Why Handmade Sudokus Are Better! A.k.a. One Of Our Best Puzzles Ever

[Music] hey and welcome back to cracking the cryptic here's today's puzzle it's a classic sodoku this has come in from John to our email address which is cracking the cryptic gmail.com and he says it's from a Japanese puzzle magazine and that doesn't surprise me when I look at the grid because the grid is symmetrical there's a sort of real beauty about it that's a big difference I think between Japanese puzzles and the puzzles that we get in the West and most of our puzzles that we get in our newspapers and magazines are computer-generated and in Japan that is unheard of everything we can get in there national media is handcrafted which do I prefer well I'm a huge fan of handcrafted puzzles and the reason for that is that I think that a setter have a handcrafted puzzle has given some thought to the solvers experience in solving and you know what how the logic will flow where the difficulties will arise how how them you know how the logic will progress a computer doesn't do that a computer relies on its algorithm now there are some good algorithms out there not many and nothing to compete with might in my view anyway they're sort of best Japanese pencil puzzle creators and there are a number of Western fantastic puzzle setters too but I'd always recommend that's the way to go and it's that communication between solver and setter that thing's important cut remember I said this we want to try the puzzle click on the link under the video that'll take you to our software you'll get to see exactly what I'm seeing we've also had a few questions while I remember about our sandwich today your app on Android it is out now but people are not finding it on the Google Play Store because they're apparently if you go onto Google Play and you just search for sandwich you don't you it's not appearing that's because Google haven't updated their lists yet we expect them to do that at some stage but until they do you will need to use the link that I provided so I'll put it in the description on YouTube in this video and also that I'll put a card up that you should see on your screen now so if you do want to play the game on Android that is the way to do it until Google sorts its life out right let's have a look at this puzzle and I hope I've set and craft the puzzles all the way forward and that that proves to be true so ones you can see I can pencil mark because of these two ones and this block and that does the same in the central 3x3 in fact twos look at these twos interact in the same way for stews into one of those squares as well so there's a one two pair out in this top three middle 3x3 block so the way my mind works to know if you're the same I immediately look at this eight because now this we can't have an 18 either of these two squares that eight is forced into one of those two positions and well that means there's an eight in one of those three squares but I can't immediately see how to make use of that so let's come back Nine's those two nines there I mean there's a nine and one of those two squares and that means there must be a nine in one of these two squares Wow what next our sentence this seven and this seven look I'm gonna get seven pencil marks at the bottom and that gives us our first digit now because of this seven on the left hand side the only places seven can go in the central 3x3 is there that means this is a seven because of the seven down here this is a seven this is a seven and we're getting a right flurry of sevens here so those are sentence so we're just left with these sort of these sevens unsolved sixes these two sixes they this is a real symmetry about how this one these ones and twos arose and how there's a six seven pair of the bottom look exactly the same way so now this this must be a six and this five now is interesting because there must be a five in one of those three squares now I don't know which these three squares in the central 3x3 block the fives going to go into but when we come up to this top block now where can the five go because of this five over on the left it can only go here it's a small pencil marks hang on now there's six this six so there's a six in one of those two squares and now there's also a six pencil march into these same squares we've got a five six pair over on the right hand side and this look without burning this is this is just gorgeous absolutely gorgeous and this is this is designed remember that this is not this is not random look at the effect of this five and six on this puzzle it is just superb so we need to think about this three by three block now because they can't be at 560 neither of these squares but we know the 5 and the 6 in this 3x3 block will be locked into one of these four squares and the critical thing to note about that is that the 506 are locked into either column eight or column nine exactly the same columns that this five and six are locked into in this top right 3x3 box so I need to put a five and a six somewhere in column seven well this squares ruled out this squares ruled out so there must be a five and the six in these two squares isn't that beautiful now this 6 here resolves actually which which all that must be in so because the supply and a six in these squares and this five and six here the forces but fives and sixes into the two squares in this 3x3 block couldn't put a five or a six in any of those squares it wouldn't work you try it you'll see put a five here that would mean this would be a five and it'd have to be a five here in this block as well because of the five over there we get repeated fives in the column so now now we've got six is here and this six here so that's the six that means that's a six and do anything with this five yes we can look the fives interact again there must be a five now in one of these two squares which means this is a five because of the five down here and okay what next eights into one of those two positions these two squares here must be a three and four lit just to complete the column and these two squares must be eight and nine and there's an eight here so that's a nine and that's an eight and that's cool because this eight now that means there must be an eight in one of those two squares so this can't be an eight anymore which means the eight is gonna be there so this is a three or four and this is a three or a four just that's just completing Row three of the grid think I use this nine now I didn't get like nine also can resolve this nine here which means we've got one three and four to place in the top left three by three block this one count this is a three or four this one can't be a one these two I think can be ones and what next is for maybe we can pen smart falls into those two squares and in this row we still need a 1 3 & a 4 so this square is a 1 or a 3 ah okay and now that means there's a 4 in one of those 2 squares we need to put a 4 somewhere in row 4 of the grid it must be in one of these two squares now that is interesting because look that marries up the fact there's a four and one of these two squares marries up exactly with the positions of a four in Row 3 so this arrangement is a classic x-wing I'll color it in let's think about what it means if we think about the finished solution there could be a four here if there's a four here there would have to be a fool here so those two squares could be fours but if on the other hand this square turned out to be the four and finish solution then looking at Row 4 the 4 would have to go there so we know the force in this 2x2 area are on the diagonals in one direction or another and the critical thing that means is that when we look down the grid here they can't be force in any of those yellow squares and well these two fours these two squares don't matter because there was already a four here so the critical stairs sorry cells I think we need to look at those squares the fact that those squares can't contain force what does that mean well one thing it means if we look at Row 9 of the grid and a square of 4 can go now it can't go in either of those two squares because of this 4 can't go here because we know that's part of the 6 7 pair and it can't go in either of these two squares because of the X Wing so there's a 4 in one of those two positions which means that another four and one of these two positions looking okay so okay so I thought that would be the step that we needed to crack the puzzle but it's not or it doesn't seem to be I might be missing something oh hang on ones are restricted as well let's have a look at once yes yes I'm going to delete this x-wing now look look at this where can ones go in column three those two positions are possible and that position is possible so these three cells let's highlight them do it in green these three positions can take a 1 in column 3 in column 4 only those two squares and in column 9 only those 3 squares because of the one here and this one here now this arrangement is a swordfish so it's just one sort of extra dimension to the x-wing so we know the ones in these particular columns can only occupy the green squares and that means that somehow the ones will be arranged no no in Finnish solution what everybody could look like those like that or like this this would be a one you know that we don't know how you're gonna resolve themselves we just know that they have to appear in these three positions now that matters because that's gonna mean we can eliminate ones from the rest of the rows this time so they can't be ones in any of these cells now some of these cells couldn't be one anyway there's a one to pair up here look so I'm just trying to spot what the implication of this is so there's these squares really matter these squares matter these two don't matter because there was one already here and this squares the yellow squares I think of the really affected squares here none of these yellow squares can contain a 1 so what does that mean just check this this box there's a lot of given information so if this square can't be a 1 it's going to be 3 8 or 9 can't see many things I can't see what's changing that if this can't be a 1 this cart this can only be 5 6 or 9 that's no good either and over here there's just there's too much too many possibilities for these squares I can't think that's going to matter what's going on then if this sort hang on hang on look let me just delete these hi Lighting's I'll put them back in if we need them I'm just gonna remember there's a swordfish there look 5 8 7 there 587 here so let's come back to this bottom left 3x3 block and a square 5 8 and 7 can go so they can't go in these squares and they can't go in these squares we need to put the numbers 5 8 and 7 in to this 2 by 2 corner where because of our X Wing we've already pencil marked fours so these four squares are five eight four five eights 4 5 7 8 quadruple and that's that's a good spot hang on let me just erm 4 5 7 8 now this one can't be a 7 this one can't be settings and 7 here these two can't be 4 okay what's still good it's not you yes it is good it is good because now we've done an x-wing trick on this 3/4 pair using the force but look now we can do an x-wing trick using the threes because if we look at where a3 can go in row 8 of the grid it can only go in these two squares because of this 3 here and the fact we just found this quadruple the 3 is locked into one of these two positions so again I mean I'm not gonna sort of keep going over it but in the finishing solution either be a 3 here and a 3 here or a 3 here and a 3 here so the effective squares there's already a 3 in row 9 we cannot have threes in any of those squares it's impossible and that means look let me look at Row 4 if we can't have a 3 in either of these two squares this must be a 3 and that is absolutely beautiful so now we get a 3/4 pair at the top there this must be a 1/4 pair there's no three in either of those two squares so there must be there must be a three in one of those two positions don't know if that matters that means in this block there's a three in one of those two positions in this block these two squares must be two and eights to complete the block and there's an 8 there so this is an 8 this is 2 that means this is a 1 and this is a 2 that means this isn't a one anymore so there's a three four pair now in this block and that's the one at the top this square this square is weak because obviously we've got this quadruple going on here so this square can only be 1 2 3 or 9 and look 1 2 9 so this square is a naked single it must be 3 that means this square must be at before that means this square is a 3 this is a four that's four that's a three and are we on the home straight now what a brilliant puzzle this is do you want to make a mistake the same so there's a three in one of these two squares eight we look along this row we need to put the numbers 1 2 & 9 in somewhere look we've got a 1 or 2 there so that one is a 9 now where do we put a 9 in this 3x3 block now only in that square another moment I do that look I've got pencil mark 1 in there so I'm going to be able to go 9 1 4 this is a 9 I normal Sudoku rules these two squares are 1 & 8 & some order that's now resolvable it must be 8 in one like that one in one of those two squares X 6 & 9 down here these two squares we still need to put a four in the central blocks that's 4 & 3 like that which means this is 3 & 5 just unwinding pencil marks I'm really hopeful that we're we're nearly there now ruled out there so this is for 7 yes look down here we need 4 7 & 8 to complete the column we have a 4 and a 7 there so this must be in heat which means this is 7 this is 4 this becomes a 5/8 pair in the center this becomes 1 or 2 still working that becomes a 1 9 this becomes a 1 therefore this becomes a 9 but knowing like that this must be a 2 we just must get four in a three to unwind that six and seven here is this fixed now because of the seven and six there this must be a six so this should be two and five which you can see is resolvable now that resolves to five and six at the top this is a 3/8 pants and that should be like that that should be eight and five now let's check yes what a puzzle what a puzzle that is now I think I got sidetracked in the middle because that swordfish I found didn't do anything for me but the x-wing on the x-wing on the fours was I mean that is quite something that really is quite something because it allowed me to find a four pair in those two squares which interacting with the five seven eightt in these positions forced this four five seven eight quadruple down there that that is just it's stunning design absolutely stunning design and it allows us to get the second x-wing on Three's that puzzle that is one of the all-time great Sudokus we've had on this channel I am and lost in admiration for it I'd love to know how you guys found it do do leave us some comments if you enjoyed it even if you didn't we like the feedback and thanks very much for watching what's a puzzle you

Channel: Cracking The Cryptic

Views: 62,196

Keywords: handmade sudoku, x wing sudoku, xwing pattern explained, sudoku xwing, double xwing, hidden quadruple, nikoli sudoku, best sudoku ever, sudoku genius, sudoku algorithm, simon anthony, mark goodliffe, swordfish sudoku, sudoku swordfish explained, sudoku swordfish, sodoko swordfish, sudoko swordfish

Id: ZsrEFgcKJvo

Length: 23min 34sec (1414 seconds)

Published: Mon Sep 02 2019