Beyond Diabolical... Sudoku Madness!

[Music] hello and welcome to Friday's edition of cracking the cryptic and on screen we have what I think is going to be an absolutely brutal classic sodoku that's been constructed for us and I have to confess we've been sitting on this puzzle for a while it's by the the constructor Derick Neill who some of you if you've been with the channel a long time will recognize the name of because Derick is invented a technique for solving Sudoku called a slot machine and we did a couple of videos on that technique way back in the day and Derek also is a constructor obviously as you can see on the screen and he featured some of his puzzles feature in our classic sodoku app so we're well very familiar with with Derek's puzzles and he sent this one in a month or so ago and I send it off to mark to test mark tested it and well when I say tested it I think he required several bifurcations to finish it and described it is absolutely monstrously hard now anyway very occasionally on the channel we we do do Sudokus that are monstrously difficult and I'm going to attempt this one for you today if I fail miserably you'll never see this video because it will just go into the ever-expanding blooper reel that sit on my hard drive but hopefully you will see it because hopefully I will find a way through if you want to have a go click on the link under the video as always so just to mention self-isolation we know that it is a trial with finding it a trial as well but we are trying to keep everyone's spirits up by doing more videos at the moment and we would otherwise do and mark is going to be doing a video today as well on the star back in puzzle so look out for that late late tonight UK time there will be some Star battle puzzles to solve on the channel one of my favorite types other than that yet this month patron reward is out for mention that in yesterday's video and if you haven't done the puzzle from yesterday's video do revisit it I will do visit it for the first time because so was puzzled is an absolutely beautiful puzzle not terribly difficult but just exceptionally elegant with some lovely logic in it so I definitely recommend yesterday's video if you haven't tried the puzzle and with that let's just get on with this let's get cracking and see how we do now I have been warned by mark this is monstrous so I'm going to be employing all techniques which means there'll be a lot of notation I imagine in this grid or digit as a - they're nines here look not all by another digit 9 there maybe maybe it's gonna be easy after all I doubt it um ah as another digit there's an 8 down there I was expecting not to get anything for a while so I'm feeling I'm feeling bullish ah got another digit there's a 7 ok slowing down now I suspect it's about to get very tough we can pencil falls out down there let's do that sevens can be penciled into one of those two squares this 3 can be pencil marked into those two squares which replaces a three in one of those two positions in box 4 it's an interesting pattern of Givens isn't it look at this look at yeah it's really nice we've got ones twos and threes going down the grid fours fives and sixes going down the grid 7 8 and 9 going down the grid and this this sort of toroidal property where this 9 pokes back in the other side and then the bottom three rows are all very very different anybody that's set that sir that's a nicety it's not what I should be looking at so let's carry on choose must be in one of these two squares that's these twos interacting sorry about this I'm not sure I'm not sure how monstrous this gets immediately it looks like I'm grinding to a halt now so we're gonna have to start looking for more advanced patterns I'm just going to check this row because we've got five digits in it three four five and six to place this square can only be a five or a six that square can be a three or a four I guess I will pencil Mar that in is four five and six as well seven in one of those two squares looking at threes a reason I'm looking at threes as I'm looking at this three and I've noticed that the threes in yeah there you go there is a pattern on threes they're nice right let's look at this so this is a swordfish pattern straight off the bat what is a swordfish and how did I spot it well I spotted it by looking I was looking at threes and I noticed that the threes in this column had a parallel here now at that point I hadn't scanned these top three rows of the grid at all all I'd seen was that there was a mirror symmetry in these threes but when I did scan up I realized it wasn't quite perfect because this three rules out this square but nothing is ruling out the top row for a three so this is a third position for a three in the rows in column five but if you don't give up hope and you continue to scan along the grid and look at the other columns you can see this column exhibits a very similar pattern the three can go in either of these two squares can't go here and it can't go here so it must be well how can we describe this the three is in a subset of three rows in three different columns of the grid now what does this mean well what this means is that in these columns these columns here there will always be a three in one position so if this was a three for example then we'd either end up with a 3 here and a 3 here or a 3 here and a 3 here hopefully that's fairly clear that's absolutely forced isn't if this is a 3 these are the only two remaining options for the threes in column two and column eight what happens if this isn't a three well if this isn't a three this will be a three and therefore there are only two possible arrangements of three in these cells here we could have this arrangement that would be one possibility or this arrangement that would be another possibility now if you're paying attention you might have noticed than in each of these arrangements of the grid there was always a three in one of these two squares there was always a three in one of these three squares and there was always a three in one of these three squares what that means we can do is we can look along these rows and eliminate threes from all of those yellow squares now in some instances that's going to be absolutely useless because this three for example is already ruling out many of the yellow squares are already so let's try and just I'd have a quick stare at this and identify which which squares are affected by this swordfish pattern there are some as definitely this one isn't these aren't this one is I think affected by it this one is so I think it's just those that are that are affected by the swordfish so we need to look at these squares and see how they are reduced in terms of their possibilities so that's just I'll make them a different color so I don't have to keep remembering them so this square can't be a three what can it be can't be a one can be a two I think hope you're three four I can't be four five or six or three can't be a seven car being a our brother can be a nine and I thought we were going to get a breakthrough but no let's look at this one so this can't be a one two or three or four I think it can be a five and I think it can be a six can't be a seven eight nine so this one's reduced a bit right look down here at this square so this one can be one I think can't be a two can't be a three because of the swordfish can be at four can't be five six seven eight or nine so that one is very reduced as well and this one can't be one two or three think it can be four can't see why it can't be five can't be six seven eight or nine so we've managed to reduce four squares to being just a single choice by using this this pattern so that is useful maybe so now we're going to have to spot something else let's have a look at this column because we now we've reduced this this sell the four digits we have are going to be more powerful than they're worth so one three four five and six this square maybe yes one four and six ruled out from this so this can only be three or five this one can be one four or five this one can be a myriad of things let's try this column you can see we need one two three four and five so that's one three or four that one's two three or five that one's one three or four so there's two fives there and there [Music] no the only thing that the only reason I'm pausing here is I'm noticing that twos are locked into one of those two positions in columns seven and I'm just wondering whether I can do anything with that but I can't see anything so I and remember that that might come in in handy later let's write let's look at this column now we've got we've not got very many digits we've got one two three four seven and nine to place so that squares restricted look that can't be 1 3 4 or 7 so this square has to be two or nine ah two or nine let me just double-check that one two three four seven and nine yeah that is right - or nice where there's a - nine pair in this column so how do we use that so that so this column is definitely the interesting one now because we've effectively got five digits placed in it we now need to place one three four and nine so this is one three or nine that one no hang on why do I say nine it can't be nine going mad one three four or seven that was nearly a bad mistake one three or seven here one or seven here just series now we pause again while I try and work out what on earth to do next eights now we can pencil mark in this block look so we can pencil my ate into those squares and in fact whose also look yeah this this not being able to be a two is nice because that locks are too into those squares now yeah this is good this is good we've got now look at those three squares we've got the numbers two eight and nine pencil marked into those three squares so these three squares are a two eight nine triple so let me just note that in so these remaining squares are one six and seven must be a six in one of those two because there can't be a six in that one so there's now there's no oh yeah we can pencil sixes up there Wow Wow I thought we were really on to a good thing they're getting that triple but we just aren't are we or if we are I can't see how we are twos in row six are locked into one of two positions by this to here and the fact that can't get to it yeah let's look at this so sorry about this and I realize this is must be very frustrating to watch but there's something going on the twos okay let's look at this so yeah these twos here so where can a to go in this box now if we look carefully as an empty rectangle here because the two is locked into either Row one here or column five one of these position one of those things must be true and this both of them are true if it's here obviously it's row five and Colin one but but the way to think about this the way to spot it is to notice the twos down here and then look for patterns that hit this is this two pair now so what can we say about this is it a useful pattern so either is if there's a two in column 5 there would have to be a two in this square that's forced so this little square here can't ever be a two now let's go through that again just so that it's very clear if I label the twos in this box obviously if the twos are in Row one that square can't be a two we'd all agree with that that's very obvious now the only other position that could exist in this box is that the twos are vertical in column 5 if they are in column 5 this square can't be a 2 and we know the 2 is in one of two positions in row 6 so it has to be here and therefore that square is not a 2 so either way this square is restricted and we need to look at it so okay so what can it it can't be two one two it could be a three is in the swordfish so that's no good so it can be a three it can't be a four it can be a five hour can be a five and it can be a six I think as well as eration seven eight nine no good no good at all that's disappointing but ah but but but but look the twos in this box are also restricted they all twos are very restricted in fact the elimination of the two from here forces the two into one of those squares where it hits this one so this can no longer be a to the two moves upwards okay so is that useful that is the question what are we meant to appreciate from that this square not being able to be a - let's check it out what can it be can't be it can be a one can't be two three four five or six or seven or that can only be a one or an eight now that might be interesting why is that interesting I'm going to check this column 1 3 4 5 & 6 to place so this squares 4 or 5 I suppose I can label that 3 4 or 6 I can't be a 7 I've got a 7 here why did I think that could be a 7 so the 7/7 can only go in two positions in row five seven is locked into one of those two square yeah oh yes okay so those and that I'm running out of colors here there is an x-wing on sevens let's look at this so if we look at row five a square the seven can go it can only go in the red squares every other square is ruled out by those three sevens there now if we look at the same thing in Row three this can't be a seven this can't be a seven and this seven rules out those two squares so we know that in Row 3 and Row 5 the 7 is locked into a red square therefore we know when we look at the finished solution that will either be a 7 here and a 7 here that's one possibility or if this is not a 7 we know for certain this has to be there will be sevens like that so again we're able to say with certainty there is either a 7 here or a 7 here and there is either a 7 here or a 7 here in the finish solution which means we can eliminate 7 from the rest of these columns now I'm only going to highlight the cells that are RC there's only impact 2 cells this matters for at all these are the only two cells aren't already seen by the 7 that are eliminated by the x-wings so let's look at this one this can't be so what can this be in fact let's ask ourselves that question this could be a 1 it can't be two can't be three four five six it can't be 7 because of the X ring can can't be 8 can be nine concen oh but it can be nine but that that is a different pattern let's come up we'll come back to this there is a y-wing there hidden triple or sorry event triple is what I like to call that so we'll come back to that and say let's just check this position because this also can't be a 7 1 2 3 can be a 4 I think can be a 5 can't be a 6 can't be a 7 could be an 8 I don't see anything better than that right so let's come back up here so if we had if we looked at these 3 squares here and they were all in the same column we would be happy days we would know exactly what that meant we'd have a triple on the numbers 1 8 and 9 and we would eliminate the numbers 1 8 & 9 from the rest of that column but these are not aligned in the same column they are bent but the critical thing here is to recognize there is one cell one of these three cells sees two of the others and it's this one this cell sees both this Square and this Square and therefore there is still some logic we can do here and in fact the logic is going to give us a digit at last because if this is a 1 this square here has to be an 8 now the only other position that could exist in the finished solution is that this is not a 1 but we know if it's not a 1 it's a 9 which means this square would be an 8 so in the finished solution there must be an 8 either in this square or in this square so this square cannot be an 8 because it's either going to see that one or that one and therefore this square is a 2 now that hopefully you can see immediately this is going to give us some some headway here so which I'm just going to take this slow so that I don't mess up anything that's a 2 that's - okay I think that's everything we get no it's not this is a - as well isn't it so that gives us all of the twos now finished but when we placed the two here we also took the pencil mark position of an eight so this must be an eight so that's an eight down there now an eight in one of those two squares and obviously in placing this eight we took the potential mark of a nine so that's a nine and that really doesn't give us much at all you're kidding me no sorry guys I can't haha I think this is our trailers run cold I don't believe it okay so we need three five and six are so this can only be a five or a six this one can be anything I don't believe it okay what am I missing now four or five here what can this square be one three four or five one four or five so let's put that in and see if that tells us anything nothing oh but but this square can't be a seven eight or a nine so look at this New York Times trick coming up column three obviously these 3 squares can't be seven eight or nine because there's a seven eight and nine in the box so where are we gonna put a seven eight and nine in column three given we can't put seven eight or nine in this square they're gonna have to go in those three squares that is a hidden triple this can't be a nine this can't be a seven this one can't be an eight so what if anything does that tell us I don't know I don't know sorry let's look at this role as finished off so this square one two three is impossible for is possible five is possible six is not possible seven and eight are both possible I can't see why not so so this square one four five seven eight this can't be four or five at least so or eight actually so this can be one what am I looking for one four five seven and eight so this can only be this can only be one or seven triple here oh this is this is good this is good yeah this is good so let's look at these three squares and again we can do exactly the same trick here that we did with those three squares before we we got this one so this square sees both of them so this is another bent triple on the numbers one seven and nine so how do we resolve it well if this is a one this will be a seven this is a nine this will be a seven so there's a seven and one of these two squares so this square here can't be a seven and neither can that one actually because that also sees this square in the square so this can't be a seven that's going to give us a seven here and this can't be a seven and look we've got penciled sevens in here so once I know this is not a seven this is a seven therefore this is a seven therefore this is a seven now now this is a seven as well obviously plus I'm winding the x-wing and we in fact we've done all the sevens I think one six pair here so this can't be a one that shifts the one up there this Square has to be has to be a three or a four there's a trick there is a trick this three four pair look at I like this I don't know what this is called because I sort of think of it as a as a crank handle type trick but look we have threes and fours in the this these are the only two positions in row five that the three and four can go into but the interesting thing is this four five sort of spur coming off this this line so what we can say here is that if this is a for this square here has to be a five but if this square is not a four then the only other place of four can go in row five is going to be that square and that will force this square to be a five so one of these cells has to contain five so that one can't contain a five and why is that important well I now got a one three four triple in column seven so this square is a five and that sees this square look so now this square as with five no no I can't believe it I'm still it's still not falling over No I don't believe it all right three this square can be three four or six looking at the row we've got a very colorful very pencil marked grid here oh hang on I know what we can yes I know what we can do here we can use this three four again but this time we're going to use it in the empty rectangle so look at this box where can a forego the four here means it cannot go in Row one so there is only those three squares that can take a fall so one possibility of the finished solution is that one of these two squares will be a fall if that's true that square must be a one the only other position that can exist in this box is that the four is in one of those two squares the four is in one of those two squares it hits this square look and we know there are only two positions for a four and row five so this square would have to be a four that would eliminate that from being a four so this square is a one every digit is like it is it's so difficult this puzzle now this is a one please let me have cracked it now this one obviously is C I have seen that it's saying this eight I'm just checking the rest of it this is going to be a four or a five this square now has to be an eight shifts the eight up there must be a four in one of those two squares which means this can't be a four so the four must be in one of those two squares I think in fact we've got we've got the eight we can remove from there as well so this becomes a four five pair this three removes why do I think that could only be a three or a six I start been sitting there for a while that can't be a six so this square must be a six so one of these two squares must be a six as well shifts this to be a five to build one this to be a four that forces this to be a for this to be a three this to be a six this to be a five I don't dare say anything but I'm hoping that we might be on the finish just finishing straight now this 7seas this eight fixes that to be a four three five four five these two squares you can see have to be three and four so that must be in that order that fixes the 3 and the 6 fix's that this is a 6-9 pair and this should be a one that's gonna be useful one six now six nine that force is this one to be the nine three one this is a 6 3 must be here three must be here now hopefully that can be a four I think it can eight nine yeah whoa I'm not unhappy with that has taken me just under forty minutes and that was difficult man that was difficult let me know in the comments how you got on let me know I did i I've suspect towards the end there I messed up a bit in it looked like them I might have had the opportunity to put in some easier digits but at least I got through it and I don't think that is I didn't bifurcate so I'm pleased with that yeah come back to star battle which I'm sure is going to be easier than that later on tonight and we'll be back soon with another edition of cracking the cryptic [Music]

Channel: Cracking The Cryptic

Views: 246,461

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Id: 8C-A7xmBLRU

Length: 39min 32sec (2372 seconds)

Published: Fri Apr 03 2020