Triples: the Single Most Important Sudoku technique?

[Music] hello welcome back to cracking the cryptic and we're going to have a look at classic sudoku today we do get asked to do a fair amount of classic sudoku i mean sometimes we just get sent puzzles people couldn't do and ask to do them well i mean there's online solvers for that don't don't write to us with your puzzles um i think sometimes people assume that that's what the channel is for though is is to solve puzzles that people have struggled with on um in their apps and that's not really what we're about but we do like to do some handcrafted sudoku occasionally uh even when it's classic and it's a really good um ground for learning the techniques that apply to all sudoku to be honest through all the variants etc now if you do like classic stoker don't forget our app which is um available has a hundred handcrafted classic sudokus some really entertaining solves in that and of course our sudoku pad app just two or three dollars which um will enable you to play classic sudoku's using our software which has been very popular and uh we've thrown in a dozen classics into that for free as well so that's all available on the links under the video along with all our other apps and uh with the patreon page and so on now this has come in from tope lincala who i think is finnish and that reminds me that that one thing that we also don't do is solve puzzles that can't really be humanly solved there is a famous the world's hardest sudoku from about 10 years ago by another finn uh which we've been sent a number of times and it just is not conducive to a human solution so we're not doing that on the channel it's interesting to some people that that exists in sudoku but it certainly does anyway let's see what we can learn from this puzzle do give it a try on the link under the video um it is just regular rules one to nine in each row column and box um and i'm going to start now let's get cracking so just looking at first for places where the same number appears in the same set of three boxes and there aren't many six i suppose two we can limit down there but given those twos and that one blocking off that cell all of those cells are not possible in box eight uh the columns look a little bit more profitable at first and not much fives limited to one of those two places six is up there somewhere nines down there and one's there and that wasn't that helpful ah this six though is ruled out of those cells so in this box which has a useful shape of given digits it must be in one of those two now that can't be a six because one of those two must be and we've kind of run out of easy stuff i suppose five is limited there oh nine sorry is in one of those two cells this nine rules out that and that nine rules out those three if i missed something here that i've just noticed has only two possible candidates so i'm using the corner marking for where a number is restricted to one of two or three positions in a box and then central marking as we do is where there's only a couple of candidates for one cell and that helps me keep track of things i've learned about the puzzle r8 is restricted down here therefore eights in one of those two and that line of thought peters out quite quickly that can only be four or seven it sees three five six two in the row 198 in the column it would be nice to kind of come up with two of these in a row or column two of these two cell restriction what's this two eight seven four nine one six that's three or five yeah there we go okay that is an interesting juxtaposition because look at this cell as well two eight seven four in the row one nine in the box that's three five or six that gives us a triple and that does tell us that that three five six are confined to those cells in the row and that can't be a five and the pencil marking we did tells us where the five is so that's quite useful these two must now be one or nine to make up the rest of the row one of those is a five but that could still be the six if that was the six in row three does this does this not get us much further forward i don't think it does hmm okay i'm gonna have to find something different two i've just seen is restricted to those two cells a bit like the nine over there wow oh one is now in one of those two since the work we did with five but i'm not getting much out of this this is tough okay that is either six or seven just by everything it can see again that's four six or seven maybe we're working on a triple but no that could be a one so that doesn't work that is four or eight i've just noticed i'm ready for six oh well look i should have concentrated a bit harder once i'd restricted six there i should have noticed that that would become 4a this is 4 7 or 8. and this is because in this row 9 and 1 are excluded from those cells well they're also both excluded from this so this is forming no hang on i'm talking absolute nonsense there thought i was getting a triple but i don't think i am after all so i apologize for that um five four two nine three six that's one seven or eight is there something still going on in this middle row one 19863 no this can be two or five again so it's not at all as helpful as i was thinking okay so not to worry about my weird thoughts there eight if eight was confined there we could put an eight there but as far as i can see eight could still be up the middle two and nine can that be a two the only places for two in the middle column are there it's quite interesting so if that was a 2 that would be a 2 we'd get a 2 there have a little x-wing on twos that's fine i'm definitely gonna need to spot something totally different that i haven't got yet now if eight was there then we'd have a four seven pair here ah what would that mean nothing very interesting as far as i can see oh look these cells they see three two eight six in the box four five in the column so they're from one seven nine and that is suddenly a triple in column one and a much more useful one especially given that we pencil marked this handily so that eight can go in that makes this a four and that's seven suddenly all the pencil marking i've done turned out to be fortuitously useful uh we get a two or a five here uh one two or five in those surely with this isn't going to peter out three and six are the remaining oops um digits in the first column must be in one of those cells what's that done for us if anything that is three or seven now that's three seven or eight well that's a quadruple is this right the reason being that two and four yes can't be in any of those highlighted cells so those are a 2-4 pair is that please help me don't just be showing an interesting pattern and not actually helping um okay that is a bit frustrating i don't actually see what that gives me but it looked incredibly interesting maybe one of these two four pairs actually does do some work um two is in one of those cells ah four four in this box has only got one location that's a simpler way of getting at that okay two so that's not too um so two is definitely in one of those two that's four so four is in one of these cells six two one nine eight four that can be three five or seven doesn't look like i'm gonna fill it in just in case it ends up forming another triple with that and one other cell i don't think it's going to one seven nine five so we've got two eight hmm what have we got those five still totally unresolved there's a five there somewhere now what maybe i've missed something else in this box doesn't look like it though there's one of three six seven and one of one five there hmm okay that's let's reassess a bit one is confined there wow i mean i'm really back to hunting for from other triples now i mean i found two including one that seemed really useful and yet hasn't actually given me all that much seven being confined to those places i mean unless that's forming an x-wing somewhere that is very hard to spot i don't think i don't think that's doing anything for me either ah six and eight pair so that can't be an eight of course so eight is actually positioned here right that's been available for a long time and i apologize for not spotting it um does that do anything now seven five four two eight i don't even know what that does in a way i'm relieved if it's not been the key to the whole puzzle just and i've been completely sideswiping it no i'm not seeing where how we're done six three eight five again this fact that two can be only in those positions seems like it ought to help a bit but i can't get it to eight five nine two this can't be a two where's two in the top row ah okay two is confined to those two cells so i should have spotted that actually so is four i think look that 2 4 can't be in any of those positions so that is a 2 4 pair so that can't be four that's giving me a six seven pair i've also just worked out two where two is in the top row it's there that puts six there in the box oh this is all coming now as celine dion almost said um that is a three or seven two four pair one eight five that is six or nine that is three seven or nine maybe they don't resolve but now going back to this six seven pair that gives me this is one or five which makes an interesting pair in the box that's one or four okay look at the pair in the box one five two nine eight four so that's three or seven six must be in one of those two cells in that box so that becomes an eight and that's not um six there that interesting logic chain runs out immediately four or six there two or four there three three one of these is a three and the other must be whatever this is because it appears in one of those two cells so those can only be from three one and nine that can't be a six so we know where six goes now in the box actually i could have done that from the 2 4 pair as well six up here is in one of those two cells in fact with the two four pair this is a one six nine triple isn't it let's remove that offset one it's not very helpful um seven is in one of those which is not useful still not done oh that's become a five since we got the two at the top of the column so that fixes one and two that fixes one there five goes in there now we've got that's not a five so that is that's a one or a four three that's four seven or nine five five five down here is here and that fixes both eight and nine this has to be an eight that is three or seven i still haven't resolved that uh this can't be five anymore so i've got an infuriating three four seven triple there but this is now a three so that fixes the triple and probably the rest of the puzzle and what a puzzle that's really clever seven three that can't be three i mean i might not be finished i thought i was yes this row surely six and seven they can go in that becomes a three uh the seven there fixes this is a six so then that gets our triple here let's just tread carefully as we finish off four and one nine and seven can't do that two four pair at the top this is a three that looks good nine there a one seven pair down the side four two one oh four seven and nine so they go in in that order one and seven and two and four and that is a lovely classic sudoku so i hope you enjoyed that really interesting puzzle actually um at least two sets of triples that seemed vital to me um in row three i think it was and column one and then still some interesting work to do maybe it was just because i didn't notice the eight there in in those sales fixing that eight for a while but really good puzzle thank you so much to topi for sending it and uh hope you enjoyed that i hope to see you again on the channel soon bye for now you

Channel: Cracking The Cryptic

Views: 327,837

Keywords:

Id: uWgu-HOm5to

Length: 20min 9sec (1209 seconds)

Published: Sun Jul 25 2021