Sudoku Tricks: The Swordfish Pattern

We take a look at the Swordfish, going back to basics first and then looking at an example from a puzzle requested by a viewer.
You can send us puzzles you'd like us to cover on the channel at
[e-mail]
If any of you are in a position to sponsor us on Patreon we would be very grateful. Our patreon page is:
/ crackingthecryptic
#Sudoku
#crypticcracking

[@MemekingSupreme]

I think it'd be fascinating to see eye tracking software / technology being used while the puzzle is being solved, to visualise where you're looking at any given moment.

[@Phant0m51]

I think that would be fantastic!

[@Taterzz]

you're not the only one. hopefully you can get enough likes for attention to get them to invest in it.

[@Melti]

livestreamers used it before, i definitely believe sudoku puzzle solving will find a use for them

[@XxxBuketSiibeLxxX]

Bingo Bongo wooow YES!!!!!

[@aniketb2010]

Something like an invisible Laser beam being constantly coming out of the Eyes activating the Screen area.

[@fredhunt4181]

Sudoku is such a beautiful game. I love watching a high level solver walk through difficult puzzles. I learn so much here.

[@cmonkey63]

Even though I had to watch this twice, while playing on my own printout, your description of a swordfish pattern made a lot of sense. Thanks!

[@donnyh3497]

Excellent lesson on the swordfish! Now I get it

[@mateusquintana8658]

23:25 That 8 at R7 C7 is not possible cause of the x wing you already had. Amazing video. Have to say, your explanations and the way you present your line of thoughts are really clean, makes it so much easier to follow! Congrats and thanks for the upload, keep it going. Cheers from Brazil!

[@traog2445]

I've recently gotten back into doing Sudoku, these videos are helping get my game play to another level.

[@alexandera189]

Very much appreciate the explanation of the logic behind the pattern in this video. I would like to see more of that. Some of the other videos on this channel are you guys just blazing through solutions and it does make it difficult follow and resolve the logic for myself at home

[@MrLlk14]

Thanks! Best video I've come across to help understand the swordfish pattern.

[@terdevify]

Fantastic tutorial! Thank you Simon, finally got the swordfish ...

[@julieannmyers8714]

I enjoyed the basics of swordfish... I've watched you use it in many solutions. Wish I'd seen this first, but I only found your channel very recently. I've been bingeing!

[@albertle4872]

That was a beautiful puzzle and brilliant explanation! I THINK I got it. Gotta practice more. Keep up the good work, thanks!

[@ThatGuy-dj3qr]

Great lesson. Thanks!

[@paparoysworkshop]

I think I finally fully understand the X-wing and swordfish. Great example. Thank you.

[@sebrofniloc]

Thanks. Helpful as always. Working through your Classic Sudoku app and it's good to find explanations of some of the concepts used in the hints there.

[@MrNikolidas]

@Cracking The Cryptic - I think the possibilities have to be offset in Swordfish puzzles, at least in ones specifically designed to be Swordfish puzzles, due to the simple fact that if the possibilities were aligned then they would be easily eliminated through an X-Wing or standard elimination before you could even get to the Swordfish itself. It looks like a delay tactic in order to force you in to a Swordfish position. I'm willing to be corrected though, it's only my theory.

[@squelchedotter]

Awesome, I just wanted to look this up!

[@mggthebest]

I just finished a Sudoku puzzle that had a swordfish and yes, it does the little spaced out numbers. Thanks to noticing that, I recognized a swordfish. :) (Like how you were talking about the possible 4s not being in a line and like shifted.)

[@kevinboyle1285]

I too am learning so much from your videos. It's interesting that I found the swordfish fours but using pairs in rows A,E&I

[@playerone82]

I am going to have to watch this one a couple of times.

[@kgy121]

I very much enjoy these.

[@BrianBernardEngineering]

at 14:52, you could also use a swordfish of 4s in rows instead of columns. Look at rows 1, 5, and 9. They can only place 4s in columns 3, 4, and 8.

[@squelchedotter]

Have you considered doing a video on alternatives to schneider notation and their advantages and disadvantages? Or are there really no good alternatives.

[@jkid1134]

WeNeedMoreFarads it’s worth mentioning that, with pencil and paper rather than online, you are MUCH more free to hybridize their notation style, as you can use all sorts of little writing tricks (like circling numbers, boxing them, drawing lines between them, etc etc) to indicate to yourself what exactly you meant by the numbers you wrote down. There are some videos on this channel where the sudoku are solved by hand, and you can see additional techniques employed there.

[@Zerg1982]

very nice video.

[@Huggy1969]

Great information, easy to grasp with your explanations. What app do you use for your puzzles?

[@Grichee]

Wow I never would have found this on my own. Trying to lear sodoku and i guess i figured out x-wings on my own but a really neat trick for the harder solves

[@swimfit57]

Great 👍

[@kachimaruTV]

At 17:53 if you remove the pencil mark 4 from c8r8 then columns 3 5 and 8 make another swordfish. There was a double swordfish! Even though it adds no extra information as 3 of the 4s are already known, its still pretty cool. Simon said "oh this is nice" and I thought he was about to point it out, would have loved to see his reaction to that.

[@MedAb8]

I think you meant to say the columns 3 4 and 8 which are making another swordfish, not 3 5 and 8.

[@vctrsigma]

Very good explanation of x-wing and swordfish. Is there any background on those names: swordfish, jellyfish, squirm-bag? Was someone just having fun making them confusing?

[@icycloud6823]

Thank you for mentioning the sudoku software that you use! ("Duncan's Sudoku Solver") You should consider putting the name of the sudoku software that you use in the description of your videos.

[@RBCharger]

When you use this program you don't have to click on the Big and Little tabs like Mark does. You can switch by just clicking your right mouse button. I think he does that as a teaching aid because you can't see him using his right mouse button so it would be confusing to magically switch like that.

[@luckyskaven13]

You spent a fair bit of the puzzle not having placed a 7 in R2C9, and so when you placed the 7 in r7c3 it was more useful than you thought because it would have then placed a 7 in r3c2

[@RBCharger]

Yeah, I think he got caught up in looking for teaching moments instead of looking just to solve the puzzle with simple sudoku. He solved the 7 in r7c3 with the 8 x-wing but if he noticed the 7 in r2c9 first it would have unwound the whole puzzle from that moment.

[@apet1572]

the problem with this of course is that you went into the puzzle purposefully looking for the swordfish. i wonder if the requester hadn't brought that up, if the swordfish would've still presented itself while solving the puzzle.

[@travholt]

I don't really see the problem in this case. He stated at the beginning that this was submitted by a viewer who had checked the puzzle in a solver and been told a swordfish was necessary to solve it, and the viewer wanted help spotting it.

[@Kyrelel]

It's a lot simpler to think in terms of rows instead of columns and ignore terms such as "swordfish or "x-wing" which are variants of the "lookout puzzle" we all did as kids

[@julieannmyers8714]

7-8 pairs in box 7, box 1! Take out old pencil marks. The x-wing, etc is not necessary if you complete your train of thought.

[@AskAScreenwriter]

Many thanks. These videos have really opened up another level in Sudoku puzzles for me! Before I started learning about XYZ-wings, WXYZ-wings, swordfish patterns, finned X-Wings and swordfishes, etc, I'd pretty much just given up on doing any of the REALLY advanced sudoku puzzles (Aside from getting things down to a two-choice 'trial and error' solution), and just tried to focus on doing the moderate to difficult puzzles without relying on pencil marks, just trying to keep everything in my head. I still have a lot of practice to go as far as recognizing some of the advanced patterns, though. Once they're pointed out, they seem obvious, but I don't notice them right away. But your examples have helped a lot so far!

[@Kavukamari]

OH I GET IT you treat the 3-xwing as a MASSIVE three that takes up all 4 of the spots in the xwing and in the other corner made up between the xwing and the new row/col pair, you expect to put a three in as well

[@SnugglesPlays]

What software/programme do you use to do your sudokus? I like the way it allows you to not only put pencil marks in but also put colours in. Where can I find it and is it free to use?

[@rilian226]

late on this one... I got to the same place Simon did where he found the swordfish. I got stuck there. Once I filled in the one square given by the swordfish, I was able to solve the rest w/ basic sudoku logic. Interesting how that one little bugaboo can unlock an entire puzzle...

[@pomonoli]

Lol around 23:55, "that's huge because it unwinds this 7-8 double...", this whole time you had 3 sevens pointing at the bottom left 3x3 with only 1 slot remaining for the 7... Sometimes you focus so much on patterns and fancy tricks you forget the easy methods.

[@rebornreaper194]

You ever play Picross? I love it and am interested in advanced solving logic and heuristics. I think you would like the game if you haven't played it before. :)

[@_BLacKWaTeR_]

what program are you using in this video?

[@RBCharger]

I think Mark got caught up in looking for teaching moments and notations instead of looking just to solve the puzzle with simple sudoku. He solved the 7 in r7c3 with the 8 x-wing but if he noticed the 7 in r2c9 first it would have unwound the whole puzzle from that moment. When he placed the 7 in r5c8 at 20:50 if he just looked up and placed the 7 in r2c9 he had the puzzle solved.

[@jeffbrunton3291]

I was slow to understand swordfish because someone explained it as the shape of the swordfish with a bill Which makes no sense at all No...... The Fairey Swordfish was a triple wing airplane, an extension of the xwing bi plane

[@ozertamer210]

19.30 Column 3 has 7 and 8 pairs. Pencil Marking on Box: D is not needed. Just put 1 which is only missing number on Column 3. I called it Column: c on my notation.

[@oldiesalternative5715]

Can someone tell me how he was able to color all those 4s in green at 14:42? I have downloaded the Duncan software but I don't see how it's done.

[@MedAb8]

He did it using a video editing software. Not during the live solving.

[@IamPapercut]

I don't get why at 17:30 number 5 go into R9C3. It looks like it could still go into R5C3 and R9C2 instead of R9C3 and R5C2 at this point. What am I missing?

[@ArthurSavage]

I believe the term is "naked single". If you look at the row, column and box 5 is the only possibility in R9C3. 8 is eliminated because of the 7-8 pair in the column.

[@thomaswilke6312]

What is the name of the computer program that you’re using? What is the name of the computer solving program that tells you the technique required to solve the puzzle? You mentioned this program at 0:55. Thank you

[@CrackingTheCryptic]

The program I'm using is called Duncan's Sudoku Solver (which you can find on Google). BUT I don't use it to solve the puzzles, I like it because it lets me place pencil-marks easily! If you want a program that will solve the puzzles as well, I'm not sure what to recommend but some of our viewers might have good suggestions.

[@howardpayne4128]

SadMan Sudoku will explain each logical step towards a solution.

[@thomaswilke6312]

Kris Cadwell Thank you! Thank you! Thank you! I just installed hoduku and it works like a charm!!!

[@thomaswilke6312]

Cracking The Cryptic thank you very much for your insights. I really enjoy your videos. They are so helpful. Keep up the great work

[@JohnWroughton]

@@CrackingTheCryptic It was a pity to find out that Duncan's Sudoku Solver doesn't work on a mac apparently.

[@sulemankhan54]

Good please send me more Sudoku primer

[@R.F.9847]

Can someone help me out? At 20:10, why are the candidates for 3 in box 8 limited to C4? I'm not seeing it.

[@ZielAmerak]

cause in box 2 and 5 the 3 are limited to C5 and C6 so in Box 8 you need a 3 in C4

[@R.F.9847]

@@ZielAmerak Right, I see that now. Thank you.

[@ericveneto1593]

So the times I'm screaming at the screen "PLACE the 7! You know where it goes!" He's live solving?

[@FrankAnzalone]

What opening song?

[@timothybexon6171]

6:55 And 9 is called an empty sudoku.

[@nigelm5777]

Andrew Stuart’s solver (www.sudokuwiki.org/sudoku.htm) picks up a different swordfish on fours, rotated 90 degrees. Isn’t it the case that more than one swordfish on the same number can often be found?

[@axemanfink3228]

where exactly is the snyder notation discussed in depth? i assume you refer to thomas snyder. but see nothing really from him describing any notation? or am i missing something? .

[@CrackingTheCryptic]

I call it Snyder notation simply to credit him for teaching it to me. I'm (pretty) sure he didn't invent it but, when he was dominating the world Sudoku championship, he certainly used it. Indeed, if you study almost all of the world's best Sudoku solvers they use this or something close to it.

[@michaelbrininstool4515]

no link to follow so I can try to solve.....bye!

[@blaquepoet100]

I know I'm very late, but why are the 4's so "interesting " that you chose to focus on them rather than the 5's for example, which were more plentiful in the puzzle. If anyone knows, please help 😊

[@evonthon]

He mentioned as he started paying attention to them that he had multiple offset pairs which he finds usually means that's the swordfish number in question.

[@Alemiha]

20:34 You'll always appear stupid at some point...never let that stop you from doing it though.

[@stephan935]

I really like your videos but the audio quality is really bad. Maybe you might want to consider getting a slightly better microphone? Keep it up!

[@jrbleau]

The audio is fine for me.