[Extreme] A Sudoku With A Sting In The Start!

[Music] hello welcome back to cracking the cryptic Sunday today and we're on classic sodoku this puzzle has come in from Sanjay and Sanjay says it has a nasty step at the start I don't know what the step is but we're going to try and find it and and see how we go now did I have anything to say yet just to let you know the classics very crap well on the way for those of you interested in that it should be out this week on all formats so Android iPhone and and on Steam so do look out for that it's going to be the same sort of thing as a sandwich today crap so 40 puzzles at the start and then another 60 puzzles sort of dripped out over the year with 5 per month and as I say were pretty proud of it it has got a star system as well so in order to access the later puzzles you will have to solve the earlier ones correctly now let's take a look at this puzzle if you want to try yourselves just click on the link under the video that'll take you to our software and you can have a go now that's sevens into one of those two squares same over there because of these sevens come to anything with ones I don't think twos can be locked into one of those squares threes into one of those two positions ah falls into one of those positions as a 3/4 pair we've just discovered right at the start now can we do anything with that so now ones are locked into these two squares sewn u18 in the grid so that's not terribly useful nines it's just cancel those nines in what I'm going to do down here so there's no fives in the grid now I don't think we can use this pair bobbins writers let's look again everything in this puzzle is upset there's nothing the success that are all offset as well so the ones are offset the two when I say offset what do I mean by that I mean that they're they don't share you know a set of three rows or three columns they are fully offset I mean maybe this puzzle would suit the slot machine technique which I'm not going to use but this sort of arrangement is what I remember Derek Neal saying often often is the starting point now I'm trying to remember what that tended to lead to if it were in terms of logical techniques it was either it was some sort of horrible X cycle that it helped you spot or a finned fin swordfish I can't do anything here this is if this is gonna be an embarrassing video I have a bit of deja vu here I tried to solve actually I wasn't really my fault but I tried to solve a video that had come in and from somebody called Jon recently because I thought it had looked like an interesting pattern and I spent about half an hour on the video getting virtually nowhere gave up plugged it into a solver and was told that there was no solution so thanks very much for that job that was a half now of my life I'll never get back I'm hoping this is not the same thing and I meant to do this apologies if you guys are seeing it I know it's very frustrating because I find it frustrating when I watch my own videos back and I think why aren't you spotting that what's absolutely in front of you now the ones and the twos always share rows so we've got three ones and twos they're always in the same rows so is that meant to be something ah right okay well it does tell me something right okay let's look at this this is this is very nasty so if we look at where the ones and the twos can go in column two here they can go here here and here that's the only options for the ones and the twos now in fact because of this funny arrangement here the same thing happens in column 4 here and column 7 so where can the ones in the twos go we're going to have to I'm going to have to highlight this in color to actually show you these positions are the only valid positions in each of these columns for the numbers 1 & 2 now this is a swordfish pattern now what does a swordfish pattern mean when we've managed to lock a digit into the same three rows in three different columns like this now we're going to have to I don't want to sort of mix up the numbers so I'm just going to talk about ones here first what this means is that there cannot be any ones in any of these squares and you may say well how on earth is that the case well the reason is the best way of illustrating this is to hypothesize we know the one is in one of these three squares let's just pick one let's imagine we pick this one if that we looked at the finished solution and there was a one here then we know neither of these squares will be a one so I can eliminate those two squares now and we you can see hopefully if you then study these positions this is a classic x-wing pattern now we've sort of the swordfish is the third dimension of the x-wing so if we looked at the solution the finish solution and there was a one here then where would the one go in column seven it would have to be here now if on the other hand the one was not here but it was here then the one in column seven would have to be here so what I'm trying to give you the impression of is that the ones we can position the ones in these three positions here in fact this one it would never be a one because of the one here but I was also looking at twos when I identified these overlapping sword fish's but but basically as the ones are in a subset of these three squares or three cells in column two then they must be in one of those three positions here at one of these three positions here that's three possible positions and we need we know we need ones in each of these three columns so they're going to have to occupy sort of a permutation of these three cells each time now that means that there will be exactly one one in these three positions exactly one one in these three positions and exactly one one in these two positions which is why I say we can get rid of the ones in all of these squares I'm gonna make those yellow and didn't meet these ones because I don't know obviously yet we're the ones go and I'm going to have to stare at this again now what does this mean okay well right got something there's a run to here and wants you here so in this box where can the number numbers 1 & 2 go they can't go in these three cells they can't go in these three cells and we can't have a one or two here because of the swordfish so these squares form a one two pair now that is that gonna be the key to break this so now 6e no I don't think it is that doesn't know it doesn't I don't think that helps us so these good grief um right this is this is really not straightforward I'm sorry about this I'm gonna have to stare this a bit longer what am I missing here ah okay oh this this is very very unusual let it's the same columns again this was me being a bit slow here apologies I should have I thought I think I should have realised this a bit more a bit more quickly but we need to look at another digit that's relevant for these three columns and see there is another digit that is restricted to exactly well a subset of rows it's not the same rows this time but let's look at sevens now sevens can only go in these top three positions here because of this seven ruling out of seven here and this seven ruling out of seven here and here view of these two squares but look if we look down here we've got it's because of this three six for this this sort of grid arrangement here is it has this weird restriction around the grid that's that keeps applying so the sevens here and sevens here locked the sevens into these three squares here as well let me color this differently let's do green and then looking at this column this seven rules out that square and the sevens we've pencil marked up here rule out these two squares so again these three squares also are the only position sevens go so there is now a third swordfish so this is swordfish and one's a swordfish on twos and a swordfish on sevens in the same three columns of the grid right through them Wow okay so now there's some there's all sorts of things that are interesting going on oh this is I mean this is a stunning this is a stunning pattern I wonder if you guys can see what I'm seeing here this is absolutely stunning so the first thing I'm looking at actually as these squares because we know that these squares that I've just highlighted are influenced by three different sword fish's sword fish's on ones twos and sevens so we know these highlighted squares cannot contain the digits one two and seven therefore these squares here must be in their rows the numbers one two and seven because we know these squares are not one two and seven so there must be a one to seven triple in each of those positions now let's look at this column now we've now got a one to seven triple in the column so the open squares here this square this Square and this square must be five eight and nine in some order that one can't be nine to start deleting just in case there's a I hidden single somewhere let's start deleting you see this one can't be a seven that one can't be a two okay so that's well that was the first thing I noticed but the other thing I was wondering about is if we now so now I says no there's no seven in these squares either because of the the swordfish on the sevens now look if we look carefully at this we've got one two in this in this row so if so this square actually maybe maybe I need to look at a different yes yes yes look at column 9 where can the numbers 1 2 & 7 go in column 9 they can't go here because of the swordfish on the seventh and the one in the two we already have we know they can't go in either of these two positions because of the swordfish so we cannot place 1 2 & 7 in any of those squares let's make those a different color now what they can't go here because of this 1 2 & 7 and they can't go here yes that's it isn't it so now we've managed to eliminate 1 2 & 7 from 5 different positions in column 9 and the sixth position is a given 8 therefore these squares are the numbers 1 2 & 7 how awesome is that Wow I am very pleased with spotting that I have to say that is that's about as good a spot as I've ever done on the channel I think it's taken me in an inordinate amount time but at least I got there right 1 2 7 so now well actually this square is fascinating isn't it because I've actually pencil not to 9 into this square from these nines so there is no way this square can be a 9 this Square has to be 1 2 7 therefore this is a 9 so that's not a 9 and now there's a 5 a pair in this column so the interaction of the swordfish is happens in wow so this square must be a 9th only place a 9 can go in the column now there must be a 9 in one of those squares surely that as surely that cannot be more to this this is yeah this square is restricted now because we've got four three the square be this square can the square can only be a five or an eight because is it three four six in the column on two seven nine there yeah so that's a five or an eight which matches that square so the rest these three squares in this row must be three four and six so that's three four six sets that's a four there's a four six in the column therefore that's a three that's four that must be a six oh yes I think I think we've broken into it now this 3 and this 3 4 so 3 here and a 3 here therefore there's a breathe there nope not there that square must be a 3 therefore this square is a 3 and I think now we've suddenly done all the threes with that so forth what can we do with fours so there must be a 4 in one of those two squares therefore this square must be a for now before in one of these two squares three four so this is five eight nine into these open positions this is a five or a nine this is a five eight or nine now there's so many colors going on in this grid now that it is it's getting a little flustered so these open positions here in column nine must be four five and six in some order now can we get that one can't be a six because of the six up here so so now this is this is good now because now there's a six in one of these two squares and that means a six down here isn't one of these two squares and that means that's a six then we've got that perform just noticing it now but I hope you'll forgive me there is quite a lot going on here now this must be a six in fact that must be s sixes are also unwinding now that's a six therefore that's a six now I'm placing this 600 of the position of a nine so this is a nine this is the only place a nine can go now up here again nine is ruled out from this square because of the swordfish interaction that we found so that's a nine now therefore this must be a five a nine or so exciting have I actually cracked this puzzle now 5s this must be the five therefore that's a seven and that's two that's the first now this square is a nine therefore that's a one and this is a not before that was about to be horrible that's an eight if I've broken this I'm gonna be distraught that's a five this must be a 1 therefore 7 - unwinding the swordfish this is a 1 7 - this must be a 7 because we know that these were this was a swordfish on sevens this square ought to be fillable now looks like it's an 8 these two squares must be 2 and 4 in some order which we can fix for that square must be a 5 therefore that's of 4 and that's a 5 that's got to be a 4 I think it looks like it's working must be a 5 up there goodness me right this can't be a 7 this has got to be a 1 or a 2 that means it's a 1 that should be a 2 at the top now this must be an 8 this is 5 therefore these squares have got to be 1 and 8 this square must be 7 yeah that's still working it's an 8 that's an 8 that's a 4 I'm going really slowly here because I'm desperate just make sure that this is this is working correctly 5 7 looks good doesn't it what a puzzle let's check oh did it right now what I'm gonna do I'm gonna go and put this into a solver now I'm going to pause the video I want to know whether this was what I was meant to do one second okay so here it is I put it in now what come do let's click grader whoa 1193 I think that makes it difficult let's just see what we were meant to spot so let's go oh we got that we got the three four at the start and the swordfish oh that's a different oh okay right so they've looked at sword fishes in in the rows here she's the same overall effect I think she bizarre the way that works okay yeah another swordfish this again it's looked at it the other way round so slipped at the Rose okay fine whoa uh yeah one two power I got this one I didn't get these other ones what's this another swordfish this time on the threes I didn't find this one okay another swordfish on sixes which I didn't find not sure okay some triple I didn't find more pairs I didn't find and this is the swordfish on sevens represented in the rose again so we did find this one now it's getting threes and sixes over here I think that's because of the restriction in column nine that that I found in a slightly different way you can see it hasn't got this triple in column 4 yet so it hasn't appreciated that these two squares must be one two or seven that's it's not interesting it doesn't understand that or it doesn't appreciate that there this still hasn't got that now it's got a triple across the middle row again we didn't need that ah now it's fine well it's sort of it's doing it a different way and now it should spot it I think no okay it doesn't need it okay so it did it a different way but there were some similarities but not a great many so what an amazing puzzle another long video today but this time yesterday I felt my brain just wasn't working properly on the irregular frame sodoku and that felt felt a bit ponderous today I think I did spot something clever and going to be very interested to know from the comments whether you guys sailed through this one a very interesting pattern indeed Sanjay thank you for that thank you for not trolling me unlike John the other day and we'll be back soon with another edition of cracking the cryptic [Music]

Channel: Cracking The Cryptic

Views: 71,378

Keywords: extreme sudoku, swordfish technique, swordfish explanation, simple swordfish explanation, overlapping swordfish, evil sudoku guide, evil sudoku techniques, sudoku solver, sudoku genius, sudoku guide, best sudoku solver, best free sudoku

Id: lPpAtnbvVR8

Length: 27min 58sec (1678 seconds)

Published: Sun Nov 24 2019