Master The Basics Of Advanced Sudoku Solving

[Music] hello welcome back to cracking the cryptic where as you can see if you're a regular to the channel I'm on a different computer today so I'm hoping my laptop holds up and I'm going to be able to show you how to solve this puzzle so Wulfric has sent this in on our Twitter account which is apt cryptic cracking closey you don't follow us and he said that the puzzle took him over an hour and he wondered whether we could find a more efficient way of doing it well I don't know yet but we shall have a look in a moment if you'd like to try the puzzle yourself then just click on the link under the video and that will take you to our software where you'll see exactly what I'm seeing here and you can solve the puzzle first or afterwards as is your your preference so let's have a look and see how we go about doing this now I'm going to use standard notation today so what do I mean by that that means I'm looking at three by three blocks and what I'm doing is I'm whoops I'm trying to identify within three by three blocks where a number can only go into exactly two positions so if you look at where you can place ones in the highlighted area it's in exactly two positions and I make little pencil marks to remind me of that fact some people think this is cheating to do this but I come from sort of speed solving background where you have to use all of the information as as much as you can as quickly as you can and I found this to be the most efficient way of doing that when I first started solving Sudoku I used two pencil mark in all of the options now that is a terrible method and I don't recommend it you have to be well I think for two reasons firstly it's time-consuming secondly you miss a lot of the beautiful logic that exists within these puzzles if you do use that method so definitely don't recommend that now let's have a look eights on this bottom block we see we can pencil markets over on the right hand side which allows me to make some more pencil marks sevens and smoke into those two squares fours look in fact this bottom box is quite interesting so the fours can only be in those two positions now oddly look at this one here now I can't pencil marker one in this bottom right 3x3 block but I can observe that the one is not in this square now I've already pencil marked four sevens and aids in two other squares so the fact that the one can't go in this square means that actually we've discovered a hidden while is a naked single by virtue of the fact that no other digit can go into this particular square this square must be a three now normally actually this you know I've been extolling the virtues of so-called Snyder notation which is this highlighting method for numbers that can only go in two positions it doesn't normally reveal this sort of three here but in this case it hasn't we'll we'll take that so this must be three in one of those two squares now three over here this can't be a three anymore well this is a three one speed and one of those two squares cause threes twos seven sevens might be better look within pencil marks and sevens into those two positions [Music] [Music] Nine's as well look ninth this line here and the nine in the top he knows a nine in one of those two squares so that means this square must be a nine which means in turn that there must be a nine by the here or here ah now the six and this four become important in Row 2 because they interact rather nicely in this top left 3x3 block you can see is only actually two positions now that the four and six can go in soup and that's these two squares so all of a sudden we are able to isolate the value of this square and this square these two squares must be five and eight and that's well it's a little bit helpful I'm not seeing what Singh instantly it means as an eight in one of those two squares because of the eight down here now similarly with the five can we do something with the five yes we can because of this five here so the fact this is a five and there's a five in one of these two squares means that in the top right box so we can pencil drop files into those two squares now and this is important if you're new to pencil marking you can see the cursor disappeared too you can see that we have threes and fives pencil marked into two squares in the same 3x3 block now that means that these two squares can only be the numbers three and five because of the logic that we're using we're saying this square here of these either of these squares is of three and either of these squares is of five so obviously two squares two unknowns I cannot put anything else into these two positions now that ought to be helpful it means that there's a five in one of these two squares [Music] what else does it do must do more than that probably but quite seeing how success six pours what am I missing here maybe this is why this puzzle is very difficult is because it's around here you get stuck and you can't make progress see we can pencil box and twos I think in the top right box it's two down here and the two on the left hand side and there must be a two in one of those two squares I don't know a great deal about ones and the other number so one two six and nine okay so here you can't see how to use that seven ah right this square here can be a six only be a six because of the six up here and the six down there so I should have spotted that much more quickly but sometimes when solving on a computer you don't spot things quickly especially not when you're talking while you're doing it now that means this square is a six it's the only place of six can go in this block allows us to pencil marks and sixes on the left hand side now all of a sudden we have this interesting 2x2 set up in this this square and that is powerful because now this too becomes powerful if we look up we can now pencil mark twos which we couldn't before and that combined with this two down here means we get some pencil marks on the left hand side but it also allows us to use this five more profitably there must be a five in one of those two squares and that gives us another digit we managed to pencil up five into one of these two positions well this position can no longer be a 5v5 here and now we've got six digits in effect or we have got six digits in Row three and we're looking to place the numbers 2 4 & 6 now let's ask ourselves what can this square be well it can only be a four because there's already a 6 and a 2 in the column so this is a 4 that gives us a 4 and a 6 here which means this is a 6 this is a 2 and suddenly we're looking like we're making more progress this can't be a 2 anymore to the muscle these two squares because there's a 3/5 pair look in this top right 3x3 block we must be looking for a 1 and 9 in these two squares which means actually look there's a 1 in one of these two positions and because of the one at the bottom in this square that means this square here is the only place of one can go so we can get to go one a pencil mark aids use this one to eliminate the pencil the one in this Square this square here must be a one and where can we put a one in column seven now Bologna in this position so one and eight like that this 8 and now immediately we can unwind this must be the eight and suddenly we get a six eight pair as well over on the left hand side so a flurry of activity there that all looks like it's helpful now in row five of the grid we need the numbers four five and seven into the empty positions now we have seven here look this so we cannot have a seven in either of these two squares there's only one position for a seven that's there let's make sure we pencil mark two sevens on the left-hand side and these two squares must be four and five in some order now can we use that somehow not immediately seeing how to do that six [Music] okay so what now what we'll do well I can pencil mark fours into these two squares I'm not sure how are useful that's going to be and in this bottom area let's look at that so we have six here and a six here and a six over on the left-hand side so actually a six in this bottom left box can only be in those two squares and a three in this bottom left-hand box can only be in these two squares this is interesting now I'm going to study this second ah now I don't know if it's helpful that look at this fall we have actually pencil mapped in this bottom left 3x3 block ones twos threes sixes and nines so that's five of the nine digits so that four in column one means that this square and this square actually can't take six of the nine digits because they also can't take four so the only options for these two squares are five seven and eight so this square can only be seven or eight because there's a five already over here and this square can only be five or seven which now that is important so let's look at this now let's look at column one in more detail you can see we've got three squares that can only be some combination of the numbers 5 7 & 8 so three digits so those squares must occupy these three cells this cell here this cell and this cell that means this cell can't be a 7 if we tried to put a 7 into this square this square would be an 8 this square would be a 5 and we couldn't fill this square at all so this square is not 7 this squared is 7 this square must be a 2 or 3 and this square must be a 2 or a 3 actually in this 7 here means we can pencil we can get rid of the 7 there and that's important because that allows us to find a 5 7 pair of the bottom look these two squares again just using our pencil marking logic a lock to being 5 & 7 and you can see that actually because this square is also a 5 or 7 there is now a pair in row 9 it's less let's make that clearer so in effect now we've got 6 digits in row 9 and we're only looking to place the numbers 4 6 9 into the open cells first thing we can say is this can't be a 7 therefore so this is the sevens well the fact that that's true means that that unwise the 7 and the 5 here which means this is a 5 and that gets us going up with the 8 and the 5 up here so all of a sudden again I feel like we're making very useful progress now just unwinding everything we've done now we've still looking to place in nine into one of these two squares well this can't be a nine so this is a nine this is the two therefore this is a nine so now there's a nine in one of these two squares and we're still looking for a five I guess into the central 3x3 box I can't quite see where that goes so that's a pencil mark the fives and you can see obviously we get to fill this digit into the two so only thing we're lacking in that box 4 5 2 3 4 5 2 3 2 3 let's check this box 1 for our yes this square look this square can only be at 4 so just comparing all I'm doing there is comparing the contents of the row with the Box in the column the only option for this square is 4 that means we need a 1 into one of these two squares and that's and the a puzzle salt now so now 1 a 9 up here 9 and 2 here this must be 3 and all of a sudden that means this is a 3 is the only place the 3 can go in the box which means this is a 2 and I think we're almost home in hose now this square here can only be a 4 or a 5 I think [Music] and sum up all those in just to keep things reasonably in check we're looking at these two squares we're looking for a 6 and a 9 so we know this is going to have to be the 9 although we've pencil marked into two positions with actually this 9 here means we go - so this is 9 this is 6 this is 6 this is 8 that's a pencil mark eights in here and do this longhand still need a 4 in the box so again we can pencil mark fours like that this square here can be 3 4 or 8 looking at the contents of the column and look over here we have an 8 and here we have a 3 so in fact this is a 4 that resolves everything 4 5 5 into this square this should be a 2 this can no longer be a - not that ever could be this must be a 1 now it's the only option for this square [Music] still need a 4 in the column that's up there 1 8 like this 8 3 is those two squares 4 5 here 5 & 3 there so that's how to do the puzzle so I hope you guys found that useful I've gone deliberately slowly today just really majoring on trying to make myself structured using the pencil marks as much as I can those of you who are relatively new to more advanced @oq I cannot recommend this method enough it'll get you through most puzzles not - I'd say the level of diabolical some diabolical Zittel see you through those but you know if you want a firm base for your pyramid in terms of you know making sure you have the basics sorted out then what I've done today is a very I think quite a sensible way of approaching solving Sudoku thanks for watching and we'll be back soon with another edition cracking the cryptic [Music]

Channel: Cracking The Cryptic

Views: 274,597

Keywords: sudoku basics, sodoko basics, sudoko basics, soduko basics, sudoku master, sodoko master, sudoko master, soduko master, best sudoku channel, hard sudoku, difficult sudoku, snyder notation, snider notation, sudoku notation, simon anthony, mark goodliffe

Id: -24S4mHY73w

Length: 19min 5sec (1145 seconds)

Published: Fri Jul 19 2019