3qr]

I am definitely no wiz at Sudoku, but like Mark, if I am ten minutes into a game and have failed to see empty rectangles, X-wings, xy-wings, sky scrapers, and a few other higher logic Sudoku tricks, then I resort to testing bivalue cells. It is not as elegant as other solution paths, but I prefer to solve (what my app calls) Diabolical puzzles, and often the solution path isn't simple. The bivalue cell test works almost every time and saves a lot of time and frustration when you are stuck. This almost always keeps me under the fifteen-minute mark.

[@carlantaya175]

I like watching your speed solves. One because I can probably do that puzzle and two because you use an aggressive approach which is more similar to the way that I want to solve. The beautiful logic thing is great and all but if it takes you 45 years to solve a puzzle then are you actually getting better at solving?

[@sssdfdsg]

What's the app you're using?

[@WhoStoleMyAlias]

I don't know how they do it, I just like to think they are more lucky guessers than I am. It took me ages to locate that conflict on the 3 starting from box 8 and I'm pretty sure that's the one cell that the setter wanted you to find as it is pretty much a walk-through from there on.

[@FloydTaylor]

timestamp 11:51 is this a particular technique? or process of elimination?

[@theatog]

So i have seen this word around quite often... bifurcating? Does 12:15 count as bifurcating?

[@bijter]

27:23, I really don't know what I was expecting. I'm usually never really good at these, since I always misread something, or put in the wrong number to mess me at the end, but for once I did not. Made me really nervous.

[@PH34RB]

20:27, used 3 slot machines (for swordfishes) and stumbled upon a few triples. 4 minutes is ludicrous!

[@PH34RB]

@Jack Martin Look for their old videos on the slot machine, it's easy to adopt and for me, a game changer with regards to swordfishes.

[@charlesmarlowstanfield]

Whatever that move is with the 3... damn. I would have been stuck forever. Was stuck for a while, came to see what you did at that point, then everything came together.

[@squallerrleon]

23:21 with one assist. Didn't see the break with the 3/6 pair at 11:38. Sometimes you just gotta put in numbers and see what doesn't work.

[@texus7079]

@ Mr Goodlife when solving i noticed you did not seem to spot the pattern of numbers that gives a free 9 and a free 2. good puzzle to enjoy, under 3 minutes

[@jonahkoehlert8747]

finished in 22:01 but i gotta be honest, about halfway through i couldnt figure it out and just picked a random way for one of the pairs to go and it luckily worked out on my first try

[@Martell364]

Managed to solve it in just a little under 18,5 minutes (18:27 to be precise) and I gotta say, I'm kinda proud of myself.

[@nicocost33]

28.11 for me, good I have such a wonderful teachers here in Mark and Simon.

[@ivanchen4110]

4:44 for me, classic one. thx.

[@aebbingeable]

Does anybody have tips to do this digitally? I really make a lot of mistakes this way. I lose the overview I think. Beautifull puzzle btw

[@tomtheultimatepro]

14:45 for me, quite happy with the logic I spotted

[@jameswiebe8956]

14:56 for me. Surprised how quick I was on this one - usually I aim for double Mark's time, and I was faster than that today.

[@paulurwin7734]

A logical way of solving the 3/6 conundrum is asking where a 3 can go in column 7. If not the top two cells the only other cell is the very bottom which forces 3's into r8c4 and r3c8, both of which block all available cells for a 3 in box 2. Now we know the 3 is at the top of column 7 it creates your matching domino with box 1 3's giving a naked single 3 in box 2.

[@nirai368]

I added the missing 9 (r1c3), 2 (r5c5), 8 (r9c7) from the pattern I recognized and It became really easy and solved it in 4 minutes 36 seconds. I got lucky there.

[@alvaropallete]

I wonder if they use software in championships, to make those useful pencil marks, or everything goes nuts on paper

[@QuantumAnswer]

21 minutes, coloring 3s did the trick for me and scanning which of those position breaks the puzzle locked 3s in box 1 and 3 to row 1 and 2 and that did it...

[@Gravi66]

11:45 for me. I guess it was quite difficult but over 10 minutes still seems to long for this one. At around 12:00 in this video i spotted a skyscraper with 3s instead: r3c58 r8c48. Either r3c5 or r8c4 (or both) must be 3 so r12c4 cannot be 3. Now in box 2 there is only r3c5 left for the 3.

[@amysteele2488]

A little over 36 minutes, pretty pleased with that

[@DWOBoyleMusic]

it took me 38 minutes but I wasn't trying to do it too fast. I think it was one of the easier classic puzzles on the channel. Still a really fun puzzle.

[@PresJPolk]

I don't time myself. I tend to do these leisurely and often have other interruptions while I solve. I got stuck hard and didn't get anywhere until I found the same thing with the 3s. And then the whole thing collapsed. I'm glad to see that is apparently how it was supposed to go.

[@MisterNohbdy]

(( *EDIT* : apparently I've completely misremembered how I did my solve at that section; I'll leave the following incorrect statement unedited for shame and laughs)) That's not how it was supposed to go. The puzzle has a hidden 58 pair in box 7 straight from the givens, which forces the 9 in row 9 into box 9, so R8C8 becomes a 3 as soon as you've solved the 7s. Thus that 3 in box 8 can be solved right at the start of the puzzle, without any of the late chaining Mark did.

[@dsquirrel]

I don’t understand - in the finished solution r8c8 is a 9, not a 3.

[@LeCrenn]

Took me 42 minutes, but I was happy to see that he used the same 3 that I did to solve it. (He just got there much faster.)

[@AndreAy1975]

Solved with a hint from the video about the 36 pair. The video failed in its objective to explain how solve the puzzle quickly. You lose time when you check out ambiguations which lead to nowhere. How did you know which one to pick?

[@negar1368]

15:50 for me. A neat classic puzzle.

[@gavinneedham2013]

Did it in 14 min and I feel super proud about that.

[@winoodlesnoodles1984]

Considering most of the competition was in that range or slow, I would say that is a great time! Congrats!

[@alienrenders]

11:11 using an app with highlighting. Over 30 minutes using the web app.

[@rebmcr]

14:10, quite pleased with that

[@chaotix37]

21 minutes of solve. Got stuck. Turns out the coloring part breaks it.

[@BramCohen]

At 7:05 You already could have determined that there was no 6 in the center because it resulted in a chain which caused a contradiction.

[@TrekBeatTK]

8 minutes! Feel very good about that.

[@frederikjn]

Why would he instantly focus on the 3/6 pair when he got 'stuck'? There is a 2/5 pair in the same box which get completely ignored, and it feels like he haven't done all the standard sudoku. In my screen I even have a 6/9 and a 5/8 pair. So many options, and he instantly choose the righ one :o I don't know - sometimes it just feel like they have tried the puzzle once before and know where the 'key' is to unlock it all. I know, unpopular thought - More likely they are just extremely skilled and know where to look all the time

[@f.w.mulder9159]

Do these contestants do it on paper or computer?

[@Coyotek4]

10:25 Nice classic!

[@miniaturecolossus5242]

21 minutes flat, I'm not unhappy with that. I take some pleasure in spotting the swordfish on the sixes. Didn't help the solve, but it was a bit neat.

[@NicholasLayton]

Weird, I thought this was possibly the easiest puzzle ever featured on the channel. First time I ever finished one of these in under 10 min.

[@kitsterling8665]

I know you prefer to solve logically in your videos to show how things are done, instead of bifurcating or using uniqueness, but is there any chance you'd be willing to hold your own puzzle challenge, between the two of you? It could be a one off thing (to celebrate 300k subscribers maybe, when that inevitably comes around), perhaps, but I'd love to see you both go head to head.

[@stevepinard5826]

12:30 - Pleased with that time.

[@MichaelJPartyka]

I would've solved this on the first try if I hadn't gotten the Empty Rectangles technique completely backwards.

[@kuraban1]

21:42 after making an early mistake and having to backtrack. Damnit. I'm astonished that anyone knocks that over in 4-5 minutes.

[@chimwemwechiundira6002]

My new discovery

[@FryGuy1013]

I used the same break-in with the 3/6 in r9c5 and thought I was clever.. but then I made a mistake and put a 5 in r9c6 and it messed me up and I had to redo most of it and ended up with a 40+ minute solve :(

[@l4sert1m33]

Me: carefully places a 2 in the middle cell and solves it without difficulties

[@hamzahussain7794]

Nice find! Didn't think about that, its a clever unique way to think about it. We can also use the same idea to put a 9 in R1C3 by looking at boxes no 4 and 7 below it.

[@Wecoc1]

Smart move indeed.

[@robertr7923]

why did you do that? I don't see why that cell is a 2

[@annihilatorg]

@@robertr7923 Because the design of the puzzle suggests the "missing" digit in a pattern. It's a gamble that pays off, no logic involved at all, just Puzzlers Puzzling.

[@l4sert1m33]

@@robertr7923 I just thought a trial and error and I put the 2 in the central square because I know that the sequence 123456789 is always shown in these puzzles. If you look with attention you'll find it. And this is a pretty big hint to solve the puzzle without difficulty. I know that the technique shown in this video is not that complicated, but I wanted to see if by putting this 2 in that specific cell to create the sequence 123456789, I was about to solve the puzzle, and I managed to solve it in less than 5 minutes. Of course this is the last way you'll be use if in a sudoku championship, but it was still worth to try and to confirm thar the sequence will be most of the times hidden in these puzzles (Basically is all luck lol)

[@JohnRandomness105]

I'm not up to timing myself yet. Still need to work on substance before trying for speed. This puzzle in the tournament was all about speed, as it was very straightforward -- easier than usual. EDIT: For a moment while placing the sevens myself, I thought to myself that grandmasters solve it so fast because they begin with 7s. 8:55 I think this puzzle is a poster-child for disciplined search for corner-pencil-marks. Just go up the digits, with occasional diversions filling cells. Then repeat.

[@atlantic_love]

Just get better at "seeing" missing numbers in particular rows and columns, and seeing two rows or columns at a time in order to determine position of number in remaining cell.