Simply Beautiful Sudoku Logic

Oh welcome back to cracking the cryptic way today we're going to take a look at this puzzle that's coming from Harry and he said that it would be great if we could talk through slowly how to solve it which I hope we'll be able to do the reason I think this might be suitable for that is that obviously if we stare at the grid there seems to be a lot of given digits so um I mean it's not always the case sometimes you can get lots of given digits and still very difficult puzzles but normally a lot of given digits is an indication that the puzzle may not be as brutal as sometimes now if you if you want to have a go at the puzzle click on the link under the video that'll take you to our software and you can have a try now let's have a look and see what we can do with this so I'll start with ones and as usual I'll try and around the grid just highlight in 3x3 blocks where I can restrict a number to exactly two positions then I will and I'll make a little pencil marks to remind me of that fact don't think I can do anything in this box though so let's move on to choose choose not really doing anything I think there's only two twos in the grid yeah okay so threes can go into one of those two positions one of these two positions some of their actual digits in the grid though an strikeforce yeah Falls you can look into one of those two squares and one of these two squares these two squares okay fives okay I'm beginning to revise my my opinion about this puzzle that's quite unusual to for an easy puzzle anyway to go this long without being able to enter a digit sixes settings can be locked into one of these two squares the guns only two settings in the grid there's only one eight so maybe nine so that place we're going to need to start so nines one of those two squares because of these nines here there are lots of nine so hopefully nines will be fruitful and okay I think I must have missed something there okay but what do we do in situations like this well the next thing I would look at would be rows and columns with a lot of given digits to see if we can identify any restricted cells so let's start with Row 2 of the grid where we need three four seven and eight and to see if we can find any squares that are particularly you know at least down to two digits say I can't actually see any and you've those squares now wondering whether I'm being trolled and this is actually a monstrous puzzle that someone's sent him under the guise of an easy puzzle on two three five and nine down here okay well that square black square is restricted that only be a two or three Allah now that is interesting that is very interesting I'm just gonna I'm just going to check there's nothing easier I've noticed something there so do do you have a look at what I might spot it off that serial three visit it's a it could be beautiful in fact I am just going to talk about it because it could be beautiful so let's look at this this square just looking at the word the interaction of the row and the column in the box can only be two or three now if we look upwards we've got a 2 and a 3 in this box at the top same as that number now this 2 and 3 obviously is preventing there from being 2 or 3 in either of these squares in column 6 so we come down the column here we know there's a 2 or 3 here therefore there must be a 2 or a 3 in one of these two squares but look we slide across here that's also a 2 or a 3 there this is very very beautiful so now let's think about this there are two options for this I mean I'm gonna do this slowly just because I think it's worthwhile let's imagine in the Finnish grid this was a three now this is a three I still need to put a two into column six and because of this 2 here the only possibility would be that Square and that would lock a two into this position here so I'm gonna actually just write the two into that square this square is the key one let's make it okay so that's option one is if this is a three now watch if on the other hand this is two now I need to put a three into one of these two squares remember the three can't go up here because of the three that's in this box so I need to put a three in one of these two squares now this time this three matters so I'd have to put the three here and this square in this example would now be a three so whichever choice I select for this square here this square has a sort of parity with it so this sort of this two-three effect going around the corner now it's incredibly difficult without noticing this two-three here to look at this Square and realize it can only be a two or a three if we compare the contents of this column just got a one and a nine and a six and a seven extra in the row so to limit this to a two or three is really quite massive now this five all of a sudden therefore I'd never have been able to eliminate five from this square but now where can a five go in this box well it can only go in one of those three squares as it can't go in the two or three Square and that means coming over here I get a digit the five in this box must be in row 9 it must be there and that took the position of a force and that means that that piston so we've got two digits now as a result of logic and now now we've got a 4 and a 3 here look so this is a 3/4 pair you can see the fours marry up in rows 1 and rows to in these two boxes so over over on this side of the grid or we need to put a 4 into Row 3 somewhere that's the other way of thinking about this I sometimes look at this for pattern here is an x-wing but a simpler way of putting it might be to say where can I put a 4 in Row 3 of the grid obviously in neither of these squares because of the force in one of those two positions and in neither of these squares because we know there's a four in one of those two positions so I know the four in this box must be in one of these three highlighted cells and there's a four here look so actually there is a four six pair as well six so what would the next step be so these three squares are some combination of six seven and eight this square is a six or seven let's have a look into these squares now so we need two three five and eight so you can see we can look the 2 and the 5 into those squares there because of the 2 and the 5 over on this side so these two squares must be three and eight and that resolves to three and four over on this side that must be that way round that gives us a four here just unwinding the pencil marks that we had earlier this square now can only be a 7 because of the 3/8 pair there now there's a seven in one of those two squares look at these sevens here what do we need one five eight two nine seven eight in one of those two squares and a one at the top there so we've now pencil them out everything in this box that we could possibly do still left with two seven and eight over here which we well the seven I suppose means it's a seven in one of those two squares let's put that in right so goodness me this is proving a lot more involved than I was expecting so one two six and nine down here now only one to six mate I should say so the eight here this is mating one of those two squares this is a 206 yeah what's the options for this square here so this square can be two three eight or nine for the state's pencil mark there and a two here so this can only be a three or a nine this one can only be this can be a lot of things I think 3 6 comma 7 3 oh no only three digits 3 6 or 9 I'm just looking down this column now to see whether I can see any other big restrictions obviously I've pencil market because I freely pen smart this block these effectively are all pairs but I could label them as such if that helps you guys to see it that we can write those in that's why I was looking at this column now that's where is restricted and all I'm doing here is comparing rows and columns and just trying to see where I've got a lot of differential between the digits you can see this where it can be three but it can't be a four five six seven that can be enough they get three nine here goodness maybe that was there no I don't think it was there from the stocks I needed the trick over here to get four and five so I think that is new logic that's not something I'm missing here so six here now what does that mean that means this is a six and this is a six just normal sodoku using the six up here but 3:9 here means we need one two and eight to complete this this block so it's still not quite sure where the two's going if that must be a seven now from the earlier pencil marks I'd highlighted six or a seven through the central notation that's gonna be an eight here it's been eight now in one of these two squares now that marries up so again that's just the way I solve you can see them the moment I pencil map these eights in here my eyes were looking upwards and downwards to check whether I could find eights in the same columns in added either of the other boxes and look so we have this pattern of eights here so we know that if in the finished solution this is an eight then this will be an eight and on the other hand the only other state of affairs that could exist is that this is an age of in which case this will be an eight so when I come down to this block down here there's no way eights can go in those squares because there will either be an eight here or an eight here and similarly on this side so that actually allows me to pencil mark eights into those two positions along with the nine so now we've got an eight nine pair in this block therefore we know these two squares now must be two three and five so with five over here this square is a two or three it's two three or five right so let's come back over here we need to into one of those two squares and you can see that's going to be useful now there's a 2/3 pair look in those two positions and that means this square here that's going to have to be a six because it can no longer be a two now where can a six go in this 3x3 block and see it can only go here in the moment I place it here a few things happen firstly I can place the five because of the pencil marks and now 502 must unwind at the top and this six means the six and the four unwind as well this 4 means these Falls also get unwound so a flurry of activity this 5 now points at this square and forces the 5 downwards so we have were able to go over 5 9 8 1 this 9 here sees this 3 9 pair at the bottom we can now unwind that finally we resolve this square over here that's going to be a 2 therefore this is a 3 because we know these forms this sort of weird pair around the corner this square now must be an aid we need needs and a 9 to complete the final row of the grid and there's a 9 here so 8 9 like that 708 into these two squares so that's a pencil not those certain animate into these two squares all this should be a 2 at the top complete that row and that looks like it's working this is not an 8 anymore these two squares need to be 1 & 2 and there's a 1 here so 1 2 1 7 & 2 2 & 3 these two squares a Turing three aren't they so that two there seems that one comes so I'm going three to like that just trying to make sure I'm not making any errors here see we know about seven and eight into these two squares this is all so sudden or an eight we look down the column we need three seven and eight to complete it there's a three over there you can see also we've already got an ace in there as well so that's the seven that's an age that's a three that's that's this seven here feeds back over into this side eight seven seven page like that that resource is 89 as well and finally three five into these squares and that is correct and it is it's a hell of a puzzle that is a really really interesting puzzle now I probably missed something at the start but even if I did I don't really mind because that was really cool this this two three effects down here and down here was was worth doing so I hope you guys enjoyed watching that be interested to hear in the comments what I missed and yeah we'll be back soon with another edition cracking the cryptic you

Channel: Cracking The Cryptic

Views: 68,775

Keywords: schrodinger cell, alternative inference chain, aligned pair exclusion, nishio forcing chain, digit forcing chain, unit forcing chain, death blossom, pattern overlay, quad forcing chains, almost locked sets, sudoku troll

Id: FVW2a42vRu0

Length: 18min 28sec (1108 seconds)

Published: Thu Sep 19 2019