The Sudoku Professor's Beautiful Lesson

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▶Today's Puzzle◀
Today's sudoku is by the Sudoku Professor Richard Stolk and he teaches Simon a thing or two! You can play it here:

Rules:

Normal sudoku rules apply. The small clue in the top left corner of a cage indicates the sum of the digits in that cage. Within each cage all digits must be different and they must be placed in a way that they are all horizontally or vertically connected in an increasing order, such that they form a snake-like pattern of one cell wide. (ie it must be possible to draw a valid "thermometer" covering every cell of a cage!)

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Our Patreon page has lots of extra content including Scott Strosahl's Puzzle Hunt and Phistomefel's latest sudoku! Watch out for our videos on how to solve Scott's hunt too - coming very soon!

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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!

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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

[richardstolk]

Well done Simon! I indeed built the puzzle with the 45-cage as basic thought, including the chessboard pattern with odds and evens.

[prahas]

At 25 minutes, anyone else whispering to the screen, "4-5 pair. 4-5 pair." (In box 6). // And, again, another terrific puzzle and solve!

[quinnencrawford]

Three laws of Thermodynamics
1. Energy is constant
2. Entropy
3. Only Simon is allowed to put the 2 in the corner

[PhilippeAnton]

There is an explanation that I find simpler, for the checkerboard on the 45 cage around 16:10: The 9-cells-long thermometer in the box has five odds and four evens. If we put an even number on a yellow cell, then its neighbors will be white and odd. And vice versa, so yellow cells all have the same parity and white cells all have the opposite. So if the thermometer fits in the cage, then all five odds need to fit in five same colored cells, this is only possible if these are the yellow ones.

[madhavsankaranarayanan]

Richard took this constraint and made it unbelievably good! Fabulous puzzle!

[clarematthews]

34 minute solve. Kicking myself for several things! Including not thinking about what numbers were necessary in the 17 and other boxes.

That was a lot of fun. Great way to start the day. Thanks for everything you do with this channel. It's added so much light and positivity to my year and to the year of so many other people. If only I had the energy to explore the discord channel properly. There's so much puzzle excellence on it from lots of excellent people.

Now to watch, and learn the legal ramifications of that two I put in the corner!

[NickyFernandez]

Great solve as always from Simon but I found it easier to break in using the 9 cell box and then consider the values within that box that are contained within box 9. Allowed most of the bottom right-hand side to be filled in.

[glum_hippo]

23:55 - felt good! Richard has such a distinctive style... you can always be sure that pairs will eventually resolve in the most unexpected way!

[thebiasedreview]

Simon approached it in a completely different way than I did. He was working through the thermo logic predominantly, while I switched to a lot of killer sum logic to deduce the digits.

[nkish]

Another classic case of me seeing some logic that Simon uses another way of getting to the digits!
At 24:45, as soon as you put 8 in the middle row of box 7, I also saw that a 5 is also limited to those cells. That being a 20 cage, you would need 7 as well to get the cage total (20). The 7 in Row 8 in Box 7 puts a 9 in R8C6, which is the high point of your 45 cage thermometer. Once you get that 9 (and already have the 852), you can get the 7, 6, 4, 3, then 1 and finish the 45 cage by min 25:00.
Another great video, thanks!

[Coyotek]

18:32 ... After a run of 'Simon' puzzles that beat me down, I'm having a nice run of solves.

Wonderful puzzle!

[alvaropallete]

6:38 the way I think about killer cages, taking the same example
5-cell cage summing up to 17:
*the minimum 5 cells could have is 15
*the difference between 17 and 15 is 2
*therefore the 2 highest digits from 1-5 are not necessarily in, but the other 3 lowest must be in
Same example with 5-cell cage summing up to 18:
*the minimum 5 cells could have is 15
*the difference between 18 and 15 is 3
*therefore the 3 highest digits from 1-5 are not necessarily in, but the other 2 lowest must be in
To sum up:
*5-cell cage summing up to 17 must include 1, 2 and 3
*5-cell cage summing up to 18 must include 1 and 2
Two more examples in the comments

[ZedarFlight]

Saw another way to resolve the thermometer in the 45 cage. At 24:45 when you put the 4, 5 pair into the 29 box with a pencil marked 9, the remaining part of that box must add to 11 without using 2+9, 4+7, or 5+6, so it's a 3, 8, 9 triple which eliminates the 3 from the top right of the 45 box

[danielrhymer]

22:52 for me and that is genuine! It helped a lot knowing parity problems, especially for the cages that had an odd number of cells as the biggest/smallest numbers could only go in certain places

[brunopolancec]

I don't even solve sudokus on my own and i still watch every upload

[markp]

18:21 final time, I also used the 45 cage to break in. Realizing that the bottom-right 4 had to add up to 14, with no 7-8-9 due to thermometer restrictions, told me that 7-8-9 was in the 31 cage, with the 7 in r9c9. I used the 17/18/19 P-pentomino cages liberally, knowing that the tail of the P had to be either start or finish of the thermometer.

[tarbosh]

Managed to solve this one without peeking at your process. A little tough to break in, but after that it seems like smooth sailing with the Thermo restriction.

[shadout]

24:45 "You can see I'm running out of ideas" immediately after pencil marking the 4-5 pair in box 6 which would have solved the direction of the thermo in the 45 cage, although he got there a minute later using a slightly different another set of pencil marks. Had me saying No! Don't dismiss your observation - it was a good one!

[MattiaBiggMattGentile]

One hour and thirteen minutes my solve, like clockwork, twice the video. I'm so glad I can do these things!

[cowboyrocker]

when you put in the 245 in box 3 in column 9 25:15 I noticed that the only way left that won't break it in box 9 for the 31 cage is if the last 2 digits is 1 and 6 to make seven which would resolve the 45 cage. Cause if you have 2, 4, or 5 in the last 2 spots for the 31 cage where would they go in box 3, and that in turn would break it