A Sudoku With Only 7 Given Arrows. Where Is The 8th?

Рет қаралды 41,289

Күн бұрын

** TODAY'S PUZZLE **
Aad van de Wetering's sudokus have attracted attention from millions of puzzlers worldwide. His latest, Where Is The 8th?, is another gem from the Dutch maestro. We won't say more for risk of spoilers but you should definitely give this one a try!
Have a go at the puzzle here:
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Rules:
Normal sudoku rules apply. Digits along an arrow must sum to the digit in that arrow's circle. Cells separated by a single knight's move (in chess) cannot contain the same digit.
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▶ Contents Of This Video ◀
0:00 Theme music & puzzle intro
1:27 Under Pressure
2:00 Hexcells stream - thank you!
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3:47 Happy Birthdays
6:18 Rules
7:36 Start of Solve: Let's Get Cracking
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Пікірлер: 115

@zaclewis1869 3 ай бұрын

I've commented on this before, but another way to look at this variant of the Phistomefel set is to highlight rows 1,4,5,6 and 9 and then remove the center box. You now have 4 sets. Now, highlight columns 2,3,7 and 8. You have another 4 sets. Remove the overlapping cells and you have your proof. I find it easier than worrying about double counting cells in the corners.

@iandlang 3 ай бұрын

This should definitely be the standard way of explaining this, much clearer for those who might struggle with set, or be seeing it for the first time

@life.with.sabine 4 ай бұрын

What is beautiful is the position of the 6,7,8 and 9 on the eight arrows. The point to each other.

@jonathanallan5007 4 ай бұрын

This may be the first puzzle aired which Simon has not liked. I think that he was so happy to have finished that he forgot to click the heart.

@johnosullivan675 4 ай бұрын

32:25 Simon finally heard me screaming at him. 🤣

@HunterJE 4 ай бұрын

39:57 I feel like you can still use the 6 logic Simon was thinking about, it's not about where the 6 can go it's where the other circled digits can go. Specifically, if you don't put the 6 in r2c3 you get four 7+ digits in green, but the 6 in the corner means there's only room left for three 7+ digits in blue.

@alanscott8245 4 ай бұрын

That was my conclusion as well.

@Kirbyfan87827 4 ай бұрын

Started the puzzle on my own, got stuck, watched the video up to Simon talking about the extended Phistomefel Ring, made some more progress, got stuck AGAIN, and followed along with the video for the rest of the puzzle. Finished in 53:20.

@tinakerr8163 4 ай бұрын

Knights move always catches me out but for me this was definitely a colouring puzzle.

@ketijasturite 4 ай бұрын

Thank you so much for the birthday wishes! It was today, we had a great time and I had an apple crumble for dessert! Thank you again! (Your pronunciation was perfect again!)

@danitajaye7218 4 ай бұрын

Apple Crisp is super-duper delicious, but it is NOT chocolate cake! LOL Just had to say it, because Simon was being so tactful. :)

@emilywilliams3237 4 ай бұрын

I love apple crumble! And it makes good breakfast if you have any left by the next morning. Happy Birthday!

@Anne_Mahoney 4 ай бұрын

@@emilywilliams3237 TBH left-over chocolate cake also makes a good breakfast. 😸

@emilywilliams3237 4 ай бұрын

Yes, it does - and left-over pound cake, and blueberry pie and ... almost any dessert, actually, with a nice cup of coffee!@@Anne_Mahoney

@emilywilliams3237 4 ай бұрын

Even if you had never found any use at all for the SET proof you did, I love that you did it, Simon. This was a live solve, and as such we get to see into your thought process. Given the title of the puzzle and the layout of the arrows and circles I was trying to figure out a way to apply SET to discover an 8th arrow myself - but of course you did it so much better. I loved this solve and this puzzle - thank you so much!

@AngryKettle 4 ай бұрын

It turned out to be useful, but I almost wish I didn't. I loved the idea of a sudoku puzzle with side quests.

@werbly 4 ай бұрын

The thing I noticed about this puzzle is that the arrangement of the arrows, with the knowledge of the expanded phistomefel pattern (that the digits are the same) appeared to force a rotational pattern, in which the digits along the arrows in boxes 2,4,6,8 were forced onto the next arrow clockwise in boxes 3,9,7,1 respectively. Presumably that's why the title is asking where the 8th arrow is because that is what he intended you to notice.

@battler4739 4 ай бұрын

Simon and Mark; I thank you both for my massive improvement in skill and enjoyment in playing Sudoku. 65 minutes today. I'm a 'Goodliffer' in Knights move Sudoku and that worked for me today.

@danitajaye7218 4 ай бұрын

I LOVED this solve! Solid entertainment and GREAT puzzle! You're amazing, Simon!!!!!

@davidrattner9 4 ай бұрын

Cherish seeing you tackle the great puzzles of Aad!! Know you much pleasure you get in seeing the dutch master work his magic!!

@jaymaybeidk 4 ай бұрын

You and your videos are keeping me motivated during exam season!! Its great to see your positivity shine through your personality and i loved the hexcells stream despite the small errors :) aads sudoku was entertaining as always and i love seeing your train of thought on it!! anyway thank you for supplying us with these videos they make my day :)

@tbi1161 2 ай бұрын

I really enjoy Aad puzzles. Thanks for featuring this one.

@Censeo 4 ай бұрын

This is one of the quickest "don't even think of a three in the corner"

@zygmunthorodyski 2 ай бұрын

Wow 144mins of pleasure, at the beggining I was stuck. Thank you for explaining this coloring trick and great puzzle. It's fun to watch later on and see where you had to make moves in same order and where you had different way of thinking ;)

@bossdoorpodcast 4 ай бұрын

I didn't know about exploded phistomofel and it is what solved the puzzle for me, so I appreciate you doing all that work!

@aurelbartmann5504 4 ай бұрын

Thank you! Your sudoks always help me when i cant sleep to get tired

@ronjohnson6916 4 ай бұрын

Wonderful break in with a nice solution path after you get it. A real joy.

@DarkChasm 3 ай бұрын

74mins, feels like a very professional puzzle, top quality Mr Aad :) loved it ❤❤❤❤

@EmonEconomist 2 ай бұрын

Took me 46:22 but I was extremely proud of myself for identifying the Phistomefel set, and the 8th arrow hinted at in the video's title, and then using it to solve the puzzle.

@bobblebardsley 4 ай бұрын

Sweet and simple rule set today - let's unnecessarily complicate it 🙂 The digits 1 to 9, of course, rode each on a different horse; in each knight's-move neighbour pair, their horse could never land them there. Eight archers rode in to deliver arrows from a numbered quiver; on each arrow was the sum the arrow's circle must become. Seven arrows may be seen; Eighth's location you may glean if with logic, and with faith, you ask yourself: "Where is the eighth?" With arrows' sum and knight's-move ban, you'll solve the puzzle - if you can, and overcome Aad van de Wetering with Sudoku, friend fair-weathering.

@longwaytotipperary 4 ай бұрын

👏🏻👏🏻👏🏻👏🏻👏🏻thank you CtC poet laureate!!! 😁

@RichSmith77 4 ай бұрын

Could this an example of nominative determinism, Mr BARDsley? 🙂

@bobblebardsley 4 ай бұрын

@@RichSmith77 Could be - bard's lea, poet's meadow. (Not actually where my surname comes from but it's nice to imagine that's what it means.)

@davidrattner9 4 ай бұрын

@@bobblebardsleyanother beauty of a poem from you!!

@davidrattner9 4 ай бұрын

@@longwaytotipperarywonderful way to respond...😁

@zaclewis1869 3 ай бұрын

I used the expanded Phistomefel set from the beginning to get me out of the jam Simon was also in around the 50:00 mark. I recognized that the arrow circles all needed "dancing partners" in the opposite sets. So, looking at 7's... you know the 7 in R8C7 needs a partner and only has R1C1 or R9C1 available. R7C2 also needs a partner, but it obviously can't be in its own box. Therefore, R7C2 has to dance with R1C1 and R8C7 has to dance with R9C1. The only thing left is R2C3 which has to dance with R1C9 and is a 6. I actually only had R1C9 down to a 6-9 pair at the point I figured that out so it would seem R7C2 could go with R1C9, but the logic actually still works and the puzzle breaks if R1C9 is a 9. All that said, I was still about 5 minutes slower than Simon in solving the puzzle. Haha.

@nathandavreux218 3 ай бұрын

Amazing solve Simon !

@pwfd 4 ай бұрын

That extended phistomefel would do wonders if you kept track of the digits there! Great solve, great puzzle as always, cheers!

@windybeach2184 3 ай бұрын

I got off to a great start with colouring, but became very stuck halfway through the puzzle and eventually succumbed to set.

@StriderGW2 4 ай бұрын

lovely break-in concept!

@xerodeus2337 4 ай бұрын

Idea for this channel I would love to see. I'd really like to get into these types of non-traditional Sudoku puzzles, but these ones are incredibly too difficult. I wish there was a way for me to find puzzles that are maybe a 3 or a 4 difficulty out of 10. Maybe you all could rate the difficulty of each puzzle as its completed, and then create playlists by difficulty, so someone like me, can go back through puzzles and play/watch the easier ones.

@seify2 4 ай бұрын

You can guess by video length

@chipsounder4633 4 ай бұрын

Click tick again, you forgot to hit the heart ❤. That was classic use of potatoheads trick for the centre cell. You knew of 6 digits within the blue side of phistomefel (2x2s) 159 were the only options. Agian, no need to apologise if one day you are running a bit late.. been a sub for over 5 years and i can garauntee you are the most punctual and attentive throughout KZfaq. Excellent work as always ❤

@richbuckingham 4 ай бұрын

I don't think he actually liked it!

@easternbrown 4 ай бұрын

r1c1+r2c1+r3c3 = r1c7+r1c8+r1c9 = r9c1+r9c2+r9c3 = r7c9+r8c9+r9c9 Demonstrable at the beginning and it came in handy for me once the grid was fillig up.

@acdlite 4 ай бұрын

Very nice puzzle. If you've seen this particular SET pattern before then it's not too tricky... Only snag was I forgot about the knight's move constraint for about 15 frustrating minutes, until I checked the rules again 😆

@stevesebzda570 4 ай бұрын

Lol @0:21 Simon predicting an early spring. Yes, you oughta know better. I just watched "Groundhog Day" ( that's where "Punxsutawney Phil" comes out and predicts an early spring or 6 more weeks of winter). Yes, you should know better, Simon. Funny one 😂

@cypher686 2 ай бұрын

I got a proper 'Ard On with this puzzle

@Mephistahpheles 4 ай бұрын

@45:45 Use the knight's on 8's from box 2, 6 & 7 to place the 8 in box 5. (Could actually have been done way back @30:00 or so, though, not much comes from it back then.)

@titusadduxas 4 ай бұрын

2:32:43 - OMG - That was a struggle. I normally like the knights move constraint but this one was a real challenge. I only found the missing arrow after I’d completed the puzzle although its placement was fairly logical.

@zhoppa 4 ай бұрын

anybody else introduced themselves to this channel with that 9 million video and unable to stop watching?

@NicD 3 ай бұрын

In my case, if not that one, one of the "miracles" around then!

@katiekawaii 3 ай бұрын

20:20 I literally gasped out loud. 😅 That's brilliant.

@longwaytotipperary 4 ай бұрын

❤ the break in!!!

@jacko_g 4 ай бұрын

Very early on, I guessed that the arrows in the "expanded Phistomefel ring" would be a pair each of 6,7,8,9, because that would just be a nice pattern. I was not disappointed! It was also nice to see how each arrow only used the digits 1-4, just for an extra bit of symmetry.

@SjoerdVisscher 4 ай бұрын

Something I noticed only after solving this and seeing the positions of the 5s: the central digit can’t go on any of the arrows!

@alanscott8245 4 ай бұрын

Approached this one a bit differently than Simon--focused on coloring the circles, which let me place the 7s and 8s much more quickly, as well as narrow down the position of the circled digit that ended up being a nine. Followed through on the set theory to determine that one of the high digits in the inner circles must be a 6 (since the arrows force the 789s into the corner circles, if one of the corners is a 6, there's not enough room for four from 789 that would result if there was no 6 in the inner circles).

@integralmystery 4 ай бұрын

I remember when Simon found more and more elegant ways to get to the Phistomefel ring. Watching him struggle with double colour corners to explain this one made me look more closely. Colour Orange: Row 1, Row 9, Box 4, Box 6 Colour Blue: Columns 2,3,7,8 remove double coloured cells in boxes 1,3,4,6,7,9 - DONE

@piarittersporn 4 ай бұрын

Wonderful puzzle.

@Nevir202 4 ай бұрын

31:10 realized right here that you can place 8 in box 8 by using knights move restrictions to force 8 into col 6 in box 5. Took me a few more seconds after that to realize 8 is also placed in box 6 by the same knight's moves. EDIY: Wow, even more surprised I noticed something that took Simon another 18.5 minutes to notice, even when he started looking in the area for a bit before that.

@Zwangsdemokrat 4 ай бұрын

Aad never ceases to amaze me!

@dustinkeier9176 4 ай бұрын

50:21 I love how Simon has taken until 50 minutes to ask where 8 in box five, when it was placeable since 31:00 😅

@maximilianarold 4 ай бұрын

44:27 that's the same thing my teacher says

@FF_Fanatic 4 ай бұрын

Toward the end, it looks to me like the easiest way to see box 1 is to do sudoku on 3s in c1 and r1 to lock 3 on the arrow alongside 4. That leaves just 134 or 234 and draws your attention to check 1s.

@vk5ztv 4 ай бұрын

Hi Simon - loved this. Just saw a new one on Logic Masters Germany - PLEASE PLEASE PLEASE do a video for Circle of Fifths by Michael Lefkowitz - it's a really fun rule set and a really nice, logical solve. Took me 42 mins so you should get through it in well under that. Cheers from Rodney from Mt Compass, Australia.

@ingiford175 4 ай бұрын

If he would have kept the coloring, he would have noticed that straight three is the bent three on the next clockwise positions... and that would give him most of box 1

@raysouth1952 4 ай бұрын

As usual, a grand piece of aad work. The SET helps a lot later on in the puzzle but you can probably do it without it.

@teresagg9809 4 ай бұрын

35:13 I'm confused. Simon proves a cell marked 69 can't be 7 therefor puts in 6 in r1c9. We already eliminated 7. What about 9 it can be a 16 pair with the 2 to make 9. Nevermind 6 is eliminated by 68 pair in box 6

@srwapo 4 ай бұрын

86:13 with a lot of looks at the video. Was just stuck after an hour didn't even think about the ring at all, then was missing a knight's move after that. This was a hard one for me.

@psiphiorg 4 ай бұрын

This one stymied me quite a bit. I thought I had solved the puzzle in about 30 minutes, but I didn't get the checkmark. I double-checked my work and found an arrow that didn't add up, and a couple of knight's-move violations. Switching a couple of digits around resolved both of those issues, probably just from a mistype at some point. But then it still didn't mark as solved, and I dug around to find another knight's move violation on the other side of the grid. Unfortunately, this one couldn't be resolved with a digit switch, due to a given digit stopping me from moving enough of the offending digit around. I got very frustrated by this and tried going back quite a bit and trying again from a different angle, and ended up in the same broken condition. So I decided to watch the video up until the point that Simon placed a digit that didn't match my board. That didn't happen until around 50 minutes into Simon's solve. Then I just erased every digit that I had placed that hadn't been placed in his grid at that point, plus the mismatched digit, and continued my solve from there. My final time (minus the time watching the video, comparing my grid to Simon's) was 57:20, solver number 377.

@MarushiaDark316 4 ай бұрын

🎶I'm arrow the 8th I am ... Arrow the 8th I am, I am ... 🎶

@majedal-baghl4917 4 ай бұрын

Props to Peter Noone! Still performing . . .

@Anne_Mahoney 4 ай бұрын

"I got married to the thermo next door"?

@MarushiaDark316 4 ай бұрын

@@Anne_Mahoney :notes: There's a naked single hiding ... in Box 4. :notes:

@chipsounder4633 4 ай бұрын

I turn 39 on sunday 11th 🎉

@keroberos7000 4 ай бұрын

I caught the symmetry, but not knowing about the expanded Phistofemel Ring made this a lot tougher. I knew the title meant the 8 likely went in the bottom-right corner early but I had to get there painstakingly since likelihood doesn't prove anything >_< Might've been easier if I felt comfortable with other set theory approaches, gotta work on that

@ConradShawActor 4 ай бұрын

TFW you could've sworn you read "king's move" and struggle for an hour.

@anaayoung9142 4 ай бұрын

Great way to find the 8th arrow 😊

@Gonzalo_Garcia_ 4 ай бұрын

18:32 for me. Great puzzle!!

@iceberg54321 4 ай бұрын

The 3 in box 7 was available for ages, and Simon never spotted it, as it saw a 59 pair by knights move.

@marcusbeach1762 4 ай бұрын

54:15 having just placed 4 in box 7 using the knights move, Simon misses that the 4 can be placed in box 1 the same way. Tiny nit to pick, but may have made the end of the ride smoother!

@lolpolowned 4 ай бұрын

Hes even missing the 4 while looking at the arrow for 10 minutes straight, he really needs to watch the pencil marks and clean em up when finished :)

@guruone 4 ай бұрын

I luv the way Simey tried to CHEAT his way thru the solve using Set Theory and FAILED miserably...... Karma, karma, Nori Nori

@henk-ottolimburg7947 4 ай бұрын

min 28: why can't the right bottom cell not be a 9? With a 1-3-5 arrow? After working on a little bit, you get a 68-pair in box 6-left. R9C7 is very restricted: now: it can only be a 5 or a 9 That makes the 1+3+5 = 9 impossible, since that sum needs both the 5 and the 9

@jimi02468 4 ай бұрын

I discovered the "exploded phistomefel" thing on my own and thought it was a new thing.

@chocolateboy300 4 ай бұрын

I got 160 minutes. I started off really strong, then I just couldn't finish. I had to end up bifurcating in the end after getting all of the sixes in. It seems like with Aad's puzzles, I always start very strong and become unable to finish. Very frustrating that I couldn't find the logic. It was very fun otherwise. I didn't even think of Phistomefel's Ring. That would have made it so much easier.

@user-xy3ob5es1d 4 ай бұрын

Easier set proof: blue columns 2/3/7/8, orange rows 1/9 and boxes 4/6, cancel doubles.

@karlmortenlunna2417 4 ай бұрын

Very nice puzzle. 34:17 for me today.

@MrPal94 4 ай бұрын

Just a question, why does Simon not turn on the option where his pencil marks will turn red when they see the same digit in row or column? Amount of times he misses simple pencil marks suggests it would be beneficial. Not sure if it works on knights move though

@Anne_Mahoney 4 ай бұрын

Actually he turns the conflict checker *off* if he ever does a puzzle where it's been set on. He's said he thinks it's borderline cheating to let the software help with that kind of thing. 😺

@user-kt9vr1wj6y 4 ай бұрын

50:51 for me nice puzzle

@ghasttastic1912 4 ай бұрын

spoilers below. the fact the eight arrow is spawned in with set is hillarious

@HunterJE 4 ай бұрын

It was strange to me how Simon kept second-guessing if that was a productive move since as he had already noted it's clearly what the title of the puzzle is talking about

@peedee-zo1yq 4 ай бұрын

Is it....'Well Aad' ....too....??

@phuybrechts6875 4 ай бұрын

At 44 , where goes 4 in box 1 . The 4 in box 4 tells 😅

@jeffreytennant 4 ай бұрын

Great solve, Simon. The easier way at 1:01 likely was using the knight's move to place 4 in box 1

@smylesg 4 ай бұрын

Joke's on you, Simon. I have it on good authority the arrow in box 9 goes from r9c9 to r7c7 and then over to r7c8.

@glum_hippo 4 ай бұрын

49:05 "There's something I'm missing here..." - isn't that always the case when anti-knight is in play? Can we now ban anti-knight puzzles? (Only joking but they do drive me crazy)

@LednacekZ 4 ай бұрын

47:41 for me. made a stupid mistake that cost me at least 10 minutes

@_-_-Sipita-_-_ 4 ай бұрын

25:07 for me.

@Starcanum- 4 ай бұрын

Just starting to watch the video, but I just want to believe that the reason there's no 8th arrow is that Aad wanted to put 3 in a corner. Hope that's right :)

@Starcanum- 4 ай бұрын

Nope, not only that, but it ended up being impossible, beautiful.

@bobfish7699 4 ай бұрын

Where has that arrow in box 9 appeared from? It not in the version I am failing to solve....

@MRichK 4 ай бұрын

He deduced it!

@NinjarioPicmin 4 ай бұрын

watch from 14:14 to 21:00

@annek3296 4 ай бұрын

And then he drew it in.@@MRichK

@pardox28 4 ай бұрын

I'm confused. The directions do not mention that we have to find an 8th arrow.

@easternbrown 4 ай бұрын

It's not obligated, but it's possible to do it

@MiroDaisuke 4 ай бұрын

The puzzle is named "Where Is The 8th?", so that's where it's mentioned, if that's what you found confusing. But no, the rules don't state you need to find it. It's just fun and interesting to reflect on the title.

@kn1tt3r 4 ай бұрын

Hidden given arrows, hidden given 6s... no wonder the video is over an hour long

@MusikCassette 4 ай бұрын

just do the general case once, than you dont have to remember the individual sets.

@adrianhead6272 4 ай бұрын

Giving clues in the titles now??? Takes the fun out of it somewhat... completed in 13m07s.

@adrianhead6272 4 ай бұрын

Another slog... the Phistomefel "trick" forces the arrows to be paired sets of 6789 (comprised of 1234), so the 6s are 123, 7s are 124, 8s are 134, and 9s are 234, AND the given numbers let you deduce the placement.