The Sudoku Professor's Perfect Puzzle

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▶Today's Puzzle◀

Today's sudoku is by the sudoku professor Richard Stolk - author of the Sudoku Variant Series over on Logic Masters Germany. This is a REALLY clever puzzle and not too tricky - you can play it here:

Rules:

Normal sudoku rules apply. Digits must sum to the small clue in the top left corner of their cage. Digits cannot repeat within cages. Clues outside the grid indicate the number of switches between connected series of digits of the same parity (odd/even) in the respective row or column. Such a series can consist of one single digit.

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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 new November monthly bonus puzzles - out now!

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▶SOFTWARE◀
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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Melvyn Mainini

▶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]

My original idea was to have twice a remaining sum of 8 in columns 3/4 and colmns 6/7. Both sums couldn’t have a switch. But in the end I couldn’t get that working, so let that thought go.
It was indeed very helpful to know immediately the parity of most cells in C9 to make quick progress.
It’s always fun to see someone else solve my puzzle, especially when it’s done with so much enthusiasm! Thx.

[stevieinselby]

"It's the 18-cage that's going to solve the deadly pattern" 🤨
What's that noise I can hear? Why, I do believe it's a 15-cage crying in the corner 😭
Don't worry, little 15-cage, some of us love you, even if nasty Uncle Simon doesn't...

[Avasjo]

its fun to see Simon do the most elegant solutions and then fail when something simple is required like simple sudoku

[carl]

Is nobody going to comment on the intro music? Fantastic job!

[HunterJE]

"Reports of my deadly pattern are greatly exaggerated..." - columns four and five

(A "deadly pattern" on 2-4 is not so deadly when one of the involved cells is already in a cage with a 2...)

[necaton]

i love when you color the grid. this looks satisfying every time.

[MattGriffiths]

I really enjoy puzzles like this that take something "extra". Finding all odd numbers, or all low numbers etc. The way this was constructed was fabulous. Good job @Richard Stolk

[alibabapirce]

so the only way you can divide this column in to two, exactly two regions if that is orange - simon 2020

and that face when he realized what he said :D

[davidellis]

Over an hour but still super happy with the result. Always a logical path, and never too stuck - a great puzzle!

[JeremyButlerquarterthru]

at 30:23... Q: "Is there definitely a 6 here?" A: YES.... Oh well. Add another logic bomb from CTC at 16:30 "There are only 4 even digits between 1 and 9". Love you guys.

[Roezaea]

49:56 Really amazing solve Simon, and a lovely puzzle. Your killer-cage skills never cease to amaze me. I had break in to the puzzle using 1/3 pair in the center and the two-switch clue in r4 to discern that that row must begin and end with even digits, with all of the odds in a connected string in the center. That alone gives you the entire parity of c1, without needing to find the composition of any cages.

[DJayMan]

Took me a while to finish, but the puzzle was definitely enjoyable from start to end. Absolutely brilliant, I loved the way that it led me through to the solve!

[louisehart]

I love running these videos at 1.5x speed - Simon's enthusiasm is delightful even at 1x, but at 1.5x it's amazing.

[sman]

Happy to have pulled it off in just under 50 min. Thank you for teaching me to pick up on parity and learn how to do my colors :D

[litlsnekxd]

, ,3 is not even last time i looked" made my day. I love you, sir!

[BozoTheBear]

A very nice puzzle, thanks Richard! As usual, I greatly enjoyed plodding through it myself, and then watching a far more elegant solution!

[nemoyatpeace]

Wow, I didn't put a single number in the grid until I had all the parities figured out. What a great solve. I started by recognizing that the 6 clue on the top meant the top corners had the same parity and marked them in light gray, then worked my way around adding more light grays and dark grays to represent different parities until I eventually had 5 in the same column and new that those had to be odd, so I could switch them to orange and the others to blue.

Much fun! Thanks.

I didn't note the 1-3 pair in rows 4 and 5 until very deep into the solve, even though I'd worked out the parity for the columns that only missed 2 cells. I'm glad I missed them because I would have put numbers in too early!

[gms]

I both love and hate that Simon explains the "why does a column/row/box sum to 45." Makes it super helpful to beginners of the channel. Gives me a short moment to completely stop paying attention to the video, which means then that I have to figure out that I've missed something highly important!

[JaymanOttawa]

One of my all time favourite puzzles on Cracking the Cryptic! So fun!

[pancakelegend]

You could do a podcast series where you interview setters.