[Hard] World-Class Killer Sudoku

[@maicoldellachiesa5021]

24:10 “There must be something easy” as he hovers over a resolved pair and proceed to do something else more complicated. Always nice watching these vids

[@pear4576]

There's a few things I wanna praise you for. Always mentioning the link in the description and recommending people to try it, Idk why I just think that's awesome. The way you explain almost everything and make it clear why something is true, I've seen enough videos to know why the 40 cage can't have a 5 in it, but new viewers might not spot that immediately so the fact you keep mentioning that and explaining is great. It might have people like me think ''I know that'' but honestly never stop doing that. And the fact you mention you can fill in a digit somewhere and then say ''pause the video and see if you can find it'', this gives people a place to look and definitely helps one improve on spotting such things. It's the small things that matter, keep it up and never stop doing that. Have a nice day :)

[@davidstorrs]

Speaking of things that matter: Good on you for being sincerely complimentary and supportive. It's all too rare on the internet.

[@nancyrene897]

I love your stuff. Just found the puzzles from 2020. especially like the cages and dominoes. I'm an 82 year old, former math teacher, you guys are keeping me young!

[@glennmelven3414]

I thought it kind of strange that Simon didn't look in the 25 cage in R8 and see that he already had 67 in it, meaning the remaining numbers had to be 1245. And then when he placed that 8 in C3 he didn't see that he also got the 23. Almost makes me feel smart.

[@mylomilk4635]

Took 41 mins, very good puzzle! I feel like this puzzle is way easier than the 10 rated dailykillersudoku puzzles. Those ones I often stare for 30 mins and not make any progress; this puzzle, even while long and resilient, never made me stuck which is enjoyable.

[@skasperl]

At 21:00 when you state 'even that doesn't give me a thing', it gives you at least the rest of the 22 cage. There is no other way to make the other two squares sum to 5 than 3/2 with the options you have (123/125).

[@Pyromonkey83]

Yikes, hard one indeed. 45 minutes to solve for me, still have a long way to go until I'm decent at Killer Sudokus. Maybe someone should make an app for this variant that I can purchase on my favorite device... Maybe someone who takes the time to make nice hand crafted puzzles.... Maybe someone who can give me good hints when I get stuck... Wonder who could do something like that. *cough cough*

[@eloib7664]

There is an app called killsud for playing killer sudokus

[@samslack4885]

Have you checked out daily killer sudoku? www.dailykillersudoku.com/ I think they're computer generated so the logic is a bit crazy (or at least I dont always see it) but there's a ton of puzzles to practice.

[@mori270697]

Took me over an hour and a half, but was satisfied to finish it before watching the video. It always amazes me how much faster you can solve a sudoku than me

[@Tehom1]

Tough puzzle! One bit of a head start that I figured out: Since 5 doesn't go in the 40 cage, etc, you know right at the beginning that 5 goes into one arm of the 38 and one arm of the 36, and similar logic for the single forbidden digit of the others. You can follow that a little more around the outside edge of the puzzle to show that a 5 goes into the long arm of the 32 too.

[@jacobknight5497]

*nice trick!* There's a nice shortcut using the geometry of the cages. once you have the 7 digit in r8c3 (8:18 in the video) you can immediately deduce that r9c4 is a 3. Compare the sum of the cages in the boxes in the bottom right of the grid (7+30+32+25=94) with the sum of the bottom right and bottom centre boxes (45+45=90) to deduce that r9c4 must equal r8c3 minus 4. The same trick can then be applied multiple times around the perimeter of the puzzle throughout the solve! Thanks for a fun and informative video as always 😁

[@davidbourke6211]

Been watching since first lockdown now and I'm hooked. Would not have even considered trying this back then but can do so now. I love the fact that Simon can graze through these puzzles nibbling at logic like a gazelle , making delicate and inevitable progress while I brute force my way to a solve in twice the time. Bravo sir!

[@bristolrovers27]

I spent half the puzzle wondering why you hadn’t sorted out the 2 and 3 in the central box. You’ve a brilliant mind but are no lover of the obvious Another great video

[@バカロン]

also 9:39 could be solved by just "if this is a 9, where do we put a 9 in the first row?"

[@kristofersokk1580]

16:19 I think easier way is to consider that after 7 and 6, the 25 cage now has to have 12 in 4 cells, so numbers 1, 2, 4 and 5.

[@nekozid]

Yea, that's precisely how I saw that it had to have a 3 in it. As he mentioned mere moments ago, 12 in 4 cells is 1236/1245; but the 6 is taken.

[@krynking9973]

the 23 pair in the middle square that you just kept looking over could have been resolved so much earlier than it was. it was hurting so much watching you hover on it for what felt like 10 minutes.

[@tomercohen7494]

Took me a little under two hours but this threw many of my methods out the window, which I loved, and afterwards, seeing you solve it has definitely enlightened me in some ways. Thanks!

[@PassionPopsicle]

Coming in four years later, seeing 28 minutes I don't think "hard", but "maybe it's easy enough I can do it myself" - so much has happened in that time!

[@gposchman]

Thank you for doing a hard Killer Sudoku. I go to daily killer sudoku, and I do poorly on harder puzzles. I realize that I don't look enough into Boxes, cages, and 45. I can individual squares and double squares fo resolution in easier puzzles, but I have trouble with puzzles where there are no real easy squares to find. I was able to get started on this puzzle, but until you worked the right middle-box, I was stumped. Once I saw how you worked out what was possible because of the relationship of 35 in 5 squares I hadn't seen how to move forward. I stopped the video and with looking up what numbers could fill a cage, there were some limited ones on this puzzle, I was able to move forward. I will use this video for a tutorial to return to. As always you and Mark are great, love the videos, the puzzles, and your apps and site. Gene

[@Wecoc1]

Nice timing, I just saw today's Numberphile video "A Breakthrough in Graph Theory" talks a bit about Sudoku

[@Tehom1]

Saw that. And they give a "medium" sudoku as an example, but it's much easier than anything on this channel. Paused and solved it in my head.

[@martinepstein9826]

Great puzzle and video! I I learned a ton watching your solve. I think the most interesting thing you missed is at 8:18. After placing the 7 in R8C3 you can immediately place the 3 in R9C4. The 25 cage is now effectively an 18 cage, which means the bottom middle and right boxes are partitioned into cages except for one cell. The cages add to 87 and two boxes add to 90 so the remaining cell must be 3.

[@jenna.elisabet]

Took me an hour to solve. A great puzzle to practice harder killer sudokus.

[@Sianistic]

spotted quite early on that R9C4 could only be a 3 ... if you take the killers in box 8 and 9, they add to 94 (7+32+30+25), with only one cell missing from the two blocks and an additional 7 in it ... And following that, you can isolate R3C2 to be a 2 (22+38+22 + 6+7-3 ), covering two full boxes, through a similar series of deductions. That said, I Ultimately gave up halfway through since I'm not used to playing Killers and gave up

[@LittleLionRawr]

That's a great one once you have the seven there! Nice!

[@nightwishlover8913]

That killer Sudoku was killer. Over on hour even with help from the video! Yeeesh!

[@Talsin1989]

It's boxing day, i shouldnt be yelling 'solve the 23 pair and the puzzle unravels!!'

[@ic3ric3]

Holy moly this was a hard puzzle and my brain was kind of hurting just watching Simon solving it

[@felixenghofer4616]

Hard one! Interesting how you got to the 6 in row 1. I solved that through the sum of the cages in the two boxes. I already had a 3 or 4 pencil marked in column 7 row 2 which means that the total is either 95 or 96, so that the cell in question could only be a 5 or a 6. Since there is already a five in the column, it had to be a six! There is some beautiful logic in this puzzle!

[@Socialdogma]

LOL at 24:10 when you say “There must be something easy” and your cursor is hovering on the 23 when there is a 3 already in the column.

[@sonalita_]

Simon often misses very obvious things. I think the problem is that he delights in finding intricate logic to the point of missing very very obvious things - like the other day, he placed a 3 and 2 cells to the left was a 23 pencil marked and he didn't scan left after placing the 3. Don't get me wrong, he's a brilliant logician but missing those very obviious things infuriates me when I'm watching him solve. I still love watching the solves though.

[@kristofersokk1580]

9:30 a simpler logic would be to consider the fact, that in row 1, 9 can only go to the 40 cage, because of the 36 cage definitely not having a 9, which then makes R4C1 a 6

[@igoretski]

I saw that too.

[@drewmichael3986]

awesome puzzle FINALLY solved in 44:20 I was stuck for like 10 minutes staring at the puzzle until I noticed that the 28 cage didnt contain a 7...

[@jackbloodraven]

Loving these videos and learning new tricks. Would be interesting if you used an eye tracker so we could see how you look around the puzzle.

[@juliannicholls]

I tried it and got to the 'beautiful piece of logic' point after about 15 minutes and then watched the rest of the video.

[@facilvenir]

It's amazing how I can see the way to solve the puzzle when I'm not actually solving it. There were so many things that I spotted instantly and it took you a while. But when I tried to solve it, I couldn't see them.

[@kristofersokk1580]

26:27 An alternate logic would be to consider that a 4 is in R9C1 or R9C3, which makes R5C1 a 5, which also solves the middle rows

[@RandomBurfness]

19:14 for me! I first fed this into Duncan's Sudoku solver and used that interface to solve it because I like it way more for killer sudokus.

[@rektys]

I had a lot of fun with this one. I was always thinking the same thing as you but 10 seconds earlier. Beautiful peace of art.

[@GreenMeansGOF]

The 22 cage could have been resolved sooner because there was only one combination adding to 5.

[@FolgoreCZ]

20:55 How on Earth did you managed to lost the thought that quickly that you didn't finnish the cage? :-D

[@Knochenkeule]

Exactly my thought :D

[@JakeDiToro]

Right? If I put a 5 here the other two cell need to add to 8. Well corollary when you put the 8 the other two have to add to 5 and there was only one way with the restricted values of the cells.

[@KeithGrant]

It's reassuring to see I'm not the only one who completely drops a train of thought before following it through to the end

[@s9ecera]

Oh no, even that doesn't give me anything. :-D Feast and famine

[@sicoles]

I can't sleep. Thank you, Simon

[@kristofersokk1580]

15:42 some geometry with 36, 24 and 12 cages and boxes 3 and 6 proves that R1C6 and R2C7 has a difference of 2, putting a 4 in R2C7

[@gordonglenn2089]

That was a good challenge. A nice easy start, then a few slowdowns along the way. Overall, a beautiful puzzle! As is typical with these, I used the arithmetic more, while Simon used sudoku more.

[@b1rdpoo]

you way of solving was a lot more elegant than mine but the logic i used to solved it was also cool.. i approached the puzzle by summing and contracting areas and boxes

[@andersingemanrasmussen3284]

I was just recommended this puzzle by some danish friends. I managed to solve it in less than two hours, but I got another solution than this one.

[@andersingemanrasmussen3284]

Ah, the checker did not verify the cages - only the normal sudoku rules 🙂

[@Socialdogma]

I used several adjacent cage combos to isolate singles not fitting in two large boxes. I spent a lot of time on this strategy. Interesting to see you didn’t go that route at all. I guess I over-complicated things.

[@vwisse]

40 minutes for me. Usually not that fast but have been doing a lot of killers lately which helped a lot

[@grahamfisher307]

I put 9 in R3C7 since firstly neither the 36 nor 12 cages could contain the number. Also it had to be part of the 24 cage, so R3C9 was the only position in block 3 where it could go.

[@john_reese]

13:57 for me. The cages set-up was a bit unusual, which made for interesting reasoning.

[@XavierShay]

1:13:13, can't believe I made it! Never got really stuck, just took ages to stop each next step. Nice.

[@Mntlchaos]

There was a bit of a sort of balance with the 25 cage and box 9: Once you had the 6 placed, you had 13 in the top row, and a 32. Note that 32+13 = 45. The 32 overlapped into box 8 by 2 squares, and the sum of those squares must thus be the same as the sum of the two squares of the 25 cage that jut into box 9! Not only does this give you the 3 in r4c9 once you place the 7 into r3c8, since there are only 5 numbers left to place in box 8 (the 789 were in the top row, and the 3 just placed), but those pairs of squares must be identical, too.

[@BlueCyann]

Ouchies! Completed without error, but made my head hurt. Interesting due to finding a bunch of cool logic, yet I know there must have been a lot of stuff I missed. Looking forward to the video.

[@draconicdusk5911]

Hard, but managed to solve it, without using the dailykillersudoku app for all possible notations. It's quite the linear path, but it's a great workout for the mind and I felt so satisfied when I beat it. Solve time 47:30

[@stronggreenflame]

you ignored the 24 cage in R3 for so long. That was the cage that helped me the most lol. once i saw that there was a 9 in R3C7 the 24 became really useful. I think you might spend too much time trying to do normal sudoku. but hey this one took me 58 minutes so who am i to judge.

[@EMBPercussion]

I solved it in 51:31 @ 24:41 Crazy logic can be found at c2r1, c2r9, c8r1, c8r9 which creates an interesting set of eights that can only be placed one way.

[@ArunIyerS]

In r7 cage with 25, once you discover 7 and 6, it immediately tells you that remaining 4 cells in the cage have to add to 12, which is restricted to 5,4,1,2 in some order. That immediately resolves several of the cells in r7.

[@v3lojt]

That was a cool puzzle indeed

[@cigmorfil4101]

16:19 The 25 cage is made up of 6 cells, 2 sum to 13 so the other 4 sum to 12, meaning they are 1236 or 1245. There is already a 6, so they must be 1245 which can all be eliminated from centre cell of box 7 to leave it containing 3. And the outer two cells of row 8 must contain 89 in some order.

[@ariel_haymarket]

I gave up trying to do this by myself after 22 minutes. Solidly filled in 17 of the 81 with a lot of pencil markings and Kakuro table consultation.

[@nityantagarwal2532]

15:31 for me Beautiful Sudoku

[@stephenbeck7222]

Tried for 5 minutes to add the 4 large outer cages to find something about the r6c9 and r7c9 but to no avail. I think I had star battle logic on the brain (and the trick you did in the recent star battle video).

[@Numberplay]

One piece of logic i figured out early on is that the moment you found the 7 in r8c3 you could figure out r9c4 was a 3 by adding up the cellls from the bottom and bottome right grids. same logic could be applied later for r3c2 and r2c7 by adding up more killer cells in the grids going around.

[@igoretski]

I used this, too. But I was still much slower.

[@thesolarfutureenthusiast1102]

Took me 2 hours. I didn't spot the 22 cage so it took some interesting logic to get there. I was adding 2 boxes + the 2 sticking in - the 2 sticking out and limiting numbers that way.

[@EndlessMystify]

Took me four hours to solve, but I did have to take a break for christmas dinner with the family in the middle, so maybe a total of around 2 hours or so.

[@jorgen_persson]

Yes. Finally a killer :-) After 01:01:01 then the "cracking-the-cryptic.web.app" said "Looks good to me!". Now it will be interesting to see how I should have solved it :-)

[@jorgen_persson]

Noooo! Just noticed that I made a mistake and because of how the software works, the solution passed (it doesn't check the sum of the cages) :-(

[@josteinmatre131]

At 23:13 it is an interesting pattern with 3 pairs on top of eachother. Based on this it is possible to exclude 1 and 5 from r3c2. I reaced this solution by testing, is it possible to reach the same conclusion by logic?

[@PhilipTa10]

Solved it in 53:57. Really happy I managed to do it before watching the video

[@no-feetmcgee5577]

Took me 4:22... I'll leave the units unmarked to protect the innocent. XD

[@christophseeliger5551]

At some point you could have tried the „outer ring“ trick again in this one, but unfortunately, it wasn’t helpful :-)

[@s9ecera]

Haha, I am so hooked on that trick that i worked on it in my solve, and managed to get the 4 i c1r1 that way :-)

[@Wiiezner]

Glædelig jul! Greetings from Denmark :)

[@skunkyprd9285]

Og godt nytår :)

[@shonuff5297]

Awesome puzzle.

[@Swisswavey]

I didn't find that hard. Yes, it took me a while, but it didn't need any unusual tricks or jiggerypokery, just straightforward adding up and eliminating options

[@carstenkruse8527]

yes....finally a killer sudoku

[@neilramsey1368]

good one

[@thepimentninja7340]

I don't understand why 7 can't be in 38 cage. It could be for exemple 9876521

[@stephentroop4649]

The Piment Ninja that’s only 7 digits and you need 8. As 9 squares add up to 45 if 8 squares add up to 38 then the 9th missing digit is 45-38.

[@thepimentninja7340]

@@stephentroop4649 thank you I am new to killer sudolu

[@rabidsamfan]

50:03. Whew. That was definitely not a walk in the park.

[@Kurgosh1]

I must have spent 7-8 hours on this one over the course of the last few weeks. Kept failing, somehow. I was making some logic mistake and making it way harder than it needed to be. Finally persevered though. Ouch

[@LearnSciSnippets]

1hr 17m to solve but very enjoyable to solve.

[@amanita8397]

solved after two hours, felt defeated realizing the video is only 30 min long

[@hazythestoner2154]

i like your uke

[@crawlertv2161]

Oh my God, I solved it! It took me almost 2 hours! I'm so proud of myself hahaha

[@04LightningFan]

After I try the puzzle myself, I enjoy watching the video of Simon completing the puzzle. Usually it's like viewing a reply of what I have just done, but this time I don't think Simon and I could have completed the puzzle in more different ways. Two examples: At the start, I noticed the 5 & 6 cages in the center box, which add to eleven, so the 6 cage must be 15, and the 5 cage must be 23, then I got the 46 in the ten cage, the 89 in the seventeen cage, and lastly I got my first digit, the 7. After I got the 9 in C7 R3, which was probably about a minute in, I noticed the 24 cage in row 3 was very restricted. Without both a 7 & 8, the most the cage can be is 8654, which only adds to 23, so both 7 & 8 must be in the row 3 24 cage. Simon didn't make any progress on that cage until after 20 minutes. This was so weird. Simon consistently, beats my time despite having the pressure of also being entertaining and explaining his logic to the camera. I did enjoy this puzzle. Normally the killer sudoku puzzles I do are computer generated. You can definitely notice a difference when you are doing a hand crafted puzzle.

[@xykontyrox4945]

39:21 for me, now I'm going to enjoy the video.

[@RB-vw8zq]

I LOVE Killer Sudoku, but must have missed this one when it came out two years ago. Stumbled on it today and gave it a go. I reached an impasse after an hour (yes, ONE HOUR), so I must have made a logical mistake somewhere. Tried it again and reached an impasse in a different situation after almost an hour again. So, another logical mistake at a different situation along the way. Frustrated, I watched Simon's solve, and he does the ting in 25-something minutes, while explaining every tiny bit of logic he uses, and he even missed the super easy 2/3 solution in row 4 for at least ten minutes, several times having his cursor over the 5 cell. Simon did not use a single piece of Sudoku or Killer Sudoku logic I am not aware of. Urgh! Why can't I do the same thing? So, (1) Simon is much quicker than I am. That is okay. He is more experienced and smarter than I am to begin with. That's fine. I am not here to set up speed records, I just want to do the friggin' puzzle. The crucial thing therefore is (2): Simon never makes any logical mistake, and I make them all the time - make a false deduction, put in some number somewhere and feel super smart about it, only to realize ten minutes later that I have destroyed the puzzle (again), and I don't even know where exactly I took a wrong turn. Thus, you can even miss a thing or two at times. Just be consistent with your logic. Simply MAKE NO MISTAKES. Piece of cake. 😘

[@ol1ver49]

Not easy! I did somehow manage to bypass the complicated logic involving the 6-9 pair on row 4, which I would never have seen. Maybe because I knew early on that row 1 column 6 had to be 2 more than row 2 column 7., I don't know. Completely different finish to Simon, as usual.

[@malice1105]

A casual 18:39:22

[@erickehr4475]

It was hard but not very hard (IMO). Finished in 26:34

[@robinbaich169]

Well, all I can say is ... OH HELL NO. I can see myself working on this one until 2025.

[@tommyisrael]

78 in 24 cage anyway you go, i saw that at the start

[@tffelpiano2830]

love it

[@iaincook5835]

It can't have been that hard - Simon didn't say "brutal".

[@nimbletim]

"this has to be a six"....presses 325942 buttons repeatedly just to type one 6.

[@theohill2521]

Alternate logic for getting the 6 in r4c1. Because the 36 cage cannot contain a 9 then the 9 in r1 must be in the 40 cage in r1 and so cannot be in r4c1

[@theohill2521]

More alternate logic for the 3 in r8c2. In the 6 cell 25 cage once it already has the 6 and 7 in it the other digits must be 1245 which leaves only the 3 available from your pencil marks

[@tajwar9547]

When I open the sudoku the cage numbers are whited out. Anyone else getting this issue? (Mobile) Edit: darkmode on Android causes this.

[@PuffyOne1898]

Fuck me that 69 pair in r4c1... I'd never figure that out even when given all the time in the world... 48:25 was my time. I actually figured out a lot of things without your help, so I felt pretty good about this puzzle.

[@2Cerealbox]

You got farther in 5 minutes than I got in an hour.

[@ariel_haymarket]

Final time 1:09:36

[@marcusgrainger3329]

blitzed you?? no chance. 40 mins for me

[@b1rdpoo]

2h for me that was hard :)

[@tommyisrael]

he went around his elbow to get to his big toe

[@brianray8484]

2:19:28

[@iosifoulis]

Resolved 27.52

[@iosifoulis]

45.12 my brain died.

[@igk6359]

my gosh it is very difficult. it took me 1:36:23 to finish this.