The Sudoku Professor
ฝัง
- เผยแพร่เมื่อ 16 ต.ค. 2024
- Today's video features the latest puzzle by sudoku professor Richard Stolk. Do have a go at this one, it is absolutely gorgeous... here's the link:
cracking-the-c...
Normal sudoku rules apply. For cells with arrows, the first N digits in all directions of the arrows must have an equal sum, where N is the digit placed in that cell. Digits may repeat in sums with a diagonal direction. Not all possible arrows are given.
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▶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
Haha, Sudoku Professor seems a bit too much of a compliment! :-)
Well done again Simon; of course you found all tricks I have put in it, occasionally taking a bit more time to do the calculations to eliminate possibilities. After solving Stephane's puzzles of this type I thought long and hard about other possible tricks to put in. The odd/even ideas came into mind quickly. All in all it was a joy to set write this puzzle.
Really enjoyed this. Great puzzle. Took me 45 minutes which I'm pleased with. I don't think I used the arrow just below the middle cell though... Is it redundant?
Simon made a meal of box 9. I just looked at the minimum value and saw that it's only just low enough.
Wait... I realise I *DID* use the fact that the cell below centre is an arrow to get its value. But then I didn't use its sum. I guess I had enough digits to finish by sudoku by then.
This is the puzzle I enojoyed the most (both solving and then watching) on this channel. Thank you for making it :)
Should have maybe been explicit whether the N digits can be more digits than actually fit within the grid.
Nice Puzzle Richard, not too hard but very satisfying. Thinking about things being odd or even is a very useful trick in any summing sudoku
"Richard Stolk takes these ideas and takes them up to 11."
My reaction too :)
He did it three times with my ideas and it's a delight every time.
Thanks for this great video.
"14 and 16 are both even" - Simon dropping knowledge bombs on us!
Things you learn on Cracking the Cryptic. ;3
and 1+2=3 .. it's too much for me
I appreciate those knowledge bombs because sometimes that's the only part of the video my simple mind can follow.
35:16 "And I think now... we've done all of the arrows"
Poor r8c2...
(Could have used it to get the 6 in r8c6, got there anyways by sudoku though so doesn't really matter.)
Yes, one of the few numbers I got a head of him.
What about that poor 6 in r3c7? Could have used that to get the total of ten for the 2 clue in r6c5.
I’d be interested to see how quickly Simon solves a puzzle when he isn’t explaining every step of the logic
@12:00 An easier way of looking at it is comparing the outies. If the arrow is a 6, the outies in row 1 equal 12. If you go down column 7, you know the two outies at the bottom can only be comprised of 178, no combination of which can add to 12. Therefore r1c7 is a 4.
This comes into play again in r9c1. It can't be a 7 because that means the single cell outie in both directions needs to match. And since the column is a 6 and the row is a 5 or 9, and 6 is not equal to 5 or 9 (things I learned from Cracking the Cryptic), I know 7 cannot be a valid option. Shame this is my Dinner puzzle and not my Free Time To Try It Myself puzzle, this one really does feel approachable.
It was a nice puzzle and I enjoyed figuring out the start.
Unfortunately I was about done with columns 7, 8, 9 with some progress on the arrows in row 5 when I accidentally reloaded the page and lost my progress. The thing I want most from the new software is for it to remember where I was when I come back to the page. Daily killer sudoku manages this even when you're not logged in. Reloading the page on accident or having to stop on my phone and having the page reload when I come back is the most common ending I get for your puzzles :(
I have the same issue, using the link on my phone. When I make good progress on a puzzle, I've taken to taking a screenshot before I take a break, so I know where I was at when I come back to it
Amy: I've done that too, but I rarely am so interested in a puzzle that I'm willing to re-enter all my progress and pencil marks.
I also have this problem, I have found that after doing the puzzle once the second time is much much faster (5 to 10 minutes instead of an hour and a half), I do hope the new version fixes the issue
55:56 without any look at the vid. This was probably the hardest puzzle I've ever solved, normally I don't even attempt anything with a time above 30 mins here. I'm proud of myself, and thankful for your channel to push me beyond what I thought was possible!
Would that be "Normal Approachable", "Mark Goodliffe Approachable", or "Quantum Physics Approachable?"
It requires logic not usual to normal sudoku - i.e. thinking about odd/even or "virtual killer cages" (as in: "these three add up to X, so the rest must be Y") and such, but the solving path is straight forward and should lead you from one step to the next. I would rate this "regular viewer of this channel approachable".
Beautiful puzzle, I finished in 26:16, you weren't slow at all Simon, just going into a lot of depth with the math to prove to the viewers that the logic is sound. It's easier for me to just solve sometimes when I don't overthink it
These videos are always stunning to me, your brain is such a sharp machine!!! Honestly, there’s something so relaxing about watching this channel.
Ah! Simon. I love the way you beat puzzles into submission with the pointy-headed mace of logic, while I flounder at them with the multi-headed flail of ignorance. Bravo Sir!
After 6 months of following this channel I managed to do this one in an hour and a half, which I’m really pleased with. It’s great to get to the end, press check and not get rewarded with red squares.
This puzzle was in my sweet spot. Too hard for me to do, but not so hard that I had trouble following Simon do it. So a pleasure to watch. :-)
26:46 this could've been done without parity. R6C6 is 5 at the minimum, so you already have 19 at the minimum for the 4 "diagonal" cells.
i love the pivot sudoku variant, it has such lovely logic attached to it and it just so nice to look at from a visual perspective :)
For me that 1 in box 4 was fascinating, as it couldn’t be in r4c3, coz there’s 6&8 staring at it and there’s 59 pair in box 6 leaving those adjacent cells with no possible digits to place... and then I went on to the centre 4 to crack through... it’s a fantastic puzzle!
28:27 Oh Simon, your scanning skills are letting you down once more...
Mind you, it's fun to yell at the screen lol
When you get the 57-59-59 bent triple you can immediately resolve the 57 pair can't be 5, but it is a little bit hard to see. Great puzzle. This is one of my favorite variants.
you read ALL of the comments? .... HI SIMON! Thank you for all of the work you and Mark do! Please remember to stay hydrated, take breaks when needed, and do some simple ones ever once in a while
I had all but like 8 squares done, got confused because I forgot 10 could be 5+5 on diagonal, and when I put my phone down it closed chrome, thus clearing the puzzle, so I just decided to only enjoy watching Simon finish it.
Had I been sober, this might have gone better. Still a very nice variant that I would like to see more of.
That was a very good puzzle. It defeated me the first time I tried, as I reached an impossible position. I redid it carefully but got to exactly the same position when I suddenly realised that on a diagonal 10 in 2 cells can be 55, and indeed must be to avoid my problem. And that was sufficient to complete it.
Everyday I watch these guys solve puzzles and I just wish I could come up with these ideas
I think this was the most enjoyable sudoku puzzle I ever did in my life. Very well done. It's funny though how at 26:30 he deduced 2 numbers in the bottom right before concluding the sum is 19 and not 17 when he could have just added the bare minimums of all 3 numbers and seen that's the only way^^
I want more of these types of sudokus!
I'm learning more about numbers from this channel than from my primary school maths.
7:45, his logic is faulty right? He just got lucky that it was true
45-10=35 for the straight arrow section. The sums on top and below the 3 won't include the 3. 35-3=32. Therefore we can find a sum for the top and bottom. 32/2 =16, not 17.5 as Simon stated.
Am I wrong?
Jk... I misunderstood what he was explaining.
Loving this ruleset! But definitely need some beginner puzzles to be able to comprehend and feel confident in solving... maybe a new app idea???
46:13. Took me probably too long to suss out what the arrows on either end of row 5 could've been, but I was able to work fairly quickly after that. Even still, the whole time I was solving this, I was thinking to myself, "How on earth did he create this puzzle? This is insane..." Really fun challenge!
33:37 You can find whether r4c3 is 4 or 5. If it's 5, then the cells to the right add to 28, and the cell to the left (r4c2) is 4. The cells below it are 28, plus the 5 means that you have 33, and must put 12 in the top 3 cells of col 3. Given the other digits in box 1, you need 12 in the remaining two, and since 5 and 9 are already used, the only way to do it is with 8 and 4, but the 4 from the 4-5 pair in box 4 is also in col 2. That proves 5 can't go in r4c3.
What a magnificent puzzle. Really enjoyed my try.
Unfortunatelly I made a mistake. My solution tampered with the arrow-rule, but the "Check" button told me I was doing all right in the end.
Is this only with these very special sudokus or have I possibly solved other sudokus wrongly before?
Didn't trust my head to not mess up a sum, so I double-checked everything against a handy spreadsheet in a second window. Which slowed me down some, but probably saved me from failure! I did miss the first chance to use parity, but once I got that clue I proceeded pretty well, ending in 52:07.
32:09 for this one, though I nearly broke it near the end but was able to back up enough to fix the problem. Fascinating puzzle, starting to like these pivot ones.
Wow, I cant believe he was missing so many obvious things but came up with so many complicated things to solve it.
Was a fun puzzle, I was solving in between the breaks at work over the course of three days so I kept losing track of my sums, and was unable to solve (I missed that the 6 was impossible on the 46 arrow in box 3). I did get to admire the construction anyway,
Including the fact that the final solve as as many repeated digits along arrow diagonals as possible, I thought that was a fun little tid bit
My first (and immediate) words as the puzzle resolved on the screen were, "Oh, good grief!"
Don't know how you'd fix it, but it is quite difficult to see the digits over the arrows. Probably just something we'll have to live with.
I figured out a lot, but I'm stuck with a contradiction. But I can't figure out how to make the cells different. it looks like column 7 is pretty much set. as is is box 3 and a few other cells, but the sum in column 9 needs a 3 which is already placed in r1c9.
I had box 3 and 5 of the digits in boxes 4-6 done immediately, but I can't get around this.
I'll refer to my previous "O, good grief!"
"Oh, good grief!" Now I noticed I used the wrong digit in my sum in column 7.I may get this back on track.
Okay, I have half the grid filled in but I'm stuck. It's been and hour and a half. Video time.
You missed a beautiful piece of logic at 14:09. When trying to solve the bottom left corner having an up and right arrow. The right most bottom cell was limited to 5,9, the topmost left cell was 6. You can deduce the following: the bottom left is not 7, because if it is 7 then cells 2 through 8 bottom row sum to the same as the first row middle 7 cells. That would force the top cell of left row equal to the right cell bottom row. Impossible since 6 does not equal 5 or 9.
Less than an hour... Not so bad for an approchable puzzle 🤣
A fabulous puzzle, which I spent way too much time on because I kept SAYING that there could be repeated digits on diagonals, but my brain then wasn't allowing me to CONSIDER repeated digits on diagonals. Otherwise I reckon I would have done this in under an hour ... instead of the 3+ hours to actually took me, after re-starting four times :)
What a nice puzzle! Cuddos to the constructor
13:13 - You can't put the same digit into a Sudoku box twice?
Wow, the things you learn on Cracking the Cryptic!!
I wish the rules were clearer. At the beginning I was operating under the assumption that all arrows had to add to the same number. But the rules are only that all sums from one point add to the same number.
@@NetMaple "For cells with arrows, the first N digits in all directions of the arrows must have an equal sum." In my comparatively pea brain, I read that as meaning that all the directions of the arrows meant all the arrows on the board.
Two things Simon missed around 4:35
1) R5C9 cannot be a 4 as the eight cells either side of it would then need to sum to an ODD number
2) The smallest digits we can place in R1-2/C7 are 4 and 5,
The arrow in R1C7 limits it to 456 and the 1 limits the sum to 10, hence limiting R2C7 to 456 as well.
~~~
Edit: He sees the first one later around the 9 min mark.
My approach to Column 7 was slightly different.
If R1C7 was 6, the numbers OUTSIDE the sum would be 12
Therefore, R8-9/C7 would need to add up to 12, and we can't make 12 from any combination of 178.
At 23:30, The South East Diagonal actually isn't as complicated as Simon makes it seem.
Once the 2 is placed in R6C5, the minimum sum of the diagonal is 5+7+2+5=19.
This seems to work, BUT putting a 5 in R6C6 forces a 7 into R4C6, breaking The North East Diagonal!
At 16:25 I don't understand you eliminate 57 from r8c1. I get why it works for the r9c1 but he eliminates it from both? Was that a lucky guess?
It had to equal 12. 13:56
Noooo, I'm so sad the starbattle solve is only on Patreon, my cheap butt can't spend the money. Great, GREAT puzzle though and anyone who hasn't tried it already absolutely should.
r6c5, could be filled in as soon as r6c7 was a 3 ;P
4:40 It can't be a 4 ... if it's looking at 4 cells in one direction (sum = x) and 4 cells in the other direction (sum also = x) then together with itself that covers the whole column. Which we know adds up to 45. And that would make 2x+4=45 and so x=20.5, and even with the new software it isn't going to be possible to make 4 cells add up to 20.5 😎
_Edit_ - ah, you spotted it!
1:17 ASTRONOMERS just got triggered.
43:06 I was a bit slow in the middle going (again), but I very much enjoyed this solve. Nice puzzle!
34:06 with the mouse over the digit 6 saying "and you can see" Simon pauses for a tiny bit, maybe noticing that the 6 decides the value of the 69? Alas, not yet.
I know that was painful!
Tried this on mobile (iPhone), but the arrows being black made my numbers super unreadable. Couldn’t tell the difference between a 2-on-arrows and a 1-on-arrows without zooming in, so gave up. Wish the arrows were a lighter color like gray or something.
Approachable is useful terminology.....
Very good roll on backgammon... unless you're on the bar!!!
Entertaining video, as always!!
Thanks for sharing.
"This puzzle is rated 3 stars out of 5, so it should be approachable, ha ha, whatever that means."
It means us knuckle heads might have a change to solve it. You can say it Simon. We won't get offended.
You didn't use the one of the arrow clues (in the middle of box 7).
56:20 solved for me. A little bit slow but very enjoyable and very beautiful puzzle!
Amazing puzzle!
At15:38 how come the parity trick logic does not also apply to row 5?
I see it now. The arrow does not go right.
Omg i was pulling my hair out for you not putting the 9 in the 8th box because of the 6 in the 7th for a long time
"If you look in the direction of the arrow ..."
We really need a non-integer Sudoku variant at some point.
i got the 2 in box 5 so early watch it be wrong when he gets to it i dont think it can though..............i feel like a genius right now
Reminds me of KenKen logic. CTC should do a KenKen video some time.
R5C9 could never be 4, cuz 45-4=41 and you can't divide it by 2. Update nvm he spotted it few minutes later.
49:23 Set all the early logic out and then took an age to spot that the 1 in R3C9 was the useful clue. Great puzzle though
1:03:19, but very enjoyable. Watching the solve, I wanted to yell out that r9c1 can't be an 8, which does speed things up a bit.
But r9c1 could be an 8?
At least up to the point that Simon works out the 4 arrow clue sums to 19, at 26:55 in the video. And Simon enters the 8 within a couple of minutes of this, so I don't see how it could have been entered too much earlier?
1:10:45 for me, happy with that as my first sudoku of this type
Solved it with a bit of help from the video.
I gotta comment before I erase the grid. Lol.
@32:44 though..
"A Double Six.!?" ("A good roll in backgammon.."), Simon said happily.
[[ Yes, a high roll and a good roll in games that involve dice ]]
One of those 6s fixes that 69 pair across the way though (in r7c7) to a 9.
That makes it a "ten" clue in the center box.
That "ten" would then make a Double Five on the other end (the same as "the Double Sixes" ) at this timemark.
That's neither here nor there though as to what I'm about to say/ask.
I couldn't think of what "a Double Five" roll was called.. so I thought about a "Double Four".
Can anybody's tell me what a "double four" is called when you roll it?
I'll just say before someone Googles it.
They're called "Boxcars".
(Simon probably knew this, but I have no idea what they call them in the UK)
"Boxcars" are "Traincars" though.
("Passenger Cars" on a train even, even though they could be transporting coal or something)
But "Boxcars" are square (you only have to worry about the front being aerodynamic (or however it's spelled) unless a backwards and forwards high speed train nowadays (but even those "middle cars" are square).
That's why a Double Four is called "Boxcars'' though.
I had a hard time thinking of what a double five is called though (although I think I remember now).
What are "Double Fives" called when you roll them though?
(And hopefully you like the "Boxcars" stuff lol) ;) 😂
Took me just under 2 hours with a good few hints from the video. At least I'm persistent, if nothing else...
Slightly disappointed this isn't Pirate Sudoku, as I first misread it.
Double-6 isn't _always_ a good roll in backgammon. It can be disastrous.
very nice one
Wonderful stuff. Lost of fun.
So many knowledge bombs dropped on us
Simon's opener for all puzzles: "Let's get cracking! Erm..."
PIVOT PIVOT PIVOT
I got the rules completely wrong to start with. I interpreted them to mean that the first n digits had to sum to numbers that were equal (as opposed to odd). A clearer way to have put it would have been "the first N digits in all directions of the arrows must have the same sum", or "sum to the same number".
@@NetMaple of course they do. at least, they do late at night when my mind is obviously not working properly (face palm).
10 mins in...I think I understand what the rules and restrictions are now...
Took me a full hour (1:00:49) - disappointing...
But still enjoyable, amazing that it has unique solution...
I solved the puzzle however, I made a mistake in calculation yet I found a solution, I mean it violates the rules but is a valid solution by sudoku rules
Didn't even think to check for row/column parity. Grrrr....
Took me 37:12, that was brutal so I'll have fun seeing what I missed.
69 Pair in the row, if you what I mean. Yeah....I see what you mean
16:54 R9C1 couldn't be an 8 as soon as R9C9 couldn't be a 6, because R1C1 was already 6.
It could be an 8, but it cannot be a 7.
An 8 would sum ALL the other digits in the row/column, so would be 45 - 8 = 37 in both directions, irrespective of what was in the furthest cell.
40:48 i thought i did very slow but got close to simon.
What’s a sudoku professor? Does this professor have a PhD in sudoku?
Once again, a brilliant solve of a brilliant puzzle. But unfortunately once again the rules were stated ambiguously. As we know from X-Sums, N is the first digit of any group of "first N" digits so the clue digit needs to be included in the counting and summing of these groups.... or does it? You on the Sudoku Council should develop a standard nomenclature for that sort of thing.
I started the puzzle just like Simon and had finished boxes 3 and 6 when I went back to recheck the rules and realized I had forgotten to include the clue digits in my calculations. I completely restarted the puzzle only to find that I couldn't make a dent in the logic. At this point, having lost my earlier work and momentum, I was too disheartened and frustrated to continue and my enjoyment of the puzzle was ruined.
Maybe my uncertainty about the rules was my fault, but the phrase "first N digits" is straight out of the X-Sums playbook, so hopefully you can see my point.
I can understand your frustration, but for me there is a big difference between 'The sum of the first X digits from that side where X is the first digit' and 'digits in all directions of the arrows'. Mainly the addition of 'directions' makes the difference for me. And makes it clear that N is not included in the count. But I agree that for clarity it could be added in the instructions.
@@NetMaple In this scenario, for example, the first two digits of the initial 2 clue in box 3 are 2+3, 2+1 and 2+6, which do not equal the same total. Moreover, the possibilities of all arrow clues increase by 1, making the logic of determining what digit to place an order of magnitude harder. Hope that clears it up a bit for you.
32:59 - r7c6 must be 6 by sudoku
* 9 by Sudoku
#CTCknowedgeBomb 14 and 16 are both even.
B e a utiful puzzel
New video :)
1:15:18 - Not impressed with myself this time.
OMG Its nine 34:13 nine!!
R9c1 canno be 7 becauce r9c9 would have to be 6
Ha first one here
2nd
I may have an addiction to your videos
Hi cousin! [I'm sure we are some way]
@Anifco67 comments are good for the algorithm you know