Endgame: The Sudoku With The MOST Crazy Finale

[Music] hello and welcome to thursday's edition of cracking the cryptic where today we've got an absolutely extraordinary looking puzzle for you this is called spilanka and it's by knt now i know that a spelunka is a cave explorer i think i think that's what spelunking is it's sort of diving in caves isn't it something that fills me with great horror um but i'm prepared to do it in sudoku world and this puzzle is yet another puzzle by kmt that's sort of got a 99 or a 100 rating on logic masters germany i was looking at knt's whole history of puzzles on budget masters germany earlier this morning and basically every single puzzle they've made is rated sort of 99 or 100 it's quite quite remarkable this is a setup of profound brilliance um and we've had this one requested quite a few times apparently it is tricky um but anyway i'm looking forward to having a go at it now what do i need to tell you about today i do have some news firstly i need to say a massive congratulations to a few of you who have somehow finished not only pack one of our sudoku packs that were released yesterday on patreon as the monthly rewards but also the doctoral pack as well now this is incredible um those of you that haven't tried it yet basically on patreon yesterday we released um a sort of standard pack of um japanese some sudoku puzzles from panthera the asylum and grockles and doctoral pack now the the standard pack is about the size of a normal monthly reward it's got a lot of really great puzzles in it and the the entries to that have been flowing in loads and loads of really delighted patrons as well so that's fantastic we didn't think anyone would solve the the doctoral pack partly because the doctoral pack has i think it's got more it was certainly got more than 35 puzzles in it and these are not sort of bitty puzzles these are substantial puzzles and yet last night at 4 am jonathan j charsh sent us in the correct solution which is really it's unbelievable frankly then the next entry we had was tom hayton and tom sent in an entry at eight o'clock this morning and then surab das at about 10 a.m and then matt boss at about 10 30 a.m so those four have solved all of those puzzles you must have been up all night my friends that is just sensational really really well done um and yeah and if you haven't had a go do have a go because it was sure that you will enjoy those puzzles mightily um now the next thing i'd like to talk about is a very moving email that we received yesterday which blew us away a bit i hope you don't mind me sharing with sharing it with you um it's from muhammad who says dear simon mark hey there my name is mohammed i'm 25 years old from palestine i studied structural engineering and university for seven years i've been working part-time in the night and summers and attended classes during the day i've always struggled with depression and anxiety but in college life got a lot tougher for me my family and for palestinians in general which did not help my depression the best time of the day for years was when i got to my bed to sleep and then i discovered your channel i never tried to solve or set sudoku your videos just had the right amount of calmness and intrigue to get me hooked i haven't missed a video in two years my graduation project's final presentation was on monday and the stress got to me and i started hyperventilating two hours before the presentation started i was trying to call someone to come and help and i saw the notification for simon's rogan video i opened it and suddenly i was lost in that beautiful puzzle time passed and the panic attack did did with it i presented my project and i am now a building engineer thank you for your help on that day and for your company over the past two years uh tearing up right i mean that sort of thing i i just wanted i got mohammed's permission to read that out um and i wanted to share it with you because well it's it's completely humbling to hear news like that um and we're absolutely thrilled you got through your presentation mohammed obviously and really just to appeal to to everyone out there there is some weird property of these videos that seems to help people who have who suffer from anxiety or insomnia and you know maybe maybe you know somebody who might benefit from them we don't know um but anyway i just wanted to share that share that with you um this channel has done remarkable things for mark and and for me but um by far the most moving is when we get these sorts of messages um and actually i'd also like to wish christine luck as well christine you wrote to us yesterday to say you submitted your thesis and you wrote some very very lovely words and we wish you all the best with that i hope i hope you get good news very soon um now now i need to be less emotional and more more so get myself into solving gear let us region let me read you the rules of sri lanka now knt has has given us uh an example as well so maybe i should put that on the screen i think i can do that like that and i will read you the rules they are as follows normal sudoku rules apply gray squares are walls and green squares are cave okay i can see what that means in terms of the finished grid anyway some of the cells must be colored gray so that all gray cells the walls are orthogonally connected to the edge and all other green cells form an orthogonally connected area the cave grey cells may not have a two by two block um so this is classic cave rules which is and cave if you're not familiar with it is a logic puzzle that's uh it's appeared in the world uh puzzle championship many many times over the years and it's it's a favorite of mine so i'm intrigued as to what knt has done um to meld it with sudoku we have seen that before um right but let me continue reading the rules a number in the top left corner of a cell indicates the sum of the digits that are seen from this cell looking to the north south east and west the cell with the clue counts once in this sum walls obstruct the view a cell with a clue must be part of the cave a cell with a clue must be part of the cave so it must be green okay uh within the field of vision of a clue digits may not repeat so that's let's just check that out so you see this 13 clue in in the finished grid here where i'm circling the cursor you can see that that is the sum of three plus one plus five plus four and indeed there's no repeated digits in three in those digits three one three four one five are all different let's try another one this this two here and the ten clue is two three four and one and they do indeed sum to ten so i can see that but there's more in addition sorry i keep having to scroll down the instructions in addition gray walls act as whisper lines i.e any two adjacent wall cells must have values that differ by at least five isolated wall cells are not bound to any constraint so let's check this out in terms of the vintage grid so you can see there's a great long string of grey sort of where i'm moving the cursor here and all the way down to the edge here and oh actually that this example does this example work maybe the example is not oh because it's only one to six okay this is presumably saying that the difference between adjacent cells in this example puzzle have to be three i think i might just pause the video and check because that's weird hang on yeah so in in the um in this example puzzle basically things have to be greater than or equal to three um and in fact i'm going to stop the video there because i've realized that when i last paused a video the sound went out of sync after it so i'm going to splice together what i do next with what i've done so far but anyway let's just let's just continue with the example because if the sound's out of sync for the example it doesn't matter too much so you can see six differs from one by five uh one differs from six by five six differs by two by four uh six differs from two by four two differs from five by three so each adjacent sort of domino here is is different from its neighbor by at least three now in our puzzle in the real puzzle it needs to be different by five so it's a much bigger constraint although of course we're looking at a bigger collection of numbers than one to six um you can see all of the green cells are orthogonally connected yeah they are just for a moment i wondered about that connection but yes that's clearly correct um and that's what we have to do so it's an interesting complicated rule set but i'm looking forward to having a try and now i'm going to stop the video and restart it one second actually pausing the video is a good thing as well because i remembered that i also need to wish claire a very happy birthday today so claire your mum jody was in touch with us and um i think you're turning 15 if i'm not mistaken um and yeah we just wanted to wish you all the very best um i hear that you watch a lot of the videos and that's that's just brilliant to hear and of course i hope that you have an amazing amount of cake um now back to me there we go all done um so hopefully well it'd be interesting to know if you guys think the sound went out of sync in that last one minute of the video and we are right do have a go at this the way to play is to click the link under the video as usual but now i get to play let's become a spelunka for the day and let's get cracking now my first i think the thing we must do here first is to highlight all of the clues cells and we know all of the clue cells are in the cave which means they are going to be made green and therefore we shall look at these clues greater than zero i mean that clue's basically finished then this clue greater than zero because well no spit well all we have to do now to complete this clue is to connect it to the rest of the green cell somewhere that's that's it that's the amount of information this cell gives us 29 that looks like it's the biggest clue in the grid so 29 has got to be at least four cells because it could be five seven eight and nine we can't repeat within the 29 clue so i want to say this cell's got to be green but is that true yeah that cell has to be green because if it wasn't if we make that cell gray how are we going to complete this 29 clue if we take it horizontally we know it's at least four cells large so it's going to have to connect to the 18. and the moment it connects to the 18 it cannot be bigger than 8 we cannot see in this direction more than 18 because that would break the 18 clue so that's not going to work that means that this cell is green um now does that mean this one has to be green maybe not actually if this 29 clue was only four cells and look like this we we grade off those what's wrong with that so this this would be five seven eight nine greater than clues so unhelpful uh i can't see what's wrong with that so maybe we maybe we have to stop here at the moment so the 23 less than 23 i mean less than 13 less than 20. what about that cell then does that is that problem oh no this is greater than zero oh good grief no okay so if this is green that would have to be a one two four string because three cells adding up to seven would have to be one two four and then this cell would be green but that's not putting any pressure on this oh actually no there is a reason that this doesn't work this cut is quite interesting right if this was green because we have to then bound the green and this has to be one two four what cell the eleven is now seeing eleven is seeing seven in this direction so it needs to take another cell but this cell means that we've now got four digits that sum to 11. the only way of four digits summing to 11 is one two three and five and that won't work so that's interesting so that means that this cell is gray right and that's actually very powerful weirdly because of a rinky dink that you may not know if you've never done a cave puzzle before i've told this story before but i like telling it because it's an indication of how how your puzzle solving skills evolve over time so when i was originally sort of trying to become part of the uk team to go to the world puzzle championship and things like that i used to practice puzzles in my lunch break when i was working as a banker in canary wharf and um yeah so i would go i would i would find a bench to sit on in canary wharf and i would have my my puzzles and i would sit there and eat a sandwich and do my puzzles and i remember doing cave puzzles and being fairly baffled by them because i couldn't understand how people were doing them so quickly because i didn't know the piece of logic i'm about to tell you and the key is and this was never explained by the way in the in the early instructions you used to get for cave puzzles it never used to say that you know bits of the cave had to connect to the wall and things like this but this criteria is really important so let's try and see what would happen if we made a checkerboard pattern in a cave cave grid like this how could this puzzle now complete itself and the answer is it cannot because because the greens have to be orthogonally connected in a sequence how are we going to connect this cell to this cell orthogonally and the answer is we can't because in doing so we would break another rule of the however these connected they would prevent this grey cell from getting to the edge of the grid which it needs to do the rules are very clear in the instructions this puzzle they didn't used to be in the in in the puzzles i was trying to do but so so this this is very important because it means you could never have a checkerboard in this in this grid and therefore let's look at this pattern these both of those squares have to be green um [Music] now i don't know if i know what that means yet but oh so now there's more pressure on this digit look so if this was if this was a green digit the 29 would see six cells straight away vertically which means means it couldn't see more than another single cell horizontally because if it did it would be an effectively an eight cell killer cage and well well i need to tell you the secret don't i mean just in case you don't know it i know most of you know it already but if you're new to cracking the cryptic we always try and make our videos new viewer friendly and there is a secret about sudoku that is important and the secret is that because of the rules of sudoku any complete row any complete column or any complete box will contain the digits one to nine once each therefore we know the sum of that complete row complete column or complete box it must be the sum of the digits one to nine and that is 45 so let's think about that in the context of a 29 clue if all the digits all nine of the digits add up to 45 how could this 29 clue be effectively an eight cell region so let's let's ask that question how could all of these cells be green and the answer is that's impossible because these have to be eight different digits according to the rules of the puzzle the missing digit from this eight cell string would have to be a 16 because 29 plus 16 is 45 and that won't work so we know that the maximum size of this region is seven cells and therefore if i do take this cell i can't take this cell and if i well i think as if i don't take this then i've got all sorts of stuff i can do along the bottom so all right so i'm not sure whether we can go much further with that greater than zero um oh all right what we can do simply though is this five clue can't connect down here because five is either going to be oh and i suppose in this puzzle it can't be a solitary five can it because if that was a five the implications of that would be i'd have to fence it off with um gray walls and then it couldn't connect orthogonally to its friends so it's it is exactly a two cell it's a two cell string this in one direction although it's either that that that or that or all that that's what i meant to do there but definitely it's not here because that would create a five cell string of greens so this is gray and that's about as useful as a chocolate teapot by the looks of things so well no uh or maybe oh no sorry i was i was wondering if i could i think i can rule this out can't i from being green because if that's green the implications of that are checker boarding because it because if this is green now the five must not see another digit in this direction or this direction it mustn't see another green digit so we we're forced to do this so we've created a two by two checkerboard and the implications of this connecting to an edge somewhere are that this 14 can't connect to the rest of the green world and we mustn't isolate greens from the rest of the green world so this cell is gray and therefore you must avoid a checkerboard so that sells grey so my let 11 could be two digits so we don't know what the 11 is doing yet so that the five clue is going either here which would make this gray and that gray oh that doesn't work oh this beaut this is beautiful this is beautiful this puzzle right why isn't this green that's a good question if this is green this is gray and now how do we get this green out of the it's sort of walled in by the great wall of gray here it has to get out to touch its friends which would require this to be green and that's going to require this seven to be made up of four different digits and well the minimum four different digits add up to is the triangular number for four one plus two plus three plus four which is ten so that's too many is because because it's greater than seven so that means that this cell is not green it's gray which avoid a checkerboard that's gray make this green to get it out make this gray to bound the five and now what do we do uh right okay so this square now is not able to be green i think i think that's right if this is green then we know that that string of digits there is a one two four string of digits but then the 14 which musk which so it need the 14 now needs another 7 to make 14 but it can't repeat any of the digits one two and four because it's already seen those already so what on earth do you put into this square well you'd have to put three in here so these these would then add up to ten and i need another digit or two to add up to four when i haven't and i can't use one two three or four to do that that won't work really what you need to be able to do is to put seven in here but you can't because this is a five clue so this is wrong that's good so that means this square is gray and now the 14 has to get out to connect to its friends so that's that's green avoid a checkerboard that's green you can have two by twos of green i think let me just double check that i think it's the grays that mustn't be two by two'd in in cave puzzles yeah so there's nothing saying that we can't have two by twos in green so we don't know what this is yet oh but we do know that the 11 cannot be five cells large because the triangular number for five is fifteen one plus two plus three plus four plus five so that's gray that gray's got to get to the edge so it probably takes this cell if it didn't it would have to these would both be green this would have to come out that's going to create an enormous path if that's green this is very constrained oh the 14 who just said the triangular number for five is 15 so this can't take any more cells so that's great now avoid a checkerboard so that's gray um okay um [Music] what does that mean so the craters are just greater than zero clue is mocking me oh i tell you what i haven't thought about yet and that's this german whispers property oh yeah yeah yeah yeah right this box is utterly utterly not broken that's the wrong way but utterly's constrained because one of the rules is that our grey walls form german whispers lines in other words every adjacent digit differs from the next by at least five now we've talked about this in the last couple of videos but there are two things to think about in terms of german whispers one of the which is you can never put a five on a german whispers line because if you do the next digit is problematical it can't be well it's got to be five different from five so it's either zero or a negative number or it's 10 or higher neither of those work so you can't put 5 into the wall now you can't put 5 in a 2 cell 5 clue because you can't use 5 and 0 so there's a 5 in one of those cells that's the first deduction but i think we can go much further than that by considering polarity what do i mean well once we know there's no 5 in grey we can consider a gray digit to either be low i.e on the low side of five or high on the high side of five so let's try making this low what's the implication for the next digit along the gray line now well because it has to be five different this has to flick to the other side of the five it's got to be six seven eight or nine you can't obviously if if we're looking for a digits five different from one two three or four it cannot be a one two three or four now the effect of that is that this digit of course flicks back the other side of 5. and that that keeps going so what that means i'm thinking is important in terms of these two digits because these two digits are ones twos threes and fours to make five in two cells so thinking about polarity in this string how could those be the low digits well they couldn't be because they would be ones two threes and fours and now we've got a sort of cross here that would need a repeated digit to work so that tells us that these are high digits so they are six sevens eights and nines these are one two three and four and now i need to include a high digit in my 14 sum and another digit as well yeah so i think this is i think this is pretty forced isn't it so if we use the minimum high digit which would be a 6 along with the 5 we'd have 11 already and 3 more in these two cells well they must therefore be a one two pair so this is one two this is five six there's no way of making that anything else this is now three or four um okay yes and in fact this is a four by whispers this is this is such a lovely puzzle already now why is this a 4 by whispers well the question i want to ask is where does the if this is a 3 where do we put the 4 along this whisper line and any position of a 4 is going to be a problem because you're going to have to put double nine around it because we need digits that are five away from four so the only we only got one digit available so if this is a four both of those are a nine that's a four both of those are a nine so that means we can get rid of four from here which means the only place before in the box is here four plus one is five that makes this a two these now these are now a two three pair none of these can be a six um this can't be a seven actually because if that was a seven it would see a three on one side of it and that won't work um so is that enough to make more progress here or do we get do we get stymied by that the answer is i don't know um seven is in one of these two cells hmm don't know so wherever the three goes here wherever the three goes it's going to have to be next to the 8 and the 9. i can't see how to do that and there might be a way but i'm not seeing it so i think we have to abandon that and start all right we've got eleven right these two cells add up to nine and they're not two seven so this is one eight three six or four five that's totally hopeless the greater than zero clue again mocking me this one they're both mocking me now they've individually mocked me um okay ah what do i look at now oh simple that green this is a seven clue it can't extend there because then then it would need to be one two four and there's a two already in the box so this is gray we can't have a two by two of gray so that's green so this is quite some german whisper string especially if that's green this is gonna well it's probably gonna have to come down here isn't it to get out oh ah sorry i hadn't spotted this this can't be green either because look there's a 2-3 pair looking at this cell so if this was a three cell sum adding up to seven it would need a two in it and it couldn't have one because none of its cells could be two so that cell's got to be gray which might be interesting um or not as the case may be so what can we say about the world now so this this two cell sum adding up to seven it's not two five it's either one six or three four whoa i wanted to put three four why have i got two four one one six or three four right and it's not three four because if it was three four how would we fill this domino on the whisper remember the whisper oscillates polarity so one of these digits has to be a low digit a one two three or four and if that's a three four pair neither of them they would see one two three and four that's impossible so this is one six oh oh this is this is really clever right okay so now this is known isn't it because these added up to nine and they're not one eight three six or two seven they're four five there's a four here three four and five go in the grid five is down there that's interesting because if this extends here that pushes the five in the corner because you can't put five on a whisper yes if that's green on it if that's gray on its own though if both of those are green then i think we are allowed to have isolated wall cells are not bound to any constraint yeah so so we we need to know whether this extends okay well actually let's have a let me just have a think about this box as well i need threes sevens eights and nines into this box and we can rule well yes what we can do is say there has to be a low digit in this domino and the only low digit available is three so there is a three in one of those two cells which means these two cells are not three which means i've got a seven eight nine triple in this column that must be important for some reason oh i tell you something as well 3 can't be next to 7 on a whisper so this is three eight or nine and that matters why i don't know um i don't know oh dear okay i've got something is nagging me about this german whisper up here is there something we should know about this this this one is not under i don't think there's any restriction applying to this wall cell but i'm i'm probably missing something there but i don't think there is so how am i meant to make progress now there's got to be a 4 in one of those cells less than 23 i mean it's just it's the most absurdly chosen you know number i mean how can this matter um i don't know so we could argue about i'm stuck i'm totally stuck i'm not seeing anything now what we could do is maybe we can use the seven eight nine triple so these squares are from one two three and six so if this is now green we have quite a big string of digits we'd known the total for most of those digits actually that would be 17. oh no uh ah hang on i know something this 29 clue cannot now be a four-cell clue because to be a four-cell clue it needs to be the numbers five seven eight and nine and it can't be so it's at least a five-cell clue so how does it not take this cell that's a good question yes it does take this cell right imagine it didn't that's the way to prove this imagine this 29 clue never saw never saw further than this cell because there's a wall well now it can see as many as it wants along here but it will only be it'll be maxed out at seeing 18's worth of digits because of this clue and that requires this clue to take the balance between 18 and 29 which is 11. you can't put 11 in that cell so this cell is green and that means we've got an enormous string of digits here most and we know we've got 17. so we need another yes we need we need more we need more don't we even even if we max that out we still don't get 29. so this string of digits this 29 sees another another cell either here or here but it sees exactly one other cell because if it saw two more cells it would see eight cells altogether and the triangular number for 8 is 36 i think so one of these digits is seen as so one of those is green i don't have a good way i don't think of notating that one of these is green the 18 can't see too many cells down this way therefore and um okay so do we know how to do better than this do we know what i suppose we can work out can't we we can work out what the um what the extra digit is that the 29 is going to have in it down here because we know these cells add up to 17 and this is either seven eight or nine and what do we need we need another twelve so we need a three a four or a five well it can't be a three because we've already got a three in there and it can't be a five so it must be a four i think that's right we need 12 more this is catering for seven eight or nine so we need three four or five but we can't repeat five we can't repeat three so it is a four we need and the four is on this side so that is the digit good grief so this is a 4 this is not in the 29 this is in the 29 this is not in the 29 so these two squares become you've guessed it gray that can't be grey or don't we have a problem with five we do so that's green which means we don't know which of these is now gray because neither of them obey the rule about the whisper so we know nothing about five oh no i was about to say this can't be a five because it will be seen by the 29 but of course it won't be because these are in different rows so this 29 doesn't see this cell um this square has to be an eight to make the 29 work so we knew those two added up to 12. so that means eight gets placed in box uh in box thingy thing up here box one this square's now not eight ah ah yeah this is in our three nine pair on the on the wisp a bit so that's a seven so i've not put 9 in this column now so 9 is down here and this column is almost completed look we need an 8 in it and we need a seven and an eight oh that might be why this 23 clue is here is that trying to tell me this square can't be seen so if that cell is seen by the 23 clue the 23 clue would see those three cells which add up to 19 and these two cells which would oh it has to add up to less than 23 as well so 22 is the maximum so this would have to be a one two pair so that would be a two and this would be a one and that would resolve the one six pair so that looks plausible but the fact is plausible is not helping me i don't want it to be plausible i want it to be complete nonsense does it break the 13 clues somehow um hmm the answer that is maybe because it's doing a lot in this column i think if this if this is green the 13 clue is then seeing those four cells it couldn't see any more because the triangular number for five is fifteen so it would see these this would become gray this would become gray this would become gray to avoid checkerboarding yeah it doesn't work it's for a complicated reason there may be a sort of simpler way of saying this but what i'm seeing the problem with this being green is because it makes this gray we've now got to deal with three individual dominoes of grayness in column four which requires three low numbers from our whispers logic but in order for this to work this has to be a seven because if it's eight these three digits have to add up to five with different digits that won't work one plus two plus three is six so this would have to be a seven and these two digits have to be low and that means there are too many low digits in this column so that is telling us this is in fact gray now avoid a checkerboard so that's green [Music] what does that do what does it do in fact i mean let's just worry about something for a moment which is that i've got virtually i'm disregarding this clue as a nonsense i've got virtually no information about the final four well five i've got four clues for five columns so something something on this left side must really do a profound amount of work i think for this to have any hope at all of solving uniquely oh i can avoid a checkerboard here look that can't be gray or we'd have a checkerboard so that's got to be green so now ah ah right now i'm going to say this is a seven oh in fact look at this there's two ways i can tell you this is a seven this is beautiful right let us consider firstly the nature of the less than 23 clues so we know that these six cells which all must contain different digits have to add up to a maximum of 22. well if we make this an eight because the triangular number for 5 is 15 15 and 8 is 23 and that is not less than 23 it is 23 so that doesn't work but what we could have also done is look at this domino now this this being a high digit is telling us that this needs to be a low digit and once this is a three this can't be a seven because that's not five away from it so that is eight that's seven and that can that confirms what we've just worked out with regard to the 23 sum it's so pretty isn't it it's really clever this it really is clever um so now now we can bound the 23 clue it simply cannot take any more cells so that cell is is is grey which doesn't give us any checkerboard opportunities so what we might need to do now well i tell you one thing we can do is we can write in the values of those four cells because we know the only way of getting as low as 22 is if we minimize these cells with one two three and five that is forced one two three five now that one is not five uh this must this is going to be resolved somehow hang on let me just stare at this for a second or two how is this resolved oh come on simon what on earth are we missing here well that can't be nine is that is that really the limit to what this tells us that seems unlikely to me that one sees a two and a three so that's oops that's become a one or a five now only which is almost very beautiful this is the sort of cinderella digit it's become very beautiful and now we want we don't want it to tick over to midnight do we how do we get this worked out i don't know i'm not seeing it sorry i'm not seeing how to do that there might be a way but i don't know what it is so where do we look now is it this 13 no uh well i said i was going to say is it this 13 clue and then i realized it was a less than 13 clue so what we're actually talking about is a 12 or less clue oh uh no okay maybe is there something going on here with the number of low digits we're allowed to use in the 13 clue or is that nonsense the answer to that is i don't know i don't think so if the 13 clue had two low digits in it i two of the digits from one two three and four in this string then these would also have to then that would force no it wouldn't i could put one in here and one in here and that would seem possible if if there is only one load digit in here though then it gets very difficult because then i would have to use five and six as my high digits because i need to keep this total down to twelve and that would make this gray and that would make that gray as well that would be hugely powerful so is there a way of concluding something intelligent about the low digits in the whispers here ah ah that's a low digit because it sees nine on its whisper that's right isn't it i can't see why that's not right it doesn't help me very much because unfortunately five away from nine gives four options but that means this is a high digit so that's a six seven eight or nine hmm oh dear um uh poppins i don't know i don't know again i'm sort of my spider sense is tingling here i can't i can't see how to do it so what what do we need to do perhaps we need to think about how this connects to the edge i mean it almost certainly takes this cell doesn't it if it if it didn't it would have to take this cell and that cell is very restricted oh well it does take this cell then that's we can say that straight away because if we try and make it not take this cell the problem with that is this digit so this if we try and make this cell gray it can only be six because it's c seven eight or nine and that means the only cells that we can or the only digits we can put next to the six on the whispers line is the digit one and there is only one of those so i could put a one here but now then now it's impossible for this to extend any further in this direction so the way that this would have to connect to the edge is still via this so whether or not this is in this is always gray oh this is right this is so clever this is you can see why knt is getting all these plaudits at the moment because look now now those two cells by whisper logic are low digits and now i've got a real problem with my 13 clue i've got three low digits used already so i can put one low digit in my 13 clue so let's put the digit one in there that's the lowest of the low digits now i've got to put in two digits that are not one two three or four so the only digits available would be five and six and that's what it must be because this has to add up to less than thirteen so this has to be uh this is not two or three now this is one five and six and this is gray and this is gray by avoiding checkerboard logic and this is one five six so we can take one out of here one out of here one out of here we can take six out of here therefore because six has to be next to one on a whisper that's got to be not six and that's seven or nine so one of these digits is four and whichever one four is will have to have nine on its whisper so that one can't be four because it would be surrounded by double nine there we go there's a small deduction so this is two or three this could be oh that could be nine sorry this could be four because i could put nine here as well oh actually hang on hang on that doesn't work right oh there's something wrong with this how can that be seven it can't be seven because seven can only be next to one and two on whispers lines and neither well one of those squares can be a two but the other one can't so that's a nine and the same is true here that can't be seven it would have to be next to at least a three on one side so that's an eight which means that this can't be four anymore so now this is four it's a two three pair in row three and the bottom cell is now a seven so seven is over in one of those cells by sudoku this square sees a uh this is a one five six it sees a one six good grief so this is a one this is a six by sudoku this is a five by sudoku we can get rid of some ones from the world we can can we do more probably um that cell can't be a five anymore so this is only two or three so the 18 clues got to come at least one cell out um because we obviously can't make those we could never have made just two cells at up to 18. if that's two this would be six oh no that wouldn't work that would have to be seven nine if this is three this would have to be six nine to only be two cells but that might work um [Music] okay so this six is ruling itself out of that cell so six in this box look is in exactly one of those two positions and i was going to wonder whether we could use the fact we need 6 in the 29 sum but actually the 6 can come in through here so we can't use that so what do we do next um your guess is as good as mine i do not know oh simple simple logic that's not a a green cell because that would be a one two four triple there's already four here so that's got to be gray which means this cell has got to be green to connect the greens to the rest of the world this cell is gray now because otherwise we'd have a string of four adding up to seven that won't work this this now this has got this green still has to get out so that's green avoid a checkerboard that's green greater than 11 doesn't even tell us that this needs to go any further so that clue is weird these two cells add up to seven and then not 3 4 so this is 1 6 which would have to be that way round or 2 5 i don't see how we resolve that i might be missing a trick um okay so what do we do next we shall look instead at ah right how is that cell now gray it's not because if it's gray it's got to be a high digit and it would have to be a six which would have to be next to one on the whisper which it can't be so that is green which means this is green to avoid a checkerboard uh oh i was about to get excited about this gray getting to the side along here but it's actually already hit the side so we don't have to we don't have to do anything extra we do know this is gray and it's next to a low so that's got to be high digit and it's not a nine so that's six seven or eight and it can't be six because it would be next to a two or a three not a one so this is seven or eight now it's going to be a very very long video because i think the first bit of the video was 10 minutes long when i just did the instructions and now i've nearly up to four well i'm at 46 minutes on the actual solving um [Music] yeah and by the way if you do watch the channel regularly this is the thing probably we debate amongst ourselves the most we try and do a mixture of puzzle difficulties the fact is that most of the puzzles we get sent now are very very very difficult puzzles uh they're puzzles that if we did them every day every video we did would be like this one they would be enormously long videos if indeed we could solve them and our senses although i'm not confident about this our senses that people like the mixture they don't always want to see monstrously hard as much as anything people don't have time to watch monstrously hard sudoku every day but we don't know because some people really do hold out for the impossibly monstrous ones and on the other hand many of you out there might be silently wishing that there were there were more easy puzzles or easier puzzles so if you do have a view please do drop a comment and let try and let us know what you want to see more of if or maybe the balance is right and that that would be good to know that too um anyway i'm hoping my subconscious has been busily working on this when i've just made those comments [Music] what do we do now i have not got a clue again it's one of these puzzles where you suddenly hit an absolute wall well how did i make that a five i've got i'm just wondering because i've got fives pencil marked in those two cells oh i know how it's because i needed to make this add up to 23 didn't i and i think that was probably the yeah okay so that was a one or a five and we had a one here so that does seem fair enough okay so have we got some other way of well let's work out what we need in this column then so we need ones sixes and nines so this is only one or nine actually and this is one six or nine which might be important maybe i don't know can't see how to do that there's got to be oh ah i can see how to do it right look at this domino that needs to have a high digit in it because it's it's a whispers line well that high digit cannot be six seven or eight all of which see this domino so there's a nine in that domino and that resolves that cell that's beautiful again this is a stunning puzzle that's a nine in the corner no song though for you that's a two three pair so this square isn't a six i think i sudoku that means six is over here nine it's also in one of these three cells by sudoku this nine and these nines are meeting up oh i tell you the other thing is that how can that now be a domino and not go further if this is a two cell sequence yes if this is a two that needs seven nine for it to be a two cell sequence if it's a three these two have to add up to 15 and there's no way of doing that now nine and seven have gone so this extends which is probably the world's most useless extension actually [Music] let me just think about this so uh okay this is this is actually quite daunting now because there is there is just nothing on the right hand side of this grid clue wise i mean less than 20 what does that mean and well i know what it means but how do i use that what is it that i'm meant to be appreciating here i have no clue um why is it sudoku or is it some weird cave logic i'm not appreciating i don't know genuinely not got a clue uh okay um these okay i've got a 2-3 pair i've just seen in row eight so i need four six eight and nine and the six and nine are over there apparently so that cell is only four or eight so if that was a four that would force the nine here if that was an eight it would force the nine here and then this would have to be well it could be anything i think it could be one two three or four so there's something there's something i'm not appreciating now but what that is i don't know if this was a 3 that would have to be an 8 this would be a two that would be fine this can be two or three i think these digits have no requirement on them at all because of this silly greater than zero clue um greater than 11 ah that doesn't mean anything and this is isolated whisper so that doesn't tell us anything about the world feel it sort of feels like it must be this 18 clue somewhere somehow someway doesn't it okay let's pencil mark this up four six eight nine so if this is gray it couldn't be it would have to be a high digit which would mean this would have to be a low digit which would mean we would have to have a four here and a double nine into those cells but that looks actually not unreasonable and then this cell would have to be a two or a three that would give me a two-three pair there which would be nice that would resolve that seven at the top oh yeah okay and that this wouldn't be a deadly pattern because of the whisper possibility to resolve it so that's that's quite interesting probably that feels almost right doesn't it now the other the alternative to that would be that this is green and then this has i don't think this has any pressure on it at all so there must be something i'm missing well it's probably many things i'm missing but there must be at least that thing that i'm missing i'm always wondering whether whoever sent me this has missed a clue off because it's just so absurd that this can solve from here there's so little information maybe this 18 is under more pressure than i think it is i don't think it's maybe i can force it to come here or something um let me think so what's the this could be as much as eight and five that's the most this could be i don't know if that's broken for some other reason but that would be 13. there's no whispers difficulty is there so oh eight look so eight is in one of those cells i've just noticed maybe it's something like that that's important so if this was eight then the 18 clue could still have an eight here so this was eight five this would be i'd have 13 i need five more so i couldn't have an extra cell then if that's maxed out that would be as far as we could take that logic so this if this is eight five this would be a two or a three and one would be in one of those cells which is fine i think there is a one down there somewhere by sudoku so wow um so these digits here are one of them is a low digit one of them is a nine and the low digit is not a one so these are two three four or nine can we somehow improve upon that they are the options so if this is eight this is nine this is eight this cell can't be four can it actually if that's four then i have to put nine in both of those that's impossible right so that's not four oh good grief that's really difficult but that's really important actually because now how's this four if this is four oh it's that's so clever actually it's really beautiful if that's a four this has to be a nine but then that has to be a low digit and the only low digit available is four which would repeat the four so this is not four and if that's not four i've got a two three nine triple in the box and a two three nine triple in the row so this is a two three nine triple so these squares are now well no the simpler question is where does four go in the box it can only go here i don't that's just madness absolute madness so that's four that's nine by whispers logic so this is now a two or a three i've got a 2 3 pair here so that's fixing this which is not two five and it's got to be one six so that's one that's six um this two three oh oh dear i might have broken this how is this 2-3 pattern getting resolved it looks deadly doesn't it i could understand it being resolved if this cell had res what's going to resolve this oh the 18 clue could resolve it oh okay so it's not deadly i thought it was going to be this digit affecting this but the 18 clue can resolve it so we have to focus on this i think these digits we now know they are oh they are five eight so this is thirteen i need five more so this has to be a two or a three it can't be a one and we can't because we can't extend it again or those three digits would have to add up to five and that's impossible so this is a two three pair um and we must we must cease then we must have a gray digit so this this row is ones twos and threes at the end of it so this is low so if this digit is gray it has to be high but it's very very easy for it to be high no falls along here anymore let's tidy up our pencil marks so now i know what these digits are these are four five and seven oh and this is the useless 20 clue um less than 20 clue let's let's be precise about it less than 20. um okay and this clue is still bazingering me uh this is the sheldon cooper of uh of spilanka um right so what do we do next the answer is i don't know ah small bit of sudoku though where does five go in that box and the answer is i don't know but it's definitely in that column so that means that scale sells an eight and that sells a five and that means that sells an eight by sudoku so now this column needs fours sevens and nines and that's interesting for the central cell which has to be a four c seven nine in the row so i was about to say these digits are known but they're not at all we don't know what this one is and until we do we're going to be a bit baffled about what these are let's put in all the options in the interests of being uh goodly-esque so this is ones twos threes and sixes and that is a weird naked single look at that six one three looking at that cell that is a two and that fixes that and that fixes that oh here we go here we go two and three over here three can't be next to seven so that's all fixed uh these cells are no longer two or three because of the three here this is a one-sixth pair which is apparently not resolved that could be gray because nine can absolutely be next to two on a whisper these digits now are known they are three five and seven i think and that is very interesting because well i was about to say for no reason talks i couldn't see anything but i just noticed that three that isn't that is actually interesting that's green because if it was if it was gray it would have to be a low number and it can't be oh that's lovely so that's green and now i avoid a checkerboard by making that green oh that's very cool i've got a horrible feeling about this you know i think i might have had a clue missed off in this box because i've got greater than 11 which is nothing i mean that's just not doing anything is it and i've got less than 20 and that's it that is literally it i'm missing something about this this does not i don't think this is going to be possible to solve i've got to get that to an edge okay so we can't get to the right okay maybe this does somehow do something this triomino has to get to the edge now it can't actually get to the edge here because both of those digits have the same polarity so it's got to get to the edge somewhere else so if it takes this cell that would have to be a four right so how does it how does it not take this cell how is this cell green that's a good question i don't think it can be because how do i then get this to the edge well i can get to the nine fine but then i can't go to the six because four and six are not not uh five five apart so i could go i could go here but then i can't get out here so this has to i think be on the path that this one takes to the edge now that gives me an idea because what is the nature of this digit is it what's its polarity and it's a sort of bishop's move is it well it's a king's diagonal move apart from this so this the next move that this nine makes is going to be here or here to a low digit and then the digit after that here must be a high digit again which is not six so i think this is seven eight or nine that does absolutely nothing it's not i mean if we'd known this was a six that well it couldn't have been a six because it couldn't be next to a one but that's the sort of thing that might you know blaze a trail so these digits i think are four seven eights and nines and we have to go to a low digit next so after we get here we have to go to a low digit this doesn't look very good does it one two five and six here okay uh that is interesting that's it's still it's still i think giving us a tiny bit more logic each time because how how can this escape this cell here how does this escape the edge without going into this row well the only way would be if it came here where it would have to be a low digit and it would have to be a four which requires its next cell to be a nine but it and the cells on both sides of it would have to be a nine that's not going to work we can't have repeated nines in this box so it's going to have to come into this cot this this row somewhere but the digits here are quite interesting ones twos fives and sixes so that yes you can't you can't we can't come here and then go up because the only high digit in this string is a six and six can only be next to one on the whisper so we can we just can't take this well we could take that cell as gray but it's not how this gets out this gets out by coming through here and hitting there for a low digit so if we come here if we can if we did take that one now we can't these two cannot be connected along a whisper it's impossible because they'd have this would have to be a six this would then have to be a one doesn't work so i think we have to take this cell and therefore this cell has to be low and that means it's a one or a two and then and then we now we could no we still can't come here we can't come here because if we come here this is a high digit which has to be a six and a one and the trail would go cold um oh well no we could take that cell i was misspeaking we could no no we actually can't full stop we can't because the only way of this being in would would create a six one pair like this and that cell would have no fill good grief right so that cell is definitively green which means that again we've got to extend up here and therefore this cell is high and it's not eight so that's six seven or nine i bet it can't be six uh it can't be six because if that's six where where's it where's its next digit and the answer is there or there so you'd have to have a one in one of those two cells but this would also be a one if this is a six this would have to be a one and this one sees both of those cells so that's quite cool so that means that tells us this is not a six it's a seven or a nine which gives us a seven nine pair in the row so these squares have got to be from one three and six there's definitely a three in them so right so can i just go no i can't this is remarkable this is absolutely remarkable in some ways this is it's amazing that the puzzle with this amount of complexity can still have this sort of logic at the end of it it's just incredible so how do we now escape this to the edge without coming into this box so imagine all of those were green how would we get this to the edge well we can get it to the edge we can go here which would be a low digit and here which would be a high digit but that would make this a six and this a one and that breaks that cell so that doesn't work so we've got to come into this box and i think if we've got to come into this box to escape to the edge which we do how do we do that without taking this cell now the answer is that we can we must take this cell because otherwise we have to make both of those gray and that breaks this again so that is now gray that's a bishop's move away from this so this is high digit which is now a six or seven now that is putting a lot of pressure on the world isn't it can this really really and truly be a six i want to say no i don't see a way of it working if it's a six um but let me just think harder about that if it's a six there would have if it's six there would have to be a one connecting this cell to this cell so there's a one in one of those two cells but they're also there would have to be another another one on this side of the six to try and get this to the edge of the grid that feels impossible but maybe that if that's a one oh no no you can't have two ones in those positions actually because that would give me that would break that down at the bottom so how does this work if this is six how does it work if we put the one here there we can actually we can't we can't do that there's a one in this row oh i hadn't appreciated this there's a bigger problem there's a bigger problem where does the one go in this box it's got to be in one of those two cells so if this is a six it can't be a six wow that's amazing that's so it's just ridiculously clever i don't think this can be a six let me explain if it's a six we have to decide how we're going to get this to the edge now we could decide we're going to take this cell as grey but the moment we do that it has to be a one and then this cannot continue in any direction here would make a two by two and that both of those would need to be a one and the one would repeat so the only way this works if this is a six is for this cell to be on the path and therefore you've guessed it a 1 but now that's going to make this cell a 1 to connect to the 6 and that's breaking the bottom of the grid doesn't work so this is a 7. i'm still not even very comfortable i understand how seven is going to work but that being a seven now gives me a five here and a six here and a five here and a seven here and a three here by our old friends sudoku now i know what these digits are so these are two three and five these digits are high digits six eight nine and these digits are somethings one and four i want to say so this being a seven take sevens out of these cells and i've got this labeled as green i can't remember why i did that but i think i did do that for a reason i think it yes i think i think it's yes this would have to be a six wouldn't it if it was gray and that would have connected to a one and broken this cell so this is a this is a reasonable green i've still weirdly in doing all the logic i've not used these clues at all now here is an interest no i thought that was going to be an interesting question it's not okay here is an interesting question how does this seven get to the edge of the grid okay and my question now is does it come through here or not if it doesn't if i make those green then to get this to the edge of the grid it has to come here that's the only way it can go and if it comes here yeah again because if it didn't take here so it would have to take those two they would have to be one and six and that would break that so if it does if it comes here this can't be a four has to be a one uh and now this can't be a one so that's a four so that's off the path which means this has to be on the path and that's got to be five away so that's got to be one and i still can't put a one in row nine still doesn't work so what that's telling us is that one of these two cells up here is on the path well it can't be this one because that cannot be a high digit and obviously to get to this we'd have to it would have to be high by bishop's move logic so it's got to be that one on the path and then it's got to be low and therefore it can't be three or five it has to be two so that gives us oh it doesn't give us enough right so the next move this takes to get to the edge is now here because it can't come here so that is how this gets this gets to the edge all the way up here and that can't be a six anymore this is absolutely remarkable now now this is now necessarily green because it can't connect to a 2 on a whisper this is necessarily green it can't connect to an 8 or a 9 on the whisper the 7 could connect here what we can't do is sort of go here and here that won't work because the next move is going to be impossible um well yeah i mean we could make a string of digits here but we could never get this to the edge [Music] in fact let's think about that more the greens all have to connect so those have got to be green anyway by so forget about getting us the edge we've got simply got to connect these greens up so now it's just down to which of these is the final so there's a one oh that's so clever i've got it i've got it how does this connect to this and the answer is i still don't know but i know it's connecting through one of those two cells and the only way it connects is via a one in one of these two cells that sees that digit wherever the one is it sees that so that's a two and that's a three and that's a one and that's a two along the bottom good grief good grief so that's five that's a three um i want to say where does one go in this column it looks like it's got to only go there i think which makes this a four that one would work very nicely with this this digit so that's possible um oh in fact it's resolved isn't it because once this becomes one it rules out the ability for this to be on the path of the gray so that's green now that is gray i don't believe it right that's what this greater than 11 clue's doing this greater than 11 clue which i thought was doing nothing and was doing nothing at all until now where all it's saying is that this can't be a six because it would only see eleven and by making that not a six we put the six in the corner if i knew a song i would i would sing it happily so six six all of these things come out this three is giving us a one here that's giving me a six and a one here it's giving me a three here seven nine pair might not be resolved yet not sure um [Music] oh i've got look i've got a seven eight nine triple in this column so that's a four and that's a six oh oh okay and i remember worrying about this before how is this resolved it's resolved by this three so that's got to be a two to make this add up to 18. twos and threes go into the grid if i get through this puzzle i mean it really should be a youtube premiere because it's such a brilliant puzzle but i think it's probably a bit soon to do one after the other day uh so this is now six by sudoku what's going on here i'm still very conscious of the fact that i have not i've not even thought about this clue i've got an eight nine pair i've got an eight nine pair in this column so that's a four that means this is a five this square has to not be four so this this is just seven eight or nine this square is seven though okay so that's seven so oh hang on what's going on why isn't this done um what's going on we've got i've got eight nine sevens and no resolution oh oh no i still don't know which of those that could be four and that could be nine that's nine that was forced to know that that works i could if that's if that's on the path that's putting no pressure on this so there's something else going on so it must be this clue less than 20 so it's 19 at max okay so if that's green i've got if that's green i've got i was expecting to get a useful number there i don't know if i do i think i get 18 which is not 19 so that's weird so if this is green oh no no no no no no right okay now we've got to be careful about connectivity here i have not spotted this but look there is a great wall of gray here and i've got to get this connected so that this here has got to connect to green so that's got to be green now if this is really clever so if that's green i then have to complete my wall of gray and i will never connect this up because because this is already adding to 18 so i can't take another digit in green so this is not right so this square is now gray but that still doesn't actually well i suppose it greenifies this column a bit further uh okay this is crazy um [Music] okay i've got a horrible feeling i'm about to get stuck i'm really sorry but i don't immediately see at all oh i see oh i see yeah now i do see making this gray of course it's a four so that's giving me a nine here but on the whisper logic because it's got to be five away and that's going to finish the puzzle is it nine eight eight eight nine nine seven yeah i've done the puzzle i just haven't done the shading so so this was double nine which still allows this to be a four okay i see good grief right i think i've got to approach this by thinking about this cell this cell is next to a gray low number so its nature is green which means this must be green now now i can see this square can't be green actually i see yeah okay this is less than 20. so i've already got 12. so if this is green this cell has to be would make this count 20 and that's too many so that's got to be grey that works from a whisper's perspective i've now got to get this green connected so that's got to be green which means this was gray after all that and therefore that screen to avoid a 2x2 and that is the finished puzzle i think wow just wow that is ridiculous isn't it that is one of the longest videos we'll ever have made on the channel incredible incredible knt i couldn't do one of these every day i wouldn't have time to live life it's it's not i mean i mean i know i'm implying that that there is more to life than sudoku and that's quite ridiculous but you know what i mean i mean i'm fried now that is just that's amazing that is an amazing puzzle and what's one of the most amazing things about it is it was incredible at the start very interesting and it stayed incredible to the end even you know it's it's just remarkable that this triumino has to get out here by logic and you you know this there was almost no clues in this part of the grid it was almost not necessary for there to be any clues which is so incr extraordinary if what a puzzle that is that is that will live long in the memory absolutely brilliant i am spelunked and i hope you enjoyed the video let me know in the comments i enjoy them especially when they're kind and we'll be back later with another edition of cracking the cryptic [Music]

Channel: Cracking The Cryptic

Views: 62,183

Keywords:

Id: p1LMrQTO35o

Length: 96min 40sec (5800 seconds)

Published: Thu Jun 02 2022