Is This Sudoku Impossible?

[Music] [Applause] [Music] hello and welcome to wednesday's edition of cracking the cryptic and uh today i'm told we're ramping up the difficulty this puzzle on screen which you can see has very few uh given digits um it's by spxtr and it's five out of five stars for difficulty on logic masters germany it's apparently had very few correct solves but i am assured it's brilliant if you can solve it which is which is great news but somewhat daunting um not least because i've rather messed up my schedule today and normally if i know i've got a very hard puzzle to attempt um i try and do it earlier in the day than this on the grounds if i fail to solve it at least i can then do another puzzle in a different video well today it's early evening here which means i get one shot or there's no video by me today and that is pressure believe me i i really really don't want there to be or i really want there to be a video this evening i know a number of you rely on it so let's wish me luck wish me luck anything to mention before we get into the rules of this one um just just do take a look at our patreon page at the moment we do have this amazing three hour 20 minute video going through last month's tracking the cryptid sudoku puzzle hunt which i know many of you enjoyed many of you actually managed to solve which was fantastic but if you did try it and you didn't get through it that video explains all and of course we've got oh we've got january's monthly bonus puzzle up as well and mark is reading out the names of all the correct solutions that we receive so do get your entries in if you manage to crack it now let me read you the rules of this one what are they very short rules given how little information there is in the grid we've got normal sudoku rules apply digits cannot repeat in the given cages orthogonally adjacent cells cannot contain consecutive digits wow okay so that means we've got one given digit that means we can't put the digits one and three in any of those positions because obviously one and three are consecutive with two and these are the orthogonally connected squares with the two so these squares can't be one and three and that's all we get apparently that this this this collection of squiggles in the diagram leads to a unique solution so let us hope that i'm able to decipher the squiggles correctly do have a go yourselves the way to play is to click the link under the video as always now i get to play i've got no clue how to start this let's get cracking um [Music] most puzzles that i attempt i have some idea where to start here not ah here not so much except i suppose box seven here must contain a two in it and the two can't repeat in this cage so it can't be in any of those cells so we know that there's definitely a two in one of these two positions that uh right okay that doesn't seem to be yielding immediate results does it two three this is a nine cell cage which means it must contain all of the digits one to nine because we can't repeat the digit in a cage that one is only eight cells that one that one's nine as well though in fact there's quite a few nine cell cages this one's nine that one's much shorter one two three that one's only eight two three four five six that one's nine as well and then this one is six um this means nothing to me by the way i um vienna um what on earth we meant to do here probably what we've got to do yeah i'm just wondering one two three four five six seven eight nine i'm wondering whether we can find some sort of equivalences between cells so for example this digit here where can that go in box four well because you can't repeat whatever we put in this cell in the cage whatever's in this cell can't go in those squares or this one because that will be in the same row so it must be in one of those two cells which no we needed to be the logic to be much tighter than that actually to make progress that's not wow this is really difficult actually this is really unusually how do we start this um this was nine cells wasn't it ah ah yeah that's interesting so whatever we put in these two cells has to appear somewhere in box nine so these two cells and these two cells are the same which is interesting oh is this is this going to be a huge coloring exercise then because i'm just looking now at this shape and thinking about well especially this square that square whatever goes in this square can't go in these positions because they are in the same cage can't go in those positions because of sudoku so we'd have to be in one of those two positions that's not good enough it's not good enough there's not enough there again um [Music] wow okay sorry about this this is not a propitious start at all there must be something that we can do here where we're going to be able to find i imagine it's going to be this square for example ah now i have well i don't have anything i don't have anything beyond an exact equivalence for one cell but what whatever goes in this square has to make we know that whatever's in this square has to appear somewhere in box three because box three will contain all of the digits one to nine so whatever's in this square has to appear somewhere in the box well by sudoku it can't appear in those three squares and these squares are all in the same cage as this one so these two squares are the same which is um sorry some message about about pablo's armchair puzzle hunt i don't know treasure hunt sorry i don't know if any of you are doing that but anyway these two squares are the same which is all very well but it's not how am i actually getting going to get a digit in this puzzle that's the question that is a bit worrying because even if i can work out equivalences for some squares it's hardly telling me actually let me just think about this from a setter's perspective how how is it i'm going to actually start this puzzle how are we going to disambiguate anything there must be there must be cells or a cell which where somehow the non-consecutive constraint is used to restrict so is that what we're meant to do if this square whatever's in this square can't have a consecutive digit in those squares ah now okay so if we can find a square a bit like this one well we need more equivalences that's what i'm concluding here we need more equivalences i need to follow i need to find cells in this grid which are like these two basically and i think i need i can't do it with this this is too loose because i don't know which one of these maps onto which one of these i need exact equivalences these two no maybe i can do it with this one what maps onto this one ah yeah the central square maps onto that one yeah that's nice that's nice yes yes this is nice so what goes in this square the answer is i haven't got a scooby-doo but whatever goes in this square is part of this cage look ah so this is the key this is the key so this square here whatever goes in this square actually is purple because whatever goes in this square can't go in those squares in box two and can't go in those squares so these squares are now all purple now what is that enough to crack the puzzle the answer is not nearly enough i don't think so purple is in one of those squares so purple is not in these squares because that's in the same cage purple's not in those squares um [Music] no sorry about this i think i'm really i think i'm just making a mess of this i've got no idea what i'm doing purple in this box actually can't go there because that if that's purple that square is seeing that square can't go there oh good grief sorry no where does purple go in box six this square and this square lock out though that cross this one shares that square this one bizarrely enough is in the same cage as this one so that square is purple and that's beautiful that's beautiful because now i can use the fact one of these is purple which means these are not purple and look because i know that the per these are both purple where do i put a purple in row four one of those squares this square must be purple and now i'm starting to wonder whether i can use the idea i was thinking about up here which is that if i can find a situation where there's a cell and this cell looks really good where its number of consecutive squares now let me be more articulate whatever is consecutive with whatever i put in the central square where does it go in this box that's the question so imagine this square is a five we now know we've got to put four and six into this box but we can't put four and six in those squares because they're orthogonally next to the five but this square is also a five so we can't put it here this square is a five we can't put it here this square is a five we can't put it here and what we learned from this is that that this square is a one or a nine because there is only one cell in box five that can be that it's possible can be um consecutive with whatever i put in this square and therefore if i put two three four five six seven and eight into this square we know that there are two consecutive digits with each of those options and there are not two consecutive set um cells available all these are ruled out by the purples so this so whatever if this is one or this two is going to give it to me this two if this is why the two is in the grid this is one or nine so this must be no it's not one or nine it it's whatever is consecutive with what i put in here so if this is one this square would have to be two which it can't be so this is nine therefore this is eight and that is the only way that we can do this there's one digit consecutive with eight with with nine and we can hide it away in the corner where it won't be interfered with by all of these squares which are all also nine and suddenly we have a start on the puzzle and that that is absolutely beautiful absolutely beautiful um now i'm just thinking we can do well we can do a few things here 9 must be down here now 9 must be down there but i was actually looking at eight let me just have a look this can't be nine anymore um because of the the nines operating on box one but i was actually thinking about this eight because this eight goes through those cells in this cage and obviously it sees that one so eight eight must be in one of those two squares but it's consecutive with nine so this can't be eight so eight is placed in box four and now eight can't be in those squares oh this is lovely this is lovely eight can't be consecutive with nine again so eight oh eight's in one of these two squares but this one strangely enough is in the same cage as this one i think it goes right the way up there so that's not eight this is eight eight's in one of those three squares uh i don't know if there's a way of figuring out which right where does eight go now in box six it can't be it's got to be in one of these three but it can't be consecutive with nine so it's got to be in one of those two um [Music] i'm not sure if that's if that's useful or not i don't i was just wondering whether i could use another digit but i don't really think i can apart from two maybe can i do anything with two two is restricted in this cage because i need to put a two in this cage because it's nine cells large and two can't go in those positions so two's in one of those cells which is well it's a little bit interesting but it's not nearly interesting enough is it um [Music] okay sorry right let's come back to it what else can we do here we have got i think to use the eights more efficiently uh ah ah now this cage is a nine cell cage so it needs to have an eight in it that eight can't be in any of those squares and it can't be in this square so there is an eight in one of those two squares this puzzle is a mate that's beautiful again now i get the eight in this but i can't believe the way that these cages are interacting where does the eight go in this in this box now it can't go next to a nine so this is an eight exactly and that fixes the eight in one of these blue squares oh that's this is beautiful so now i know that these blue squares map to each other we looked at that about 15 minutes ago but this one can't be eight because it would be next to a nine so this square is eight that means that one is not eight oh and this is going to do work this is going to do beautiful work on box eight where does yeah it we can't have an eight repeating in the cage we can't have an eight in those squares by sudoku two and eight are not the same digit there's a knowledge bomb from cracking the cryptic which means that square is eight which means that square is eight and i which means that square is eight and i've done the eights i've done the eights that is awesome that is absolutely amazing um i know it's taken me a long time to do the eights but that that that i'm quite proud of actually um now now the two now the two plays a role where does two go in this cage it now can't go there that's an eight so it must go there because this is a nine cell cage again it needs a two so two is in one of those cells and i think what we're going to do in a moment is have a look at seven ah before we do that twos in those positions look they lock twos out of all of those cells so there's definitely a two in one of these two positions in box four so there's definitely a two in one of three positions in box six one two three four five six uh this one isn't a nine cell cage oh that's quite interesting though because this isn't a nine cell cage it's an eight cell cage but the eight cell cage can't contain an eight look these eight see every cell in it apart from that one which also couldn't have been an eight but so the digit that's missing from this cage is eight so it has every other digit in it so it must have a two in it i don't think i can use that fact actually but it's mildly interesting um [Music] let's have a look i think i'm gonna have to have a look at oh forget twos let's forget twos let's just ask what about this square what ever goes in this square can't repeat in those squares and it can't be eight or nine so those two squares are the same digit that's nice these two cells have to be the same which means whatever these are goes in down here oh i know what i might be able to do now i might be able to look at nines again because i've just yeah i can look at nines again this is a purple because it's a nine and i can't put nine next to eight so that's what i've got to remember is that purples were nines weren't they that means there's another that means there's a 2 9 pair here i think it does so all of a sudden i actually know quite a lot about nines in fact i know more than i think i know because this nine sees that nine so that's a nine and that's going to give me all the nines that must be a nine now it's not letting me put it in but it is most certainly a nine and then that's a nine and that's a two which means there's a two down here these nine pencil marks can disappear and now these two squares are not these don't need coloring anymore so these two squares are the same digit oh this is lovely this is really amazing what goes in this square the answer is i do not know but i know it's not two eight or nine which are these digits so whatever goes in this square has to find a home somewhere in box eight well where's its home if it can't share the same cage it must be in this square so all these three squares are blue therefore blue is one of those squares blue is one of these squares there's a lot going on in this puzzle it is really really clever but very intricate um [Music] so now green is in one of these two squares anyway let's have a look at sevens i think i think that's where we're gonna have to look so my my eyes are drawn to this set this this k box because of the eight in the center which rules a seven out of four cells five cells because this is an eight and it can't have a seven next to it so seven is in one of just two positions in box one and therefore seven is in one of those positions i think in box four uh sorry about this i'm not sure if that matters or not seven now can't be in these positions in box two that does not look very useful but i'm actually i'm gonna fully pencil mark it here because i don't really see what we can do if we can't do sevens um seven in here well that looks completely hopeless um seven in here ah we've got another eight in the center of a box so let's pay special attention to this one oh yeah this is oh this is very clever again we can i think place seven in this box because seven can't be next to eight which means it's ruled out of this square as well so there are two positions for seven in the in this box here but this one's impossible because if this is seven this is seven as well and it therefore that this seven would be next to the 8 which is not going to be work work so that is not 7 which means this square is 7. that ah that gives me a 7 there that must be 7 now seven is down the left hand side of box seven seven is not next to the eight here so seven is in one of these two positions in box nine one of those three positions in box three and seven um seven can be in four positions i think in box eight oh and i haven't really pencil marked it in box five either so seven it looks like it can be in three positions there well that that is useful but it's not nearly as good as i've only got two sevens out of that that is a worry um that is a worry how on earth do you do this then the answer is i do not know maybe i've got to look at sixes sixes are any time you get a digit in this puzzle in the center of a box it is powerful that you can see six is ruled out of those squares so six is locked into one of two positions in box four six couldn't go here because if we place the six there it will definitely be next to a seven so six is not in those two positions in box five so six is in one of four positions six is not here or here oh dear dear dear so six is in one of four positions here as well six looks like it could be green because then that would plonk a six down here and i can't see why that's impossible um [Music] right what on earth do we do next i'm sorry about this this is this is definitely hard though this puzzle um so there must be there must be more weak points in the puzzle mustn't there my eyes are drawn to this domino actually now let's think about this so whatever goes in these two squares oh in fact there's a seven here sorry that seven is seeing that seven through the cage that's useful that gets me another seven that gets rid of a seven in box three that's not useful but let's come back to these two squares because these two squares now are better than they were because whatever goes into these squares can't go in any of those squares therefore these two squares must be the same as those squares let's make those gray and that's really interesting because gray is not seven and we know there's a seven in one of those three squares this triple is a seven gray triple you don't hear that very often so these two squares whatever they are form a triple together with the seven in box seven um [Music] right um [Music] okay so does that actually matter is the question i am wrestling with hang on hang on can we not yes yes we can these two squares are also interesting aren't they because whatever you put in these two squares can't be in those squares and we can't put nine in either of these squares or eight so these two squares and these two squares are equivalent i'm running out of colors here i'll make those orange so these are and these can't be eight look so these two squares map to these twos oh my goodness this is becoming absurd so one of these two squares well these two squares are both orange but one of them is also blue oh okay there's a bit of a logic there's a bit of logic we can do in here which i've just noticed as a result of thinking about the way these these interact this square oh wait a minute no this square is this square is quite interesting actually this square is quite interesting because well let's start with where i was i don't think this can be a six because if it's a six let's look at it oh my goodness i didn't mean to do that if this is a six you can see from the pencil marking now we can't have a six in these two squares and we can't have a six here so this square would have to be a six but now you can't put a six in box two that is really hard to see but it's true because this six locks all those out from being six and this six via this cage sees those two squares so there would be nowhere for a six in box two so this is not six now that's really cool because that means there's a six in one of those three squares which rules six out of those two squares and means six is now locked into one of two positions in box five now the other thing i was thinking about this square is it's really peculiar in terms of its power in box five generally whatever you put in this square either has to go in this square which is is that always a problem though this can't be seven so we can't put sevens in there and whatever you whatever you put in this square doesn't that six argument always apply isn't it is it true to say i suppose what i'm coming to is is it true to say that whatever you put in this square has to appear in this square in box five is that true and if so that is really really weird because whatever goes in this square in box five it now can't be in those squares it can't be in these squares it can't be in those two squares this can't be a two it's impossible the two is up here so whatever goes in these squares has to be in one of these squares and if it's here whatever it is can't be placed in box two of the grid that is right that is right isn't it so these two squares are now mirrors oh and this is gorgeous now because this means there's an overlap with the grey ah yeah whatever goes in these two squares which we know are not these two squares are not nine and eight because they can't be goes into that square so actually i tell you what i'm going to do i'm going to actually look at what these squares can be this one's probably the most restricted because it's got it it sees it in fact the 2 is really quite powerful isn't it because it rules out 1 and 3. so this square has to be 4 5 it can't be six yes this square let's go through it it can't be one that's consecutive with two it can't be two obviously can't be three it's consecutive with two it can be four it can be five it can't be six seven eight or nine this can only be four or five therefore this can only be four or five therefore this can only be four or five therefore one of these two squares is a four or a five but i don't know which one and one of these squares is a four or a five um okay i'm very sorry if you guys are spotting immediately how to disambiguate this i'm sure there probably is something simple to do it but i'm i should also look at the blues actually shouldn't i because these blues are effectively any digit this square that's the one i'm going to look at first because the sixes are a little bit interesting there so this square is not affected by the two so much this could be one three four five it can't be six it would be consecutive with seven so these squares are also there for one three four or five and that means what i don't know ah this is really very difficult [Music] um so i need to limit these down how do i do that that's the question how do we limit these cells is there something i feel like it's something to do with these colored cells here um [Music] but i can't quite see what it is oh dear this is not i realize this is not the most efficient solve i've ever done um now come on think i'm trying to think about whether there's any sort of restriction surrounding these digits that i haven't appreciated or any way of limiting further these squares i mean one thing if this square is a five yeah if this square is a four i forget that if this square is a five if this square is a five do i have a problem with six in column six if this is a five where do i put the six in column six i can't then put it in either of those two squares because it would be consecutive with five i can't put it here because there's a six in one of those cells so i'd have to put it here where it can't go you can't put a six in these two squares because if you do where do you put the six in box five there's nowhere to put it these two squares see that one because this is all part of the same cage yeah okay i i could have seen that more easily i'm just starting to appreciate it now by asking where six could go in this cage up here you can't put six in those two squares ever because there's nowhere for a six you can't put six here because of the seven so the six is in one of those squares which is still an awful lot of license but it does make it clearer that now you can't make this square a five and this is massive if you can't make this square of five because then you couldn't put a six in the column it must be a four and we get another digit and we get rid of fours in those squares actually and we know this is a four so we know there's a four in one of those two cells therefore we know there's a four in one of these cells now this row perhaps we need 1 3 five and six we know that the six is in one of these this is a one three or a five oh got it i've got it i've got it i'm proud of this one it's really obvious when you when you think of it but this square i know the value of and i know the value of it because it's gray and it can't be consecutive with four so that square cannot be three or five or you'd have to put it in there with the four and it will break the puzzle so that must be a one which means this is a one four pair now which means these squares now we know are our snooker maximum one four seven that can't be one these that's ah that square is not one now so that gets rid of one from the whole of the triple um three five six into those squares this column maybe we need two no we don't we need three five and six let's put it in and see if we can see this one can't be three because it's next to two so there's definitely a three in one of those ah where does the three go in the column it can't go next to four either so the three must go at the top the five can't go next to the four so that's a six that's a five that can't go next to four wow okay and now these are a two five pair to complete the box and five can't go next to six so five and two go in two now must be here by sudoku five is not here anymore in fact just looking at the column you can see this square's got to be a three or a six and it can't be see the seven tells us the order three and oops three and six go in therefore this is a five this column now perhaps we still need three and six again don't we and again the two now helps us three and six the five here sees this this cell so all of the blue are now three three is here by sudoku three is in i think it's in one of those two squares oh no hang on hang on this is really brilliant this is brilliant again this puzzle is ridiculously clever threes look at the threes so the threes are plonking a three into one of these cells but think about orange if we know that blue and orange overlap these two squares are both orange in fact i might as well label them as orange now um because because the blue restriction has effectively been used up so we have to put a three actually into one of those two squares by sudoku which means the three is there which means there's a three in one of these two squares which we know where it goes it goes here so that's not three and i think i've done all the threes yes i have have i done all the nines yes okay so that's good but the puzzle is not yet completed although i do feel a bit better about it than i did about 10 minutes ago um [Music] now what do we do next are there any obvious weak points that i should be looking at perhaps row five where i need to place one five and six yes that can't be six so that's one or five this can't be five so this is one or six this can't be one so that's five or six oh that's extremely annoying i think the technical expression is bobbins um so what am i missing here probably a lot okay maybe i ah now if this is five or six this must be five or six as well because it's orange that must be five or six so this is not seven for sure get rid of the 7 there we know the 7 in this box is definitely in one of these two positions sorry about this i'm grinding to a halt again there must be a two in one of those squares can we go further than that is oh this this puzzle this this shape here is so powerful it's but it's really hard to see so this domino i think is also mirrored whatever goes in these two squares can't go there in box five can't go here can't be eight because the eight's already gone can't be nine so it is in those two squares so this is another relationship these squares are also in a relationship with each other i'm sorry i didn't spot that before but it's it's quite tricky to spot all these things going on um now maybe that's enough is it so whatever goes in this square and this maybe i just get rid of the two highlighting to be honest these two squares are definitely the same digit so let's look at the options this square it could be one it can't be two three four four's consecutive with three it could be five six or seven i think this from this squares perspective one five six and seven look like they're all possible that is incredibly annoying um this was not this was not profitable was it oh sorry okay that's not what we're meant to do next i don't think i think we're going to have to look somewhere else maybe i need to consider this square because these greens maybe they can be used 1 4 5 and 7. seven doesn't look possible because this can't be seven so this is actually one four or five it can't be four because of the four there so this comes ah and it can't be five because that is also consecutive with four so those two squares i think are one which moves a one down there removes one from that one which removes one from this one in fact where does one now go in this box it can only go in that square which is probably useful this square's got to be five six or seven now this one fixes the five that fixes the six that six is orange so that becomes a six those two squares become five and seven therefore this stops having the ability to be a six as well five seven here these are two and six ah ah but like the montagues and the capulets we must keep the one and the two apart so the two must shift over to this side in fact we could have done that with the five as well the six must go there that must be a two that fixes that this isn't a two in the bottom row once one four and six in this column that can't be a four or a one so this is a six this becomes a one four pair it feels like that must be resolved but i can't see how this one fixes the 1 and the 4 over that side so now if we look along here look the six is no longer in this position we've got five and seven into these squares the five can't go next to the fourth good so the five goes in the seven goes in that removes the possibility of this being seven therefore this yellow can't be seven and has to be five seven here is in one of those two squares but can't be next to six that fixes the four over there that four fixes the one and the four down this side these two squares now have got to be one and four which we can do fixes the one and the seven that fixes the seven over here that must mean this is a five and i'm inching i am i'm aware how slow it is towards a solution here these are a two-six pair the five resolves the order there's a two in one of those cells which is still not resolved i don't think i don't believe it there's got to be a seven in that square actually by sudoku that fixes the two this square should be a four there needs to be a four in one of those squares it must be here the orange six is done and we're left with placing one and five and it does look no i made a mistake oh no i haven't the five goes here the one goes here oh my goodness me i think this is right i'm gonna click check yes what a nightmare that was at the end for some reason i scanned down and thought i had to put the one here and i was like no it's above a one and it's next to a two um that got incredibly fiddly i mean what a brilliant puzzle that is i mean it's something else that i i i'm gonna i'm sure i've been a little bit slow in places and there were many points where i suddenly thought oh it means that you know there was one up here where it somehow it communicated through this cage i think and i just didn't see it and i'm sure that happened all the time but it's quite difficult at least for me to keep track of all of the relationships between the cages i did my best and some of the logic here around the four was absolutely this square was amazing the effect it had and the fact that this square and this square are mirrors i think that is unbelievably beautiful logic and the start was beautiful logic as well it really is a clever puzzle this but not easy let me know how you got on i do read the comments and look forward to them and thanks so much for watching and we'll be back later with another edition of cracking the cryptic

Channel: Cracking The Cryptic

Views: 464,148

Rating: 4.9491625 out of 5

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Id: wO1G7GkIrWE

Length: 53min 12sec (3192 seconds)

Published: Wed Jan 06 2021