Why Handmade Sudokus Are Better! A.k.a. One Of Our Best Puzzles Ever
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- Опубліковано 1 вер 2019
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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 eleven-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
![[Extreme] A Sudoku With A Sting In The Start!](http://i.ytimg.com/vi/lPpAtnbvVR8/mqdefault.jpg)
![[Extreme] A Sudoku With A Sting In The Start!](/img/tr.png)
I find it charming when Simon gets genuinely excited over an elegant piece of logic.
20:36 "by normal sudoku rules" - at it again, you've been playing too many variants
samuel barky Can you really play too many variants?
Lucas Snowball_Cathug yeah if you sacrifice your original sudoku prouesse in the process but no they are good fun
The X wing of 9s in rows 6 and 7 can be spotted early and makes resolution much easier than what you did with the 3s and 4s
A beautiful puzzle. Makes me wish for more classical handcrafted sudoku puzzles on your channel.
That was actually the first time I recognized a swordfish on my own. Actually found a second swordfish as well. Unfortunately both were fairly useless towards solving. I was sure I was missing something. Ends up it was the x-wings.
Couldn't find the 5,7,8 solution, so I got stuck on that point, but definitely a great one indeed!
A new trick added to my arsenal. I feel myself getting better and better with every one of these video's! Thanks!
This was fun to solve for me as well. Compared to other puzzles, it felt like I was much more rapidly using (semi) advanced techniques, and that they flowed into each other.
Our solves were very different though! I had some early eliminations make a naked 56 pair in c8 that made r8c8 a 2, and getting that early led to lots of other divergence.
First sudoku I've done in a long time, took me an entire day of working on it piece by piece but that's faster than I thought I would be so I'm proud of myself
The beauty of a hand crafted sudoku.
I’m just learning all the strategies and seriously enjoying it. I was able to finish this one by myself! Then watched how you did it.
Beautiful puzzle, I agree. I got stumped at my initial attempt, that 4578 was a doozy, I don't think I possibly could have seen that without your video, but as soon as you pointed it out, the rest unraveled just fine.
There's also a swordfish on 9s and if you combine that together with the swordfish on 1s you can get the digit 2 in the last box when you check the sets for column 8. I completely missed the quadruple set in box 7 and the usually easy to spot x wing logic and struggled mightily here.
Absolutely brilliant. I'd love to know from which magazine this was.
I enjoyed this puzzle. Would you be able to do more swordfish identification sudoku?
This video is a excellent tutorial for working through difficult sudoku puzzles. I have watched it twice in three days.
I attempted this puzzle looking to learn how to do X-Wings, and then found myself stuck on the swordfish section.
Was nice to see we had the same logic up until that point, but since I didn't know how to resolve the swordfish your video helped me learn a new sudoku tactic.
Great video, helped me heaps.
An elegant design.
Another entertaining and informative video
Coming to this very late. Took me 61 minutes to solve, because I didn't find that 4 xwing until I had been stymied for a while and decided to add candidates to the full board. I can't tell where to look for stuff like that yet without all candidates being explicit.
recently discovered your channel, really enjoy it, your explaination is very clear for me and im improving in my own solving and logically thinking (as a computer science student)! Thank you!
One of the first thats on the channel that I could resolve. Getting better.
Instead of using the x-wing on 3s in columns 3 and 4. I ended up managing to eliminate a 1 in column 3, row 4 and then used solution uniqueness to say that column 4 row 4 is a 1
Phenomenal
9:07 this is how far I got by myself
Same. I saw the X-wing but not the quadruple
The swordfish turned out to be a red herring😅😂
Fun puzzle. found the x-wing in 9's that helped. Are the any sudoku books you would recommend with hard and above difficulty?
I did the slot machine on 7's, than watch you do it and realized I didn't have to slot machine at all. Crazy. I didn't finish it.
i found an early X wing on 9s that helped but got stuck because I didn't spot the 4578 in lower left.
At the 12 minute mark, is it valid logic to say that a 34 pair in the x wing on row 4 would create an unresolvable puzzle, therefor it must be a 14 pair and the 3 goes in column 9?
Yes, I did that.
No, you can't use uniqueness when the 4 cells occupy 4 different boxes.
I did that too, when I gave up on finding anything else!
No, Bart is correct. Uniqueness is always a less-than-elegant piece of logic, but it only applies two pairs in two boxes.
There is a somewhat similar deduction, though, which is that if R4C9 is 1, an X-Wing on 3 appears in the same cells (or 3/4 pairs in each column). Combine this with the hidden quadruple that was apparent at the time (Simon spots it around 16 minutes, I spotted it before the X-Wing on 4), there's nowhere to place the 3 or 4 in box 7.
Amazing solve, another logic path involves the swordfish on 1's with a, I think it was an X-wing on 9's making a 56 pair in column 8. My solve also involved two sets of hidden triples. My solve took far too long to post my time though.
This puzzle was beautiful and brutal. Took me over an hour.
After an hour I got to the 4 x-wing and found a 9 x-wing which led me nowhere, after only finding a few more pairs and triples, (i don't usually wright in triples so and I'd never heard of a swordfish as I don't do many Sudoku) my brain started hurting and I gave up. Watched your video and I see now why I missed the key to the puzzle. I really should pay more attention to triples.... ^>^
Very interesting, far from quick. I didn't need a swordfish - found an X-wing on 9s lower right before I found the one on 4s, and was able to deduce the 3 at the end of column 4 by uniqueness. .One day I'll do a puzzle the same way as simon, but so far nowhere near - yet I've solved the same way as Mark quite often - go figure.
I agree, a great puzzle. But -- I'm beginning to notice the nature of these puzzles compared to picture puzzles (another hobby) where you work really hard up to a certain point, and then the rest just falls into place. That 'breaking point' is a common theme with puzzles, and gives me hope when working on one. The satisfaction comes when I reach that certain point, and then it all just comes together.
That swordfish did the trick for me.
Can't believe you ignored it.
It's funny how my mind was immediately able to see that puzzle-breaking 3/4 double X-wing in rows three and four* that would have resulted from placing the 1 in the 1/3 cell in column nine, but would have never been able to get the 4578 quad in the lower left box and probably have been stumped for a while, compared to you figuring out all the wildly difficult 4578 stuff ahead of time and using that to backdoor resolve the same 1/3 cell. Almost fried my brain trying to follow that one!
* heh, "3/4 in 3/4." Now that I type that out, I notice that pretty cool bit of meta-symmetry that ironically breaks the puzzle. Nifty!
I found the x-wings on 4 and 9 but couldn't make much progress on them
I got tripped up by the 56 in the bottom right box, for some reason I thought they had to be a pair, and didn't think about it, started over 3 times. What can I say, it was a long week.
Several miss steps in the middle, I did see the 578, but until the x-wing with the 4's I didn't see it as useful. Then the 3's x-wing and resolving the 3 at the end brought it home for me. Frustrating but great.
The 3 in row 4 can also be found by uniqueness.
Just did it using uniqueness.
They try not to solve via uniqueness.
I missed the X wing on both the 3s and 4s, so I went through and fully notated a majority of the puzzle (and was at about the same point in the puzzle). I was then able to find an x-wing on 9s in row 6 and 7, both having to be in columns 5 and 8. From this, the whole puzzle collapses. Excellent puzzle, I really enjoyed the solve, even if I got suck for a while.
Is there a way to use SET to make this puzzle easier?
Bought the Android app and can't stop playing it. Average solving time seems to be around 20 minutes (I'm not great). The app is brilliant!
you are great!
Thank you 😊
Doing better than I. I've only done 3 so far. My first time was 16 minutes and the next 2 were much longer.
I still need to wrap my head around all this x wing, y wing business
A grade or two above my level , great to follow but on my own I missed too much
i got to the point where you started finding the xwing and the quadruple
I solve puzzles a little differently than most I guess. I use a ton of pencil marks. I tried it twice to see if I could do something different, and I solved it the same way both times. The first time it took me 22:56 and the second time it took me 22:42. At least I improved on my time a bit. Nice puzzle though.
4,6,8 , 9 diagonal doubles haiku battleships .
I don't understand the trick you used in 17:00 the 3 can go in others positions than the ones you marked
He's specifically talking about putting a 3 row 8. It can't go in columns 1 or 2 because of the quadruple in the lower left. It can't go in column 5 because of the 67 pair. It also can't go in columns 8 or 9 because of the 3 in column 7. So the only viable spots he's able to put a 3 in row 8 is column 3 and 4. Hope this helps
I don’t know how useful it would be, but I noticed that row 4 column 9 is a 3 because otherwise it would end the puzzle with 2 solutions with an x-wing of 3s and 4s
Exactly the same for me, that's how the puzzle broke for me
Couldn't you have used the X wing on the 4s to place the central 4? I did that and it broke the whole puzzle open without the swordfish.
I got to the point where you found the x-wing on 4s, and realised then that uniqueness meant that row 4 col 9 had to be a 3. I didn't then see the 4s x-wing until much later! I kept seeing something like the 4578 quadruple in the bottom left but couldn't work out what it was telling me.
When I saw the x-wing in row 3,4 / column 3,4, I immediately knew that there had to be a one in the lower left corner (4,4) because if there wasn't a one there, then there would be two possible solutions to the Sudoku with the swapping of the 3s and 4s in the x-wing
Gave up and just watched the video. :D I missed the 3 x-wing that cracked the puzzle.
same :/
i got right before the xwings and got stuck, couldnt notice this.
Over my head
This one took me over an hour, and required spotting the two obvious pairs at the start, two X-wings, one quadruple, and an empty rectangle, and then the whole puzzle collapsed.
Ugh...this one required a swordfish (which I hate trying to find) and a type 3 unique rectangle, the most complex of the 4 types. Beautiful setup of the givens, though!
Was this puzzle winnable by an easier method or what that method Absolutely Required? Just wondering, because I want to play harder sudoku puzzles for now, but not this hard, because I didn't fully get the concept of the sword fish thing. edit: of levels 1-6 on the website I print my sudoku puzzles on I usually do levels 3-5 of 6 (4 on average). Have beat level 5 and 6, but I don't think the levels 5 and 6 are as difficult as what advanced players would consider a 6/6.
I understood everything up to the last xwing of the 3s around 18:00. I don't get why 3s can't go anywhere else in those columns
Because there needs to be a 3 in row 3 and row 8. And the 3’s in rows 3 and 8 are limited to column 3 and 4
I have brought the Android App, and am loving it. One way I have found of getting round it not being on the Google Store App, is to use the website to find it using your link, and then add it to your wishlist. You can then use the Play Store App and retrieve it through that. Hopefully that will help some people who prefer to use the App rather than the site
36 minutes... took me over 15 minutes to discover a 3 that pretty much unlocked the puzzle
Edit: having watched the video, the bit that took me ages was resolving the 3, 4 x wing. I ultimately figured put the column 9 row 4 had to be a 3 to prevent two possible solutions to the x wing. The it was quite plain sailing.
Your videos are making me so much better at solving, just bought sandwich sudoku.
This is my first soduku for years and I made it in 54 mins then watched your solution and are amazed over your clear commenting and speed =)
Nice trick with the 5 and 6 in column 7 - shame I didn't see it! I can't quite remember what I did, but I didn't use any X-wings at all!
12:15 you could use unique rectangle to deduce that 1 has to be either in r4c4 or in r4c3, therefore you can remove the 1 from r4c9 and it becomes a single
That 34 x-wing can be considered a square and it would avoid any 3. So the r9c4 would be a 3
Not sure I understand what you're saying but r9c7 has a printed 3 in it so r9c4 can't be a 3.
I just started practicing sudoku techniques, I was able to get through this one without hints in 23:00, I'm sure my app filling all candidates helped bring this time down drastically. I managed to find several hidden doubles, two x-wings, and what I think was an x-chain (though I'm fuzzy on the name of it) to get through this. really proud of myself and this really was a cool puzzle.
17:36 why only 3's are locked into those cells only??
can anyone answer this??
Row 3 is obvious. As for row 8, notice that box 9 already has a 3 and the remaining cells are already pencil marked. Therefore, 3 can only go in columns 3 and 4 for rows 3 and 8.
Handmade Sodoku are far too easy for me.
36:34 for me (including a toilet break). I used two swordfish, a jellyfish and uniqueness - that was probably overkill.
So you were actually able to do it in 6:34 if you don't account for the break (that's what my wife would tell me)? Very good!
Finds two x-wings, doesn’t mark them, forgets them. Lol you should keep x wings highlighted a certain color tbh. Good work
I don’t think you needed to use any x-wings or swordfish. I managed to solve it in a little over 28mins, and I would consider myself an amateur. I think your expertise distracted you. The symmetry of the puzzle must have coincidentally produced all of those advanced techniques.
I took about 30 minutes to get to pretty much the same as at 10:00 but with a few additional pencil ✏️ marks. However I then failed to see the xwing and gave up to watch the video.
31:42! I really took my time with this one
Comments on the symmetry... immediately finds a 12 pair... fails to use the symmetry to obtain the corresponding 67 pair. Goes off on a tangent. A year later - nothing's changed...
Finished in 11m40s.
I came, I tried, I failed
They are better because they dont contain xyzw Medusas or death blossoms or grouped xyz cycles..
How does someone create a handmade sudoku?
This took me an HOUR on my own before watching. Now I'll watch so I can figure out what a "swordfish" is and hopefully not take as long the second time.
No swordfish. It was the bottom left quad that I missed to opened it up.
I got to this weird point where I had "all cells that can be one" were colored green. In box 4, there were two banks of green in rows 4 and 6. I said "what if the one is in the first bank?" and colored everything that choice would eliminate blue. I then said "what if the one was in the second bank?" and highlighted everything that would be eliminated by that chain. Anything that was both blue and highlighted I eliminated, taking out about half the candidates for that number. Was that a swordfish by coloring? He used the same move in the same area on the same digit, but mine seemed to be a bit stronger unless he opened some other moves that intersected the same area.
I’m happy I managed in 44. I tried to spot a quadruple once I scanned more closely in that box and found the 5 7 8. Thought to myself Curses, the 4 can still be at the top! Then I found the X that eliminated those top 4’s and got excited!
At 10:30 in the video when you spotted the 4's...I used uniqueness to know that the the 3 had to be at R4C9 it unlocked the puzzle much faster
Edit: it meant not having to use x-wings at all, or finned and also when you found the 4's it placed a 4 in the center box of the grid immediately
I did the same as you. I have noticed that the guys who run the channel try to avoid using uniqueness and then try and show how a puzzle can be done logically in a different way. Unfortunately for me, although finding the three was much faster, I still solved the entire puzzle slower than the video :-(
You got lucky placing that 3 there as that was not a uniqueness situation as it spanned 4 different boxes. Uniqueness requires that it only be 2 boxes and 2 rows/columns.
@@glennmelven3414 If R-4 C-9 had been a 1 it would have caused a uniqueness problem and because there was already a 4 in that 3x3 it had to be 3 in R4 C9
@@glennmelven3414 In row 4 there could only be the digits 134 in three boxes.
In row 3 there were already the digits 34 in columns three and four.
If we placed a 1 into the final column of row four, it would force a uniqueness problem with 34s in both rows three and four. Hence we had to place a 3 into the final column of row four to stop the problem from occurring
@@barneytrubble It's not a uniqueness problem. In uniqueness switching the values between 3 and 4 would mean that every 3x3, row, and column are unaffected. In this case the row and columns are unaffected, but the 3x3's aren't.
took me 2 hours to solve : |
Solved in 24:36
All that effort to show a swordfish with the 1s but didn't use it to solve for the 1s in the end.
Yeah Simon because the people that wrote the algorithms don't care about the solvers? Ehm.. Yeah way to make a point, ad hominems are not arguments...
l am no expert on fallacies but Simon didn't say the developers don't care so yours is a straw man argument, and you can't infer it from what he did say, since it's possible that we have not yet developed the algorithms sufficiently well to rival human setters so that's a false inference.
@@richardfarrer5616you'll have to watch the video again in the beginning and pay more attention, he clearly says that the reason why human set puzzles are better are because the human setter cares about the solver and the logical part, you're misrepresenting what I said.
@@sotolf Indeed. He says at about 1:06 "The setter of a hand-crafted puzzle has given some thought to the experience of solving ..." and goes on to say "a computer doesn't do this". Is that the part you were referring to? If so, I stand by my earlier comments that nowhere does he say that the people who wrote the algorithms don't care about the solvers. That's just your interpretation and, since you are putting words into his mouth, that's why I described your argument as a straw man.
@@richardfarrer5616 a computer can't think, it's executing an algorithm. An algorithm does what the programmer decided it to do, so to say that a computer doesn't do it is to say that the programmer didn't care to add or deal with it. Are you struggling to understand that or are you just being disingenuous? And belive me there are generators that generate good looking symmetrical puzzles with a pleasing logical path of solving. Look at hodoku or enjoy Sudoku as examples.
@@sotolf Did you read my original response? I pointed out that it may not be possible currently to program an algorithm which matches the capabilities of a human. Even if there are algorithms which "generate good looking symmetrical puzzles" then
1) they may not be as good as humans at designing puzzles (Simon's assertion)
2) a particular programmer may not know of the best algorithms
3) a programmer may not have access to the resources to run the best algorithm
Therefore there is no implication that developers don't care. They may just be unable to do as well as they would like. I've no problem in conceding that some developers just want to churn out puzzles but that is irrelevant to the discussion. Your supposed implication is only valid if programmers have the ability to create something as good as a human composer but choose not to.
Also, you attacked Simon for making what you claimed to be an ad hominem argument and then accused me of struggling to understand or being disingenuous. A little consistency, please.