The New Sudoku Trick That Almost Nobody Knows

[Music] hello and welcome to sunday's edition of cracking the cryptic where i'm under a bit of time pressure today it's my father's birthday happy birthday dad if you're watching uh i'm expected out to lunch i've no idea how long lunch might go on for but it might be a while um so i was meant to get a video done earlier this morning and of course i have failed so we're going to be looking at this puzzle and i'm hoping shy i'm hoping shy this isn't an absolute monster it's called binary fission and it's a classic sudoku and shai wrote to us and said that she's really proud of this one and if shai says she's proud of it that basically means it's going to be awesome um now interestingly i haven't heard from the testers i need to put this into a solver sometimes they tell me put it into a solver and it'll and the soul will say it's absolutely monstrously difficult but i've not been told that today so it might be approachable although i do know that shy's puzzles recently have all been showcasing sort of unusual logical techniques so we'll have a look at this i don't quite understand binary fission in the title someone will have to explain it to me at the end um now before we kick off and i read you the rules which won't take long um i want to just mention of course this incredible puzzle pack we've got going on um over on patreon at the moment this is available free on patreon um it's panthera and the asylums um basically introduction to japanese some sudoku and these puzzles are beautiful because they're so colorful and because you basically get a picture once you complete them correctly so if you um hopefully many of you all know the rules of japanese some sudoku but if you don't read the rules and you'll understand um but each of these puzzles leads to a picture don't get stung we can perhaps imagine what that mom might be um i don't know what that one is um eclipse there and there's a not an alarm clock dedicated to simon so i haven't actually done that one yet so i should really do that and find out what what has been dedicated to me um anyway i say do have a go at those you will enjoy them and these are preparation for our november monthly reward on patreon which is coming in just a week's time where there will be a whole plethora of these puzzles for you to solve all of different difficulties going right through the difficulty scale and they are gorgeous so we're looking forward to releasing that in due course now let's get on with binary fission i'll read the rules here we go normal sudoku rules apply there i've said it that's it so do have a go as always i'm cracking the cryptic you can play the puzzles yourselves the way to do it is to click the link under the video in the video description and that will allow you to play the puzzle on whichever device takes your fancy and with that i get to play let's get cracking so twos i can see have to go in one of those squares i should probably go in order with shai's puzzles because i notice shy often hides the tricks that she's put she hides in the puzzles in the early digits so it's probably famous last words here ones have to be in one of those cells um ones have to be in one of those cells already this looks quite strange to me i don't know whether this is just me being oh me being pessimistic but whenever you get sort of cells locked into diagonals i always get nervous that there is some unusual structure going on in the grid i don't know if i can do any more two pencil markings threes so these corner pencil marks by the way the reason i put these in the grid are they are telling me when when a digit can only go in exactly two positions within a box so corner pencil marks are box logic they are looking at boxes and telling me something about the box central pencil marks are telling me about the cell and the limits on that cell so um one thing i'm noticing here which i might try and keep track of just because i've noticed it and often it's important is the three in row two can only go in one of two places um now i don't have a good way of pencil marking that so i'm just going to orange it for the time being and uh we'll carry on ignoring that until i get stuck when i'll come back to it so 4 in box five has to be in one of two places i'm not quite seeing an o four in box nine has to be in two places 505 there's a 2-5 pair um actually let me do that long hand in case you're new to pencil marking so in this box using box logic the two was locked into one of two places and the five was locked into one of the same two places so this has to be a two five pair in some order so i immediately switched the pencil marks around to the central cells because i know that no this cell is a two or a five and this cell is a two or a five and the moment i get this what i'm doing so i'm scanning around the grid and looking back into this box i'm wondering if this seven has acquired more potency now that it can't go in this cell for example or this eight but unfortunately i don't think i don't think there is much else going on there at least nothing i'm seeing quickly five look at see you're getting all these offsets it's weird um hmm okay let's try sixes ah or two things i'm saying about sixes one they're in those positions and therefore those positions in box six but perhaps more interestingly those six is a pinching box nine and you've got to put the six in the same position the fours go into so that has become a four six pair four six pairs so we've got anything else going on with sixes yes sorry i just missed that one as well six can go into one of two places in box one and two places in box seven seven we've only got one seven in the grid so the seven has let itself down frankly that's not doing much at all the eight oh dear yeah the eight also look orco nines nines at least i can get a pencil mark from that always seems like a small victory night second pencil mark on nines okay so this is not this is not going well i've not got anything um [Music] oh dear oh dear oh dear so what should we do now we i think we've got we've got choice basically and neither of them are very appetizing but what we can do is we can try and look for um weak cells so the best way of finding weak cells frankly is to find rows and columns that are stacked with digits so i'm thinking about row two where although i don't know exactly the order of this two and five because i know these are the digits two and five i know that none of those four cells are two and five and they're obviously not one four or nine either so these squares are three six seven and eight so that square is seven or eight only that square is three six or seven i see i'm not terribly i'm not a terribly big fan in classic sudoku of labeling cells with three options at least not at this stage um six seven or eight but i really am a bit stuck here column five is where i might look next oh no what i might look at next is box nine actually because the four six pair we've got here means that these other squares have to be ones twos threes and nines although yeah that's square that has to be a one or a nine only c's two and three that square has to be a two and a three only because it sees one and nine but that one can be most things and that one can also be most things this is not going very well um let's come back let's have a look at column five then we've got ones fours fives sevens and eight so that's square ah one seven and eight only because it sees four and five in its box one four five seven and eight so that one is four five or seven that one isn't is basically useless one four five or eight that one's a bit better that one can't be that one can be four seven or eight because it sees one and five in the row so there is almost there's almost a triple but not quite the one in this column can only go in one of two places the five can only go in one of two places right so let's take a look at that so we've got so we've got a weird thing going on with ones look so if that's a one you push a one here and you push a one there because there's this sort of spindle thing going on with ones in that sort of two shaped backwards z because the ones are locked into one of those two we've got this in fact there's a very strange pattern of ones going down the grid sort of interacting through these two cells just sorry i'm just gonna stare at this for a bit longer um [Music] so if this is a one this is a one and this is a one and that would be a one and that would be a one so you almost get an awful lot of joy in fact you may even get all of the ones in the grid because that would be a one that would be a one one two three four five yeah you would get all the ones in the grid so if that's a one in one you all the ones immediately get placed if that's the one on the other hand you get a one here oh it doesn't oh no and you get a one here one in one of those two i'm not sure there may be a way of fixing that but i don't quite see it so i'm sorry i think i've misled you with that right let's have a look at fives so fives there's just nothing going on in box in boxes four and six there is nothing going on i don't like the look of five fives at all i'm afraid um bother right so we're gonna have to try and find more weak cells i think where are we going to find them from problem is we've got very little there's very little places to even think to look here because all of the other rows and columns i think and boxes have only three digits in them so we're going to be trying to find we really are going to be trying to find a needle in a haystack here cells like that that's restricted you see that she sees four six eight in its column and three different digits in its row in two five and three and in fact it sees one in its box so that square can only be seven or nine which is almost interesting with that one we should probably check these corners because that's somewhere that the patterns can be hidden but let me let me just see if i can see anything else that's obvious so that square that sees all the low digits so this is six seven eight or nine which is a yeah i'm not really prepared to pencil mark that that one um two three four five one seven or eight i think let me just double check that it sees two three four five six nine yeah one seven or eight so that's actually not very restricted um two seven there really aren't many places i really don't think there are this is a nightmare shy where have you hidden the magic in this one one two three four six and seven what about that square then one three seven that's no good three two three four ah that square is that square is very restricted actually hang on one two three four six and seven so one four that squares only one or four i think i'm just going to double check this one as well because i wasn't expecting that one two three can be four can't be five six seven it can't be eight or nine yeah one or four for that square so so maybe i've got to go along here again one four five six eight nine whoa whoa one that sees one four five six that's only eight or nine so again it's almost interesting with these three these three cells are a bit sus but they don't i was wondering if we were going to get some sort of bent triple there but we just don't get it those those are four different digits not three different digits one let's check this one uh so that one is useless basically well not quite absolutely useless but it can be five six as well five six or eight so we're stuck that's what we're learning we've got stuck you are that oh actually that is interesting if that square is not a one you do have a bent triple [Music] those three square let me just highlight those three squares and show you what i'm talking about um imagine this square is not a one that's a seven eight nine bent triple so if they were all in the same column of the sudoku we would instantly say oh well it's a seven eight nine triple and we could delete seven eight and nine as options from the rest of the column like this square for example but they're not in a line they're in that they're bent around the corner but it's still interesting because you'd always get a nine in one of those two squares as a result of the bent triple because if this couldn't be one whether it was seven if it's seven this is nine if this is eight this is nine so you always get a nine in one of those two pointing at that square and forcing that to be a one that's really that's quite beautiful actually because what we can it's almost like a diagonal sudoku yeah well yes in fact i can delete one from that square oh no hang on that's nonsense what i was thinking was either this square is a one if it was a diagonal sudoku we would be it would be very powerful either this square is a one in which case it's a one or this square is a one because there is a bent triple ah so does this work through the crankshaft then so if we got a one here the one in column five is that we know is here so either you get a one here and a one here oh this is you're right this is it yeah this is it got it right this is really smart this is well it's classic shy is what it is and it it's it was hard to spot this one but i think i have certainly spotted something i do not know what this is called it's like um it's like a possible bent triple that may or may not exist it's like it's not like a finned bent triple but it's it's something like that it's sort of a hypothetical bent triple because we've got a situation where either this is not a if this is not a one we have the bent triple and we get the one here or this is a one but if this is a one column five comes into its own and we can say that the one in column five has to be here but if the one in column five is here well lots of things happen but the point is that either you get a one here and a one here in the finished grid or you get a one here and a one here so there's this weird offset of ones that must exist but that means if we consider row three in isolation there is a one in one of those two squares for certain and if we consider row seven in isolation there is a one in one of those two squares for certain so that square cannot be a one and that's a four and therefore in the central bar oh this is massive this is massive right in the central box where does four go it's got to go there according to my pencil marks uh maybe it's not well i've seen one other thing i can do from this but let me just see what else this is doing i'm seeing it's tidying up the four and the six over here that was the other thing i saw but actually maybe that's not enough oh it may be it is that six is now useful so maybe we've just got to really yeah our pencil marks are doing wonders here because now six in box one can't go there anymore so must go here according to what we've just done now six yeah where does six go in this box it's got to go here by sudoku and that's in an orange cell so oh not only do we get the six in that box how many sixes have we got the answer is once i've done that one perhaps all of them yeah i've got all the sixes when i place this six i displaced my my orange three possibilities so that square's become a three that's the world's most disappointing three it's hardly done anything at all but anyway let's fill that in and see whether that makes the world a clearer place uh so we've got a seven eight pair here now oh i've got a seven eight pair and cut this is massive i've got a seven eight pair in column five so that's become the one now this is not the one so that now we have our friendly neighborhood bent triple which we know forces a nine into one of the wings at least one of these red squares is nine so that's not a nine so that's a one one must be in one of these two cells uh seven eight is also dealing with that square but let me just follow through with the ones just see if we can do anything else with those um yeah we can place a one i think in box one we can place yeah we can place all the i think we can place all the ones yeah we can wow um so now this squares are five because of the seven eight pair that's very high so that gives me an eight here um does that do anything else it puts a five in one of those squares i can obviously see the eights doing some other things and that this digit should be known so that that's become a nine now we we don't know this isn't a nine though you can't assume that it's still possible this is also a nine right so we now can we do more there's a nine in this domino in box four seven eight here so this square here must be a four so that ah that's beautiful so four has to be here which places the nine as well so nine is now in that domino in box six how many fours have we got the answer is many there's got to be one more there i think that's all of them um okay so where should we look now that square's not five so this box needs threes sevens and eights let's put that in and see what we can do yeah we can see the three has to be in one of this these two squares so combined with this three gives us a three here now we know we need sevens eights and nines along row one don't know if we can tidy that up somehow i can't quite see how that's got to be a seven eight or nine okay okay we've got to pause for breath and i think start to think again now fives sevens and eights complete column one so this is a five or a seven in the corner here two three there's gotta be a nine down here that's not interesting so twos fives and seven so this is two or seven this is two five or seven this ah there we go where does eight go this is a good question in column three it can only go there so eight seven go in the grid eight goes here we get a seven nine pair seven comes out of this square and out of this square which is rather gorgeous so that becomes an eight now we found an eight nine pair in box six which was one of the most recalcitrant boxes wasn't it so this one is starting to behave itself all of a sudden get rid of the twos in the corner here and the five oh yeah get rid of the five from there that's nonsense we don't need that anymore um there's got to be an eight in this domino in case that matters for anything oh this eight down here hang on how did i how did i not spot that when i put the eight nine pair in that is one of the questions that no doubt you're going to be asking me in the comments that's now an eight this nine is now a seven that's a nine that's a seven that's a nine that's a nine in the corner it doesn't get a song but it's still very welcome this has got to be a two five two or a five don't think we know um this seven is powerful that's putting seven there could have got that from the eight as well obviously the seven is resolving everything down here down here down here um that square's got to be a two or a five don't know if we know which yet and it looks like rows row four is going to be quite handy doesn't it twos fives and sevens so this is five that's two that's seven that's two that's two that's five that's five that's two this square is a three seven pair which worryingly is not resolved this square here is resolved uh i see that that unwinds all of those put the five in there hopefully we can click tick and we have solved shy's binary fission binary efficient is that something to do with these digi digits going around this sort of loop of four it's so so clever i i mean i say this every time we look at one of these classics by jovial shy philip newman sam kappelmann lines they're coming up with completely innovative ideas um i bet you if you put this into a solver it would not find this it would find something else probably but it wouldn't be this this is beautiful it really is shy as ever take a bow thank you again for entertaining us um and let me know how you got on in the comments thanks so much for watching back soon on cracking the cryptic [Music]

Channel: Cracking The Cryptic

Views: 371,504

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Id: ynkkMxQPUpk

Length: 27min 46sec (1666 seconds)

Published: Sun Oct 24 2021