Killer Sudoku: New Logic And Patterns

[@tbpotn]

At 11:00 or something the 2 pencil marked in the 45 cage combine with the 2 in the Bottom middle cage to force a 2 in the 20 cage of the top middle box. Ruling out a 2 in the middle box top right.

[@glennmelven3414]

When he highlighted that and said it did nothing I was a little shocked.

[@snork_games]

Came to the comments to make sure someone else noticed

[@KumaKaori]

Which in conjunction with the 234-9 in the box to the right lets you place a 2 in the top left box :).

[@zatchstar90]

yep. there were a lot of points in this video when I was yelling at simon. like when he put the 1-3 pairs in the top left and said he couldnt solve them yet

[@imouttagum]

i was so frustrated that he didnt notice

[@johnblazer7661]

Always get a laugh out of how Simon starts giggling when he has about 6 cells left.

[@ItsSansom]

The excitement is palpable. He's like a child about to open his presents on Christmas morning

[@Pyromonkey83]

Hey Simon, Great solve as usual, but I think this puzzle actually deserves a bit of a revisit. Not because the way you went about it was wrong, but because there is actually some really beautiful logic hidden within this puzzle in the top left and bottom right corners. You spotted the "wings" of the 1s, but it actually goes further than that. Because of the way that the "squiggly" boxes are arranged, they actually create exact triples that mimic the top left 12 and bottom right 10 cage boxes, but in mirrored order. For example, r1c12+r2c1 is a triple that has the exact same triple as r124c1, and is exactly the same triple as r1c124 (in this case, 1,3,8). The exact same logic persists in the bottom right box, because of how the "strings" are dangling on the edge. It also limits the corner boxes that you noted must be 2 more than the addition of the wings. I'm not 100% sure that this was intended, but the logic does present itself this way, and was actually how I solved the puzzle. I can't even begin to understand how to set something like this, but I thought it was absolutely breathtaking how the puzzle unfolded from this starting point, especially once you find the 3 "hidden" 1s in the grid.

[@BlueCyann]

Yes! This was my solving path as well, for all that me actually noticing the horizontal/vertical triples was a bit delayed. When I revisited the lower right and all of a sudden realized, "oh hey, that's actually a 145 triple .. and THAT is actually a 145 triple, too!" and saw the effect on the puzzle, it was great.

[@zuesieoby]

Pyromonkey83 found the same! Good job

[@Paolo_De_Leva]

I was immediately able to identify those triples by colouring the *wings* of the 7-cells cages, but I could not see the (well known) trick that allowed Simon to fill with *1s* the non-cage cells. 😤

[@timsullivan4566]

SIMON (after finishing at 23:26): "I think I was a bit slow..." ME (after re-starting at 24:30): "BLEEP you, Simon!" LOL

[@57thorns]

And yet, when I watch him I agree. He keeps losing minutes on deductions that can be done in seconds using "simple sudoku rules" with digit already in cages, rows or columns. And he it still doing it that fast.

[@erickehr4475]

Handy hint when adding a huge number of cells in a killer sudoku - as soon as you get a total over 45, subtract 45 and move on. You are far less likely to make a mistake but the final answer will still be useable. Here adding up all the cages is even easier using this method as you can completely ignore the two 45 cages! The final answer would be 42, and thus give the same shortfall of 3 as you found when properly summing everything to get 402.

[@BlueCyann]

You say this like it's easy to mentally subtract 45 from 53 or something. (J/k it's actually a good tip. I am just SO bad at holding numbers in my head, I can't help but laugh.)

[@lucaslorenz2887]

@@BlueCyann In fact, when you know you are aiming for the full grid total, you can also subtract only ever 90 - easier to do and gives the same merit of being able to leave out both 45 cages :)

[@v.sandrone4268]

This the first time I have heard of mod 45 calculations being recommended in practical usage... my maths teacher wife will be thrilled to hear this.

[@n3soccer_39]

I love how happy he gets when he hits a breakthrough

[@timeomnivore]

32:54 for me. Really liked that start with seeing the 1s in the empty cells. The whole puzzle came together brilliantly.

[@Darkness3827]

One of the things you missed with the 2 in the upper-left 45 cage was that it forced the 2 in the top-middle box into the 20 cage which resolved the 2 and the 7 in the top-right of the center box. Never-the-less, a really good solve.

[@Tahgtahv]

I noticed that too. Also the 8/9 in r7c7 was resolvable by the 45 cage, and he had a 6/7 sitting in row 5 that was resolvable for a while.

[@beansock]

yes this is how I solved it, interesting to see the bendy x-wing logic though!

[@snowfloofcathug]

The two’s also marry up with the top left box to give us a two in the top left of the top right box

[@89roddy]

This is a brilliant puzzle!! Solving it was great fun! I love it how it is unfolding step by step with every new piece of logic that I applied. This is one of the best “normal” killer sudokus I've ever seen. “Normal” means here that there are no additional rules, just the normal killer rules.

[@selenasilverstep7981]

probably a better way to go about this (at around 9:15) the 3 in row 4 put the 3 in row 6 in the 20 cage, which make it 3-8-9, which solve the 28 cage on the left and force the 20 cage above as 2-5-6-7, which put the 6 in the 45 cage at (3,3). this 6 divide the 45 cage in half, which put 7-8-9 in the top half and 2-4-5 in the bottom half. then the number in r4c1 can only be 1, after which everything follows nicely.

[@18lolable]

The logic on the 31-cell cage could've been done a lot earlier btw (as soon as you find the 138-triple in the 12-cage). A seven-cell 31-cage always needs a 1 and a 3, since the deficit of 14 means there's either 6-8 or 5-9 missing from the sequence The triple in the 12 cage only leaves 2 squares (and the 3 in r4c9 resolves them, which in turn resolves the complete 12-cage)

[@BlueCyann]

Similarly with the 145 triple in the 10 cage in box 9. (It can be determined as 145 from early on due to the 2 in box 10 needing to be in the 33 cage, and 136 being impossible via at least two different (but related) logical paths.) The 33 cage has to contain 1,2, and 6; it can only be missing two digits that sum to 12. So with 145 NOT in the 33 cage in box 9, the two "outer" cells must contain both a 1 and either a 4 or 5, with the 12-summing "partner" of the remaining 4 or 5 being in r7c7. So you have a 145 triple along both row 9 and column 9, and r7c7 is either 7 or 8. This is what pyromonkey was talking about in their comment down below.

[@neville83]

Another way of looking at it is to note that the corner cell i.e. R1C1 sees the entire 31 cage, and therefore cannot contain a 1 or 3, hence must be an 8. This logic works for the bottom right portion as well.

[@bfish89ryuhayabusa]

I had to come back to this video for a couple of hints, but the way everything unfolds is really satisfying.

[@JalebJay]

35:04 Took me a few moments to actually examine the sum of the 3 empty cells. Afterwards, it felt pretty straight forward.

[@canardlaquais5075]

Incredible puzzle design. Solved it in 17 minutes. Loved every moment of it.

[@alexkendall9809]

Absolutely splendid logic!! This puzzle further opened my eyes if the possibilities and application of the 45 rule. Never thought to apply it to 3 'bent' squares (27 cells), I'd thought this technique was limited to straight chutes/strips. I love how you deduced the sum of the three blank squares too, I would have never thought of that!!! :D

[@ol1ver49]

Just about the longest I've ever spent on any sudoku (made the same mistake as Simon with the 6 and the 1-3 (not 1-5) at the top left, but didn't spot it, so had to start again today). But I was determined. My only "cheat" was to watch the video as far as finding out what the three blank squares were, since I knew they'd be crucial and I was sure Simon would go there first - I didn't trust my arithmetic. Finally solved it today, then watched and found that I'd done it more or less the same way as Simon did - I think this must be an unique path, because often my solves are different.

[@RandomBurfness]

I got a time of 23:31! After getting the first digits and then discovering the trick with row 5, the whole puzzle pretty much fell apart. Great killer sudoku!

[@thumper8684]

Simon does the count at 4:30. It is 402. Thank you Simon.

[@terryshiells1527]

1:07:10 20 mins of which was trying to find a way into the puzzle and then losing count 3 times while trying to add up all the cages.

[@antonioliles5027]

Calculator... that is why I keep the calculator open on my desktop.

[@canardlaquais5075]

Shortcut for the long part: the 31 cage needs a 1 and a 3 (only a 5-9 pair or a 6-8 pair should be missing). Those have to be outside the first box because of the 12 cage.

[@ruimeireles1695]

The 12:35 to 15:48 section could have been resolved with a much simpler logic. The 31 box has 7 cells, so it must exclude 2 digits that sum to 14. The R1C1 cell sees all of the cells in the 31 box, so it must be one of the 2 excluded digits. Given the available options for R1C1, it can only be a 8, and the R3C3 must be a 6, so that they sum to 14.

[@SourabhDas95]

At 10 mins or so, with the 2 restricted in the 45 cage, that could've been quite powerful since the r9c4 2 sees r1c4. That would restrict a 2 into the 20 cage in box 2 which not only disambiguates the 2 in box 5 but along with the pencil marked 2's in box 3, restricts the 2 in row 1 into box 1 which becomes a write-in

[@lakarto19]

To be honest, for me, this puzzle was a really frustrating, rewardless grind until I noticed the two very specific geometry tricks... (1. adding up every single killer number in the grid to deduce the initial three 1's // 2. adding up the cells in the three bottom boxes to figure out that r4c9 + r9c4 = 5) After that, the puzzle got a lot easier and more enjoyable... hopefully I can do better next time.

[@sh3lton]

Brilliant puzzle, brilliant solving

[@57thorns]

Tons of counting in this one, worked ok now that I had slept. Still took me an hour. I notice the three empty squares but miscalculated the sum last night :-( The hidden communication between the corners of the grid are beautiful.

[@no-feetmcgee5577]

Absolutely wonderful! I'm amazed at the number of different solve paths, all of which feel "right" but also challenging. I must admit, I was dubious when the puzzle began with, as Simon put it, a "horrific" amount of arithmetic, but the rest made up for that. In the end, I'm just happy I did it in under an hour-- 59:59, to be precise. XD

[@DougCube]

At 9:45 you could have noticed a 23 locked-pair on r5c1-c2. Then the 20-cage in box 5 must contain a 3 and be a 389 triple. This and the 8 in r6c2 forces an 8 in r5c6. Well, you eventually found it at 17:23.

[@Qazqi]

I'm still really bad at killers judging by the lower-difficulty ones I do on dailykillersudoku, so I'm surprised I even managed to get through this one. 20:32 with a somewhat similar solving path, but there were numerous places where you missed easy numbers and jumped to some other logic before spotting them. For example, at 22:00 you ruled out a 7, but didn't notice the 9 by the same logic. I've noticed Mark seems to be better on average at spotting those free numbers. I've been forcing myself to occasionally go back to pairs I've already entered and see if they're resolved, and I feel like it's helping me to spot the freebies a bit better.

[@DougCube]

The 3 placed in r8c3 at 17:44 could have been done as early as 9:09 because is was already a hidden-single for col 3 at that point.

[@Habreno]

27:42, though I didn't realize some easy logic and got stuck for about 7 and a half minutes watching the video.. The summation at the 7:30 ish mark completely broke the puzzle open for me, and it fell quickly after. Not a hard puzzle, but a very beautiful one. Tough to put into words some of the logic.

[@menace2584]

I certainly could never solve this but sit in amazement that anyone could. Enjoyed.

[@VenomMorph]

Who else was screaming to the screen around 15:31 "YEEESSSSSS SIMON YOU CAN!!!!!! THERE IS 3 STARING AT THAT CELL FROM ATHER SIDE OF THE ROW!!!!!!!" damn sorry for capsing that but damn how ciuld he missed that. Also 2s in 45 plus 2 from Box8 really impacts 20 cage, but soemhow Simon decided that locking those twos is not much of a help...

[@Answerisequal42]

Simon: He is one of the best solvers of sudoku in the world. Me (an intellectual): hehe Kwak

[@MrPipat]

The color feature is so helpful with these killer sudokus

[@manuc.260]

I spent way too much time on this, partly because surprisingly even if I didn't calculate what the 3 uncaged cells added up to, so I didn't got those 1's till much later, I found another logical path for the solve

[@ol1ver49]

Very enjoyable and satisfying to complete

[@drewmichael3986]

At 9:54 Simon mentions the interconnectivity. Then I realise that the top central box has to have a 2 in the 20 cage. This resolves the 2 ij the central box as the 2 in the 20 cage is impossible.

[@chaotix37]

36:12.. I have no idea what to do first. Some logical deductions are too good. Overall its a fun puzzle. For instance, 23 pairs are formed in r5c12 also it forces to have a 3 in a 20 cage. resulting to a 389 triple.

[@BlueCyann]

Took me just over an hour, I think half of which was trying to add up the values of all the caged cells and get the same sum twice ... Anyway, the rest was great. Though my solving path was very different. I didn't even look at the 28 cage to start narrowing that down, so everything that followed from that was right out. I wound up going to the 10 cage in box 9 instead (only 145), then the 12 cage in box 1 (138 OR 129 initially), so it took a while to get going. I think all the play on KS dot com I did a couple of months ago kinda conditioned me to miss some obvious sums if they're not spoon-fed, even as it gave me the skills to do stuff like figure out that 145 at all. Thank god for hand-made puzzles, though. One of the computer generated ones might look exactly the same on the surface, but then all the elegant geometry is missing, you're reduced to grinding out arithmetic and almost nothing else. I miss the complex interaction of shapes and numbers so much when it's not there.

[@ThatGuy-dj3qr]

So much math!!!! I will gladly stick to Classic Sudoku. It doesn't make my head hurt like this type of puzzle.

[@gordonglenn2089]

What a great puzzle, such beautiful symmetry. Thanks, Simon, for doing that brute force addition at the start ;-)

[@thorbjrnhellehaven5766]

@9:47 - @10:10 R9C4:2 lock out R1C4 -> the 2 has to be in the 20-cage for this box -> 2 can't be in R4C6, it must be [7] -> R4C5 must be [2]

[@MubarkAlKhatlan]

I solve it in 2:50:00 I'm going to cry now .. goodbye.

[@snowfloofcathug]

Mubark AlKhatlan But you *did* solve it. And I’m impressed. Now please do let your mind rest for a bit

[@Robin19358]

hey, at least you didn't give up like i did! Good job, and you'll get faster quickly if you keep trying like this!

[@antonioliles5027]

Don't feel bad man. Took me 2:22:15

[@skasperl]

10:10 well, it would disambiguate the 2/7 in box 5, am I right?

[@skasperl]

15:27 well, there is a 3 in c9r4...

[@kraljevo8]

Get yourself someone who looks at you like Simon looks at the "Check" results after solving a good sudoku.

[@wgray8231]

Is it possible to use the web app so solve custom standard sudoku? That would be a very nice feature.

[@jannickwalther5860]

im a sudoko noob but i enjoy your videos ! maybe i can learn somehow ^^

[@hangugeohaksaeng]

Very enjoyable for sure.

[@PuffyOne1898]

my god it took me at least 4 times longer than you did to add all the cages up. 42:19 was my time.

[@iosifoulis]

23.13 ty for the puzzle

[@brianmead5102]

really good thank you

[@SporeMystify]

I had reached the state at 8:11, and noticed that I had either numbers or complete cages for every square in the top middle, left middle, and complete cebter boxes, except for two squares from where the 33 intrudes. So I totaled up everything. 45+4+20+13+20+1+28+6=137. But 3 boxes should total 135, meaning its 2 too high, even before adding in those two squares. Clearly I'vd made a mistake in my reasoning here, but I've been redoing the math over and over and can't spot it.

[@countknersis700]

I got this done. The slow way. Lack of confidence instead of trusting in myself. Edit: I found my 1's because of how the 45 cages work together with the 33 and 31 cage.

[@neilramsey1368]

Great puzzle

[@thesolarfutureenthusiast1102]

Having to add up all the boxes feels unnecessary. Just give us the 3 1's but that aside great puzzle. I was nowhere but did spot and enjoy some of the brilliant logic encase within.

[@garrethstegman3487]

I’m always yelling at the screen to do simple sudoku when something is obvious

[@57thorns]

13:36 With the corners of the center square ready to be solved, (there is a 2 in the 20 cage and it is not in the 27 cell in the center), you embark on a complex interweave of complexities. And you still break the puzzle in less than a third of the time I took. yes, the deduction at 14:34 was completely unnecessary as the cell could be neither 7 nor 9 because of simple sudoku rules.

[@57thorns]

22:10 This cage is a 7, 8 or 9, it can't be 7 because of this 7 in the 45 cage. And completely miss the 9 that is in the same 45 cage.

[@eneskaval3032]

that was great thank you

[@deleetiusproductions3497]

I am interested to see how this gets solved

[@Xarlus]

well, you could watch the video.

[@deleetiusproductions3497]

C. Rodat I hadn’t had time to watch it yet

[@erickehr4475]

13:32 for me. I am pleased with that.

[@rrafje4387]

I spotted the three blank cells adding up to 3 only *after* having solved the puzzle. Took me 2 hours.

[@57thorns]

19:00 Again, using that the 45 cage holds every number, you only need to count the numbers, not add them, to figure out the configuration.

[@OjingeoChaemuchim]

Lurking in my home because of Korean coronavirus pandemic. Maybe Seungjae is also?

[@kamikazegargoyle]

took me just shy of an hour :O

[@vlahovivan]

took me too long to do this, but a fun puzzle anyways

[@emphyriohazzl1510]

A delight :)

[@solfeinberg437]

Only took me three times - after watching the video (and continuing to watch the video). Good grief!

[@katharinakartenstein4100]

Am I wrong or is killer Sodoku easier than classic sodoku

[@keepmylittlesecrets]

54:35

[@leporid257]

it's way too hot rn to watch simon in two shirts please help

[@martinarcher1503]

while i like this format his explanations sometimes are woefully inadequate, especially for someone who has never done a killer sudoku before. At 5.30 right at the start he says row 1 column 7 must be a 6,8 or 9, with no explanation why it can't be a 7 also. Why can't it???

[@charliekelland7564]

The explanation starts at 5:05 and follows a logical chain that concludes with 2 cells in box 3 having to sum to 14 ... so neither can be 7 (as you cannot repeat digits within a box) :)

[@paulgoldstar]

The link up above (cracking-the-cryptic.web.app/...) does not work at all. I clicked on the link. It gave me the exact puzzle that you have just showed us. I put the 1s in the three squares just like you did. I clicked on the "Check" button. And it gave me this.That doesn't look right!In other words, that puzzle does not work at all.

[@frac]

Your typing is getting worse, I think. You rarely type the correct number into a cell on the first try.

[@RealNovgorod]

Killer Sudoku from South Korona!